ISSN NUMBER: 1938-7172
Issue 7.6 VOLUME 7 | NUMBER 6

Editor:
Michael A. Fiedler, PhD, CRNA

Contributing Editors:
Penelope S Benedik, PhD, CRNA, RRT
Mary A Golinski, PhD, CRNA
Alfred E Lupien, PhD, CRNA, FAAN
Dennis Spence, PhD, CRNA
Cassy Taylor, DNP, DMP, CRNA
Steven R Wooden, DNP, CRNA

Guest Editor:
Kenneth J. Taylor, DNP, CRNA

Assistant Editor
Jessica Floyd, BS

A Publication of Lifelong Learning, LLC © Copyright 2013

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
A comparison of 4 airway devices on cervical spine alignment in cadaver models of global ligamentous instability at C1-2
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GENERAL
The effect of steep Trendelenburg positioning on intraocular pressure and visual function during robotic-assisted radical prostatectomy
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Sleep-disordered breathing and postoperative outcomes after bariatric surgery: analysis of the Nationwide Inpatient Sample
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PATIENT SAFETY
Efficacy of intraoperative dexmedetomidine infusion of emergence agitation and quality of recovery after nasal surgery
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Postoperative residual neuromuscular blockade is associated with impaired clinical recovery
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PHARMACOLOGY
Effect of preemptive and preventive acetaminophen on postoperative pain score: a randomized, double-blind trial of patients undergoing lower extremity surgery
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Airway
A comparison of 4 airway devices on cervical spine alignment in cadaver models of global ligamentous instability at C1-2

Anesth Analg 2013;113:126-132

Wendling AL, Tighe PJ, Conrad BP, Baslanti TO, Horodyski M, Rechtine GR


Abstract

Purpose The purpose of this study was to examine the effects of 4 different airway devices (Macintosh, Lightwand, Airtraq, and Fastrach LMA) on cervical spine alignment in cadaver models with upper cervical instability.

 

Background Trauma patients with suspected spinal cord injuries may require rapid sequence intubation to secure their airway. Unfortunately, neurological injury can occur during emergency intubation in patients with an unstable cervical spine. The most appropriate technique for endotracheal intubation which minimizes cervical movement in patients with unstable upper cervical spine injury is not known. Indirect laryngoscopy devices such as the AirTraq are commonly used during rapid sequence intubation; however, the AirTraq has not been compared to other devices such as the Macintosh, Lightwand or Fastrach LMA. This study sought to compare these 4 devices in cadaver models with a C1-2 fracture.

 

Methodology Three lightly embalmed cadaver subjects with minimal stiffness of the joints were used for this study.  All three cadavers were males with a mean age of 83 years and weight of 61 kg. The mean flexion-extension of the three cadavers was 8 degrees, 29 degrees, and 25 degrees. Lateral bending was 7.2 degrees, 12.4 degrees, and 20 degrees. Axial rotation was 43 degrees, 46 degrees, and 54 degrees. An unstable spine was produced by the surgical creation of a complete segmental injury at C-1 to C-2 joint. This resulted in an unstable type II odontoid fracture.

 

Study intubations were performed by two anesthesiologists and three paramedics (in New York paramedics can perform field intubations). All had prior intubation experience; however, the amount of prior experience was not recorded. All providers had the opportunity to practice using each of the airway devices; the AirTraq size 3, Lightwand Surch-Lite 15”, Fastrach LMA size 4, and Macintosh #3 blade. Intubation procedures with each devices were based on manufacturer recommendations. Each provider intubated each cadaver 3 times with each device, in random order, and following the same technique. A 7 mm endotracheal tube was used for all intubations. A stylet was used for Macintosh intubations. In-line stabilization was performed by a single individual with >20 years of experience in caring for trauma patients. An electromagnetic motion analysis device (Liberty Device, Polhemus Inc., Colchester, VT) was used to assess the amount of angular and linear motion of the C1-2 vertebrae. Each intubation technique was performed 3 times per trial, and each trial was repeated for a total of 3 trials per airway device with each provider and cadaver. This resulted in 39 intubations with each airway device.

 

Result A total of 153 intubation trials were performed for each of the devices and each axis of movement. There were three failed intubtions with the Fastrach LMA. Overall, the greatest movement occurred in the flexion-extension axis, with approximately 3 degrees more movement compared to the lateral (side to side) axis or axial rotation axis (P < 0.0001).

 

Overall, the Lightwand resulted in 40% less extension when compared to the Fastrach LMA and Macintosh blade. The Lightwand resulted in significantly less movement in the flexion-extension axis compared to the Fastrach LMA (mean difference: 3.2º, P = 0.003), and in the axial rotation axis (mean difference: 1.6 º, P = 0.01). The Lightwand also resulted in significantly less flexion-extension movement compared to the Macintosh blade (mean difference: 3.1 º, P = 0.005), and less axial rotation movement (mean difference: 1.4º, P = 0.03). No differences in movement were found between any of the other devices. There was a positive correlation between time to intubation and amount of movement in all axes. That is, the longer it took to intubate, the greater the cervical spine movement (r = 0.6, P < 0.0001).

 

 

Figure 1. Comparison of Movement in the C1-2 Level

Figure 1

Note. *P < 0.05 when comparing the Lightwand to the Fastrach LMA and Macintosh blade for flexion-extension and axial rotation.

