ISSN NUMBER: 1938-7172
Issue 6.1 VOLUME 6 | NUMBER 1

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, FAAN
Lisa Osborne, PhD, CRNA
Dennis Spence, PhD, CRNA
Cassy Taylor, DNP, DMP, CRNA
Steven R Wooden, DNP, CRNA

Guest Editor:
Terri M. Cahoon, DNP, CRNA

Assistant Editor
Jessica Floyd, BS

A Publication of Lifelong Learning, LLC © Copyright 2012

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

AIRWAY
Shoulder and head elevation improves laryngoscopic view for tracheal intubation in nonobese as well as obese individuals
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GENERAL
Clinical presentation, treatment, and complications of malignant hyperthermia in north america from 1987 to 2006
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OBSTETRIC ANESTHESIA
Combined spinal epidural vs epidural labour analgesia: does initial intrathecal analgesia reduce the subsequent minimum local analgesic concentration of epidural bupivacaine?
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PATIENT SAFETY
Risk factors associated with ischemic optic neuropathy after spinal fusion surgery
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PEDIATRIC ANESTHESIA
Predictive factors for difficult intravenous cannulation in pediatric patients at a tertiary pediatric hospital
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REGIONAL ANESTHESIA
Perioperative nerve injury after total hip arthroplasty: regional anesthesia risk during a 20-year cohort study
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Airway
Shoulder and head elevation improves laryngoscopic view for tracheal intubation in nonobese as well as obese individuals

J Clin Anesth 2012;24:104-108

Lebowitz PW, Shay H, Straker T, Rubin D & Bodner S


Abstract

Purpose This study evaluated whether the sniff versus ramp position provided the best laryngoscopic view during intubation in a group of lean and obese patients.

 

Background Alignment of the oral, pharyngeal, and laryngeal axes is often difficult while attempting to place obese patients in the sniff position when completely supine. This clinical observation resulted in the development of the ramp position in which the head and shoulders are elevated so that the external meatus of the ear is horizontal to the sternum. It is unclear however what position provides the best intubating conditions across a full range of body mass indexes (BMI).

 

Methodology This was a prospective study of adult patients presenting for anesthetics that required standard oral endotracheal intubation (N=189). The study was a repeated measure, within subjects design. Data were collected on BMI, dentition, Mallampati classification, thyro-mental distance, neck circumference and atlanto-occipital extension. Prior to induction, each subject was placed on a Troop Elevation Pillow (a commercial device to elevate the shoulders and head) in addition to a 7 cm high foam head cushion. The patient was induced and paralyzed with muscle relaxant using doses at the discretion of the anesthetist. A Macintosh 3 or 4 blade was used for laryngoscopy. The laryngoscopic view was graded according to the Cormack and Lehane scale first with both Troop pillow and foam head cushion and second after the Troop pillow was removed and the foam head cushion remained. These positions were named “ramp” and “sniff” respectively. This order of positioning was not randomized; each subject served as his own control, always with the ramp view first followed by the sniff view.

 

The same anesthetist graded the laryngoscopic view in both positions. The vocal cords were sprayed with an undefined volume of 4% lidocaine while in the ramp position; this was the only intervention between laryngoscopic views. Data were collected on the subjective difficulty in lifting force and the need for external laryngeal manipulation during laryngoscopy.

 

Result There were no correlations found between the laryngoscopic grade and Mallampati classification, thyromental distance, neck circumference, neck extension, or dentition. The ramp laryngoscopic view was rated as equal to or better than the sniff position in 89% of patients (p < 0.0001). A lean, overweight, obese or morbidly obese BMI did not influence these results. The background of the laryngoscopist (CRNA; 1st, 2nd or 3rd year resident; attending MD) also did not influence the results. No data were reported on lifting force or laryngeal manipulation.

 

Conclusion Elevating the head and shoulders in an attempt to align the external ear with the sternum is more likely to improve the laryngoscopic view than hinder it. An improved view in the ramp position is more likely as the patient’s BMI increases. The authors observed that short anesthetists were more likely to report a high-grade laryngoscopic view in the sniff position.

 

Comment

The key points were 1) that there was no correlation between laryngoscopic view and any of the routine preoperative airway assessments that we are taught to perform and 2) the ramp position is vastly superior for laryngoscopic view (and potentially ease of intubation) compared to the sniff position. The first conclusion is a slap in the face of anesthesia dogma along with previous research and clinical experience. I would have liked to have seen the actual data on this, but it was not provided. The second conclusion is somewhat believable. Maybe the ramp position improves the laryngoscopic view because it contributes to creating a larger space in the upper airway. How might this occur? Increased lung volume is thought to exert caudal traction on the upper airway, preventing its collapse.(1) If placing the patient in the ramp position effectively increases lung volume, then through this mechanism, it may be increasing the upper airway size and improving intubation conditions.

