ISSN NUMBER: 1938-7172
Issue 4.12 VOLUME 4 | NUMBER 12

Editor:
Michael A. Fiedler, PhD, CRNA

Contributing Editors:
Penelope S Benedik, PhD, CRNA, RRT
Mary A Golinski, PhD, CRNA
Gerard Hogan Jr., DNSc, CRNA
Alfred E Lupien, PhD, CRNA
Lisa Osborne, PhD, CRNA
Dennis Spence, PhD, CRNA
Cassy Taylor, DNP, DMP, CRNA
Steven R Wooden, MS, CRNA

Assistant Editor
Jessica Floyd, BS

A Publication of Lifelong Learning, LLC © Copyright 2010

New health information becomes available constantly. While we strive to provide accurate information, factual and typographical errors may occur. The authors, editors, publisher, and Lifelong Learning, LLC is/are not responsible for any errors or omissions in the information presented. We endeavor to provide accurate information helpful in your clinical practice. Remember, though, that there is a lot of information out there and we are only presenting some of it here. Also, the comments of contributors represent their personal views, colored by their knowledge, understanding, experience, and judgment which may differ from yours. Their comments are written without knowing details of the clinical situation in which you may apply the information. In the end, your clinical decisions should be based upon your best judgment for each specific patient situation. We do not accept responsibility for clinical decisions or outcomes.

Table of Contents

EDITORIAL
  Is the Approach and Management of the Difficult Airway Changing?
Download Text File

AIRWAY
  Comparison of succinylcholine and rocuronium for first-attempt intubation success in the emergency department
Download Text File

  An algorithm for difficult airway management, modified for modern optical devices (airtraq laryngoscope; ctrach™): a 2-year prospective validation in patients for elective abdominal, gynecological, and thyriod surgery
Download Text File

The lma ctrach in morbidly obese and lean patients undergoing gynecological procedures: a comparative study
Download Text File

Safety and efficacy of laryngeal mask airway supreme versus laryngeal mask airway proseal: a randomized controlled trial
Download Text File

Routine clinical practice effectiveness of the glidescope in difficult airway management: an analysis of 2,004 glidescope intubations, complications, and failures from two institutions
Download Text File

Propofol versus sevoflurane for fiberoptic intubation under spontaneous breathing anesthesia in patients difficult to intubate
Download Text File

3,423 emergency tracheal intubations at a university hospital: airway outcomes and complications
Download Text File

National survey to assess the content and availability of difficult-airway carts in critical-care units in the united states
Download Text File

 

SPECIAL ISSUE

This is a special Single Topic Issue of Anesthesia Abstracts. This issue is devoted to Airway Management and our changing approach to difficult airways. It was prepared exclusively for Anesthesia Abstracts subscribers by Dennis Spence, PhD, CRNA. Dr. Spence is an Assistant Professor at the Uniformed Services University of the Health Sciences Graduate School of Nursing. He is the Clinical Research Director for the Phase II Clinical Site at Naval Medical Center San Diego, CA.


Editorial
Is the Approach and Management of the Difficult Airway Changing?

As anesthesia providers, we are considered the experts in airway management. This means that we are both knowledgeable and proficient in all facets of airway management, and can apply this knowledge and skill in all settings and patients. We are paid to critically think and evaluate a situation and rapidly apply our expertise to safely manage the situation.  Below are some scenarios that you may be faced with during your career. As you read them, think about how you would apply your expertise to manage them and how they may have been managed 5 to 10 years ago.

1. You evaluate your next patient and determine she is a potential difficult airway because mouth opening is less than 2 cm. The patient is scheduled for a total knee arthroplasty. The surgeon requests general anesthesia. You have never done an awake fiberoptic intubation. What are your options? How are you going to intubate the patient? What if the patient wants to be “asleep” for the intubation? What do you do if at a small facility with limited resources and nobody to assist with the FOB? What drugs or techniques will you use to keep the patient spontaneously breathing? What route, oral or nasal? What are the potential complications? What is the success rate of asleep spontaneous breathing anesthesia for fiberoptic intubations in patients with known difficult airways?

2. A patient is scheduled for a septorhinoplasty and uvulopalatopharyngoplasty for moderate to severe Obstructive Sleep Apnea Syndrome. You decide to perform an asleep intubation using a Glidescope. You easily intubate the patient on the first attempt. A colleague in the next room needs the Glidescope and takes it. No others are available. After completion of the septorhinoplasty the surgeon places the mouth gag accidentally extubating the patient. You attempt to reintubate the patient with a Macintosh 4 and have a grade 4 view. Two attempts are made without success. The patient is awakened and an awake FOB is performed successfully. Question: Could the patient have been easily reintubated with the Glidescope? Do you provide the patient with a difficult airway note? If the patient was never accidentally extubated would you provide them with a note? Should you not have released the Glidescope to the other room? Does the Glidescope have a higher success rate than a fiberoptic scope? What other airway adjuncts could have been used?

3. What is the success rate of an LMA CTrach when used in morbidly obese patients?

4. Are rapid sequence induction intubating conditions similar with rocuronium and succinylcholine? What are the RSI dosages for each?

 

Multiple factors make it challenging for us to secure the airway without complication. Productivity pressures and emergency situations may limit the amount of time we have to perform a thorough airway examination, and prepare the equipment and personnel needed to safely manage the airway.  These pressures also limit the ability of educators to teach anesthesia students how to use a variety of airway equipment and adjuncts. My hope is that the scenarios made you think about how you would manage these situations. I also hope it makes you think about what you need to do to maintain your knowledge and skill in difficult airway management, and how you can ensure future anesthesia providers are airway management experts.

There is no question that new supraglottic airway and video laryngoscopy devices have changed how we approach the difficult airway and patients at risk for aspiration. Their development has revolutionized airway management, and I expect in the next several years the Difficult Airway Algorithm will be updated to include these new devices and management techniques. However, I wonder at what cost? Are we going to produce a new generation of anesthesia providers who have never done an awake fiberoptic intubation? Or never used a bougie introducer? Are we doing a disservice to a patient with a potential difficult airway by intubating them with a video laryngoscope on the first attempt? What if they go to another facility without a similar device? Are we putting the patient at risk if we don’t provide them with an airway note? These are the unanswered questions that will need to be addressed in the very near future.

This issue of Anesthesia Abstracts is devoted to airway management. I have selected a series of articles on a variety of topics related to airway management. As you will see, the articles support the argument that the approach to difficult (and routine) airway management is changing. As you read them think about the scenarios and questions I raised earlier. Think how you could apply what you learn from them to your clinical practice. If you teach students, take the time to discuss the topics with them. This is the essence of evidence based practice.

Dennis Spence, PhD, CRNA


© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 12, December 30, 2010




Airway
Comparison of succinylcholine and rocuronium for first-attempt intubation success in the emergency department

Acad Emerg Med 2011;18:11-14

Patanwala AS, Stahle SA, Sakles JC, Erstad BL


Abstract

Purpose To compare the difference in first-attempt intubation success with succinylcholine or rocuronium in adults requiring intubation in an emergency room.

 

Background The two most common skeletal muscle relaxants used in the emergency department are succinylcholine and rocuronium. Succinylcholine has been demonstrated in several studies to be superior to rocuronium for providing ideal intubating conditions for rapid sequence intubation (RSI). However, in many studies the dose of rocuronium was below the recommended RSI dose of 1.2 mg/kg. Additionally, succinylcholine is considered ideal because of its short duration of action whereas rocuronium’s duration of action can be upwards of 45 to 60 minutes following an RSI dose. This can be problematic in a failed intubation; and currently sugammadex, a new reversal agent that can rapidly reverse non-depolarizing muscle relaxants, is unavailable in the United States. In contrast, succinylcholine is contraindicated in patients with hyperkalemia and other conditions.

 

Methodology This was a retrospective study of all intubations between July 1, 2007 and October 31, 2008 at a large emergency room in a Level I trauma center with an emergency room residency program. All information from intubations was recorded prospectively in a quality assurance database after the procedure. Exclusion criteria included age less than 18 years, or administration of medications other than etomidate for sedation, and rocuronium or succinylcholine for muscle relaxation. Data recorded included:

  • demographic variables
  • difficult airway predictors
  • medications administered
  • airway devices used
  • number of attempts
  • reason for intubation
  • laryngeal grade view
  • provider experience level

 

Predictors of difficult airway included

  • blood or vomit in the airway
  • facial trauma
  • cervical immobility
  • obesity
  • airway edema
  • small mandible
  • short neck
  • large tongue

 

The primary outcome was first-attempt intubation success rate and the secondary outcome was number of attempts. Logistic regression modeling was used to identify predictors of first-attempt intubation success. A P value < 0.05 was considered significant.