 

 

Conclusion The Lightwand resulted in less motion in cadavers with unstable C1-2 fractures when compared to the Fastrach and Macintosh blade. Anesthesia providers should balance the risk of hypoxemia, hypercarbia, and aspiration due to prolonged or failed intubation with the risk of neurological injury when choosing the device for intubation in trauma patients with suspected cervical spine injuries.

 

Comment

Intubation in patients with suspected cervical spine injury can be challenging. In recent years indirect laryngoscopy with devices such as the AirTraq have being used more and more to facilitate intubation in this patient population. This study provides some nice evidence, at least in a cadaver model, of how much the c-spine is really moving with the AirTraq and several different airway devices.

 

I found it interesting that the investigators chose to use the Lightwand as one of the airway devices. I must admit it has been years since I have used this device, and I am not sure how commonly it is used in trauma patients these days. I suspect video laryngoscopy is probably one of the more common alternative devices used instead of traditional laryngoscopy. The advantages of the Lightwand are it limits cervical neck motion (as these results demonstrate) and ability to be used in airways with secretions and blood. However, it does take a fair bit of practice to be proficient with it and can be difficult to use in patients with dark skin. So I question the relevance of these findings.

 

It is not surprising that the Fastrach LMA and Macintosh blade resulted in more neck extension. Although I am not sure of the clinical relevance of only 2-3 degrees of increased movement in patients with suspected cervical spine injury between the Fastrach LMA and Lightwand. I think when intubating patients with suspected cervical neck injuries. the priority should be securing the airway in a way that minimizes the risks of hypoxia and aspiration while at the same time reducing or eliminating neck movement.

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 2013 Anesthesia Abstracts · Volume 7 Number 6, June 30, 2013




General
The effect of steep Trendelenburg positioning on intraocular pressure and visual function during robotic-assisted radical prostatectomy

Br J Ophthalmol. 2013 Sep 24. doi: 10.1136/bjophthalmol-2013-303536. [Epub ahead of print]

Hoshikawa Y, Tsutsumi N, Ohkoshi K, Serizawa S, Hamada M, Inagaki K, Tsuzuki K, Koshimizu J, Echizen N, Fujitani S, Takahashi O, Deshpande GA


Abstract

Purpose The purpose of this study was to measure Intraocular Pressure (IOP) before, during, and after robotically-assisted radical prostatectomy. A secondary aim was to look for opthalmic complications that may have been due to changes in IOP.

 

Background The number of robotic-assisted radical prostatectomies performed each year continues to increase dramatically as more and more centers worldwide purchase robots. Robot-assisted prostatectomy requires steep Trendelenburg position throughout the procedure; often as much as 45°. Several complications involving the eyes have been reported in robotic prostatectomy cases including ischemic optic neuropathy. Theoretically, Intraocular Pressure (IOP) may increase significantly during a long procedure in steep Trendelenburg. And, at least one group has previously reported an average 13 mm Hg increase in IOP during these cases. Normal IOP is between 10 mm Hg and 20 mm Hg in awake patients.

 

IOP is largely determined by the flow of aqueous humor, blood volume in the vascular layers of the eye (choroid), central venous pressure, and extraocular muscle tone. Both extreme head down position and pneumoperitoneum are likely to increase IOP by increasing CVP and hydrostatic pressure in the eye. Previous studies have not established a save level of IOP elevation during long surgical procedures in steep Trendelenburg position. 

 

Methodology This was a prospective, observational study at one clinical site that included 31 consecutive robot prostatectomy patients. Men with glaucoma, retinal vascular disease, or corneal disease were excluded. All patients were examined in the ophthalmology clinic one month before prostatectomy and again one month postoperatively.

 

All anesthetics were standardized with propofol, remifentanil and fentanyl, and rocuronium. End Tidal CO2 was kept between 30-40 mm Hg. On the day of surgery, IOP was measured at the following 10 time points:

  • T1 Supine, Awake, before induction of anesthesia
  • T2 Supine, Immediately after anesthetic induction
  • T3 – T8 Trendelenburg 23°, Immediately after positioning & every hour
  • T9 Supine, During anesthesia before emergence
  • T10 Supine, 30 min after emergence

 

Result Thirty-one men aged from 54 years to 74 years old completed the study (mean 66 years). Mean operative time was 4.6 hours (range from 3 hours 47 min to 6 hours 9 min). Mean blood loss was 364±196 mL (range 80 mL to 810 mL). No eye complications were discovered at the postoperative eye exam, however 5 of the 31 patients were lost to follow up and did not have the postoperative exam.

 

Pre-induction IOP averaged 18 mm Hg immediately before induction of anesthesia (range 9 mm Hg to 29 mm Hg). IOP pre-induction through post-emergence from general anesthesia is shown in figure 1. Maximum IOP in any patient at any time was 36 mm Hg. As time passed intraoperatively, more and more patients had an IOP ≥ 25 mm Hg; peaking at 50% of patients by T8 (5 hours into the case).

 

 

Figure 1: Intraocular Pressure During Robot Prostatectomy

Figure 1

NOTES: T1 = preanesthetic IOP. T2 = Post-induction, supine IOP. T3 - T8 asleep + Trendelenburg. T9 = asleep + supine. T10 = Supine after emergence. Not all cases continued until T7; T7 included n=18, T8 included n=4. Data from Hoshikawa Y et al. Br J Ophthalmol Published Online First: Sept. 2013.

 

IOP increased significantly when patients were placed in steep Trendelenburg position, but, initially, was still within the normal range. As the length of time in Trendelenburg position increased, so did IOP. By T8, 5 hours into the case, 50% of patients had an IOP ≥ 25 mm Hg. Mean IOP in all patients throughout the entire procedure was 24 mm Hg. At an eye examination one month postoperatively, no patient had any evidence of complications.