 

I have some issues with methodology in this study. Although relatively precise devices were used for positioning, the authors do not speak to the fact that a Troop pillow plus 7 cm aligns a 5-foot, 265 pound person differently than a 6-foot, 265 pound person. The authors did not report that, in each case, the elevation properly aligned the external auditory meatus to the horizontal plane of the sternum. Across a broad span of BMIs, it is hard to believe that the same device height will create the same alignment. Likewise, a standard 7 cm foam pillow does not always place patients of varying size in an accurate sniff position.

 

The methods reported however probably do reflect the real clinical world. I once came upon a difficult airway scenario in which a 400 pound patient was experiencing difficult mask ventilation following difficult and unsuccessful intubation attempts. The bed was reversed and with this patient’s weight on the longer and unsupported side, it appeared that the patient was in a slight Trendelenburg position along with her head well below her chest wall and protuberant abdomen. Sadly, when I suggested that we attempt to put the patient in a ramp position, the response was, “she already is!” Clearly, the presence of 3 or 4 folded blankets under the shoulders does not mean the ramp position is automatically achieved. This positioning technique requires a careful visual assessment prior to induction and often a lot of adjustment, which is probably why not everyone takes the time to do it.

 

No data were provided on sample group demographics; we don’t know the range of patient age, weight, or even BMI; just the mean and standard deviation were reported. This is a cardinal breach of research reporting, although the reviewers and editors are responsible for publication without it. No data were reported for the effects of lifting force or laryngeal manipulation, although data were reportedly collected. Last, if you are going to conclude that “short people got no reason,” (Randy Newman) provide the data to support it! Again, the editors should have caught these omissions. Unfortunately, for a research study, this was a relatively data-free report.

Penelope S Benedik, PhD, CRNA, RRT


Van De Graaff WB. Thoracic influence on upper airway patency. J Appl Physiol 1988;65:2124-2131


© Copyright 2012 Anesthesia Abstracts · Volume 6 Number 1, January 30, 2012




General
Clinical presentation, treatment, and complications of malignant hyperthermia in north america from 1987 to 2006

Anesth Analg 2010;110:498-507

Larach M, Gronert G, Allen G, Brandom B, Lehman E


Abstract

Purpose The purpose of this study was to describe the epidemiologic characteristics of ‘real or suspected malignant hyperthermia (MH) episodes’ reported to the North American Registry database during a 19 year period: 1987-2006. This research included descriptions of presentation of malignant hyperthermia syndrome, treatment-both pharmacologic and non pharmacologic, and factors associated with significant complications.

 

Background Malignant hyperthermia is an inherited muscle disorder that is triggered by volatile anesthetic agents as well as the depolarizing muscle relaxant succinylcholine. The last systematic evaluation of malignant hyperthermia; including clinical characteristics, treatment, and other complications; was published in 1970 – before the use of dantrolene. The Adverse Metabolic/Musculoskeletal Reaction to Anesthesia report (AMRA) is the current document to be completed by providers if an individual they are caring for has an episode related to metabolic or musculoskeletal reaction to anesthesia. The AMRA form contains relevant medical and anesthetic history. It is submitted to the Registry for entry into the MH data bank.

 

Methodology AMRA reports received by the MH Registry from 1987 through 2006 were examined by the researchers. Data specific to clinical presentation, treatment, and complications were analyzed and described. Inclusion criteria included:

  • The episode occurred in the U.S. or Canada
  • At least one anesthetic drug was given
  • The episode was ranked by the MH Clinical Grading Scale as ‘very likely’ or ‘almost certain’ MH

The clinical grading scale estimated the probability of MH episode without the use of diagnostic testing. It is based on points assigned for clinical and laboratory findings.

 

Each reported episode was analyzed for the order of appearance of clinical signs (see notes). The following information was documented regarding treatment:

  • time intervals between induction and:
  • first clinical sign
  • maximum end-tidal Pco2
  • maximum temperature
  • first dantrolene dose
  • time interval between first clinical sign and first dantrolene dose
  • initial and total dantrolene dose administered
  • adjunctive treatment

 

Results A total of 286 cases met the inclusion criteria. There were 112 “very likely” cases of MH (39.2%) and 174 “almost certain” cases of MH (68%). The demographic data showed:

  • 75 % were males
  • 69.4% were Caucasian
  • 29% had a muscular body build
  • median age was 22 years
  • ages ranged from 116 days to 78 years
  • 45% of those with an episode were 19 years or younger

 

Significantly, 9 patients (3.3%) reported an unusual metabolic response during a previous anesthetic and 77 patients (51%) had ≥ 2 unremarkable general anesthetics prior to their MH episode.