 

Result During the study time frame 621 patients required intubation. A total of 93 were excluded for missing data, 83 because they were < 18 years, and 47 who did not receive etomidate and succinylcholine or rocuronium for intubation. This left 327 patients for analysis; 35% (113) in the succinylcholine group and 65% (214) in the rocuronium group. No significant differences were noted between the two group’s demographics, difficult airway predictors, reason for intubation, intubating device, laryngeal grade view, or physician experience. The mean age of the sample was approximately 47 years and BMI was 27 kg/m2. Seventy-two percent required intubation for airway protection.

The incidence of a grade 3 or 4 laryngeal view was 18.6% in the succinylcholine group and 12.1% in the rocuronium group (P = 0.14). A majority, 71.6% of patients, had one or more predictors of a difficult airway.

Direct laryngoscopy was used in 63.7% of patients in the succinycholine group compared to 56.5% in the rocuronium group (P = ns). The second most common device used was the Glidescope, with 32.7% of patients in the succinycholine group and 35.5% in the rocuronium group having this device used for intubation (P = ns). A Glidescope was used in 84% of cases when direct laryngoscopy was not used. Intubations were attempted by third-year residents or attending physicians in 45.1% of patients in the succinylcholine group compared to 41.1% in the rocuronium group (P = ns).

First-time intubation success was similar between the groups, with 72.6% successfully intubated in the succinylcholine group compared to 72.9% in the rocuronium group (P = 1.0). The median number of intubation attempts were similar between the groups (P = ns). All patients were successfully intubated. The median dose of etomidate was 0.25 mg/kg in both groups. The median succinylcholine dose was 1.65 mg/kg. The mean rocuronium dose was 1.19 mg/kg. The amount of muscle relaxant administered was not a significant predictor of first time intubation success (succinylcholine: OR = 0.58, 95% CI: 0.29-1.13, P = 0.11 & rocuronium: OR: 1.1, 95% CI: 0.51-2.4, P = 0.81). In the univariate regression, while not statistically significant, male gender was associated with a lower likelihood of successful first-attempt intubation (P = 0.07), as was presence of predictors of a difficult airway (OR = 0.55, 95% CI: 0.31-0.99, P = 0.05). Patients were about half as likely to be intubated on the first attempt with direct laryngoscopy when compared to an attempt with a Glidescope (95% CI: 0.34-0.96, P = 0.03). However in the multivariate logistic regression, the only significant predictor of first-attempt success was the laryngeal grade view, with the odds of success being 55.18 time more likely with a grade 1 or 2 view compared to grade 3 or 4 (95% CI: 19 - 161, P < 0.001).

 

Conclusion In this study of emergency room rapid sequence intubations, first-attempt success rates were similar when succinylcholine or rocuronium was administered in the doses used in this study.

 

Comment

Emergency room intubations can be very challenging because of a myriad of factors. Typically little is known about the patient, positioning is usually not optimal, and patients are considered full stomachs. Therefore, it is critical that intubating conditions be optimized. In this study the authors used optimal RSI doses of succinylcholine (approximately 1.5 mg/kg) and rocuronium (approximately 1.2 mg/kg) and found similar first-attempt intubation success rates. These results, I believe, are similar to what many anesthesia providers experience when using similar doses of both drugs, and thus I think the findings are clinically relevant.

One issue I sometimes see with rocuronium is that anesthesia providers, especially trainees, tend to use too low a dose. For similar intubating conditions in an RSI the 1.2 mg/kg dose is needed. However, the trade off is a longer duration of action, and with a potential difficult intubation this may not be ideal. Similarly with succinylcholine the larger dose is required if you want fast, optimal intubating conditions. I think the take home message for this is to remember to dose your muscle relaxants at the appropriate dose given the clinical situation. How many times have you seen someone give the standard dose of 50 mg rocuronium or 100 mg of succinylcholine without even thinking about whether it is the correct mg/kg dose? I know I have. Do we do this because of the vial size (i.e., 5 mL vial of rocuronium)?

The second finding in this study I found interesting was that the Glidescope appeared to be the “go-to” device at this facility for difficult airway management. While the investigators did not provide specifics on when the decision was made to use the Glidescope, their results suggest it may be useful in the emergency department. In the univariate regression analysis its use was associated with higher success; however in the multivariate analysis only laryngeal grade view was a significant predictor of failed first attempt. This is probably because the study was underpowered, and I suspect with a larger sample size it may have been found to be a significant predictor of success. Several studies1, 2 have found the first-time success rate for experienced and novice providers are significantly higher with the Glidescope when compared to direct laryngoscopy.

Dennis Spence, PhD, CRNA


1. Nouruzi-Sedeh P, Schumann M, Groeben H. Laryngoscopy via Macintosh blade versus GlideScope: success rate and time for endotracheal intubation in untrained medical personnel. Anesthesiology 2009;110:32-37. 

2. Aziz MF, Healy D, Kheterpal S, Fu RF, Dillman D, Brambrink AM. Routine clinical practice effectiveness of the Glidescope in difficult airway management: an analysis of 2,004 Glidescope intubations, complications, and failures from two institutions. Anesthesiology 2011;114:34-41.


The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences,  or the United States Government.


© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 12, December 30, 2010





An algorithm for difficult airway management, modified for modern optical devices (airtraq laryngoscope; ctrach™): a 2-year prospective validation in patients for elective abdominal, gynecological, and thyriod surgery

Anesthesiology 2011;114:25-33

Amathieu R, Combes X, Abdi W, El Housseini L, Rezzoug A, Dinca A, Slavov V, Bloc S, Dhonneur G


Abstract

Purpose To evaluate a new difficult airway algorithm which incorporates the Airtraq laryngoscope and the LMA CTrach™ for difficult intubations.

 

Background The ASA difficult airway algorithm has been designed to help providers when faced with a difficult airway. However it does not include devices such as the Airtraq laryngoscope (AR-L; VYGON, Ecouen, France) and the LMA CTrach™ (LMA-CT; SEBAC, Pantin, France). These devices provide a better view of the glottis and have been found to be successful rescue devices after failed direct laryngoscopy. This study evaluated a new difficult airway algorithm which incorporated these devices when faced with a difficult airway.

 

Methodology This was a prospective validation study to evaluate a new difficult airway algorithm implemented at a tertiary care facility in France. At this facility there are 15 senior anesthesiologists who manage two operating rooms at a time. Each operating room was staffed by a nurse anesthetist. The nurse anesthetists managed all initial intubation attempts in patients requiring general anesthesia for elective surgery with a Macintosh laryngoscope (MAC-L) with a bougie introducer if needed.  If difficulty was encountered the staff anesthesiologist was called to manage the airway. Prior to implementation of the study the anesthesia providers received training with the AR-L and LMA-CT and had to demonstrate their use successfully in 10 simulated difficult airways.

Patients presenting for elective abdominal, gynecologic, and thyroid surgery were included. Patients were excluded if they were pregnant, had active reflux symptoms, limited mouth opening of less than 25 mm, severe fixed flexion deformity of the cervical spine, or history of difficult intubation.  A decision tree for muscle relaxant choice and airway management approach is presented in Figure 1. Based on the algorithm if a patient had less than 3 risk factors for difficult intubation, the anesthesia provider could use either a nondepolarizing agent (NDNMB) or succinylcholine depending on how easy it was to ventilate the patient. If the patient had ≥ 3 risk factors for a difficult airway then succinylcholine was used as the primary muscle relaxant. Facemask ventilation difficulty was graded with the following scoring system:

  • Grade I: ventilation without the need for an oral airway
  • Grade II: oral airway needed to mask ventilate
  • Grade III: difficult or variable mask ventilation requiring oral airway and two person mask ventilation with peak pressures > 25 mmHg
  • Grade IV: impossible mask ventilation with no evidence of chest rise or end-tidal CO2

If mask ventilation was difficult (grade III or IV) then succinylcholine 1 mg/kg was administered. This was done to minimize the duration of apnea. If mask ventilation was easy (grade I or II) then the NDNMB was given 3 minutes after the induction agent. All anesthesia providers were required to follow the difficult airway algorithm listed in Figure 1. After confirmation of mask ventilation ease or difficulty a MAC-L (size 3) or AR-L was used for the initial attempt with or without a bougie introducer. Impossible intubation was defined as >2 attempts with either a MAC-L or AR-L with a bougie introducer and change in head position and use of laryngeal manipulation. Mask ventilation was recommended if SaO2 <90% and between intubation attempts. If impossible mask ventilation occurred despite changes in position or mask size then the LMA-CT was immediately placed. If ventilation was unsuccessful with the LMA-CT then transtracheal jet ventilation was attempted. A difficult airway was defined as a grade III or IV ventilation difficulty, or failed direct laryngoscopy with a MAC-L and bougie introducer.