 

Conclusion Intraocular pressure increased above the normal range and increased steadily over time while patients were in steep Trendelenburg position during general anesthesia for robotic prostatectomy. No postoperative complications were detected due to the increase in IOP.

 

Comment

We’ve all done long cases and we’ve all done cases in Trendelenburg position. But never have I done as long a case in as extreme Trendelenburg position as robot prostatectomies. When we started doing them the surgeons were getting used to the robot controls and the cases could take 5 or more hours; almost all of that in all the Trendelenburg the OR bed would do. Right away we noticed that the eyes were swollen at the end of the case. There were commonly collections of fluid beneath the conjunctiva. We also noticed an increased incidence of corneal abrasions despite the fact that the eyes were protected and left undisturbed as the head was solidly in our sphere of influence. Measuring Intraocular Pressure (IOP) is a rational part of following up on these observations. While this study didn’t tell us if or how increased IOP might be contributing to corneal abrasions, it did provide evidence that while IOP increased above normal values during robot prostatectomies, no persistent eye injuries resulted in patients with normal preoperative IOP. It also doesn’t tell us how long IOP must be elevated to cause patient harm. But the longest case in this study was about six hours and no eye injury resulted. Interestingly, they did not appear to have used any potent inhalation agent for maintenance of general anesthesia in this study. I’m guessing that most of us probably use inhalation agent during these cases in the USA. It is likely that inhalation agent would affect IOP but since it wasn’t used in this study we don’t know how it affected IOP during long periods of steep Trendelenburg position.

 

In my experience, once surgeons gain (a lot of) experience with the robot they can do most prostatectomies in about two hours, sometimes slightly faster. In this study, only 32% of patients had an IOP ≥ 25 mm Hg two hours into the surgery, so it seems unlikely that IOP would cause an injury in patients with previously healthy eyes. But that doesn’t mean the increase in IOP might not make patients more vulnerable to corneal abrasion. To be clear this is my speculation, but from what I’ve seen I suggest we take extraordinary precautions to prevent patients from rubbing their eyes postoperatively. Given how well we protect eyes intraoperatively I suspect the eye injuries we saw most likely occurred postoperatively and it seems reasonable that a swollen eye might be more prone to these injuries.

Michael A. Fiedler, PhD, CRNA


© Copyright 2013 Anesthesia Abstracts · Volume 7 Number 6, June 30, 2013





Sleep-disordered breathing and postoperative outcomes after bariatric surgery: analysis of the Nationwide Inpatient Sample

Obes Surg. 2013;23:1842-51

Mokhlesi B, Hovda MD, Vekhter B, Arora VM, Chung F, Meltzer DO


Abstract

Purpose The purpose of this study was to determine if sleep-disordered breathing (SDB) was associated with worsened postoperative outcomes after bariatric surgery.

 

Background Sleep-disordered breathing (i.e., obstructive sleep apnea) has been identified as a risk factor for postoperative complications. Previous investigations reported increased rates of pulmonary complications, hypoxemia, emergent intubation, and intensive care unit transfer in patients with sleep-disordered breathing after surgery. Between 40-50% of patients undergoing bariatric surgery may have sleep-disordered breathing. Therefore, it is postulated that sleep-disordered breathing would increase the risk of adverse outcomes in patients undergoing bariatric surgery. However, there is limited research on outcomes in patients with sleep-disordered breathing undergoing bariatric surgery. The investigators of this study hypothesized that sleep-disordered breathing would be independently associated with worsened postoperative outcomes in patients undergoing bariatric surgery.

 

Methodology This study used the Nationwide Inpatient Sample database to examine outcomes in patients with sleep-disordered breathing after bariatric surgery. The investigators used ICD-9-CM codes to identify patients undergoing bariatric surgery between 2004 and 2008 and stratified them based on whether or not they had a diagnosis of sleep-disordered breathing. Demographic data, Charlson comorbidity index scores, health insurance type, income, teaching hospital status, and region in United States were recorded. The primary outcome was to compare in-hospital death, hospital costs, and length of stay between sleep-disordered breathing and non-SDB patients.

 

Secondary respiratory outcomes included:

  • need for emergent intubation and ventilation
  • continuous positive airway pressure use (CPAP)
  • tracheostomy
  • pneumonia
  • respiratory failure

 

Cardiac complication outcomes included the need for percutaneous coronary procedures and incidence of atrial fibrillation. The investigators used multivariable linear and logistic regression to compare differences in outcomes while controlling for comorbidity index, age, gender, insurance status, geographic region, teaching institution, income, weekend admission, year of surgery, and surgical procedure code.

 

Result A total of 91,028 patients were included in the analysis (sleep-disordered breathing n = 33,196 vs. non-SDB n = 57,832). The prevalence of sleep-disordered breathing was 36%. Patients with sleep-disordered breathing were slightly older (43.5 vs. 44.2 years, P < 0.01), tended to be male (30% vs. 14%, P < 0.01), were more commonly covered by Medicare (11.4% vs. 9.5%, P < 0.01), and tended to have a slightly higher comorbidity (P < 0.01). 

 

The overall incidence of in-hospital death was very low; however, patients in the non-sleep-disordered breathing group had a statistically significantly higher rate of in-hospital death (0.3% vs. 0.1%, P < 0.01). Total hospital charges were significantly higher in the non-sleep-disordered breathing group ($39,977 vs. $37,934, P < 0.001). Length of stay was significantly longer in the non-sleep-disordered breathing group (7.1 days vs. 5.8 days, P < 0.01). However, patients with sleep-disordered breathing had higher rates of:

  • atrial fibrillation
  • respiratory failure
  • use of CPAP
  • need for emergent intubation (P < 0.01; Figure 1).