 

Data for 284 MH events showed the following:

  • Both succinylcholine and a volatile agent were used in 153 cases (53.9%)
  • Volatile agent but no succinylcholine was used in128 cases (45.1%)
  • In 2 cases (0.7%) no volatile agent or succinylcholine was used
  • In 10 cases, a liquid crystal temperature strip was used and did NOT trend with core temperature probes

 

Presentation patterns:

  • First or only MH signed noted:

hypercarbia (38%)

    • sinus tachycardia (31%)
    • masseter spasm (20.8%)
  • Induction of anesthesia to first clinical sign averaged 30 minutes in those <19 years vs. 94 minutes in those >19 years
  • Temperature abnormalities were among the first three signs detected in only 63.5% of cases.
  • Median maximum temperature was 39.1°C
  • 79.6 % of cases had muscular rigidity

Pharmacologic Treatment with Dantrolene

  • Time between the 1st sign and the first dose of dantrolene averaged 30 minutes

Complications

  • 181 patients had data regarding complications
  • 63 patients (35%) experienced 1 or more complication other than recrudescence, cardiac arrest, or death
  • The likelihood of a complication increased 1.6x for every 30 minute increase in time between the first sign and the first dantrolene dose
  • The likelihood of a complication increased 2.85x for every 2°C increase in maximum temperature
  • Maximum temperature was identified as an independent predictor for an MH complication

 

Conclusion Recognizing the limitations of this study (incomplete data, underreporting, and possible biased reporting), the data suggested that MH susceptibility was expressed primarily in males. Additionally males experienced a longer period of anesthesia before the first sign of the syndrome, something that is clinically significant when identifying MH. The most frequent initial signs of MH were hypercarbia, sinus tachycardia, or masseter spasm. Temperature abnormalities were only a “relatively early sign.” Unremarkable previous anesthetics did not preclude any individual from having MH. Skin liquid crystal temperature indicators were inaccurate; they should not be used for detection of MH. Finally, the longer the delay in administering dantrolene, the greater the incidence of complications.

 

Comment

I found this information to be extremely valuable for understanding the evolution and current treatment guidelines of malignant hyperthermia. Indeed we now label MH as a syndrome because we know not every patient will exhibit the same clinical signs nor will they always appear in the same order. This fact, coupled with the fact that MH susceptible individuals have received triggering agents without exhibiting symptoms of MH, reminds us to never let down our guard. As troubling as that is, it forces us to remain as vigilant as possible and to be prepared no matter what. Additionally, I find the information regarding the correlation (or lack thereof) between skin temperature strips and core temperature probes very troubling. Many times I have opted for the skin strips due to cost efficiencies however now I will alter my practice. And last but not least, when treating a person who is exhibiting signs of the syndrome, the earlier the administration of dantrolene, the better for prevention or lessening of complications. Immediate treatment with dantrolene is essential!

Mary A Golinski, PhD, CRNA


© Copyright 2012 Anesthesia Abstracts · Volume 6 Number 1, January 30, 2012




Obstetric Anesthesia
Combined spinal epidural vs epidural labour analgesia: does initial intrathecal analgesia reduce the subsequent minimum local analgesic concentration of epidural bupivacaine?

Anaesthesia 2012 Mar 15. Epub ahead of print

Patel NP, Armstrong SL, Fernando R, Columb MO, Bray JK, Sodhi V, Lyons GR


Abstract

Purpose The purpose of this study was to determine if using an initial dose of intrathecal fentanyl during labor would affect follow-up dose requirements for epidural local anesthetic analgesia.

 

Background The combined spinal-epidural (CSE) technique is a well-established method to provide analgesia for labor and delivery. Advantages of CSE include rapid onset and better sacral analgesia. Some studies have also suggested that the intrathecal part of a CSE may improve the effectiveness of the epidural component. Previous studies have demonstrated that CSE contribute to better dermatomal spread and higher probability of epidural success, but no study could be found that addressed the question of CSE impact on epidural local anesthetic requirements during the late stages of labor. This study attempted to address that question.

 

Methodology This was a prospective, randomized, double-blinded study. All women were low risk singleton pregnancies in active labor, with cervical dilation between 2 and 6 cm. Women were excluded that had pre-eclampsia, were on oxytocin inductions which had an infusion rate change during the study assessment period, received opioid medications within the previous 4 hours, or entered the second stage of labor before the study ended. Women who qualified were assigned randomly to either the CSE group or an epidural-only group. Three anesthetists were involved in the study. The first anesthetist performed the randomization procedure, the second performed the regional blocks, and the third, who was blinded to the procedure performed, assessed the impact of the anesthetic on the laboring patient and assigned follow-up doses according to protocol.