The primary outcome was success rates for tracheal intubation based on this difficult airway algorithm. Secondary outcomes included incidence of complications such as hypoxemia (SaO2 <90%), aspiration or evidence of airway trauma.  Descriptive statistics were used to analyze the results. 

 

 

Figure 1. Algorithm for muscle relaxant choice and airway management

 

Result During the two-year study period 12,225 patients had elective surgery. Four patients were excluded because they were known difficult airways. This left 12,221 patients for the analysis. Demographic data is presented in Table 1. Of these patients n = 98.5% (12,033) had < 3 risk factors and n = 1.5% (188) had > 3 risk factors for a difficult airway. 

 

Table 1. Demographics

Variable

n (%) or mean ± SD

Number of participants

12,221

Obesity (BMI>30 kg/m2)

789 (6.5%)

Morbidly obese (BMI>50 kg/m2)

104 (0.85%)

>3 difficult airway risk factors

188 (1.5%)

Patients with airway management difficulties

125 (1.0%)

Men

Age, yr

BMI kg/m2

Interincisor distance, mm

Thyromental distance, mm

Retrognathia

Severely limited jaw protrusion

OSA

Mallampati class

  I

  II

  III

  IV

Neck circumference, cm

66 (52.8%)

50 ± 13

43 ± 14

33 ± 4

64 ± 5

16 (12.8%)

10 (8%)

82 (66%)

 

5 (4%)

32 (25.6%)

75 (60%)

12 (9.6%)

44± 5

 

 

Most patients (99%) with < 3 risk factors for a difficult airway were easy to mask ventilate. A slightly lower, but similarly high rate of easy mask ventilation was seen in patients ≥ 3 risk factors (93%). Overall intubation success rate was extremely high with most patients intubated on the first attempt with a MAC-L or MAC-L + bougie (99.75%). Only two patients were impossible to mask ventilate; 1 during induction and the other after an AR-L intubation attempt. Both patients were successfully ventilated and intubated with a LMA-CT. One of these two patients intubated with the LMA-CT after a failed AR-L attempt was morbidly obese with a BMI of 40 kg/m2.

 


 

Hypoxemia (SaO2 < 90%) occurred in 0.7% (n = 87) of patients, and only 17 patients (0.1%) had SaO2 drop briefly <80%. One patient with five difficult airway risk factors and a long bushy beard was impossible to mask ventilate.  Only 16 of 789 (2%) obese patients experienced transient hypoxemia with SaO2 <80%. Mask ventilation improved after administration of succinylcholine in 56 of 90 patients who had difficult mask ventilation after induction of anesthesia. None of the patients who were easy to ventilate were difficult to ventilate after receiving a NDNMB. Dental trauma occurred in two patients and none aspirated.

 

Conclusion Tracheal intubation was highly successful in this facility which utilized a new airway management algorithm. More aggressive use of neuromuscular blockers in combination with a bougie introducer, Airtraq and LMA CTrach™ were believed to contribute to this high success rate.

 

Comment

This is another study demonstrating how the approach to airway management is rapidly changing, especially in potential difficult intubations. This institution’s practice of aggressive administration of succinylcholine to anticipated difficult airways and in those with difficult mask ventilation is probably controversial; however I think it does reflect a changing practice of many providers. Past teaching was that one would confirm ease of mask ventilation before administration of the muscle relaxant. This study provides some evidence to suggest that after administration of succinylcholine mask ventilation may improve. Clinically I think this is what many of us experience; however the problem is that you are never 100% sure that it will improve ventilation. I think the important take home message is that you ensure you have rescue devices available such as an LMA if difficult or impossible mask ventilation occurs. Additionally, always remember to call for help early.

It is important to point out that this was not a randomized controlled trial. The investigators were simply evaluating the validity of this new difficult airway algorithm. Therefore, one cannot assume causation. Future investigators may want to compare this algorithm with the current difficult airway algorithm in a clinical trial.

I must admit I have never used the Airtraq or LMA CTrach™ clinically. I think these and other devices such as the Glidescope are all similar and the key to success is experience. Another important point is that anesthesia providers need to maintain their proficiency with the bougie introducer. In this cohort the bougie introducer facilitated successful intubation on most 2nd intubation attempts. Bougie introducers are cheap and easy to use and I think anytime an anesthesia provider attempts an intubation one should be within arms reach.

Dennis Spence, PhD, CRNA


The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences,  or the United States Government.


© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 12, December 30, 2010





The lma ctrach in morbidly obese and lean patients undergoing gynecological procedures: a comparative study

J Anesth 2010;24:849-53

Yildiz TS, Ozdamar D, Arslan I, Solak M, Toker K


Abstract

Purpose The purpose of this study was to compare ventilation and intubation success rates with the LMA CTrachtm in morbidly obese and lean women undergoing gynecologic surgery.

 

Background Morbidly obese patients may be more difficult to ventilate and intubate. Because of the decreased functional residual capacity, morbidly obese patients are more prone to hypoxemia during periods of apnea. Any device that could allow for maintenance of ventilation during intubation attempts would be beneficial to anesthesia providers. The LMA CTrachtm is a modified Fastrack LMAtm (intubating LMA) that has a detachable LCD screen that allows real-time visualization of the glottis while allowing near continuous ventilation. Recent research suggests this device has improved intubation success in anticipated and unanticipated difficult airways.

 

Methodology This was a prospective, comparative study of 60 adult females presenting for gynecologic surgery. Thirty morbidly obese patients (BMI >40 kg/m2) were compared with 30 lean patients (BMI <30 kg/m2). Exclusion criteria included symptomatic or untreated gastroesphogeal reflux, pregnancy, patients who were not NPO, severe cardiac or respiratory disease, or mouth opening < 3 cm. Baseline demographics and airway examination results were recorded.

In the operating room a standardized induction sequence was used for all patients with propofol, fentanyl and sevoflurane. After confirmation of mask ventilation, rocuronium 0.8 mg/kg was administered. Laryngoscopy was then performed using a Macintosh blade by a second or third investigator. The laryngeal view was graded according to the Cormack and Lehane scale. The principal investigator was blinded to this result. The principal investigator then placed the LMA CTrach according to manufacturers guidelines. The principal investigator had 50 successful intubations with the CTrach prior to starting the study. The size was chosen based on manufacturer’s recommendations. If epiglottis down folding was noted an “up-down” maneuver was employed to obtain an optimal view of the glottis. Additional attempts were made to optimize ventilation. The quality of the initial glottic view was graded with an endoscopic video grading system (EVGS). The EVGS grading system was similar to the Cormack and Lehane scale:

  • grade I entire glottis visible
  • grade II partial glottic aperture visible
  • grade III free edge or ventral face of epiglottis visible
  • grade IV no recognizable structures or whiteout screen

If impossible mask ventilation occurred or if after three insertion attempts a grade IV view was seen then the patient was intubated with direct laryngoscopy.

Data recorded included time to satisfactory ventilation through the CTrach and duration of tracheal intubation with the CTrach. Performance measures included success rate of ventilation and intubation, quality of initial glottic view via CTrach, and number of successful intubation attempts. Additionally, the incidence of sore throat, dysphagia, and blood on the CTrach was recorded. Descriptive and inferential statistics were used to analyze the results. A P value < 0.05 was considered significant.

 

Result Baseline demographics were similar between the two groups, with the exception of height (obese patients: 159 ± 7 cm vs. 165 ± 7 cm, P = 0.002), weight (obese patients: 115 ± 11 kg vs. lean patients 72 ± 13 kg, P <0.0001) and BMI (obese patients: 42 ± 11 kg/m2  vs. lean patients: 25 ± 4 kg/m2, P = 0.0001). Mallampati classification was similar in both groups. Mouth opening was 1 cm less in lean group (4 cm vs. 5 cm, P<0.0001), whereas sternomental distance was 1 cm less in obese patients (13 cm vs. 14 cm, P = 0.002). Mean arterial oxygen saturation was ≥98% in both groups. Anesthesia was uncomplicated in all patients.

There were no significant differences in the Cormack and Lehane or EVGS grade views between the groups. In the obese group n = 27 patients had a Grade I or II view with direct laryngoscopy compared to n = 28 in the lean group (P = 0.88). All but one patient had the CTrach successfully placed with adequate ventilation. That patient was in the lean group. The median time to successful ventilation was between 20 and 22 seconds in both groups (P = 0.33). One patient in the lean group could not be ventilated with the CTrach so she was intubated via direct laryngoscopy.

