ISSN NUMBER: 1938-7172
Issue 8.4

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

Assistant Editor
Jessica Floyd, BS

A Publication of Lifelong Learning, LLC © Copyright 2014

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

Table of Contents

  Editorial: Residual neuromuscular block in the PACU: can you see it now?

Incidence, predictors, and outcome of difficult mask ventilation combined with difficult laryngoscopy

Neuraxial anesthesia decreases postoperative systemic infection risk compared with general anesthesia in knee arthroplasty

Effect of using a safety checklist on patient complications after surgery: A systematic review and meta-analysis

The Implementation of Quantitative Electromyographic Neuromuscular Monitoring in an Academic Anesthesia Department

A Randomized, Double-Blind Comparison of Licorice Versus Sugar-Water Gargle for Prevention of Postoperative Sore Throat and Postextubation Coughing

The effect of transversus abdominis plane block or local anaesthetic infiltration in inguinal hernia repair

Editorial: Residual neuromuscular block in the PACU: can you see it now?

This issue of Anesthesia Abstracts includes a report on residual neuromuscular blockade in the PACU that is both highly informative and unusually forthright. The report could be the poster child for Evidence Based Practice. For the last 7 years we’ve been seeing reports about residual neuromuscular blockade in PACU patients. At first, they were hard to believe; after all, we were using intermediate duration nondepolarizing relaxants and reversing them when necessary. We monitored block, or recovery from block, with a peripheral nerve stimulator or “appropriate” clinical tests. We followed the rules – so patients must be reversed when they got to the PACU. And, besides, they rarely looked weak in the PACU. But despite our belief, there is scientific evidence that almost 1% of PACU patients experience a Critical Respiratory Event (CRE) after general anesthesia.1 These CREs include severe hypoxemia and upper airway obstruction and are usually not linked to residual neuromuscular block at the time they occurred. Some patients can remain up to 50% paralyzed when they arrive in the PACU and look just fine. While many of them recover without incident, we now know that they are at much greater risk for Critical Respiratory Events such as hypoxia.


Part of the problem is history. Many of us were educated at a time when a sustained tetanus or head lift was the best available test of neuromuscular function. We learned them. We used them. We followed the standard of care and didn’t detect the bad outcomes that sometimes resulted from residual block, so we thought the standard of care was working. Now, however, we have more accurate and more reliable methods to detect residual neuromuscular block. Clinical tests and peripheral nerve stimulators could detect residual block down to 50% or 33%, but newer quantitative block monitors can detect residual block down to 10% or 5%.



Figure 1: Remaining Neuromuscular Block Following Common Tests

Figure 1



Part of the problem is culture. The authors of this report ran hard up against culture. They discovered that some anesthesia providers in their department had a “poor understanding” (their words) of muscle relaxant pharmacology, clinical signs of recovery from neuromuscular blockade, and the limitations of reversal drugs. All anesthesia providers were given scientific evidence that residual neuromuscular block was not uncommonly present in PACU patients and placed patients at risk for Critical Respiratory Events. Despite this attempt to educate, even highly experienced anesthesia providers continued to believe that no change in their practice or assessment of residual block was needed. Fourteen months into departmental efforts to eliminate residual block, anesthesia providers were still rejecting the quantitative neuromuscular block monitors and patient were still arriving in the PACU with residual block. If it were not for a bad patient outcome, clearly due to residual block despite neostigmine administration and usual tests for recovery from block, I wonder if this cultural log jam would have ever been broken.


These authors openly said they were “concerned” about the use and monitoring of neuromuscular blocking drugs in their department. They looked for residual neuromuscular block in their PACU and found it ... too much of it. We have good evidence of a problem and solutions to the problem are known to us. Are you brave enough to look at neuromuscular blockade practices, monitoring and assessment of neuromuscular block, and residual paralysis in the PACU in your department? Or, will history and culture prevent you from facing the problem? Will you practice based upon evidence or belief?


Michael A. Fiedler, PhD, CRNA

1. Murphy GS, Szokol JW, Marymont JH, Greenberg SB, Avram MJ, Vender JS. Residual neuromuscular blockade and critical respiratory events in the postanesthesia care unit. Anesth Analg 2008;107:130–7.

© Copyright 2014 Anesthesia Abstracts · Volume 8 Number 4, April 30, 2014

Incidence, predictors, and outcome of difficult mask ventilation combined with difficult laryngoscopy

Anesthesiology 2013;119:1360-9

Kheterpal S, Healy D, Aziz MF, Shanks AM, Freundlich RE, Linton F, Martin LD, Linton J, Epps JL, Fernandez-Bustamante A, Jameson LC, Tremper T, Tremper KK, Multicenter Perioperative Outcomes Group


Purpose The purpose of this study was to determine the incidence and identify predictors of difficult mask ventilation combined with difficult laryngoscopy from the Multicenter Perioperative Outcomes Group.


Background Over 30 million procedures requiring anesthesia are performed annually in the USA. The Centers for Medicare and Medicaid and the Joint Commission both require preprocedural evaluation for potential difficult airway in patients requiring anesthesia or sedation. Current airway evaluation criteria mainly focus on the risk of difficult intubation rather than encompassing both difficult ventilation and intubation. Recent research has demonstrated that risk factors for difficult mask ventilation may differ from those for difficult intubation. Thus, further research is needed to identify risk factors for a difficult airway, both difficult mask ventilation and intubation, which can help inform guidelines for airway management.