 

The study was divided into two phases. The first phase involved the administration of either a CSE or epidural alone. The CSE group received an intrathecal dose of bupivacaine 2.5mg and fentanyl 5 µg. This was followed by placement of an epidural catheter for use later in labor. In the epidural-only group an epidural catheter was placed and 20 mL of a bupivacaine 0.1% with fentanyl 2 µg/mL solution was administered. The second stage of the study involved adjusting the dose of epidural bupivacaine based on a Visual Analogue Score (VAS) for pain on a scale of 0-100, with 100 being the worse pain.

 

Thirty minutes after the initial injection of either the intrathecal or epidural, each woman was evaluated for pain, sensory block height, motor block, adverse effects, and duration of analgesia. Follow up epidural injections were on “patient demand” with the concentration of bupivacaine based on the VAS obtained 30 minutes after the previous injection. The baseline epidural follow-up injection dose was set at bupivacaine 0.07%. The target VAS was 10. Women with a VAS at the 30 minute interval of less than or equal to 10 received a reduction in bupivacaine concentration of 0.01%. Women who had a VAS greater than 10 received an increase in the bupivacaine concentration of 0.01%. Thirty minutes after the on-demand injection, the initial evaluation was repeated. The study was considered “ended” for each woman 30 minutes after the second on-demand injection.

 

Study data was evaluated using a repeated measures ANOVA with Tukey-Kramer multiple comparison tests for time based data, while a Kaplan-Meier analysis and log rank tests were used for durations of analgesia. Significance was set at a P<0.05 (two-sided). Sample size was estimated at 39 patients per group and the final results contained 40 patient per group.

 

Result Patient characteristics and obstetric data were similar in both groups, and the median cervical dilation was 3.5 cm before the first injection with a range of 2 and 5 cm. There were no significant differences between mode of delivery and time to spontaneous delivery between the two groups. The intrathecal dose had a 22% shorter duration than the initial epidural-only dose; 81min vs 104 min (P = 0.0003). Time between injections after the first follow-up injection was similar. The VAS was similar in both groups at various time intervals. The concentration of follow up bupivacaine injections was significantly greater, maximum sensory block height was significantly lower, and hip flexion was significantly weaker in the CSE group.

 

Conclusion Several studies have concluded CSE to be more effective for laboring patients, while others have determined that there are no significant differences between CSE and epidural-only analgesia. This study indicated that CSE has some drawbacks that other studies failed to notice, suggesting that it is possible an epidural only approach to labor analgesia may be superior to CSE. This study found no quantitative analgesia advantage of CSE over standard epidural-only analgesia beyond the initial dose. In addition, the intrathecal dose had a 22% shorter duration of action than the initial epidural-only. The required mean epidural concentration of bupivacaine increased following the intrathecal injection for CSE techniques. Even with these statistically significant findings, there may not be a noticeable clinical impact in most situations.

 

Comment

This was a very interesting study. It was well done statistically, and the use of three different anesthesia providers during different stages of the study was an effective way to assure proper blinding of the randomization, anesthetic technique, and evaluation. This study had a unique focus; the concentration of agent for on-demand follow up doses after CSE or epidural-only initial doses. They found that women who received a CSE needed an epidural follow-up dose sooner than epidural-only analgesia. But more than that, the parturients who started with a CSE also needed a higher concentration of bupivacaine, had weaker hip flexion, and had a lower sensory block level.

 

In the end, these two techniques had similar clinical outcomes. However, I found two distinct differences in this study that mirror my clinical practice. The first would be the more rapid onset of intrathecal analgesia, and the second is the need for a follow-up epidural injection sooner after an intrathecal injection than would be needed following an initial epidural-only injection. Both of these observations are clinically significant in my opinion. I find the rapid onset of the intrathecal injection to be very beneficial in most situations, and I can avoid the need for a quick follow-up epidural injection by starting an epidural infusion soon after the intrathecal injection. In about 95% of cases, I find no additional adjustment is needed before delivery. I should add that the addition of a small patient controlled epidural analgesia (PCEA) dose for the epidural (5cc every 30 minutes) helps to eliminate the need for adjustments.

 

Most women have a change in sensation when the baby’s head presses firmly on the perineum just prior to delivery. The PCEA gives them just enough rapid response, and the perception of control, that they seem to get by this phase with less difficulty than they would without the PCEA. I know of some anesthesia providers who use an epidural-only, periodic injection technique and swear by it. As I have always said, anesthesia is more of an art than a science, and this is especially true in obstetric anesthesia. We find differences in patient populations, facility idiosyncrasies, and physician preferences that influence how we all approach each situation. It is always nice to find studies such as these that tend to verify that different techniques have similar results, and the differences can be either useful or managed for the situation at hand.