The glottis could easily be seen in 85% of patients (grade I or II). Four patients in the obese group had an EVGS grade IV view, while in the lean group n = 1 had a grade III view and n = 2 had a grade IV view. Intubation success rates, either blind or under direct vision, were similar; 96% successful in the obese group (n = 29) compared to 90% successful in the lean group (n = 27) (P = 0.22). Four patients in the obese group and n = 5 in the lean group required a second intubation attempt. Total intubation time was twice as long in obese patients, 69 s (25-75 percentile = 45-126 s) when compared to 33 s in lean patients (25-75 percentile = 20-60 s) (P = 0.001).

Significantly more patients in the obese group had blood on the LMA (11 vs. 2, P = 0.005). While not statistically significant, n =2 patients complained of sore throat, and n =5 complained of dysphagia in the obese group compared to no patients in the lean group.

 

Conclusion This study demonstrated that a majority of obese and lean patients could be ventilated and intubated with the LMA CTrach. Time to intubation was significantly longer in the obese group. Based on the results the investigators did not recommend using the LMA CTrach as a routine airway device during elective general anesthesia in morbidly obese patients.

 

Comment

The LMA was developed by Archie Brain in 1982 and was approved by the Food and Drug Administration in 1991 around the same time propofol was coming to market. Probably next to the pulse oximeter, the LMA is one the most important inventions that has directly improved the safety of anesthesia. Multiple versions of the device have come to the market over the years, with each new device improving on the previous one. The LMA CTrach improves on the intubating LMA (Fastrack LMA) design by adding a small, detachable video monitor to allow for direct visualization of the glottis during intubation.

I found this study interesting because the investigators used a homogeneous population, women undergoing gynecologic surgery, to compare success rates for the LMA CTrach between morbidly obese and lean women. While their sample size was small, they did demonstrate that a majority of morbidly obese women could be easily ventilated with the LMA and had what would be considered an easy airway (grade I or II view) with direct laryngoscopy. As expected the LMA CTrach had more grade I views when compared to the results for direct laryngoscopy (86% vs. 73%). However, because the sample was homogeneous I would be cautious to generalize these results.

Intubation time was significantly longer in the obese group, probably because they required more manipulations and reinsertions to obtain an optimal view of the glottis. This is probably why the investigators in their conclusion did not recommend routine use of this device in morbidly obese patients. In four obese group patients no recognizable structures could be identified. This is not surprising given the increased amount of soft tissue seen with obesity. The increased number of attempts to obtain an optimal view with the LMA CTrach probably contributed to the higher number of patients with a sore throat and dysphagia in the obese group. I suspect if the sample size was larger this difference may have been statistically significant.

There were some limitations to this study. First, no power analysis was conducted and the investigators developed their own scoring system for rating the grade view with the LMA. While I agree with their EVGS grading scale, it does not have established reliability. Also the investigators should have controlled for LMA cuff pressure, since pressures greater than 60 cm H2O are associated with higher incidences of sore throat and dysphagia. The high success rate may not be able to be replicated by other providers unless they have similar experience with the LMA CTrach. In this study all LMAs were placed by the principal investigator with experience placing more than 50 LMA CTrach intubations. I recommend if anesthesia providers have this device, they practice using it because it may be beneficial in the “cannot intubate, cannot ventilate” scenario.

Dennis Spence, PhD, CRNA


The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences,  or the United States Government.


© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 12, December 30, 2010





Safety and efficacy of laryngeal mask airway supreme versus laryngeal mask airway proseal: a randomized controlled trial

Eur J Anaesthesiol 2010;27:602-7

Seet E, Rajeev S, Yousaf F, Wong J, Wong DT, Chung F


Abstract

Purpose To compare the safety and efficacy of the LMA Supreme with the LMA ProSeal in ambulatory surgical patients.

 

Background Laryngeal mask airways have become popular devices for ambulatory surgical procedures. Newer LMA devices are beginning to replace the routine use of endotracheal intubation for a variety of procedures because they have modifications which improve the seal and allow for separation of the respiratory and gastrointestinal tract. Devices such as the reusable LMA ProSeal are popular because they can be used in patients at risk for aspiration. A new disposable device, the LMA Supreme, has similar characteristics as the ProSeal, however there are conflicting results on the oropharyngeal leak pressures for both devices. Knowing the oropharyngeal leak pressure is important because it reflects the degree of airway protection and amount of positive pressure ventilation that can be delivered.

 

Methodology This prospective, randomized, controlled trial included 105 patients scheduled to receive general anesthesia with LMA for ambulatory surgical procedures. Exclusion criteria included recent upper respiratory tract infection or contraindications to LMA placement such as BMI > 40 kg/m2, symptomatic hiatal hernia or severe gastroesophogeal reflux disease. Subjects were randomized to have an LMA ProSeal or Supreme placed after a standardized induction. LMA size selections was based upon manufacturers’ recommendations. Additionally, the anesthesia provider based the LMA Supreme size determination on oral airway size selection, with a size 3 LMA Supreme for an 80 mm oral airway, a size 4 for a 90 mm airway, and a size 5 for a 100 mm oral airway. After confirmation of ventilation, the LMA cuff pressure was adjusted to 60 cm H2O with a manometer. Oropharyngeal leak pressure was determined by closing the expiratory valve and setting the flow rate at 3 lpm and the pressure at which an audible leak was heard over the mouth was recorded. Maximum leak pressure was 40 cm H2O.

General anesthesia was maintained with desflurane and an air-oxygen mixture. All patients were allowed to breathe spontaneously. Fentanyl was titrated to maintain heart rate and blood pressure within 10-20% and a respiratory rate less than 18 per minute. After 1 hour the cuff pressure was rechecked and adjusted to ensure the proper pressure. At the end of the surgery the LMA was removed and the patient taken to the recovery room. A blinded data collector evaluated for the presence or absence of sore throat, dysphagia, and dysphonia at 1, 2 and 24 h.

The primary outcome was oropharyngeal leak pressure with both devices. The secondary outcomes included ease of insertion (0-100 mm scale), number of insertion attempts, time taken for insertion, and any pharyngolaryngeal adverse events. Additionally, first attempt success rate was calculated and occurrences of nerve injuries or aspiration were recorded.  Patient satisfaction was evaluated at 2 hours with a 0-100 mm visual analogue scale. Descriptive and inferential statistics were used to analyze the results. Logistic regression was used to determine the factors associated with oropharyngeal leak pressures. A P value <0.05 was considered significant.

 

Result A total of 99 out of 105 subjects were included in the analysis; n = 50 in the Supreme and n = 49 in the ProSeal groups. No significant differences were noted in demographic variables, duration of anesthesia, LMA size, type or duration of surgery, intraoperative fentanyl, or PACU time.

The oropharyngeal leak pressure was significantly lower in the LMA Supreme group, with a mean pressure of 21 ± 5 cm H2O at leak (95% CI: 20-22) compared to 25 ± 6 cm H2O (95% CI: 23-27) in the ProSeal group (P < 0.001). The first attempt success rate was 10% higher in the Supreme group (Figure 1; P = 0.04). No differences were noted in ease of insertion, incidence of blood on the LMA, or laryngospasm (ProSeal: 10.2% vs. Supreme: 7.8%, P = 0.68). Provider satisfaction scores with the two LMAs were similar. Patient satisfaction scores were also similar. No significant differences were noted in pharyngolaryngeal adverse effects between the two groups at 1, 2 or 24 hours (P = NS). The incidence of sore throat between 1 and 24 hours ranged from 3.9% and 19.6% in the Supreme group and between 10.2% and 20.4% in the ProSeal group; dysphagia between 5.9% and 17.6% in the Supreme group and 8.2% and 22.4% in the ProSeal group; and dysphonia between 9.8% and 19.6% in the Supreme group and 10.2% and 16.3% in the ProSeal group. No significant predictors of oropharyngeal leak pressure were identified. No aspirations or nerve injuries occurred in either group.

 

 

Figure 1. First attempt success rate

Figure 1

 

 

Conclusion The LMA Supreme had a lower oropharyngeal cuff leak pressure when compared to the LMA ProSeal. However, the success of first attempt insertion was significantly higher in the LMA Supreme group, therefore it may be a better airway rescue device.