Methodology The Multicenter Perioperative Outcomes Group collects prospective data from electronic medical records at four academic medical centers: University of Michigan, University of Colorado, Oregon Health and Science University, and University of Tennessee. For this study, investigators examined data on all adult patients undergoing surgery under general anesthesia from 2006 to 2012. Cases which required rapid sequence induction without mask ventilation, planned awake or asleep fiberoptic intubation, awake tracheostomy, primary use of a supraglottic airway, preexisting endotracheal tube or invasive airway, or cases performed without general anesthesia were excluded. Variables included in the analysis which were proposed to be predictors of difficult airway included the following:

  • Age ≥ 46 years
  • BMI ≥ 30 m/Kg2
  • Thyromental distance <3 cm
  • Mouth opening <3 cm
  • Mallampati class 3 or 4
  • Diagnosed or treated sleep apnea
  • Snoring
  • Presence of teeth
  • Limited or severely limited jaw protrusion
  • Thick neck
  • Neck mass or radiation


Difficult mask ventilation and difficult laryngoscopy were evaluated by the anesthesia provider using a 4-point scale and entered into the electronic anesthesia record. Grade 3 was defined as mask ventilation that was inadequate to maintain oxygenation, unstable mask ventilation, or mask ventilation requiring two providers. Grade 4 mask ventilation was defined as impossible mask ventilation noted by absence of end-tidal carbon dioxide and lack of chest wall movement during positive-pressure ventilation attempts despite airway adjuvants and additional personnel. The use of neuromuscular blockade did not affect the designation of mask ventilation difficulty. Difficult intubation was defined as a Grade 3 or 4 Cormack-Lehane laryngoscopy view or four or more intubation attempts. Laryngoscopy view included both video and direct laryngoscopy. The use of neuromuscular block during induction of anesthesia was recorded.


The primary outcomes were predictors of a difficult airway, defined as Difficult Mask Ventilation combined with Difficult Laryngoscopy. Secondary outcomes included the initial rescue technique and the ultimate airway management technique. Logistic regression was used to identify predictors of difficult airway. Investigators then developed a difficult airway prediction score and a risk index classification system based upon identified predictors. A P < 0.05 was considered significant.


Result There were 176,679 cases that met inclusion criteria. Of these patients, 2.5% were Difficult Mask Ventilation and 4.4% were Difficult Laryngoscopy. The overall incidence of a difficult airway – Difficult Mask Ventilation + Difficult Laryngoscopy – was 0.4% or 1 in 250 patients (n = 698 cases). Significant predictors of a difficult airway and their odds ratios were:

  • Mallampati class 3 or 4 (OR = 3.2)
  • Neck radiation changes or neck mass (OR = 2.6)
  • Male sex (OR = 2.5)
  • Thyromental distance <3 cm (OR = 2.4)
  • Presence of teeth (OR = 2.4)
  • Body mass index ≥30 kg/m2 (OR = 2.2)
  • Age ≥46 (OR = 1.9)
  • Presence of beard (OR = 1.6)
  • Sleep apnea (OR = 1.6)
  • Thick neck (OR = 1.5)
  • Limited neck extension (OR = 1.5)
  • Limited jaw protrusion (OR = 1.5)

Patients with 7-11 risk factors were 18.4 times more likely to have a difficult airway when compared to those with 0-3 risk factors.


Table 1. Difficult Airway Techniques

Initial Airway Management Technique n = 698

Intubation without

supraglottic airway

91% (n = 635)

Ventilated using

supraglottic airway

7.6% (n = 53)

Awoken w/o supraglottic airway placement

1.3% (n = 9)

Surgical Airway

0.1% (n = 1)

Final Airway Management

Direct Laryngoscopy

n = 461


62% with bougie or

introducer (n = 284)


Video Laryngoscopy

n = 163


2% with flexible introducer

(n = 3)


Fiberoptic Intubation

n = 35

63% asleep without

supraglottic airway


29% asleep via

supraglottic airway


9% awake


Blind Intubation via

Supraglottic Airway n = 6




Intubated with Lighted Stylet n = 7




Alternative Anesthetic

Technique n = 17


88% supraglottic airway or

facemask (n=15)

12% regional

anesthesia (n=2)

Case Cancelled n=9




Notes: Some rows do not add up to 100% due to rounding.


A risk index classification system was developed by the investigators to help stratify patients quickly, with higher classes representing the greatest risk of being both difficult to ventilate and intubate (figure 1). The Odds of a difficult airway – difficult mask ventilation + intubation – were significantly greater in classes II-V compared to class I. 


Figure 1. Difficult Airway Risk Index Classification System

Figure 1

Note. Odds of a difficult airway (difficult mask ventilation + intubation) were significantly greater in classes II-V when compared to class I. For example, patients with 7-11 risk factors were 18.4 times more likely to have a difficult airway when compared to those with 0-3 risk factors. OR = odds ratio.


A majority of the patients received neuromuscular blockers during induction of anesthesia (96%). Investigators found patients who received neuromuscular blockers had slightly lower rates of difficult mask ventilation compared to those who did not (2.6% vs. 3.6%, P < 0.01). In 2.7% of cases of difficult airway, the provider documented improved facemask ventilation after onset of neuromuscular blockade.


Conclusion The occurrence of the worst-case scenario of difficult face mask ventilation plus difficult laryngoscopy was an infrequent, but not rare event. Most of these patients could be intubated via direct or video laryngoscopy. The difficult airway risk index classification system developed in this study may aid in the development of clinical guidelines and help identify patients at risk for a difficult airway.