Steven R Wooden, DNP, CRNA


© Copyright 2012 Anesthesia Abstracts · Volume 6 Number 1, January 30, 2012




Patient Safety
Risk factors associated with ischemic optic neuropathy after spinal fusion surgery

Anesthesiology 2012;116:15-24

The Postoperative Visual Loss Study Group


Abstract

Purpose The purpose of this study was to identify risk factors for Ischemic Optic Neuropathy after spinal fusion surgery by examining the American Society of Anesthesiologists (ASA) Postoperative Visual Loss Registry.

 

Background Spinal fusion surgery is associated with improved quality of life; however these types of surgeries are also associated with large blood loss, prolonged duration, and in rare cases, Postoperative Visual Loss. Postoperative Visual Loss is purported to be caused by Ischemic Optic Neuropathy. Visual deficits range from blurred vision to permanent blindness. The estimated incidence ranges from 0.017% to 0.1%. Numerous risk factors have been identified for Ischemic Optic Neuropathy including:

  • anemia
  • hypotension
  • large fluid shifts
  • venous congestion of the orbits
  • large blood loss
  • atherosclerotic vascular disease
  • obesity
  • diabetes
  • hypertension

 

Unfortunately, most reports of Postoperative Visual Loss are limited by small sample sizes and lack detailed information on perioperative events. The ASA Postoperative Visual Loss registry includes a large collection of detailed information on Ischemic Optic Neuropathy cases associated with prone spinal surgery. This study identified risk factors for Ischemic Optic Neuropathy after prone spinal fusion surgery using the ASA Postoperative Visual Loss registry.

 

Methodology This was a multi-center case-control study comparing 80 cases of Ischemic Optic Neuropathy after prone spinal fusion surgery with a randomly selected control group of 315 subjects from 17 academic centers. The 80 cases of Ischemic Optic Neuropathy were taken from the ASA Postoperative Visual Loss registry; inclusion criteria included age ≥ 18 years, spine fusion as the first and only surgery associated with admission, surgery date between 1991 and 2006, prone position for portion of procedure, anesthetic duration ≥4 hours, and surgery between T-1 and S-5 spinal levels. Patients with a history of perioperative cardiopulmonary resuscitation, stroke, multiple staged spine surgery preceding Ischemic Optic Neuropathy, and incomplete or inadequate data were excluded. Current Procedural Terminology codes were used to identify prone spine surgical procedures from the 17 academic institutions. A total of 43,410 potential control cases were identified. Four cases to every one Ischemic Optic Neuropathy case were randomly selected from eligible cases. Cases selected were matched by year of surgery.

 

Data collection and analysis were performed in stages. Multivariate analysis was used to identify risk factors for Ischemic Optic Neuropathy. A P < 0.05 was considered significant.

 

Result Multivariate analysis identified male gender, obesity, use of a Wilson frame, anesthetic duration, increased blood loss, and less colloid administration as risk factors for postoperative Ischemic Optic Neuropathy (see Table 1). Some factors were associated with decreased risk of Ischemic Optic Neuropathy. For every 5% colloid administered (as a percent of total non-blood replacement) there was a 0.67 reduction in the odds of Ischemic Optic Neuropathy (P < 0.001). However, the difference in average percent of colloid administration between case and control subjects was only 4%. Anemia and prolonged hypotension (blood pressure > 40% below baseline for 30 minutes) were not independent predictors of Ischemic Optic Neuropathy. Table 2 presents the relative risk of patients developing Ischemic Optic Neuropathy based on multiple risk factors. This table can be used by clinicians to evaluate patients’ risk for developing Ischemic Optic Neuropathy.

 

 

Table 1. Risk Factors for Ischemic Optic Neuropathy

Risk Factor

Risk Increase

Male Gender

2.35*

Obese BMI > 30

2.83

Wilson frame

4.30

Each hour duration

1.39

Each Liter blood loss

1.34

NOTE: *Male gender P = 0.005. All other P values = 0.001. 

 

 

Table 2. Risk of Ischemic Optic Neuropathy after Major Prone Spine Surgery

Gender

Obesity

Wilson Frame

Duration (h)

EBL (L)

Colloid (%)

Relative Risk

Female

No

No

5

1

10

1.0

Female

Yes

No

5

1

10

2.83

Female

No

Yes

5

1

10

4.30

Female

No

No

7.5

1

10

2.26

Female

No

No

10

1

10

5.12

Female

No

No

5

2

10

1.34

Female

No

No

5

3

10

1.78

Female

No

No

5

1

0

2.24

Female

Yes

Yes

10

3

0

249

Male

No

No

5

1

10

2.53

Male

Yes

No

5

1

10

7.17

Male

No

Yes

5

1

10

10.91

Male

No

No

7.5

1

10

5.74

Male

No

No

10

1

10

12.98

Male

No

No

5

2

10

3.39

Male

No

No

5

3

10

4.52

Male

No

No

5

1

0

5.67

Male

Yes

Yes

10

3

0

632

Note. Results presented as relative risk of Ischemic Optic Neuropathy compared to the lowest risk set compared to row 1.