 

Comment

Laryngeal mask airways are popular devices for airway management for many ambulatory surgical procedures. Technological advancements and experience has increased to the point that many anesthesia providers feel comfortable placing LMAs in patients who were previously not considered candidates. The LMA ProSeal was the first device which had a channel for placing an orogastric tube. The LMA Supreme is easier to place and has the added feature of a being disposable and having a built in bite block. These improvements combined with newer anesthesia machines which have the ability to deliver pressure support and synchronized intermittent mechanical ventilation (SIMV) increases the patients and cases that the LMA can be used safely for. Knowing the leak pressure of the LMA Supreme allows the anesthesia provider to adjust the amount of pressure support or tidal volume delivered to maximize ventilation while reducing the risk of insufflating the abdomen.

In this study it appears that the incidence of pharyngolaryngeal complications was lower with the Supreme LMA when compared to the ProSeal. However, the differences were not statistically significant. It is important to point out that this study was not powered to detect differences in pharyngolaryngeal complications.

I liked how the investigators adjusted the cuff pressure after placement and periodically during the case to keep it less than 60 cm H2O. This group has previously demonstrated that keeping the LMA cuff pressure less than 60 cm H2O reduced the incidence of sore throat, dysphagia and dysphonia.1 Since learning about these findings I have been routinely checking the cuff pressure and keeping it less than 60 cm H2O. I would recommend other anesthesia providers consider doing this as well.

Dennis Spence, PhD, CRNA


1. Seet E, Yousaf F, Gupta S, Subramanyam R, Wong DT, Chung F. Use of manometry for laryngeal mask  airway reduces the incidence of pharyngolaryngeal adverse events. Anesthesiology 2010;112:652-7.


The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences,  or the United States Government.


© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 12, December 30, 2010





Routine clinical practice effectiveness of the glidescope in difficult airway management: an analysis of 2,004 glidescope intubations, complications, and failures from two institutions

Anesthesiology 2011;114:34-41

Aziz MF, Healy D, Kheterpal S, Fu RF, Dilman D, Brambrink AM


Abstract

Purpose To evaluate success, failure, and complication rates of the Glidescope video laryngoscope and to identify and predictors of failed intubation at two academic institutions.

 

Background The Glidescope (Glidescope; Verathon Inc., Bothell, WA) is an indirect video laryngoscope reported to be effective in the management of the difficult airway because it provides a better view of the glottis compared to direct laryngoscopy. Several studies have found higher success with the Glidescope when compared to direct laryngoscopy performed by novices. However there are limited studies describing its “real-world” effectiveness with routine use in potential difficult airways.

 

Methodology This was a retrospective observational study of adult patients undergoing general endotracheal anesthesia at Oregon Health and Science University, Portland, Oregon (OHSU) and University of Michigan Medical School, Ann Arbor, Michigan (UMHS).  Data retrieved from the electronic medical record included anthropomorphic details, history and physical assessment, airway examination results, induction agents, Cormack-Lehane view achieved, number of attempts, intubation device and adjuncts, and success, failure and complications with the Glidescope. Patients were identified as difficult intubations is they had a Mallampati III or IV airway; thyromental distance < 6 cm, mouth opening < 3 cm; neck pathology from surgical scar mass or radiation; obese neck; or reduced cervical motion. Principles of the ASA difficult airway algorithm were followed at each institution. Most intubations were performed by CRNAs or anesthesia residents.

 

The primary outcome was intubation success with the Glidescope. Secondary outcomes included identification of predictors of failed Glidescope intubation, and incidence and characteristics of complications. Logistic regression was used to model predictors of failed Glidescope intubation attempts. Descriptive and inferential statistics were used to analyze the results.

 

Result Between May 2007 and December 2009 71,570 patients underwent tracheal intubation. A total of 44 cases were excluded. The Glidescope was used in 2.8% of patients (n = 2,004). In these cases the Glidescope was use primarily because patients were obese (BMI > 30) or due to preoperative predictors of difficult intubation. At OHSU there were 7 Glidescopes and at UMHS there was 1. Providers at OHSU had more experience with the Glidescope, with 51 providers using the Glidescope an average of 22 times each compared to an average of only 10 times by 91 providers at UMHS. The mean age of intubated patients was 54.5 ± 15.4, with 56% being men with an average BMI of 31.99 ± 10.89. Approximately one-third had a Mallampati III or IV airway, 13% had less than 3 cm mouth opening, and 14.72% had a thyromental distance of less than 6 cm. Less than a third (29.14%) had an obese neck, 5.2% had a history or neck radiation/surgical scar or mass, and 31% had limited cervical range of motion. A comparison of success and failure data and airway examination data are presented in Table 1. 

 

 

 

Table 1. Patient demographics

 

Success

(n = 1944)

Failure

(n = 60)

P value

Age, years

53 ± 15

52 ± 15

0.21

Male sex

1108 (57%)

32 (53%)

0.83

BMI

32 ± 11

33 ± 13

0.68

Mallampati III or IV

646 (33%)

29 (48%)

0.025

Thyromental distance < 6 cm

276 (14%)

19 (32%)

0.002

Mouth opening < 3 cm

249 (13%)

12 (22%)

0.15

Abnormal neck anatomy

656 (34%)

32 (53%)

< 0.0001

 

 

Success rates were high with the Glidescope, with 97% (n = 1,944) patients being successfully intubated. When anesthesia providers used the Glidescope as the primary airway device, the first attempt success rate was 92% (n = 1,610 of 1,755). The success rate was 98% (n = 1,712 of 1,755) irrespective of the number of attempts (Figure 1). As a rescue device it was successful 94% of the time (n = 224 of 239) after failed direct laryngoscopy (Figure 2). Success rates were slightly lower in patients with at least one predictor of a difficult airway (96%, n = 1,428). In 98% of the successful intubations, a grade I or II view of the glottis was achieved. In 60 patients the Glidescope failed as a primary or rescue technique for a 3% failure rate. In 35% of the failures the Cormack-Lehane grade view was I or II, whereas 65% of failures (n = 39) had an inadequate Glidescope laryngeal view. Of these failed Glidescope intubations, there were 29 patients with grade III or IV views, there were 2 electrical failures, 1 excessive fogging of the lens, and in 3 failed intubations patients did not receive neuromuscular blockers. In 2 of 3 cases in which neuromuscular blockers where not used, awake intubations with sedation and topicalization were attempted unsuccessfully.

 

Figure 1. Glidescope success with first and subsequent attempts

Figure 1

Note. Overall rates presented as % above each bar. 

 

 

 

Figure 2. Glidescope success as rescue device after failed direct laryngoscopy

Figure 2

Note. Overall rates presented as % above each bar. Number of intubations at each institution presented on bar.

 

 

Predictors of failed intubation with a Glidescope are presented in Table 2. The four strongest predictors were neck pathology, with scar, radiation or mass; thyromental distance < 6 cm; and limited cervical range of motion. Additionally there was a higher failure rate at UMHS compared to OHSU. Age, gender, BMI, Mallampati score, and mouth opening were not significant predictors of failed Glidescope intubation. Complications occurred in 1% (n = 21) of intubations with the Glidescope. Most were minor lip or gum lacerations (n =13), however in n = 6 patients more serious complications occurred; one vocal cord trauma, one tracheal injury, one trauma to the hypopharynx, one tonsillar perforation, and two dental injuries.

 

 

Table 2. Predictors of Failed Glidescope Intubation

Variable

Odds Ratio

Neck pathology, with scar, radiation or mass

4.39; 95% CI: 2.04-9.46

Thyomental distance < 6 cm

2.53; 95% CI: 1.38-4.64

Limited cervical range of motion

1.76; 95% CI: 1.01-3.06

Institution: UMHS

2.28; 95% CI: 1.3-4.01

Note. Receiver operating characteristics area under the curve result was 0.73, indicating acceptable discriminate ability to predict failed Glidescope intubation.

 

 

Conclusion Intubation success rates were very high when the Glidescope is used as a primary or rescue device. However patients with neck pathology, reduced thyromental distance, limited range of motion, and providers with less experience may have higher failure rates with the Glidescope. As a result, providers should maintain competency with other airway devices, especially in patients with neck pathology.

 

Comment

This was one of two studies published in the same issue of Anesthesiology by the group at UMHS. This time they teamed up with investigators at OHSU to report intubation success rates with the Glidescope. This is the largest study published to date on Glidescope intubation success in patients with difficult airways. Despite its weakness of being a retrospective study I think the results are representative of what is seen in clinical practice. The Glidescope has a high success rate when used as the primary intubation technique or rescue airway device after failed direct laryngoscopy. I venture to say with future updates of the difficult airway algorithm that the Glidescope and other similar devices may be included on the algorithm. 