The results of this study are important because they help define and identify what constitutes a “difficult airway.” I liked how they included both difficult ventilation and intubation in their definition because it really represents the worst-case scenario. Fortunately, the incidence of Difficult Mask Ventilation combined with Difficult Laryngoscopy is extremely low, about 0.4%.


The majority of the difficult airways were successfully intubated with direct laryngoscopy with over half of them requiring a bougie. The next most frequent rescue device which enabled successful intubation was video laryngoscopy. Video laryngoscopy is rapidly becoming the “go-to” airway technique when faced with a known or difficult airway. However, I think it is important that we continue to maintain our proficiency with direct laryngoscopy with or without a bougie because there may be times when a video laryngoscope is not available.


So how can we apply these results to practice? I think if you are faced with a patient with 4 or more risk factors you need to be especially prepared for a difficult airway. Always be prepared, have an extra pair of experienced hands available, and call for help early! Consider use of a supraglottic airway as a rescue device when you cannot ventilate.


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 2014 Anesthesia Abstracts · Volume 8 Number 4, April 30, 2014

Neuraxial anesthesia decreases postoperative systemic infection risk compared with general anesthesia in knee arthroplasty

Anesth Analg 2013;117,1010-15

Liu J, Ma C, Elkassabany N, Fleisher L, Neuman M


Purpose The purpose of this study was to test the theory that neuraxial anesthesia decreases postoperative infections and related complications compared to those who had general anesthesia for knee arthroplasty surgery.


Background In the USA, total knee arthroplasty is one of the most frequently performed surgical procedures, estimated at >500,000 annually. The typical demographic profile of knee arthroplasty recipients includes numerous comorbidities. Depending on the health history and other considerations, neuraxial and/or general anesthesia is most frequently used. Neuraxial anesthesia is thought to improve surgical outcomes by reducing the physiologic surgical stress response. It blocks noxious afferent inputs and minimizes metabolic disturbances. Surgical trauma combined with general anesthesia, on the other hand, is linked to a range of metabolic and endocrine disturbances and is a source of immune suppression. Very little evidence-based data exists supporting the association of anesthesia type and postoperative infectious complications. This study aimed to determine whether or not neuraxial anesthesia decreased postoperative infectious complications post total knee arthroplasty compared to general anesthesia.


Methodology This study was carried out as a retrospective analysis of an existing database. Data was acquired from the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database covering 2005-2010. The NSQIP database houses a plethora of information including, but not limited to, surgical outcomes from hundreds of hospitals across the USA, patient-specific demographics, preoperative risk factors, intraoperative variables, and postoperative events for 30 days. Data in the NSQIP database used for analysis included:


   1. CPT code for either partial or total knee replacement as the principle procedure

   2. Primary anesthetic technique of general anesthesia, epidural anesthesia, or spinal anesthesia

Exclusion Criteria included:

     1. bilateral knee replacement

    2. anesthesia type other than general, spinal, or epidural

    3. preexisting infections    

         a. infectious conditions as documented in the data base i.e., pneumonia, SIRS, sepsis, septic shock, contaminated wounds

    4. ventilator dependency

The primary outcomes variables assessed included the following post-surgery infectious complications within 30 days postoperatively:

  • superficial wound infection
  • deep incisional wound infections
  • organ space surgical site infections
  • surgical wound disruption
  • pneumonia
  • urinary tract infection
  • sepsis
  • septic shock
  • any systemic infectious complication

The researchers compared outcomes for 30 days postoperatively for those who had knee arthroplasty with neuraxial anesthesia and those who had knee arthroplasty with general anesthesia. Appropriate statistical analysis was performed to validate the findings.


Result A total of 16,555 medical records in the database met the inclusion criteria for analysis. Of those, 9,167 patients received general anesthesia, 6,875 received spinal anesthesia, and 513 received epidural anesthesia for the primary procedure. All told, n = 7,388 patients received either spinal or epidural anesthesia. Several significant differences were found between groups in demographics and in the prevalence of comorbidities.


       1. The neuraxial group:

            a. Was Older 

            b. Had lower BMIs

            c. Was partially dependent or completely dependent in regards activities of daily living

            d. Was more frequently diagnosed with hypertension requiring pharmacologic management

        2. The GA group had more:

             a. Preoperative renal disease

             b. Coagulopathies

             c. Prior surgeries within 30 days 

There was no difference in overall mortality between the two groups. The neuraxial group had a statistically significantly lower incidences of post-surgical pneumonia (odds ratio = 0.51, P = 0.035) and composite systemic infections (odds ratio = 0.77, P = 0.006). Using logistic regression analysis with risk adjustment techniques considering comorbidities, the neuraxial group was associated with a lower odds of pneumonia and any systemic infection compared to the GA group.


Conclusion Information analyzed from the NSQIP database demonstrated that those who had neuraxial anesthesia for total knee arthroplasty had a 49% reduction in pneumonia risk and a 23% reduction in the risk of systemic infectious complications compared to those who had general anesthesia. The reduction in pneumonia risk could be related to the fact that there were less systemic immune disturbances in the neuraxial group as well as the absence of airway instrumentation, which can lead to increased risk of airway trauma and atelectasis formation.