 

 

Conclusion This study determined that obesity, male gender, use of the Wilson frame, longer duration of anesthesia, greater estimated blood loss, and decreased colloid administration were independent predictors of Ischemic Optic Neuropathy after prone spinal fusion surgery. Anesthesia providers should use these results and prediction models when planning for spinal fusion surgery.

 

Comment

Postoperative Visual Loss is a rare, but devastating, complication that can occur after spinal fusion. This is the first large case-control study to identify risk factors for development of Ischemic Optic Neuropathy after spinal fusion. I believe these results will help inform anesthesia management for spinal fusion surgery and now furnish anesthesia providers with some evidence upon which to base their decisions and informed consent process.

 

In this study obese men who had prolonged surgery on a Wilson frame with significant blood loss were at the greatest risk for developing Ischemic Optic Neuropathy. The authors speculated the reduced risk for females was secondary the protective effects of estrogen on specific optic nerve disease found in animal studies. Also preexisting diseases such as atherosclerosis were not predictors of Ischemic Optic Neuropathy, which the authors suggested may mean Ischemic Optic Neuropathy is more strongly influenced by perioperative factors than underlying disease.

 

Obese patients who have prolonged surgery on a Wilson frame have the greatest increase in intrabdominal pressure thereby causing increased venous engorgement and pressures in the head and orbits of the eye. This can be further exacerbated if the head of the bed is lower than the level of the heart, which is common with this type of surgery on the Wilson frame. Elevated venous pressure in the orbit leads to interstitial edema and reduced intraocular perfusion pressures, which may contribute to the development of Ischemic Optic Neuropathy. This can be further exacerbated with excessive crystalloid administration and increased blood loss; in this study higher amounts of colloid administration appeared to confer a small reduction in risk of Ischemic Optic Neuropathy.

 

I think these results have the potential to reduce Ischemic Optic Neuropathy by giving anesthesia providers and surgeons evidence of factors they may be able to modify to reduce risk. If I have an obese male presenting for spinal fusion I might point out some of these risk factors and ask the surgeon if he can use another frame besides the Wilson frame and possibly consider reducing his surgical duration or performing a staged procedure.

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 2012 Anesthesia Abstracts · Volume 6 Number 1, January 30, 2012




Pediatric Anesthesia
Predictive factors for difficult intravenous cannulation in pediatric patients at a tertiary pediatric hospital

Pediatr Anesth 2012;22:223-229

Cuper NJ, de Graaff JC, van Dijk AT, Verdaasdonk RM, van der Werff DB, Kalkman CJ


Abstract

Purpose The purpose of this study was to identify factors that affect successful peripheral IV catheter insertion in pediatric patients. Successful insertion was qualified by the number of attempts and the length of time required to obtain access.

 

Background Pediatric patients may be traumatized if multiple attempts are required to start an IV line. Age and BMI of the patient are believed to be predictive of a difficult cannulation, but supporting evidence is lacking. Different techniques might be employed to maximize success of the first attempt and to minimize the development of fear if predictive factors for difficult intravenous cannulations could be recognized in advance.

 

Methodology This prospective observational cohort study included patients, ages 0 to 18 years, in two departments of a pediatric referral hospital. During a 5 month period, data was collected on all intravenous cannulations in the operating room (OR) and on the outpatient care unit. Many patients in the OR underwent a mask induction with sevoflurane prior to IV attempts. If requested by the patient, the IV was inserted prior to inhalation anesthesia, often with the prior application of a local anesthetic, EMLA (Eutectic Mixture of Lidocaine and prilocaine). The IV insertion was performed by an anesthesia provider: anesthesiologist, resident anesthesiologist, nurse anesthetist, or nurse anesthesia graduate student. In the outpatient care unit the patients had EMLA applied and were awake for the cannulation. In the outpatient care unit IV insertions were performed by either a resident pediatrician or a nurse. The data collected included whether the first attempt was successful and the length of time to successful cannulation. Success was defined as the IV cannula in place and flushed with saline without signs of extravascular injection. Attempts were defined as punctures of the skin. Redirection of the needle tip while below the skin was not a separate attempt. Time was measured from the initial application of the tourniquet until the IV line was partially secured and flushed.

 

Factors recorded to determine predictive value included patient age, gender, Body Mass Index (BMI) or weight-to-age score, presence of dark skin, wakefulness, surgical specialty, and occupation of the cannulator. First attempt success rate percentage and the time to cannulation was presented as mean and standard deviation for the all groups then delineated by age categories. The impact of each variable on the success and time to cannulation was analyzed by univariate logistic regression and univariate Cox regression. Independent predictive variables were investigated using multivariate regression models.