 

In contrast, pneumonia rates (1% vs. 0.6%, P < 0.01), and need for tracheostomy were higher in patients in the non-sleep-disordered breathing group (0.13% vs. 0.08%, P = 0.02). 

 

When the investigators adjusted for covariates, they found patients with sleep-disordered breathing had a lower odds of in-hospital death (OR = 0.34). Sleep-disordered breathing was associated with a decrease in mean hospital charges of $869 and a decrease in the length of stay of 0.25 days when compared to non-sleep-disordered breathing patients (P < 0.001). Patients with sleep-disordered breathing were 4.4 times more likely to require emergent tracheal intubation and mechanical ventilation, 14 times more likely to require postoperative CPAP, and atrial fibrillation was more common (OR = 1.3).

 

There were 717 (1.2%) patients in the non-sleep-disordered breathing group and 1855 (5.6%) in the sleep-disordered breathing group who required emergent intubation. A significantly higher proportion of patients in the sleep-disordered breathing group required emergent intubation and mechanical ventilation on the day of surgery or the first postoperative day as compared to non-SDB patients (90% vs. 63%, P < 0.001). Outcomes were much worse in non-sleep-disordered breathing patients who required emergent intubation (Table 1). In those patients who required emergent intubation, the in-hospital mortality rate was 13.8% in the non-sleep-disordered breathing group as compared to 1.1% in the sleep-disordered breathing group (P < 0.01). Likewise, length of stay, incidence of respiratory failure, and pneumonia were all significantly higher in non-SDB patients requiring intubation after bariatric surgery (P < 0.01).

 

 

Figure 1. Comparison of Outcomes

Figure 1

 

 

Table 1. Outcomes in SDB vs. non-SDB Patients Who Required Intubation

 

Non-SDB

SDB

In-hospital mortality

13.8%

1.1%

Total charges

$134,471
± 142,897

$42,989
± 46,829

Length of Stay (days)

15.5 ± 19.9

4 ± 4.9

Respiratory Failure

60.3%

14.9%

Pneumonia

20.8%

2.3%

Note. SDB = “sleep-disordered breathing." Outcomes all worse in non-SDB group, P<0.01.

 

Conclusion Sleep-disordered breathing was independently associated with significant postoperative cardiopulmonary complications (emergent intubation, CPAP use, respiratory failure, atrial fibrillation), but not with increased in-hospital mortality, total charges, or length of stay in patients undergoing bariatric surgery. However, non-sleep-disordered breathing patients tended to be intubated later in their admission, and when they were intubated they experienced higher mortality, hospital length of stay, respiratory failure, and pneumonia.

 

Comment

Obstructive sleep apnea is a form of sleep-disordered breathing that has been found to be associated with postoperative respiratory complications. This study confirms this finding; however, the higher rates of postoperative complications in sleep-disordered breathing patients did not equate to higher rates of in-hospital death or increased length of stay. In contrast, the investigators found that in a subset of non-sleep-disordered breathing patients who required emergent intubation, both length of stay and in-hospital mortality rate was much higher.

 

So why these findings? Overall, bariatric patients have a high rate of moderate to severe Obstructive Sleep Apnea (40-50%), and many may be on CPAP therapy. One could thus speculate that providers and nurses taking care of sleep-disordered breathing patients would be more vigilant. In this study, patients with sleep-disordered breathing were intubated earlier in the postoperative period than non-SDB patients, and thus their prognosis was probably better. It is not known why they were intubated earlier, but providers may have had a lower threshold for intubating them because they had sleep-disordered breathing (or some other comorbidity). Patients with sleep-disordered breathing are more prone to the respiratory depressant effects of opioids and sedatives administered postoperatively, especially in the early postoperative period. Patients in the non-sleep-disordered breathing group were intubated later in their postoperative course. This could have been due to other complications which took longer to manifest or to be recognized. It is also possible that some of the non-sleep-disordered breathing patients in fact had undiagnosed Obstructive Sleep Apnea and this contributed to the worsened outcomes when they required intubation.

 

There are several limitations to this study. The results were retrospective and there is the possibility of coding errors. Since these results are from a large database we cannot determine exact reasons for complications or examine other covariates which may have influenced the outcomes. For example, it is not known if the atrial fibrillation was preexisting or developed postoperatively. Atrial fibrillation is very common in OSA patients so I suspect many had this prior to their surgery.

 

I think the take home message from this study is that we need to be vigilant for the potential for postoperative respiratory complications in patients undergoing bariatric surgery. Anesthesia providers and surgeons should continue to screen these patients for OSA and plan postoperative management accordingly.

Dennis Spence, PhD, CRNA


Bariatric procedures performed:

  • Laparoscopic gastric bypass 44.5 %
  • Open gastric bypass 25.8 %
  • Laparoscopic gastric band 16.0 %
  • Open high gastric bypass 6.2 %
  • Sleeve gastrectomy 3.0 %
  • Laparoscopic gastroplasty 2.4 %
  • Vertical banded gastroplasty 2.1 %


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 2013 Anesthesia Abstracts · Volume 7 Number 6, June 30, 2013




Patient Safety
Efficacy of intraoperative dexmedetomidine infusion of emergence agitation and quality of recovery after nasal surgery

Br J Anaesth 2013;111:222-228

Kim S, Kim J, Lee J, Song G, & Koo BN


Abstract

Purpose The purpose of this study was to determine whether or not a dexmedetomidine infusion would reduce the incidence of emergence agitation in patients who underwent nasal surgery. Additionally, the authors measured the effects of the dexmedetomidine infusion on hemodynamics during emergence and quality of recovery within the first 24 hours.