According to the American College of Surgeons NSQIP website, each year that a hospital uses information from their quality improvement program, it has the opportunity to massively improve patient care outcomes. The statistics are astounding; preventing 250-500 surgery/anesthesia related complications, the ability to save 12-36 lives, and an overall reduction in healthcare costs exceeding millions of dollars is almost hard to imagine. What was happening before we had this data? Irrespective of the answer, the good news is related to the explosion in healthcare informatics and the utilization of this type data. Both the contribution of and resulting analysis of quality improvement programs is beyond beneficial to the recipients of our care, the institutions, and us as CRNAs. Becoming intimately involved in the quality and outcomes improvement processes is critical. We have such a key role within the surgical team; our ability to consistently use techniques that are considered best practice is truly non-negotiable. This study was a fine example of using an existing database with an overall aim to discover which type of anesthetic, in certain patient specific scenarios, had the potential to prevent postoperative complications. It was not highly complex or extremely technical. However, it is grounded in rigor. I encourage all anesthetists to find out how you can contribute in meaningful QI endeavors.


Mary A Golinski, PhD, CRNA

National Surgical Quality Improvement Program (NSQIP) database

© Copyright 2014 Anesthesia Abstracts · Volume 8 Number 4, April 30, 2014

Effect of using a safety checklist on patient complications after surgery: A systematic review and meta-analysis

Anesthesiology 2014;120:1380-9

Gillespie BM, Chaboyer W, Thalib L, John M, Fairweather N, Slater K


Purpose The purpose of this study was to conduct a systematic review and meta-analysis of studies that compared complications before and after implementation of a surgical safety checklist.


Background The use of surgical checklists such as the World Health Organization’s (WHO) 19-item checklist, which has been implemented in 122 countries around the world, has been found to reduce morbidity and mortality. Checklists are designed to enhance the culture of safety in the operating room by improving communication and team work. A recent systematic review reported potential safety hazards were more likely to be identified when checklists were used. However, the results of many studies in this review reflected local or regional practice patterns, rather than worldwide patterns. The authors of this study sought to confirm the positive effects surgical safety checklists might have on reducing complications.


Methodology This was a systematic review of published studies that evaluated the effects of surgical safety checklists on complications after surgery. The authors searched MEDLINE, CINAHL, Proquest, and the Cochrane Library to identify articles using the keywords:

randomized controlled trial

  • checklist
  • mortality
  • surgery
  • morbidity
  • intervention
  • complication

Reference lists of retrieved articles were hand searched for further studies. Studies were included if they were randomized controlled trials, prospective or retrospective cohort studies, quasi-experimental and interrupted time series studies. Populations included patients undergoing elective or emergency surgical procedures; comparison of a surgical checklist with a control group where a surgical checklist was not used; and postoperative complications; any complication, surgical site infection, mortality, pneumonia, estimated blood loss > 500 mL, and unplanned return to the operating room. Only articles written in English were included. Study quality was evaluated with a modified version of the Methodological Index for Nonrandomized Trials which produces scores ranged from 0-20. Results were pooled and meta-analysis techniques were used to analyze the results. The number needed to treat was reported, which indicates the number of patients needed to be treated to reduce the complication in one patient.


Result There were seven studies with a total of 37,339 patients included in the meta-analysis. All articles were published between 2009 and 2012. All studies were observational, and most used a prospective cohort design using historical controls. All but one study used the WHO Surgical Safety Checklist. The other study used the Association of Perioperative Registered Nurses Comprehensive Surgical Checklist, which includes items from the WHO checklist and Joint Commission Universal Protocol. The mean quality score of the studies was 12.6 indicating moderate study quality.


Use of surgical checklists in surgery was associated with a reduction in complications, surgical site infections, and blood loss (P < 0.05). No significant reductions were found in rates of pneumonia, mortality, or unplanned return to the operating room (P > 0.05). Results are summarized in table 1 and figure 1.



Table 1. Outcomes vs. Checklist Use



No Checklist


P value

# patients

Any complication












Surgical Site Infection












Blood Loss > 500 mL






Unplanned return to OR






NOTES: NNT = Number Needed to Treat


Figure 1. Comparison of Outcomes 

Figure 1

NOTES: SSI = Surgical Site Infection. EBL = Estimated Blood Loss.


Conclusion Use of surgical checklists were associated with fewer postoperative complications. Checklists protect patients and minimize risks by improving team cohesion and coordination.



Several years ago I was in Djibouti, Africa and had the opportunity to provide some humanitarian anesthesia support at the local hospital. I recall one week when I was there the general surgeon I was working with asked me about the WHO Surgical Checklist. He had recently attended a conference in Europe in which they talked about implementation of the checklist. The surgeon asked if we would help train his staff on the checklist. By the time we returned to the United States several months later his surgical team was using the checklist in almost every case, and he felt it was helping reduce complications. This just goes to show how much impact the WHO safety checklist has had globally.


Therefore, the results of this study are not surprising. There is so much we have to remember these days that having a checklist to remind us of critical steps is very important. At my facility we are also undergoing training on TeamSTEPPS, which I believe when combined with use of surgical checklists, can really help improve teamwork, communication, and reduce complications. It will allow us to move towards being a high reliability healthcare organization. To learn more about high reliability concepts I encourage readers to check out the book Managing the Unexpected: Resilient Performance in an Age of Uncertainty by Weick and Sutcliffe.


At our institution prior to every case we do the checklist and everyone introduces themselves. The part I think is really important is that every member of the team, from the lowest level, is empowered and encouraged to speak up if they see something not right. When going through the checklist every member of the team must be engaged, and should not treat the “timeout” as just another check in the box. The critical next step is to determine if the successes with the use of surgical checklists can be sustained.