 

Result A total of 1,261 patients were included in the study; 1,083 in the OR and 178 in the outpatient care unit. The overall percentage of patients who experienced successful first cannulation attempts was 73.1% and 80.7%, respectively. Only 13 out of all patients had failed cannulation. In the OR the most commonly used site was the dorsum of the hand (85%) followed by the foot. In the outpatient care unit with all patients awake, the most commonly cannulated sites were the lower arm and the antecubital fossa. The mean time to cannulation in the OR was 140 seconds compared to 182 seconds in the outpatient care unit where all patients were awake. The mean time to cannulation in the OR decreased as age increased with neonates and infants requiring 235 seconds and adolescents requiring 103 seconds. Predictive variables were analyzed separately for the OR and the outpatient care unit. In the OR the factors associated with lower probability of successful cannulation were younger age; scheduled for maxillofacial, neurosurgical, or general surgery; and insertion being performed by someone other than a nurse anesthetist. Also in the OR, awake patients, female gender, and being scheduled for maxillofacial or urologic surgery were associated with longer cannulation times. For awake patients in the OR, the use of EMLA had no impact on either success rate or time to cannulation. In the outpatient care unit with all awake patients, no factors had significant association with successful first attempt or time to cannulation.

 

The researchers reported findings similar to previous studies with younger age being a predictor of more difficult IV insertions. The suggested explanation for the expertise of nurse anesthetists over all other providers was their greater experience. A previously held premise that greater BMI or weight-to-age would impact the difficulty of cannulation was not supported in this study.

 

Conclusion Intravenous cannulation in pediatric patients can present challenges with some patients requiring more than one attempt. Younger patient age was most strongly associated with difficult or prolonged IV cannulation.

 

Comment

The children that I know the best, my girls, hate needles! Convincing them to allow an IV insertion before anesthesia would be a mammoth accomplishment. They would want to have the best practitioner starting it, and they would likely allow a single attempt. Many pediatric patients are similar. If risk factors could predict which patients are likely to require more than one attempt for cannulation, anesthesia practitioners could develop the best plan for pediatric patients. If there is no contraindication and it is the patient’s preference, mask induction with sevoflurane or nitrous oxide is a viable option to obtaining IV access. The induction can usually be supplemented with intravenous agents like lidocaine, opioids, neuromuscular blocker, and propofol, as needed. However, IV induction is necessary for certain circumstances such as non-triggering anesthetics or rapid sequence induction. The authors of this study could have expanded the list of variables to include techniques used such as warming the site or visualization of the vein with ultrasound, visibility or palpability of the vein, medication history, history of prematurity, presence of disease, and surgical history.

 

The finding that EMLA application did not influence the success of cannulation nor time to cannulation was of interest as some practitioners would anecdotally disagree. This additional information might be predictive of difficult cannulation. The researchers recognized a legitimate clinical issue and attempted to find some answers to develop solutions. I would like to see this study conducted with a tighter methodology and see if more predictors might be identified. That would be great practical information to have in our toolbox.

Terri M. Cahoon, DNP, CRNA


© Copyright 2012 Anesthesia Abstracts · Volume 6 Number 1, January 30, 2012




Regional Anesthesia
Perioperative nerve injury after total hip arthroplasty: regional anesthesia risk during a 20-year cohort study

Anesthesiology 2011;115:1172-1178

Jacob AK, Mantilla CB, Sviggum HP, Schroeder DR, Pagnano MW, Hebl JR


Abstract

Purpose The purpose of this study was to determine if the use of regional anesthesia increased the risk of perioperative nerve injury after total hip arthroplasty.

 

Background The incidence of postoperative neurological complications after total hip arthroplasty ranges from 0.08% to 7.6%. The incidence of neurological complications after regional anesthesia for lower extremity procedures is estimated to be between 0.03% and 1.5%. Most cases of perioperative nerve injury resolve within weeks to months; however some injuries may be permanent. A recent large cohort study examining the association of regional anesthesia with perioperative nerve injury after total knee arthroplasty reported regional anesthesia did not increase the risk for a perioperative nerve injury. Although, complete neurological recovery was less likely if a patient had received a peripheral nerve block. Thus it is essential that anesthesia providers understand the risks associated with performance of regional anesthesia in patients undergoing total hip arthroplasty.

 

Methodology This retrospective cohort study examined risk factors associated with perioperative nerve injury after total hip arthroplasty at the Mayo Clinic in Rochester, MN. Using the Mayo Clinic Total Joint Registry, investigators examined records between January 1, 1988 and July 1, 2007.  Patient, surgical, and anesthetic characteristics were retrospectively collected from the registry. Anesthetic technique was classified as (1) general anesthesia, (2) neuraxial anesthesia, (3) combined general + neuraxial anesthesia, and (4) peripheral nerve block. Only patients undergoing the first elective total hip arthroplasty during the study period were included. Patients undergoing bilateral or staged procedures were excluded. The primary outcome was the presence or absence of a perioperative nerve injury within 3 months of the surgery. Multivariable logistic regression was used to analyze the results. A P < 0.05 was considered significant.

