ISSN NUMBER: 1938-7172
Issue 8.13

Michael A. Fiedler, PhD, CRNA

Contributing Editors:
Mary A Golinski, PhD, CRNA
Dennis Spence, PhD, CRNA
Steven R Wooden, DNP, CRNA, NSPM-C

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

Massive hemorrhage: a report from the anesthesia closed claims project

Anesthesiology 2014;121:450-8

Dutton RP, Lee LA, Stephens LS, Posner KL, Davies JM, Domino KB



Purpose The purpose of this study was to review the Anesthesia Closed Claims database to determine the frequency of, and factors associated with, hemorrhage claims.


Background Massive hemorrhage is a rare but life-threatening event that may occur during surgery or delivery. Failure to recognize and appropriately treat hemorrhage is associated with higher morbidity and mortality. Technological advances taken from combat casualty care have improved patient survival from massive hemorrhage; for example 1:1:1 PRBC: FFP: Platelets and damage control surgery principles. Despite these advances, massive hemorrhage remains a life-threatening surgical and obstetric complication.


Methodology The authors examined the Anesthesia Closed Claims database for surgical and obstetric anesthesia cases with claims for hemorrhage between 1995 and 2011. For this time period there were 3,211 claims. Of these, in 141 hemorrhage was a primary event in the claim and 3,070 were for other primary events.


The authors examined risk factors, clinical factors, management, and communication issues for all claims. They also examined risk factors for hemorrhage and coagulopathy to determine if they were associated with hemorrhage claims. Obstetric risk factors related to hemorrhage included:

  • placenta accrete/increta/percreta
  • retained placenta
  • uterine atony
  • uterine rupture
  • placental abruption
  • placenta previa

Obstetric risk factors related to coagulopathy included:

  • amniotic fluid embolism
  • placental abruption
  • intrauterine fetal demise


Surgical risk factors related to hemorrhage included:

  • thoracic or lumbar spine surgery
  • robotic/laparoscopic/minimally invasive surgery
  • major vascular surgery
  • cardiac surgery
  • large tumor surgery
  • major trauma
  • liver surgery

Surgical risk factors related to coagulopathy included:

  • preexisting use of anticoagulants or platelet inhibitors
  • liver disease
  • preoperative increased PTT


Two reviewers independently examined each claim and associated factors. Interrater reliability was calculated. Hemorrhage claims were compared with nonhemorrhage claims using descriptive and inferential statistics. All claim payments to the plaintiff were adjusted to 2012 dollars using the Consumer Price Index.


Result There were 141 (4%) hemorrhage claims out of 3,211 claims for the study period. Seventy percent of the hemorrhage claims were for surgical bleeding (n = 98) and 30% were for obstetric bleeding (n = 43). Thoracic and lumbar spine procedures accounted for 24% of the surgical claims and cesarean delivery for 16% of the obstetric claims. Emergency surgery accounted for 29% and trauma for 4% of all hemorrhage claims.


Injuries were more likely to result in death, anesthesia care more often judged less than appropriate, and payment amounts significantly greater in hemorrhage compared to nonhemorrhage claims (Figure 1).



Figure 1. Hemorrhage vs. Nonhemorrhage Claims

Figure 1



Most surgical (81%) and obstetric claims (79%) had at least one risk factor for hemorrhage or coagulopathy. The three most common risk factors for surgical claims were thoracic or lumbar procedures (36%), robotic/laparoscopic/minimally invasive surgery (8%), and major vascular surgery (8%). In addition to hemorrhage risk factors, 16% of surgical claims had a risk factor for coagulopathy. The three most common risk factors for obstetric claims were placenta accrete/increta/percreta (30%), retained placenta (23%), and uterine rupture (16%). In addition to hemorrhage risk factors, 28% of obstetric claims had at least one risk factor for coagulopathy.


Most of the hemorrhage events were recognized in the operating room (72%), followed by the recovery room (21%). In 33% of the cases, hemorrhage was the direct result of unexpected organ or vessel injury. In 26% of claims, hemorrhage was severe enough to cause an immediate change in vital signs.


Significant delays in recognition and treatment of bleeding were common across all claims (Figure 2). Poor communication was common, occurring in 60% of claims. In 13% of the claims the surgeon failed to communicate to the anesthesia provider the seriousness of the bleeding, in 7% of the claims the opposite occurred, and 9% of the time both the surgeon and anesthesia provider failed to communicate the seriousness to each other. In 7% of the claims the surgeon did not take blood loss seriously. In 6% of the claims there was miscommunication about the availability of blood products. In 6% of claims there was a failure of communication between members of the anesthesia team including a delay in calling for help.



Figure 2. Response to Massive Hemorrhage

Figure 2



Conclusion Delayed recognition of bleeding, delayed transfusion, and poor communication were common across insurance claims involving hemorrhage. Institutions should develop massive transfusion protocols, train staff in crew resource management, and simulate massive transfusion emergencies. Greater emphasis should be placed on team communication and promotion of teamwork.