Dennis Spence, PhD, CRNA

WHO Checklist


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 2014 Anesthesia Abstracts · Volume 8 Number 4, April 30, 2014

Patient Safety
The Implementation of Quantitative Electromyographic Neuromuscular Monitoring in an Academic Anesthesia Department

Anesth Analg 2014;119:32331

Todd MM, Hindman BJ, King BJ


Purpose This report of a department-wide quality improvement project described the implementation of quantitative neuromuscular blockade monitoring during every case where nondepolarizing muscle relaxants were used. It included assessing the incidence of residual block in PACU patients before and after implementation of quantitative monitoring.


Background Residual neuromuscular block results in clinical weakness, dysfunction of respiratory and pharyngeal muscles, and a higher rate of respiratory complications in PACU patients. Residual paralysis is much more common than we once believed, occurring in up to 40% of PACU patients in some studies. Quantitative assessment of neuromuscular function during use of nondepolarizing relaxants and to verify reversal of nondepolarizing relaxants is more accurate than traditional nerve stimulators and clinical tests such as sustained head lift. Few clinicians, however, regularly use quantitative assessment of paralysis. Some clinicians attempt to visually or tactilely assess fade in the Train-of-4, but studies show this cannot be accomplished reliably until 1 twitch is absent, about 70% paralysis.


Methodology This was a quality improvement project begun after two senior members of the anesthesia group became concerned about how muscle relaxants were being used and monitored in their department. (IRB approval was secured for publication of this report.) Patients were being taken to the PACU without administration of a muscle relaxant antagonist based upon the time since the last dose of muscle relaxant. Neostigmine was administered as a reversal agent and then the patient extubated almost immediately without an assessment of recovery from neuromuscular blockade. Some clinicians deemed patients ready for extubation when they were “breathing and had 4 twitches in a Train-of-4.” Departmental records of patient morbidity and mortality revealed 20 patients reintubated in the PACU who definitely or possibly had residual neuromuscular block, though residual block was frequently not recognized at the time of reintubaiton. Prior to the start of this project neuromuscular block was monitored with a peripheral nerve stimulator or clinical signs.


At the start of the project all 30 ORs were equipped with quantitative neuromuscular blockade monitors that were integrated into the patient monitoring system and recorded on the anesthesia information management system (computerized anesthesia record). The monitors displayed a bar graph of twitch amplitude and the Train-of-4 ratio. At the same time, a department-wide education program was implemented which included how to assess neuromuscular block with the new quantitative blockade monitors and the incidence and risks of residual paralysis.


Result During the first six months of the project little progress was made in reducing the incidence of residual paralysis in PACU patients or clinician use of quantitative neuromuscular block monitors. Many clinicians did not believe the new block monitors were valuable or even accurate. Then, seven months into the quality improvement project, a PACU patient needed an emergency reintubation due to profound paralysis despite having had neostigmine and assessment with a qualitative peripheral nerve stimulator prior to extubation. This case was discussed in a departmental M&M meeting, and anesthesia providers recognized it was a failure of neuromuscular blockade monitoring. Following this event, efforts to educate the anesthesia providers and to use quantitative neuromuscular block monitoring whenever a nondepolarizing relaxant was used were increased. From this point on, patients arriving in the PACU were sampled for residual neuromuscular block.


The percentage of patients who received neostigmine for antagonism of neuromuscular block and quantitive neuromuscular blockade data were compared between August 2011 (Time 1) and December 2012 (Time 2). From the start to the end of this 16 month period almost all parameters relevant to residual paralysis in the PACU improved. The median Train-of-4 ratio increased from 0.94 to 0.98. While this improvement is small, note in Table 1 that the interquartile range of Train-of-4 ratios improved noticeably and the lowest Train-of-4 ratio increased from nonexistent to 0.53. The percentage of patients with a Train-of-4 ratio ≤ 0.8 was reduced by over two-thirds. Use of neostigmine to antagonize residual block increased by almost one-third and use of quantitative neuromuscular monitoring increased to 95% of patients whom had been given a nondepolarizing relaxant. No further PACU reintubations were needed between the end of the quality improvement project and submission of the manuscript for publication. No neuromuscular monitoring was used in 9% of patients, but neuromuscular monitoring (qualitative or quantitative) was associated with a significantly improved Train-of-4 ratio upon arrival in the PACU (0.95 vs. 0.87, P=0.0028). Also, use of a quantitative Train-of-4 monitor to assess reversal after neostigmine administration was associated with a 10% increase in the Train-of-4 ratio (P=0.0001).



Table 1: PACU Neuromuscular Blockade Data


Time 1*

Time 2*

P Value

TOF Ratio
median, (IQR)

0.94 (0.87-0.99)

0.98 (0.94-1.00)


Lowest TOF Ratio




TOF Ratio ≤0.8
number, (%)

16 (17%)

5 (5%)


% Patients Reversed




% Quantitative Monitoring




Notes: *Time 1 n=96. Time 2 n=101. TOF = Train-of-4. IQR = Interquartile Range.



Conclusion The use of quantitative neuromuscular blockade monitoring and extensive education of anesthesia providers resulted in a significant reduction in the number of patients who arrived in the PACU with residual neuromuscular block. The process, however, was difficult and required not only additional equipment for each OR but also a change in the culture and beliefs of the individual anesthesia providers.



This abstract and comment is accompanied by an editorial at the beginning of this issue.


Residual neuromuscular blockade is defined as a Train-of-4 ratio less than 0.9 (less than 10% residual block). Residual block is much more common then we used to think. It places patients at risk for Critical Respiratory Events even when they don’t look weak clinically, even if we administered neostigmine, and even if we checked them with a nerve stimulator. (And, it turns out, too many of us don’t antagonize or assess with a nerve stimulator too much of the time.) If you don’t believe this is true, it is time for soul searching and literature searching. You might start with the following abstracts and comments in previous issues of Anesthesia Abstracts.