 

Result A total of 12,998 patients were included in the analysis. Just over half of patients were female (52%), with a mean age of 65 ± 14 years; 76% underwent a primary total hip arthroplasty and 24% a revision. General anesthesia was used in 60% of cases, neuraxial in 37%, and combined neuraxial-general anesthesia in 3%. Peripheral nerve blocks were used in 19% of cases. The use of peripheral nerve blocks significantly increased over time, from 0.3% during 1988-1992, 0.1% between 1993-1997, 2.6% for 1998-2002, and to 67.1% between the years 2003 and 2007. Starting in 2002 the use of posterior lumbar plexus catheters for postoperative analgesia was introduced and this resulted in the dramatic increase in blocks from 2003 to 2007 (P < 0.001).

 

A total of 93 cases of perioperative nerve injury were identified in the registry for an overall incidence of 72%. The incidence of peripheral nerve blocks did not change over time despite the increase in use of peripheral nerve blocks starting in 2003. The rate of perioperative nerve injury did not differ between patients who did and did not receive a peripheral nerve block between the years 2003 and 2007. Five risk factors were identified as being associated with perioperative nerve injury. For every 10 year increase in age the odds of a perioperative nerve injury decreased by 0.8 times (P <0.001). Females were 1.7 times more likely to experience a perioperative nerve injury than males (P = 0.014). For every 30-minute increase in operative time the risk of injury increased by a slight 1.1 times (P = 0.003). Patients who had a posterior surgical approach performed were 1.9 times more likely to experience an injury (P = 0.017). The use of neuraxial anesthesia and a lower extremity peripheral nerve block were not identified as risk factors (P = NS).

 

Of the 93 cases of perioperative nerve injury, a combined sensory and motor nerve injury was documented in 83% of the cases. Two-thirds of these patients still had a neurologic deficit prior to hospital discharge (67%). In a third of these cases a neurological consult was obtained. Of the 93 cases of perioperative nerve injury, 50% experienced complete resolution and 46% partial recovery during a multi-year follow-up period. Only 4% of patients had no improvement in their neurological symptoms at a median of 2 years after surgery. The time to maximal resolution of an isolated sensory deficit was 7.3 years compared to 4 years for a combined sensory and motor deficit (P = 0.027). The type of anesthesia or regional anesthetic technique used did not affect the degree of neurological recovery or time to resolution of deficits.

 

Conclusion The incidence of perioperative nerve injury after total hip arthroplasty was <1% in this large cohort study of more than 12,000 patients. Regional anesthesia (neuraxial or peripheral nerve block) did not increase the risk of perioperative nerve injury after total hip arthroplasty. Neurologic recovery was not affected by the use of regional anesthesia.

 

Comment

This is the second large cohort study examining perioperative nerve injury after lower extremity arthroplasty from this research group at the Mayo Clinic (see Anesthesia Abstracts January 2011, Volume 5, Number 1).1 In this groups’ previous cohort study of over 12,000 cases of total knee arthroplasty they found the incidence of perioperative nerve injury to be similar to this current study (0.79% vs. 0.72%). In their previous study use of regional anesthesia did not increase the risk of a perioperative nerve injury, but the presence of a peripheral nerve block made full recovery less likely. In contrast, the current study of total hip arthroplasty patients found a peripheral nerve block did not worsen the prognosis for nerve injury recovery. Looking at the results of these two studies I believe we can conclude that the use of regional anesthesia does not increase the risk of a perioperative nerve injury in these surgical populations. But rather, other patient characteristics (i.e., female gender) or surgical factors (posterior surgical approach; longer surgery) may play more of a role in the development of perioperative nerve injuries.

 

Interestingly, we tend to talk to patients about the risk of nerve injury before performing a regional block. And, in this case, there appears to be almost no actual risk such an injury will occur. On the other hand, we tend not to talk to patients about the risk of nerve injury before a general anesthetic where the risk of nerve injury is very real. In a 1990 closed claims study, nerve injury made up 15% of all malpractice claims, most commonly the ulnar nerve in men and the brachial plexus in women. Perhaps we would be wise to discuss the risks of anesthesia based upon evidence rather than tradition?

Dennis Spence, PhD, CRNA


1. Jacob AK, Mantilla CB, Sviggum HP, Schroeder DR, Pagnano MW, Hebl JR. Perioperative nerve injury after total knee arthroplasty: regional anesthesia risk during a 20-year cohort study. Anesthesiology 2010;114:311-7.


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 2012 Anesthesia Abstracts · Volume 6 Number 1, January 30, 2012