Another important point from this study is that the success rate for the Glidescope was significantly lower at the UMHS when compared to OHSU. This is probably because of less experience and access to the device at UMHS. There is a learning curve with the Glidescope, though it is not as steep as with direct laryngoscopy. I suspect at OHSU there is a greater acceptance for using the Glidescope for management of the potential difficult airway when compared to UMHS. 

One of the trends I have noticed in recent years is that anesthesia providers are approaching the potential difficult airway differently than how we did in the past. In the past a potential or known difficult intubation may require an awake fiberoptic intubation. I think there is a trend to elect to perform an asleep intubation on a potential difficult airway with the Glidescope as opposed to doing an awake fiberoptic intubation. While the results of this study suggest a high success rate, I am concerned that the ability and decision to do an awake fiberoptic intubation will become a lost skill (and art) as new providers enter practice in the era of indirect video laryngoscopy. Staff anesthesia providers who teach nurse anesthesia students and residents should ensure their trainees know when and how to perform an awake fiberoptic intubation. Not only the technical skill of driving the scope, but how to topicalize the airway and provide appropriate sedation to facilitate a smooth intubation. Additionally staff should maintain their proficiency and ensure their trainees know how to use other rescue devices and airway adjuncts such as the bougie introducer. This latter point is especially important because not all facilities can afford to buy one, let alone multiple, Glidescopes.

Dennis Spence, PhD, CRNA


The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences,  or the United States Government.


© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 12, December 30, 2010





Propofol versus sevoflurane for fiberoptic intubation under spontaneous breathing anesthesia in patients difficult to intubate

Minerva Anestesiol 2010;76:780-6

Péan D, Floch H, Beliard C, Piot B, testa S, Bazin V, Lejus C, Asehnoune K


Abstract

Purpose The purpose of this study was to compare the effectiveness of propofol and sevoflurane when used for spontaneous breathing anesthesia in patients requiring elective fiberoptic intubation for a known difficult airway.

 

Background Patients with advanced head and neck cancer, facial gunshot wounds, and maxillo-facial malformations may require fiberoptic intubations (FOI) because they have risk factors suggestive of a potential difficult airway. The American Society of Anesthesiologists and French Society of Anesthesia and Intensive Care have recommended that a patient requiring a fiberoptic intubation for a known difficult airway maintain consciousness and be spontaneously breathing. These patients may require multiple operations and thus it is critical to minimize the stress response, pain, and recall with fiberoptic intubations. Anesthesia providers need to adequately prepare the airway and provide sufficient anesthesia to ensure patient cooperation while avoiding airway obstruction and subsequent hypoxemia. A recent research studies suggested propofol and sevoflurane can be used to facilitate spontaneous breathing anesthesia during fiberoptic intubations in patients with normal airways. However, these two agents have not been evaluated in patients with potential difficult airways.

 

Methodology This was a prospective, randomized study comparing outcomes for FOI with a target controlled infusion of propofol or inhalation anesthesia with sevoflurane in patients with anticipated difficult airways. Eighty consecutive patients >18 yrs and <80 yrs old with anticipated difficult airway secondary to facial trauma, head and neck cancer, or maxillo-facial malformation were randomly assigned to one of the two groups. Patients were excluded if they were ASA IV or V, had a bleeding disorder or were on anticoagulants, high risk for aspiration, anticipated difficult mask ventilation, or had no palpable cricothyroid membrane.

In the operating room no premedication was administered. Standard monitors were applied and a bispectral index (BIS) was used to monitor depth of anesthesia. The airway was topicalized with aerosolized 5% lidocaine for 15 minutes. All patients were preoxygenated for 4 minutes with 100% oxygen via an endoscopy mask. Intubations occurred in the semi-sitting position. Oxygen was continuously administered via the endoscopy mask throughout the FOI. Patients in the propofol group received a target-controlled infusion of propofol with a 6 μg/mL plasma concentration targeted in three minutes. Patients in the sevoflurane group received an inhalation induction with 8% sevoflurane and 10 LPM oxygen. When a Ramsey score of 5 was reached in both groups a nasal FOI was attempted via the endoscopy mask. During the procedure propofol and sevoflurane were titrated to maintain a Ramsey score >4. Spontaneous ventilation was maintained throughout the procedure and manual assisted ventilation was provided if required. After confirmation of end tidal CO2 and bilateral breath sounds anesthesia was maintained with sevoflurane and sufentanil. A difficult airway cart was in the room and a surgeon immediately available to perform a surgical airway if needed. Six anesthetists, all experts in difficult airway management, performed all intubations.

Baseline demographics and airway examination results were recorded. The primary outcome was procedure duration, and secondary outcomes included intubation success rate, induction duration, vocal cord adduction at time of FOI, and ETCO2 after intubation. Additionally a 0-100 visual analogue scale was used to evaluate technical difficulty, anesthesia difficulty, and patient satisfaction. Frequency of procedural recall, procedural complications, and hemodynamic responses were recorded. Descriptive and inferential statistics were used to analyze the results. A P < 0.05 was significant.

 

Result Eighty patients were enrolled, but two were excluded leaving n = 39 in each group. No significant differences in baseline demographics or airway examination results were found between the two groups. The average age was approximately 49 years in both groups, with >76% being men with a BMI around 21.5 kg/m2. Eighty-two percent of subjects had a Mallampati IV airway; median mouth opening was 2.3 (2-3.5) cm and average thyromental distance was approximately 6.8 ± 13 cm.

Intubations were equally distributed between the six anesthetists. Fiberoptic intubation was successful in 97% of patients in the propofol group compared to only 90% in the sevoflurane group (P = NS; Table 1). Five failed fiberoptic intubations occurred; n = 1 in the propofol group and n = 4 in the sevoflurane group (P = NS). Three patients experienced obstructive dyspnea with hypoxemia (propofol group n = 1 vs. sevoflurane group n = 2). One patient in each group required transtracheal jet ventilation, and one of these two required a temporary tracheostomy (group not reported). One patient in the sevoflurane group required retrograde wire intubation and n = 2 patients in the sevoflurane group were awakened and rescheduled for surgery at a later date.

Induction and procedure duration were significantly shorter in the sevoflurane group (P < 0.05; Figure 1). No significant differences were observed in procedure complications, with the exception of significantly more subjects in the sevoflurane group having a MAP or HR >20% of baseline (sevoflurane group: 74% vs. propofol group: 49%, P < 0.05). Median propofol effect site concentration was 4.5 (3.4-6.1) μg/mL and sevoflurane concentration was 3.8% (2.67-5.3) at the time of tracheal intubation. In both groups average BIS scores increased approximately 10 points from start of the procedure to the time of tracheal intubation (Table 1). Five patients reported recall during the FOI in the sevoflurane group compared to none in the propofol group.

 

 

Figure 1. Comparison of fiberoptic intubation times

Figure 1

Notes: Results are presented as median with interquartile range 25-75%. *P < 0.05 versus propofol.

 

 

There were no differences in procedure complications between groups (Table 1). The vocal cords were adducted (closed) in 15% of patients in the propofol group compared to 8% in the sevoflurane group (P = NS). Approximately 75% of patients in the propofol group experienced coughing during the FOI compared to 54% in the sevoflurane group (P = NS). Apneic episodes were twice as common in the propofol group (41% vs. 20%, P = NS). End tidal CO2 was approximately 41 mm Hg in both groups at the time of tracheal intubation.

 

 

 

 

Table 1. Fiberoptic Intubation characteristics and procedural complications

 

Propofol

N =39

Sevoflurane

N = 39

Successful FOI

97%

90%

BIS start of FOI

65 (47-75)

66 (53-85)

BIS at tracheal intubation

77 (52-86)

77 (62-96)

Technical difficulty (0-100 VAS)

2.5 (0.75-5)

2.4 (0.37-4)

Anesthesia Difficulty (0-100 VAS)

1.8 (0.5-3.8)

2.2 (0.5-4.7)

Patient Satisfaction

9 (8-10)

9 (8-10)

Movement

15%

8%

Apneic events

41%

20%

Hypoxemia with apneic event (SaO2 < 93%)

5%

8%

Bleeding during FOI

5%

21%

Salivation during FOI

26%

10%

Lung aspiration

0

3%

Notes: Data are % or median (25-75 percentile). One patient in sevoflurane group had lung aspiration. Apneic events occurred within two minutes of induction of anesthesia. P > 0.05 for all pairwise comparisons. 

 

 

Conclusion In patients who were difficult to intubate propofol and sevoflurane provided high success rates during fiberoptic intubation. These results may be relevant to other populations in whom difficult intubation is not anticipated and/or in those patients with severe mental disabilities.