  • Residual neuromuscular blockade and critical respiratory events in the postanesthesia care unit from Anesthesia Abstracts December 2008 (source Anesth Analg 2008;107:130-137).
  • Intraoperative acceleromyography monitoring reduces symptoms of muscle weakness and improves quality of recovery in the early postoperative period from Anesthesia Abstracts July 2012 (source Anesthesiology 2011;115:946-954).
  • Intraoperative neuromuscular monitoring site and residual paralysis from Anesthesia Abstracts October 2012 (source Anesthesiology 2012;117:964-72).
  • Postoperative residual neuromuscular blockade is associated with impaired clinical recovery from Anesthesia Abstracts March 2013 (source Anesth Analg 2013;117:133-141).
  • An ipsilateral comparison of acceleromyography and electromyography during recovery from nondepolarizing neuromuscular block under general anesthesia in humans from Anesthesia Abstracts March 2013 (source Anesth Analg 2013;117:373-379).

We certainly wouldn’t take patients to the PACU extubated and partially paralyzed on purpose, so there is no way to design a “controlled trial” study in the typical manner. So, this group approached the problem from a quality improvement perspective. First, they looked at residual paralysis in the PACU under the status quo of anesthesia delivery. Then they equipped every OR with a quantitative neuromuscular block monitor and educated all anesthesia providers about the need for its use and how to use it. Then they looked at residual paralysis in the PACU after anesthesia providers were consistently using quantitative neuromuscular block monitoring.


This is where we have to put our thinking caps on because when you look at the average improvement it doesn’t necessarily look like much. The average Train-of-4 ratio increased from 0.90 to 0.95, only a slight improvement and both at or above our definition of no residual block. But we must remember that most patients (over 50%) arrive in the PACU without residual paralysis. Many of those with some residual paralysis don’t have any complications just by sheer luck. Residual paralysis is not a rare event, but the Critical Respiratory Events they cause seem to be rare in part because we’ve previously not connected them with residual paralysis. What this report showed me is that routine use of a quantitative neuromuscular blockade monitor significantly reduces the risk of Critical Respiratory Events caused by previously undetected residual paralysis. The range of Train-of-4 ratios was narrowed so that almost no one had a Train-of-4 less than 0.94. The most severe residual paralysis was completely eliminated (lowest Train-of-4 was initially 0 and improved to 0.53). The percentage of patients with a Train-of-4 ratio of 0.8 or less went from 17% down to only 5%. And, while initially 23% of patients who had received a nondepolarizing muscle relaxant got no neostigmine at all, by the end of the project everyone was reversed.


For years I withheld reversal if patients had a sustained tetanus or a sustained head lift. I reasoned that they were already antagonized and they'd met the test I’d given them to prove the reversal had worked. I was dogged in teaching our graduate students to use the peripheral nerve stimulator during the case and after reversal. This and other studies have convinced me that what I believed was wrong. Everyone who is going to be extubated should be reversed (unless there is a strong reason to believe the risk of doing so outweighs the benefit). Peripheral nerve stimulators and clinical tests of neuromuscular recovery are clearly inadequate to prevent residual paralysis. We have the evidence needed to show us the risk residual paralysis poses to patients and the evidence to teach us how to prevent residual paralysis in the PACU. Now we must base our practice on that evidence and change our clinical habits.

Michael A. Fiedler, PhD, CRNA

Interquartile Range (IQR) is the middle 50% of a distribution of data between the 1st quartile and the 3rd quartile. The other 50% of the distribution of data lies below (25%) and above(25%) the IQR.

© Copyright 2014 Anesthesia Abstracts · Volume 8 Number 4, April 30, 2014

A Randomized, Double-Blind Comparison of Licorice Versus Sugar-Water Gargle for Prevention of Postoperative Sore Throat and Postextubation Coughing

Anesth Analg 2013;117:614-21

Ruetzler K, Fleck M, Nabecker S, Pinter K, Landskron G, Lassnigg A, You J, Sessler DI.


Purpose The purpose of this study was to test the hypothesis that gargling with a licorice-based solution immediately preceding intubation with a double-lumen tube prevented post-extubation sore throat and coughing better than a placebo sugar-water solution.


Background Numerous pharmacologic and nonpharmacologic approaches have been used in efforts to prevent sore throat following extubation. Unfortunately, successful and dependable prevention of postoperative sore throat has been elusive. While sore throats can and do occur following extubation from all types of endotracheal tubes, the size of the double-lumen tube and need to manipulate it for correct placement often results in a high incidence of postoperative sore throat. A very small clinical trial (n = 40) conducted more than a decade ago revealed that gargling with licorice significantly reduced the risk of post-extubation sore throat. Several active ingredients have been isolated from licorice. One of these ingredients, glycyrrhizin, has anti-inflammatory properties due to its inhibition of cyclooxygenase. It also inhibits prostaglandin formation and prevents platelet aggregation. Other ingredients, such as liquilitin and liquiritigenin, are known to have antitussive properties. Another, glabridin, has antioxidant and ulcer-healing properties which may promote tracheal and laryngeal healing after tissue trauma. The authors of this study set forth to assess whether these active ingredients would prevent sore throat after extubation from a double-lumen tube.