 

Background Emergence agitation is a phenomenon characterized as excessively aggressive behavior leading to potential patient self-harm upon awakening from anesthesia. Patients with emergency delirium may extricate themselves or pull out IV lines. General anesthetics administered in Ear, Nose, and Throat (ENT) surgery are associated with a 54% rate of aggressive emergence.

 

Most anesthesia providers prefer to extubate nasal surgery patients fully awake due to the surgically packed nasal passages and potential for residual airway irritants. However, an awake extubation has the potential to exaggerate emergence agitation.  Dexmedetomidine is a selective α2-receptor agonist which provides analgesia, sedation, anti-emesis, and sympatholytic effects without respiratory depression.  Dexmedetomidine infusions have been associated with a decreased incidence of emergence agitation in the pediatric population, in addition to improved quality of recovery following pediatric spinal surgeries. These effects have not been studied in adults.

 

Methodology This was a prospective, randomized, double-blinded study.  One-hundred, ASA I-II patients aged 20 to 58 years who underwent nasal surgery requiring bilateral surgical packing for 24 hours postop were included.  Patients were randomized into a dexmedetomidine (Group D) or a control group (Group C).  Group D (n=50) received an infusion at of 0.4 µg/kg/hour.  The infusion was initiated on anesthetic induction. Group C received a placebo consisting of an equal volume-of saline solution.

 

All patients received IM Midazolam 0.04 mg/kg and IV glycopyrolate 0.1 mg.  Anesthetic induction consisted of a 4 mL/kg crystalloid bolus followed by propofol (1.5-2 mg/kg), fentanyl (1 µg/kg), and rocuronium.  Maintenance anesthesia consisted of 0.6-1.4 age-adjusted minimum alveolar concentration of desflurane. Upon surgery completion, patients were orally suctioned, glycopyrolate and neostigmine were administered, and desflurane was discontinued. The point at which desflurane was turned off was recorded as “time zero.” In preparation for emergence noxious stimuli were mitigated and then the anesthetist made continuous verbal requests for the patient to open their eyes.  Extubation took place when three requirements were met:

  • spontaneous ventilation
  • response to verbal stimuli
  • BIS value > 70

The dexmedetomidine or saline infusion was discontinued subsequent to extubation.  Emergence time was defined as the interval from “time zero” to 2 minutes post-extubation.

 

The Ricker-sedation agitation scale was used to assess agitation during emergence (see notes). A four-point scale was used to assess coughing during emergence.  Heart rate (HR) and mean arterial pressure (MAP) were recorded at the following times:

  • induction
  • 10 minutes post-induction
  • 30 minutes after surgery start
  • 2 minutes after extubation

In the post-anesthetic care unit an 11-point numerical rating scale was used to assess residual sedation, a 10-point scale to assess pain, and a 4-point scale to assess nausea and vomiting.  A 40-item quality of recovery questionnaire (QoR-40) was used to assess patients recovery during the first 24 hours post-surgery.

 

Results Data from 100 patients were analyzed.  Group D had a lower incidence of emergence agitation (28% vs 52%, P=0.041), but there was no difference in the frequency of dangerous emergence between groups.  Neither group had agitation lasting longer than 5 minutes post-extubation.  Despite the addition of a low dose dexmedetomidine infusion in Group D, there was no difference in the age-adjusted MAC between groups. There was no difference in the time from desflurane discontinuation to extubation between groups (8.7 min vs 7.8 min, P=0.09). The time to first verbal response was longer in Group D (8.1min vs 7.0 min, P=0.044).

 

On emergence there were no differences in respiratory rate or coughing between groups. No complications occurred during emergence.  The most stable emergence hemodynamics occurred in Group D. In the PACU, there was no difference between groups in the patients’ need for antiemetics or analgesics.  PACU length-of-stay was comparable in both groups.   Quality of recovery measured by the QOR-40 was higher in Group D (183 vs 178, P=0.041), with pain being the most improved dimension among Group D participants.

 

A significant limitation of this study was that it was not possible to control for the effects of pain and preoperative anxiety on emergence agitation. The results may have been influenced by a higher baseline pain and/or preoperative anxiety level in one group or the other.

 

Conclusion The dexmedetomidine infusion decreased emergence agitation following nasal surgery without delaying the time to extubation.  Furthermore, dexmedetomidine resulted in: (a) more stable hemodynamics during emergence, (b) no increase in PACU length of stay, and (c) a slightly greater quality of recovery during the first 24 hours.

 

Comments

When administering an anesthetic for a patient undergoing nasal surgery requiring bilateral nasal packing, I'm often dreading the emergence far before it is time to actually "wake the patient up."  Here’s why:

  • 54% of these patients experience emergence delirium
  • Emergence frequently induces tachycardia and/or hypertension
  • An aggressive emergence can cause excessive nasal bleeding 
  • Potential laryngospasm secondary to residual blood and/or debris in the patient's airway
  • The inability to ventilate through the patients packed nasal passages
  • The risk of personnel in the OR having blood coughed on them by the patient
  • Delivering a bloody patient to the PACU who doesn’t look like they’ve been cleaned up

 

This well executed study suggested the addition of a low-to-moderate dexmedetomidine infusion could decrease the rate of emergence agitation in this surgical population by nearly half. The results also implied there was no delay until the patient was ready to extubate. These factors offer a substantial benefit to this surgical population.  A more smooth and controlled emergence has the potential to prevent patient self-harm and protects surgical staff from blood spray.  Furthermore, preventing premature self-extubation is critical, as treating a laryngospasm or reintubating is quite complicated following nasal surgery.