 

Comment

In this study the authors found that fiberoptic intubation success with sevoflurane was high and comparable to propofol. They also found that induction time and time to intubation was significantly shorter with sevoflurane. I question the clinical relevance of a less than 2 minute difference in these two outcomes. While the success rate was greater than 90% for both techniques, there were 5 failed fiberoptic intubations (4 of 5 in the sevoflurane group). Also there were two serious outcomes in which the patients required transtracheal jet ventilation. In one case a tracheostomy was required. Additionally there was one lung aspiration in the sevoflurane group.

These results make me question the routine use of “spontaneous breathing anesthesia” for patients with known difficult airways. A safer option would be to perform an awake fiberoptic intubation with adequate airway topicalization and sedation with dexmedetomidine. Additionally it is important to administer an anticholinergic such as glycopyrrolate to aid in penetration of the aerosolized 5% lidocaine. In this study the investigators did not administer glycopyrrolate prior to airway preparation.

The authors in their discussion point out that the study was underpowered to detect statistically significant differences in success rate and procedural complications. Additionally, all of the anesthetists had extensive experience with difficult airway management using spontaneous breathing anesthesia. Thus, generalization of these results is limited. If I was faced with an uncooperative patient with a known difficult airway I might us this technique. However, I would ensure the airway was prepared appropriately and that I had an extra anesthesia provider and a surgeon who was able to perform a surgical airway in the operating room with me. If anesthesia providers want to add this technique to their armamentarium I recommend they first gain experience with young, healthy patients without suspected difficult airways.

It is important that anesthesia providers know when and how to do an awake fiberoptic intubation. As is seen in other abstracts in this edition, newer indirect video laryngoscopes (i.e., Glidescope) are excellent choices for a difficult airway. However, it is very difficult to get a video laryngoscope blade into a mouth with less than a 3 cm mouth opening (see Table 1). Therefore, a nasal fiberoptic intubation may be the only option.

 

Dennis Spence, PhD, CRNA


Ramsay Sedation Scale

  • 1   Patient is anxious and agitated or restless, or both
  • 2   Patient is co-operative, oriented, and tranquil
  • 3   Patient responds to commands only
  • 4   Patient exhibits brisk response to light glabellar tap or loud auditory stimulus
  • 5   Patient exhibits a sluggish response to light glabellar tap or loud auditory stimulus
  • 6   Patient exhibits no response

More information about the Ramsay Sedation Scale is available on Dr. Ramsay’s web page:

http://5jsnacc.umin.ac.jp/How%20to%20use%20the%20Ramsay%20Score%20to%20assess%20the%20level%20of%20ICU%20Sedation.htm

 


 

The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences,  or the United States Government.


© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 12, December 30, 2010





3,423 emergency tracheal intubations at a university hospital: airway outcomes and complications

Anesthesiology 2011;114:42-8

Martin LD, Mhyre JM, Shanks AM, Tremper KK, Kheterpal S


Abstract

Purpose To evaluate airway outcomes and predict complications from emergency tracheal intubation performed at a University hospital.

 

Background Emergent tracheal intubation outside of the operating room can be very challenging. Anesthesia providers must act quickly to secure the airway in hypoxic and unstable patients they know little about. Furthermore, these locations often lack optimal resuscitation equipment. Difficult intubations outside the operating room are reported to occur at a rate of 8-12%, whereas they occur at a rate of approximately 6% in the operating room. Complication rates were also reported to be higher outside the OR, with a 2-4% incidence of aspiration, 1.6-9% incidence of esophageal intubation, and 0.5-7% incidence of oropharyngeal trauma.

In large academic centers anesthesia residents frequently are first to respond to emergency intubations outside the operating room. Complication rates vary, with some studies reporting slightly higher rates with anesthesia residents. These differences may be attributable to variation in anesthesia resident experience. This study reviews the outcomes and complications from a large series of emergency intubations at the University of Michigan, where a majority of the intubations were performed or overseen by senior anesthesia residents without the presence of an anesthesia attending.

 

Methodology This was a retrospective observational study of all non-operating room emergent intubations performed by anesthesia residents and staff anesthesiologists at a tertiary care institution between December 5, 2001 and July 6, 2009. Patients were excluded for any of the following: age < 18 years, required endotracheal tube exchange, intubation in perioperative areas, or required urgent nonoperative awake fiberoptic intubations. Data retrieved from the electronic medical record included time of day, location, attending physician presence, number of attempts, laryngoscopic view, adjuvant equipment used, medications, and complications. Normal working hours were defined as Monday through Friday between 0700 and 2300 hours. Anesthesia responders were senior anesthesia residents with a minimum of 24 months of anesthesia training. They were typically accompanied by a first and/or second year resident. Staff anesthesiologists were physically present “in house” 24 h a day, and either participated in the intubation or were present at the intubation when requested by the senior anesthesia resident. 

The primary outcome was composite airway complications which included aspiration, esophageal intubation, dental injury, and pneumothorax. Aspiration was defined as immediate periinduction observation of gastric contents at the glottis or in the endotracheal tube. Esophageal intubation was defined as recognized or unrecognized esophageal intubation. Secondary outcomes were frequency of difficult intubation. A difficult intubation was defined as a Cormack and Lehane grade III or IV laryngoscopic view or three or more attempts by the anesthesia provider. Descriptive and inferential statistics were used to analyze the results. Logistic regression was used to determine predictors of the primary outcome; presence or absence of airway complications. Results were presented for when intubation was performed with or without the presence of an attending anesthesiologist. A P < 0.05 was considered significant.

 

Result Over 8 years, 3,923 emergent intubations were performed; 3,423 met inclusion criteria. The majority of the subjects were male (56.4%) with an average age of 58 years (Table 1). Of these intubations, 60.3% occurred in the ICU, followed by 38.6% on the general care ward, and 1.1% in the emergency room. Induction agents were used in 75% of the intubations, with etomidate used most often (57%) followed by propofol (18%). Muscle relaxation was used in a majority of the cases to facilitate intubation (72%); with succinylcholine used 59.6% of the time. The most common airway adjuvant used was the bougie introducer (15.6%). Difficult intubations occurred in 10.3% of cases. Attending staff anesthesiologists were present for only 39.9% of the difficult intubations (Figures 1 and 2). In 10 of 351 difficult intubations (2.8%) an LMA was used as a temporizing agent; with the LMA being successfully placed in 8 cases. In 52% of difficult intubations a bougie was used to facilitate intubation. A total of 9 surgical airways were required, with 33% of these patients developing anoxic brain injury (all 3 arrested before anesthesia arrival). Six of the surgical airways occurred after failed intubation; two of these patients had uncontrolled airway bleeding and one patient had unanticipated tracheal stenosis.

 

Table 1. Characteristics of All Intubations

 

Complication

(n = 144)

No Complication

(n = 3279)

P value

Age, years

57.8 ± 16.7

58.4 ± 16.3

0.78

Male sex

89 (62%)

1,841 (56%)

0.18

Location

   Floor

   ICU

   ER

 

77 (54%)

64 (44%)

3 (2.1%)

 

1,245 (38%)

2,000 (61%)

34 (1%)

 

<0.001

<0.001

0.20

Evening/Weekend hours

67 (47%)

1,521 (46%)

0.97

Attending present

48 (33%)

1,091 (33%)

0.99

Reason

   Cardiac arrest

   Respiratory arrest

   Airway protection

 

71 (49%)

67 (47%)

3 (2.1%)

 

1,455 (44%)

1,701 (52%)

70 (2.1%)

 

0.24

0.21

1.0

Muscle relaxant

   Any

   Succinylcholine

   Nondepolarizer

 

91 (63%)

73 (51%)

18 (13%)

 

2,375 (73%)

1,967 (60%)

408 (12%)

 

0.02

0.03

0.99

Grade View: III or IV

28 (20%)

282 (8.7%)

<0.001

≥ 3 attempts

23 (16%)

64 (2%)

<0.001

NOTES: Data are n (%) except for age which is years ± SD.

Percents are within group (complication or no complication) for each parameter.