Methodology This was a randomized, double-blind, clinical trial. A total of 236 ASA I-III adult patients 18 years to 90 years old having surgery that necessitated the placement of a double-lumen tube were randomized into 2 groups. Immediately prior to anesthetic induction, each group gargled with the following solution:

  • Group I - Licorice 0.5g (Extractum Liquiritiae Fluidum)
  • Group II - Sugar 5g (placebo)

Subjects were instructed to gargle for at least 1 minute while sitting, without swallowing any of the solution. Within 5 minutes after gargling, general anesthesia was induced using a standardized regime. A non-depolarizing muscle relaxant was used for all participants, and each patient was intubated with an unlubricated double-lumen endotracheal tube following complete neuromuscular blockade; 37-cm L for females and 39-cm L for males. Inflation of the endotracheal tube cuff was to 20 mm Hg at insertion and maintained at 20 mm Hg after position changes and throughout the anesthetic. Upon conclusion of the surgery, intercostal nerve blocks were administered with ropivacaine 0.1%. Patients also received IV Paracetamol (acetaminophen) 1,000 mg and deep extubation followed. If additional postoperative analgesics were necessary, piritramid 3 mg IV was given as needed. (Piritramid is a synthetic opioid used in Europe and similar to morphine.)


Outcome measures included an assessment of: 

  • sore throat and pain with swallowing 30 minutes after PACU arrival
  • sore throat 1.5 hours after PACU arrival
  • sore throat 4 hours post extubation
  • sore throat on postoperative day one (morning)
  • post-extubation coughing immediately following extubation,  and at 0.5 and 1.5 hours after PACU admission, 4 hours after extubation, and on postoperative day one morning

Additionally, patients were queried as to whether or not they experienced any adverse effects from the gargle.


Results Analysis was performed on 117 patients in the licorice group and 116 in the sugar-water group. Demographic profiles between groups were similar. The following outcome variables were all statistically significant (figure 1):


    1. Sore throat 30 minutes after PACU arrival:

        a. Licorice group: 22/117 

        b. Sugar water: 42/116

    2. Pain with swallowing 30 minutes after PACU arrival:

        a. Licorice group: 22/117

        b. Sugar water: 43/116

    3. Sore throat 1.5 hours after PACU arrival:

        a. Licorice group: 12/117

        b. Sugar water: 41/116

    4. Sore throat 4 hours after PACU arrival:

        a. Licorice group: 24/117

        b. Sugar water: 52/116

    5. Sore throat on POD #1, morning:

        a. Licorice group: 24/117

        b. Sugar water: 46/116


Figure 1: Post-Extubation Pain in Licorice vs. Sugar Water Gargle Groups

Figure 1

Notes: Licorice group n=117, placebo group n=116.



Coughing immediately following extubation was significantly less frequent in the licorice group. However, when measured independently at 30 minutes, 1.5 hours, and 4 hours following extubation, the reduction in coughing was not statistically significant. The same holds true for the severity of coughing at the same time intervals. Overall, the intensity of coughing was significantly lower in the licorice group. However, when measured independently, significance was not established at 30 minutes, 1.5 hours, and 4 hours following PACU arrival. Participants reported no adverse effects as a result of licorice gargle.


Conclusion Licorice gargle immediately preceding intubation with a double-lumen endotracheal tube significantly reduced the unpleasant and frequent postoperative complication of sore throat. Additionally, the incidence and severity of coughing, which can further aggravate an airway, was minimized by licorice gargle compared to placebo.



At first glance, this research may not appear to be “scientific” or even important enough to warrant our attention. However, given the common occurrence of sore throat reported after endotracheal intubation, especially great for those intubated with double-lumen tubes, this research does indeed deserve our attention. This is a great example of outcomes research. It offers a simple solution to a real reported patient problem. Licorice solutions, such as the one used in this study, can be easily incorporated into our clinical practice and the cost-benefit ratio is phenomenal. This is not something we are typically used to, but we should be. Identification of these low-risk techniques that are so simple to use and substantially improve patient satisfaction should be present in larger quantities. In this era of high-cost, high-tech and complex processes, it is refreshing to realize we have not lost the ability to discover safe, simple, and cheap preventative interventions. 


Mary A Golinski, PhD, CRNA

Both solutions, licorice and sugar water, were diluted in 30 mL of water and administered in small brown opaque bottles prepared by an independent apothecary. A licorice gargle solution is inexpensive.

The reader is referred to the following website for a comprehensive review of licorice as well as an extensive reference list:

© Copyright 2014 Anesthesia Abstracts · Volume 8 Number 4, April 30, 2014

Regional Anesthesia
The effect of transversus abdominis plane block or local anaesthetic infiltration in inguinal hernia repair

Eur J Anaesthesiol 2013;30:415421

Petersen PL, Mathiesen O, Stjerholm P, Kristiansen VB, Torup H, Hansen EG, Mitchell AU, Moeller A, Rosenberg J, Dahl JB


Purpose The purpose of this study was to compare pain scores and analgesic consumption during the first 24 hours following inguinal hernia repair in patients who received either an ultrasound-guided transversus abdominis plane block (TAP block) or an ilioinguinal nerve block and wound infiltration (INB + wound infiltration).


Background Open inguinal hernia repair is a common ambulatory surgery which is associated with moderate to severe pain during the first 24 hours postop. Pain after inguinal hernia repair can delay recovery and may also be related to the development of persistent postsurgical pain. Ilioinguinal nerve block plus wound infiltration is commonly administered for postoperative pain; however, its duration of action is limited to 6 to 8 hours. Ultrasound-guided TAP block is a regional anesthetic technique used to block sensation to the anterior abdominal wall between T9-L1 (iliac crest to the costal margin). The TAP block involves injection of local anesthetic between the internal oblique muscles and transverse abdominis muscles. It has a reported long duration of action of >24 hours. The investigators of this study hypothesized that an ultrasound-guided TAP block when combined with paracetamol (acetaminophen) and ibuprofen would provide prolonged analgesia after inguinal hernia repair when compared to an ilioinguinal nerve block plus wound infiltration or placebo. 