 

A concern within the study was the researchers' choice of postoperative evaluation tool.  The QoR-40's ability to accurately assess patients post-surgical recovery is controversial at best.  Furthermore, the QoR-40 scores between the studied groups differed by only 5 points.  While this finding was statistically significant, it lacks clinical relevancy.  A strength of the study was the use of desflurane for anesthesia maintenance, as it contained an appropriate effect size. That is, if the results suggested a lower incidence of coughing with desflurane, anesthetists could feel confident that those results would be the same or even better when isoflurane or sevoflurane is used.

 

Approximately 84 million americans suffer from various forms of cardiovascular disease.  When these patients experience episodes of tachycardia and hypertension, their risk of myocardial infarction and stroke increase significantly.  In 2010, the direct and indirect costs of MI and stroke were nearly $450 billion in the United States alone.  This study determined patients who received a dexmedetomidine infusion experienced more stable hemodynamics throughout the emergence process, with mean arterial pressure 10 mmHg lower and heart rates between 10-15 beats per minute lower than the control group.  There is direct clinical applicability of these results, in that we can reduce the risk of cardiovascular morbidity in at risk patients by including a low-to-moderate dexmedetomidine infusion lasting until extubation during nasal surgery.

 

I have administered supplemental dexmedetomidine infusions in anesthetics for a number of surgical procedures.  My experience is that patients benefit both intraoperatively and postoperatively.  Whether patients suffer from cardiovascular disease or not, hemodynamic stability and a "smooth" emergence benefit our surgical patients.

Kenneth J. Taylor, DNP, CRNA


Ricker-Sedation Agitation Scale: 1= minimal or no response to noxious stimuli and 7= pulling at tracheal tube/striking at staff.

Four-point cough scale: 0= no cough, 1= single cough, 2= persistent cough lasting < 5 seconds, 3= persistent cough lasting > 5 seconds, or bucking.

QoR-40: A 40 item questionnaire assessing 5 dimensions of postoperative recovery: (1) patient support, (2) comfort, (3) emotions, (4) physical independence, and (5) pain; producing a global score and a subscore for the 5 assessed dimensions.


© Copyright 2013 Anesthesia Abstracts · Volume 7 Number 6, June 30, 2013





Postoperative residual neuromuscular blockade is associated with impaired clinical recovery

Anesth Analg 2013;117: 133-141

Murphy GS, Szokol JW, Avram MJ, Greenberg SB, Shear T, Vender JS, Gray J, Landry E


Abstract

Purpose The purpose of this study was to see if there was an association between clinical signs and symptoms of residual neuromuscular blockade in patients with a Train-of-Four Ratio less than 0.9 (TOFr) in the post anesthesia care unit (PACU).

 

Background Residual neuromuscular blockade, as defined as a TOFr less than 0.9 measured by acceleromyography, is a common occurrence in the PACU. Most patients tolerate a small amount of muscle weakness very well. However, some patients may experience significant muscle weakness which can lead to airway obstruction, hypoxemia, prolonged PACU stay, and serious complications which may delay recovery.

 

Previous research by this team found a high incidence of residual paralysis (TOFr less than 0.9) in patients who experienced critical respiratory events, such as airway obstruction and hypoxemia. In another study they found that use of acceleromyography was associated with fewer symptoms of residual paresis during the first 60 minutes after surgery compared to standard qualitative measurement of the Train-of-Four with a peripheral nerve stimulator. Many subjects with a TOFr less than 0.9 reported symptoms of “feeling weak” or having “difficulty speaking.” In this study, the investigators presented a secondary analysis of these latter results to determine the incidence and severity of symptoms of muscle weakness segregated by Train-of-Four Ratio (TOFr less than 0.9 or a TOFr greater than 0.9).

 

Methodology This was a secondary analysis of data from a prospective, randomized, controlled trial of patients who where monitored intraoperatively with either acceleromyography or a conventional peripheral nerve stimulator. During the first 60 minutes in the PACU a standardized tool was used to assess 16 symptoms and 11 signs of residual paralysis. The investigators evaluated patients for residual neuromuscular paralysis (TOFr <0.9) on arrival to the PACU with an uncalibrated TOF-watch SX. They then stratified these patients into 1 of 2 groups for analysis based on a TOFr greater than 0.9 or TOFr less than 0.9. In the previous investigation of 155 patients, 14.5% (n = 11) of patients in the acceleromyography group had a TOFr <0.9 compared to 50% (n = 37) in the peripheral nerve stimulator group. In this secondary analysis, the 48 patients with a TOFr less than 0.9 constituted the Residual Paralysis group and the other 101 patients without residual paralysis (TOFr greater than 0.9) made up the Control group.

 

Patients were evaluated on arrival to the PACU and every 20 minutes for a total of 60 minutes. Data was collected on TOFr, and on the incidence of 16 subjective symptoms (presence or absence reported by patient) and 11 signs (presence or absence assessed by blinded investigator) of residual paralysis. Patients were also asked to rate the severity of the symptoms of residual muscle weakness using a 0-10 verbal numeric rating scale. Recovery was assessed with the Quality of Recovery-9 scoring system (QoR-9), with scores ranging from 0 (extremely poor QoR) to 18 (extremely high QoR). Statistical analysis was appropriate. A P < 0.01 was considered significant.