 

 

 

Figure 1. Airway techniques used in difficult intubations with grade I & II views and ≥ 3 attempts

Figure 1

 

 

 

Figure 2. Airway techniques used in difficult intubations with grade III & IV views

Figure 2

 

Airway complications occurred in 4.2% of all intubations (n = 144), with aspiration occurring in 2.8% of cases. Seven-day and 30-day all-cause in-hospital mortality rates were 25% and 37%, respectively. Airway complication rates (Figure 3) were similar to those observed when anesthesia attending staff was present. Four predictors of airway complications were identified when intubations were managed by senior anesthesia residents without anesthesia attending presence. Complications were:

  • 6.7 times more likely when three or more attempts were required (95% CI: 3.2-14.2, P < 0.001)
  • 1.9 times more likely with a grade III or IV view (95% CI:1.1-3.5, P  = 0.03)
  • 1.9 times more likely when intubation was on a general care floor (95% CI: 1.2-3.0, P = 0.004)
  • 4.7 times more likely in the emergency department (95% CI: 1.1-20.4, P = 0.037)

When all intubations were analyzed, only two predictors were identified:

  • three or more attempts (adjusted odds ratio: 8.0, 95% CI: 4.5-14.3, P < 0.001)
  • location on the general care floor (adjusted odds ratio: 2.0, 95% CI: 1.4-2.8, P < 0.001)

 

Figure 3 Airway Complication Rates

Figure 3

 

Conclusion There was a high incidence of difficult intubations among emergent, nonoperative intubations. In this study, utilization of a senior resident accompanied by additional anesthesia responders was associated with lower airway complication rates than previously reported. Use of airway adjuvant devices such as the bougie introducer was found particularly helpful. Airway complications occurred more frequently with multiple intubation attempts (≥ 3), grade III or IV laryngoscopy view, and locations on the general care floor and emergency department. These environments or situations may require additional experienced anesthesia providers.

 

Comment

This is another study from the group at the University of Michigan who has published frequently on airway management (see Prediction and outcomes of impossible mask ventilation in Anesthesia Abstracts, May, 2009). In this study the authors described their institution’s complications and outcomes for emergent nonoperative intubations which were managed predominately by senior anesthesia residents. I found this study interesting because I think it reflects what occurs at many large academic centers; that senior anesthesia residents manage nonoperative intubations. The controversial part which may vary between institutions is how frequently staff anesthesiologists are present when trainees are performing the intubation. The controversial part which may vary between institutions is how frequently anesthesia attendings are present when trainees are performing the intubation. I personally think the ideal situation is too have an experienced staff CRNA or attending anesthesiologist present that can provide critical assistance or take over when necessary. There is a fine balance between allowing anesthesia trainees to gain autonomy and independence with intubations outside the operating room and patient safety. However, it may not always be possible to have staff available, especially after hours. Based on these results I think trying whenever possible to have a team of experienced anesthesia responders (senior anesthesia resident with one or two additional anesthesia trainees) and an attending staff anesthesia provider present when an intubation is required on a general ward or emergency room is most critical.

Some interesting and important points from this study are worth commenting on. First, I liked seeing a bougie introducer was used most frequently when faced with a difficult intubation. This is an important device that we must ensure our anesthesia trainees and junior staff are proficient in using, and these results further support this issue. Second, what I found interesting was that there was an increased risk of airway complications in the emergency room. At first glance this would seem counterintuitive; however, in my experience when anesthesia providers are finally contacted by emergency room personnel there usually have been multiple failed attempts at intubation. This increases the risk of airway trauma and bleeding, which makes it even more important to ensure multiple airway adjuvants and experienced anesthesia personnel are available to assist. Additionally. having an “airway box” with multiple laryngoscope blades, handles and airway adjuvants (i.e., portable Glidescope, Fast-track LMA, bougie introducer) that can be taken to nonoperative intubations is also very important.

Dennis Spence, PhD, CRNA


The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences,  or the United States Government.


© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 12, December 30, 2010





National survey to assess the content and availability of difficult-airway carts in critical-care units in the united states

J Anesth 2010;24:811-14

Porhomayon J, El-Solth AA, Nader ND


Abstract

Purpose Survey of academic intensive care units (ICU) to determine the availability of a Difficult Airway Cart.

 

Background The American Society of Anesthesiologists has published an algorithm and guideline for management of the difficult airway. This guideline recommends having equipment and personnel with expertise in management of the “cannot intubate, cannot ventilate” scenario available. While large academic ICUs have personnel with expertise in airway management, it is unknown to what extent a Difficult Airway Cart is readily available in these units.

 

Methodology This was a survey of 300 academic institutions with surgical and medical ICUs with >12 beds. Surveys were sent to medical or anesthesia directors at these institutions. It was assumed that responsibility for management of the difficult airway fell under the department of anesthesia at academic institutions. The survey asked about the training in the use of a Difficult Airway Cart and what type of equipment was available in the cart. Prior to mailing the survey it was piloted among the investigators ICU and Anesthesiology staff. All items on the survey were yes or no questions.

The questionnaire asked about the availability of the following categories of equipment and training:

 

1. Basic aids to difficult airway management

a. Curved and straight blades

b. Tracheal tube stylet

c. Gum elastic bougie

d. Oral and nasal airways

2. Alternative ventilation devices

a. LMA

b. Combitube

c. Pre-assembled cricothyriodotomy set

d. Jet ventilation

3. Non-invasive airway device

a. Fiberoptic bronchoscope

b. Lighted stylet

c. Video laryngoscope

4. Invasive airway device

a. Percutaneous cricothyiodotomy set

b. Percutaneous tracheostomy set

c. Retrograde intubation kit

5. Intubation confirming device

a. ETCO2 measurement device

b. Ready difficult airway cart

6. Difficult airway cart and difficult airway management related questions

a. Check cart daily

b. Consultant responsible for airway

c. Aware of location

d. Training in use of difficult airway cart

e. Difficult airway algorithm present

f. Airway related complication

g. Airway related death

h. Difficult airway evaluated by expert

i. Difficult extubation with continuous access

7. 9 additional questions asked about presence of other difficult airway management issues and training programs in the ICU.

 

Descriptive statistics were used to present the results.

 

Result Sixty-percent of surveys were returned (n = 180). Difficult airway carts were available in 70% of ICUs with a majority (69%) not having an anesthesia attending responsible for the Difficult Airway Cart. The carts were checked daily 80% of the time or after use. A majority of units (60%) reported they were not trained in the use of the equipment. Only 51% of units had a difficult airway algorithm and 80% had a list of available equipment on the cart. 

All ICUs had curved and straight blades and tracheal stylets in the Difficult Airway Cart. Ninety percent had oral and nasal airways but only 50% of ICUs had gum elastic bougies available on the Difficult Airway Cart (Figure 1). Only 50% of ICUs surveyed reported that patients with a potential difficult airway were evaluated by an airway expert. Only 16% of ICUs reported difficult airways were extubated with continuous access (tube changers). Approximately one-third (30%) reported an airway related complication and 15% of ICU directors reported an airway related death.

 

 

Figure 1. ICU difficult airway cart survey results

Figure 1

Note. Results are percentage availability of airway devices.

 

 

Conclusion A Difficult Airway Cart should be available in all ICUs. This survey demonstrates variability in equipment and training across units. Formal training in difficult airway management is recommended. Further discussion is needed on what equipment should be available on a Difficult Airway Cart.

 

Comment

Anesthesia providers are frequently called to intubate patients in the intensive care unit. Intubations outside the operating room can be challenging because of multiple factors. Typically patients are in acute distress and critically ill. Furthermore the environment may be unfamiliar and there may be a lack of personnel with experience in management of the difficult airway. Finally, presence of difficult airway equipment may be lacking. It was nice to see a published survey which describes what type of difficult airway equipment and training was available in a many academic institutions.

However, a majority of ICU directors reported their staff did not receive training on how to use the equipment. This is a little scary, but not surprising because difficult airway management is usually the responsibility of anesthesia personnel. I think the important point readers should take from this finding is that they ensure their ICU nurses and physicians receive regular training on the equipment in the Difficult Airway Cart. Even though they may not use it, at least they can help the person coming to do the intubation. This can sometimes mean the difference between life and death. In this survey, 15% of ICU directors reported an airway related death. I wonder if better training would have changed this result.

One promising result I saw in this survey is the presence of a video laryngoscope. The investigators do not describe what type of instrument, but I suspect in many centers this might be a Glidescope or some similar device. Glidescopes and similar devices have been found to improve the success of difficult airway management. However, a bougie introducer was only present in 50% of the surveyed ICUs. A bougie is a great airway adjunct, and may be extremely beneficial when needing to intubate a patient in the ICU who may not be in an optimal position.

I think the important take home message is that one should not rely on the ready availability of difficult airway equipment in an ICU. At many facilities where I have practiced there is a difficult airway box which includes equipment such as a Fast-track LMA, bougie introducer, multiple blades and handles, and many times a portable Glidescope. I recommend our readers verify what equipment they have available to take to an out of the OR intubation, and go check what equipment is in the Difficult Airway Cart in their ICU.

Dennis Spence, PhD, CRNA


The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences,  or the United States Government.


© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 12, December 30, 2010