Methodology This was a prospective, double-blind, placebo-controlled study of 90 adult ASA 1-3 patients undergoing open inguinal hernia repair with mesh. Patients were randomized to one of three groups: 

  1. TAP group: preoperative TAP block under ultrasound-guidance with 25 mL 0.75% ropivacaine plus placebo INB + wound infiltration (TAP block injection at level of umbilicus in midaxillary line between iliac crest and costal margin.)
  2. Ilioinguinal nerve block plus wound infiltration group: with 50 mL 0.375% ropivacaine plus placebo preoperative TAP block (10 mL INB + 40 mL injected subcutaneously and subfascially into deeper layers.)
  3. Placebo group: placebo preoperative TAP block plus placebo INB + wound infiltration


All patients underwent a standardized anesthetic induction and maintenance with propofol and remifentanil. The airway was managed with an I-gel supraglottic airway. Ten minutes before the end of surgery, all patients received 0.2 mcg/mL sufentanil. The inguinal hernia repair was done with mesh. Postoperatively all patients received oral paracetamol 1 gm and ibuprofen 400 mg every 6 hours starting 30 minutes before surgery. In the post anesthesia care unit, all patients received PRN morphine in an initial dose of 5 mg followed by 2.5 mg as needed. From 2 to 24 hours oral ketobemidone 2.5 mg was available PRN. (Ketobemidone is an oral opioid with some NMDA-antagonist properties; 2.5 mg ketobemidone is equivalent to 6 mg morphine and has a duration of 3-5 hours).


The primary outcome was pain scores while coughing (0-100 mm VAS) at 0, 2, 4, 6, 8, 19, and 24 hours postoperatively. Secondary outcomes were pain at rest, morphine consumption during first 2 hours, and ketobemidone consumption from 2 to 24 hours. Sample size and statistical analysis were appropriate. Power analysis was based on a 50% reduction in pain scores between the TAP group and placebo group. A P < 0.05 was considered significant.


Result A total of 86 subjects completed the study (TAP group n = 29, ilioinguinal nerve block plus wound infiltration group n = 30, placebo group n = 27). There were no significant differences in baseline demographics or perioperative medications administered. Pain scores while coughing and at rest were similar over the first 24 hours in all three groups (Figure 1). However, average pain scores for the first 6 hours were significantly lower in the ilioinguinal nerve block plus infiltration group both during rest and while coughing compared to the TAP and placebo groups (P < 0.001; Figure 1). Morphine consumption in the post anesthesia care unit was significantly lower in the ilioinguinal nerve block plus wound infiltration group compared to the placebo group (0 vs. 5 mg, P < 0.003) but similar to the TAP group (P = NS). Ketobemidone consumption was similar between groups (P = NS).



Figure 1. Pain Scores at Rest and Coughing

Figure 1

Note. AUC = area under the curve, a measure of pain scores. Subscript indicates the time period in hours. Mean difference for pain scores between ilioinguinal nerve block plus wound infiltration and TAP group at rest was 15 mm and while coughing was 23 mm. The mean difference between the ilioinguinal nerve block plus wound infiltration and placebo group at rest was 10 mm and while coughing was 21 mm.



Conclusion An ultrasound-guided TAP block did not reduce average pain during the first 24 hours after inguinal hernia repair. Average pain scores during the first 6 hours were significantly lower in the ilioinguinal nerve block plus wound infiltration group when compared to a TAP block or placebo. Ilioinguinal nerve block plus wound infiltration also reduced opioid consumption in the early recovery period compared to a TAP block or placebo.



I was somewhat surprised by the results of this study, given my clinical experience with ultrasound-guided TAP blocks for inguinal hernia repair. I have found, in general, this block provides prolonged analgesia after inguinal hernia repair. So why was it not more efficacious when compared to ilioinguinal nerve block plus wound infiltration or placebo? Well, first the groups received different volumes and concentration of local anesthetic. The ilioinguinal nerve block plus wound infiltration group received a total of 50 mL of 0.375% ropivacaine whereas the TAP block group only received 25 mL of 0.75% ropivacaine. This most likely favored the ilioinguinal nerve block plus wound infiltration group. Additionally, there can be variable spread of the local anesthetic during the TAP block when administered at the level of umbilicus and mid-axillary line, which may produce variable block of L1 and may have a shorter duration of action. The local may also spread more anteriorly rather than posteriorly towards the paravertebral space. Paravertebral spread may be why some patients experience prolonged analgesia after a TAP block, especially after a blind technique via the Triangle of Petit. A limitation of this study is that the investigators did not evaluate the sensory block, so we do not know if the TAP blocks even worked.


Overall the pain scores were very low across all three groups, and the differences are probably not clinically relevant. That does not necessarily mean I would not recommend an ultrasound-guided TAP block or ilioinguinal nerve block plus wound infiltration technique to a patient. However, I suspect in the United States most surgeons do not perform an ilioinguinal nerve block plus wound infiltration block for inguinal hernia repair with 50 mL of local anesthetic. So given other studies suggest the TAP block is efficacious, I would still recommend it to patients. As use of ultrasound technology continues to grow, I recommend anesthesia providers learn how perform TAP blocks.


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 2014 Anesthesia Abstracts · Volume 8 Number 4, April 30, 2014