 

Result There were 48 in the Residual Paralysis group and 101 in the control group. No differences (P = NS) were found in:

  • baseline patient characteristics
  • anesthesia duration
  • fentanyl dose
  • rocuronium dose or number of redoses
  • time from neostigmine dose to extubation or PACU admission

In the Residual Paralysis group, 25% had received rocuronium redosing within the last 45 minutes of surgery compared to only 11% in the Control group (P = 0.003). The median TOFr on admission to the PACU was significantly lower in the Residual Paralysis group (0.75 vs. 1.01, P < 0.0001). In the Residual Paralysis group, 65% of patients had a TOF between 0.7 and 0.9. Also, 35% had a TOF < 0.7. No difference was found in PACU length of stay between the two groups (Residual Paralysis group = 81 ± 30 min. vs. Control group = 73 ± 40 min., P = NS).

 

The incidence of signs and symptoms of residual muscle weakness in the PACU were significantly higher in the Residual Paralysis group at every time point (P < 0.003; Figures 1 and 2). Likewise, patients in the Residual Paralysis group reported a higher severity of overall muscle weakness and number of symptoms (P < 0.0001; Table 1). At 60 minutes, 83% of patients in the Residual Paralysis group still had at least 1 symptom of muscle weakness compared to only 26% in the Control group (P < 0.0001). Upon admission to the PACU, the most common symptoms reported by patients in the Residual Paralysis group compared to the Control group included:

  • general weakness (91% vs. 45%, P < 0.0001)
  • difficulty with 5-sec eye opening (89% vs. 36%, P < 0.0001)
  • difficulty with 5-sec head lift (74% vs. 15%, P < 0.0001)
  • difficulty with tracking object with eyes (63% vs. 34%, P = 0.001)
  • blurry vision (63% vs. 34%, P <0.001)
  • inability to speak (61% vs. 25%, P < 0.0001)

 

At 60 minutes a significant number of patients were still experiencing symptoms of residual muscle weakness in the Residual Paralysis group, including:

  • general weakness (73% vs. 19%, P < 0.0001)
  • difficulty with 5-sec eye opening (29% vs. 9%, P < 0.0001)
  • difficulty with 5-sec head lift (13% vs. 3%, P < 0.003)
  • difficulty with tracking object with eyes (19% vs. 2%, P < 0.001)
  • blurry vision (23% vs. 2%, P = 0.001)
  • inability to speak (19% vs. 3%, P = 0.002).

 

Conclusion Patients who presented to the PACU with Residual Paralysis experienced a greater incidence and severity of symptoms of residual muscle weakness compared to those with in the Control group.

 

Figure 1. Symptoms of Muscle Weakness

Figure 1

 

Figure 2. Signs of Muscle Weakness

Figure 2

 

 

Table 1. Muscle Weakness: Control vs. Residual Paralysis Groups

 

Severity of Weakness Reported

Number of Symptoms

Control

Residual Paralysis

Control

Residual Paralysis

PACU admission

4 (0-9)

7 (3-10)

2 (0-11)

7 (3-16)

20 minutes

3 (0-8)

7 (2-10)

1 (0-13)

5 (1-13)

40 minutes

3 (0-8)

5.5 (2-10)

0 (0-12)

3 (0-11)

60 minutes

2 (0-8)

5 (0-10)

0 (0-11)

2 (0-12)

Note: Control = TOF TOF > 0.9. Residual Paralysis = TOF < 0.9.

Results presented as median (range). Overall weakness evaluated with a 0-10 verbal numeric rating scale. Total number of symptoms ranged from 0 to 16. All differences P < 0.0001 at every time point.

 

Comment

There are a lot of reasons why patients report feeling weak immediately after surgery. The residual effects of volatile anesthetics, opioids, and neuromuscular blocking agents all contribute to these symptoms. In this study the investigators evaluated patients’ self-report of symptoms of residual muscle weakness and confirmed that that a TOFr < 0.9 was associated with significantly greater patient complaints of symptoms of muscle weakness. These results also suggest these symptoms impair the quality of recovery of patients during the immediate postoperative period though the difference was pretty small.

 

The number of patients who received rocuronium within the last 45 minutes of the surgery probably contributed to the increased symptoms of muscle weakness in the Residual Paralysis group. It is sometimes difficult to avoid administration of a neuromuscular blocking agent within the last 45 minutes of surgery because surgeons may require neuromuscular blockade to facilitate closure and completion of the surgery. I think this finding highlights the importance of maintaining close communication with the surgeon, and if possible consider minimizing administration of neuromuscular blocking agents in the last 45 minutes of surgery.

 

I encourage anesthesia providers to use quantitative measures of neuromuscular blockade such as acceleromyography. These devices are much more sensitive and have been associated with decrease residual muscle weakness in the PACU compared to traditional qualitative measurement with a peripheral nerve stimulator. For example, residual neuromuscular blockade was 5.5 times more likely to occur in patients who have their TOF monitoring done with a peripheral nerve stimulator at the eye muscles compared to use of acceleromyography at the adductor pollicis (see Anesthesia Abstracts, Volume 6, Number 10, October 2012).1

 

When using an acceleromyograph it is important to calibrate it prior to use. This means you have to test it prior to administration of the loading dose of the neuromuscular blocking agent. If calibration is not done then the device tends to underestimate the degree of residual blockade. Thus it is possible that some of the patients in the control group may have had residual paresis and this contributed to the their symptoms. I don’t extubate patients until the TOFr is > 0.9, and if I forget to calibrate the device prior to induction, then I am extra vigilant because I know some patients may still experience residual weakness due to an underestimation of the degree of residual blockade. I encourage anesthesia providers to use acceleromyography devices whenever possible.

Dennis Spence, PhD, CRNA


1. Thilen SR, Hansen BE, Ramaiah R, Kent CD, Treggiari MM, Bhananker SM. Intraoperative neuromuscular monitoring site and residual paralysis. Anesthesiology 2012;117:964-72.


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 2013 Anesthesia Abstracts · Volume 7 Number 6, June 30, 2013




Pharmacology
Effect of preemptive and preventive acetaminophen on postoperative pain score: a randomized, double-blind trial of patients undergoing lower extremity surgery

J Clin Anesth. 2013;25:188-92

Khalili G, Janghorbani M, Saryazdi H, Emaminejad A


Abstract

Purpose The purpose of this study was to assess the efficacy of intravenous acetaminophen for managing postoperative pain following lower extremity orthopedic surgery. The study also compared preemptive versus preventive administration techniques.

 

Background Preemptive analgesia techniques are best described as the administration of an analgesic agent prior to a painful stimulus. The theory supporting this involves altering the processing of afferent pain input and the prevention of central sensitization. In contrast, preventive analgesia is best defined as averting central sensitization by blocking afferent pain signals caused by tissue trauma from the time of incision until final wound healing. Both techniques have been studied extensively but specific methods, terminology and even definitions vary. Acetaminophen’s mechanism of action is unknown. It is theorized to inhibit prostaglandin synthesis in the central nervous system and to stop pain impulses by a nociceptive blocking action in the periphery. There have been no previous clinical trials assessing the effectiveness of preemptive or preventive intravenous acetaminophen for managing pain following lower extremity orthopedic surgery procedures.

 

Methodology This study was carried out as a double-blind, randomized, placebo-controlled trial. ASA physical status I and II patients scheduled for lower extremity orthopedic surgery under spinal anesthesia were randomized to one of three treatment groups, each with 25 patients:

  • Placebo Group:  saline placebo 100ml IVPB 30 minutes before surgery & prior to skin closure
  • Preemptive Group:  preemptive IV acetaminophen 15 mg/kg in 100 ml IVPB 30 minutes before surgery & 100 ml saline placebo prior to skin closure
  • Preventative Group:  saline placebo 100 ml IVPB 30 minutes before surgery & IV acetaminophen 15mg/kg in 100 ml IV push prior to skin closure

 

A standardized premedication dose of IV diazepam was administered two hours prior to surgery and a 15 mg bupivacaine spinal anesthetic upon arrival to the operating room. Routine monitors were applied. Pain scores (verbal rating scale 0-10) were assessed 5 minutes prior to the spinal anesthetic and 6, 12, 18, and 24 hours after surgery. Post operatively, if the patients complained of pain, meperidine 0.05 mg/kg was administered and total consumption recorded for 24 hours.

 

The primary outcome measure included assessment of pain scores across all three groups post operatively. Secondary outcome measures included timing and dose of first meperidine administration. Additionally, sedation scores were recorded as well as any adverse reactions during the 24 hour post- operative period.

 

Result There were no statistically significant demographic differences between groups including the duration of surgery (range 71- 79 minutes). The following findings were significant:

  • pain scores were lower in the preemptive and preventive groups 6 hour postoperativly (p< 0.001)
  • total dose of meperidine was 19 mg greater in the control group compared to preemptive group (p < 0.003)
  • time to first request for analgesic was longer in both preemptive and preventive groups compared to control (0.008)

The most common side effects or adverse events observed for all three groups were nausea and vomiting.

 

Conclusion Preemptive and preventive administration of intravenous acetaminophen appeared to be a beneficial method to manage postoperative pain in patients having lower extremity orthopedic surgery under spinal anesthesia. Additionally, the administration of intravenous acetaminophen reduced total meperidine requirements in this group of patients during the first 24 hours post operatively.

 

Comment

The most beneficial factoid I gained from this research was that the concept of multimodal methods of postoperative pain management is continuing to gain ground. We have relied on traditional methods of treating postoperative pain for too long. Narcotics for moderate pain and more narcotics for moderate to severe pain has outlived its utility. The plethora of adverse effects related to narcotic use simply mandate innovative and different approaches for patient quality, safety, and satisfaction. This study unfortunately continued to show that postoperative nausea and vomiting was the most common side effect experienced. Multi-modal therapy is intended to minimize side effects of high dose of single agents like narcotics. The explanation for this could be related to the he concerns I have involving the methodology of this study and the limited information regarding confounding variables that may have influenced the results. For example, the same dose of bupivacaine was administered to all patients in the study. Was this dose and the hydration status for some a contributing factor to PONV? Other questions exist related to possible explanations for PONV. Was it induced by meperidine? Overall, though, I do applaud the researchers for investigating non-traditional approaches for postoperative pain management as I believe studies like this will multi-modal acute pain relief.

Mary A Golinski, PhD, CRNA


Central Sensitization: A state in which neurons become activated by noxious stimuli and are sensitized to the stimuli. They become hyper-responsive to all subsequent stimuli.


© Copyright 2013 Anesthesia Abstracts · Volume 7 Number 6, June 30, 2013