To me, the most striking finding from this study was the high rate of poor communication. Management of a patient who is bleeding out requires close communication with the surgical team, nursing, and blood bank, along with aggressive administration of blood products and rapid control of bleeding to prevent morbidity and mortality. Anesthesia providers must stay current on the latest evidence for fluid and blood product resuscitation and have a plan in place on how they will manage the patient who is hemorrhaging. Even in the best of cases, the patient may not survive; however, we must ensure that all members of the healthcare team at our institutions stay up-to-date on the latest evidence and that systems and protocols are in place that will give the patient the best shot at survival. Certainly, it is critical to have a surgeon who can apply damage control principles and quickly obtain hemostasis. If you see the surgeon struggling to control bleeding, politely ask them if they would like someone to call for another surgeon or interventional radiology. In crisis situations it is best to have all the help you can get!


As I read this article I thought of an excellent book I recently read called Managing the Unexpected: Resilient Performance in an Age of Uncertainty by Weick and Sutcliffe. I think the principles the authors describe can help you manage crisis situations (e.g., hemorrhaging patient). The authors discuss how high reliability organizations such as nuclear power, aviation, and emergency rooms have developed ways to handle the unexpected (e.g., uterine rupture; patient with an unexpectedly low hematocrit in the recovery room). Weick and Sutcliffe reveal how high reliability organizations have a mindful infrastructure and personnel who act mindfully; that is, they are able to notice the unexpected and can prevent or contain it. They continually track small failures, resist oversimplification, remain sensitive to operations, maintain capabilities for resilience, and take advantage of shifting locations of expertise. 


High reliability organizations learn from near misses, or actual misses such as those cases discussed during a morbidity and mortality conference, and don’t accept simplification (i.e., “I am not going to assume that low hematocrit is a false reading”). They have situational awareness and are able to look at the big picture and are willing to speak up (sensitive to operations). High reliability organizations are resilient and do not collapse in the face of a hemorrhaging patient; they are able to quickly assess the situation and rapidly pool resources. They also drill for the worst-case scenario. And finally, these organizations have a deference to expertise, which means they encourage diversity of opinion and look to the expert at the time, who may not necessarily be the “leader.” If we put this into context, if the Chair of the Anesthesia Department, who only does anesthesia once a month, suddenly is faced with a hemorrhaging obstetrical patient, a faulty assumption might be that he can handle it or does not need help because he is the “boss.” However, this logic would be faulty. In fact it might be best to call in other “experts,” such as an anesthesia provider who recently returned from a deployment on a surgical team in Afghanistan and took care of a lot of trauma patients.


In conclusion, I think there is a lot we can learn from this study. Please take the time to ask yourself, “Does my institution function like a high reliability organization? If not, what can you do to make it so?


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 13, November 5, 2014

Factors associated with postoperative exacerbation of sleep-disordered breathing

Anesthesiology 2014;120:299-311

Anesthesiology 2014;120:299-311



Purpose The purpose of this study was to examine factors associated with exacerbations in postoperative sleep-disordered breathing.


Background Sleep-disordered breathing ranges from snoring to severe obstructive sleep apnea (OSA); it also includes central sleep apnea. Central sleep apnea results when the brain temporarily stops sending signals to the muscles that control breathing. OSA has been found to be associated with postoperative respiratory complications. Exacerbations of OSA symptoms have been reported to be the worst on the 3rd postoperative night and appear to recover by postoperative night seven. It has been suggested that rapid eye movement rebound might contribute to worsening sleep-disordered breathing symptoms. However, further research is needed to characterize sleep-disordered breathing parameters during the early postoperative period. Understanding these changes may aid in the development of clinical guidelines to prevent postoperative respiratory complications.


Methodology This was a prospective observational study conducted on adults >18 years old undergoing elective surgery. All patients completed an unattended sleep study preoperatively and again on postoperative nights one and three. Postoperative studies were completed either in the hospital or in the patient’s home. Patients with suspected abnormal electroencephalographic findings or those who used continuous positive airway pressure (CPAP) on any perioperative night were excluded. Anesthesia providers and surgeons were blinded to the sleep study results. Patients were managed according to institutional guidelines. Obstructive Sleep Apnea was defined as an apnea-hypopnea index (AHI) of ≥5. Data collected included demographics, type of anesthesia (regional or general), total morphine equivalents, invasiveness of surgery, and comorbidities. Statistical analysis was appropriate.


Result A total of 376 patients completed sleep studies preoperatively and on Postoperative Night #1 (PON#1). There were 242 patients who also completed a sleep study on PON#3. Of these 242, the average age was 59 years, body mass index was 29.5 kg/m2, and neck circumference was 38 cm. Forty-five percent (45%) were men, and 54% were ASA II. A majority of surgical procedures were considered moderately invasive; 47% had general anesthesia and 53% regional anesthesia. In patients receiving general anesthesia, the types of surgery were general (29%), orthopedic (27%), and spinal (16%). In those receiving regional anesthesia, the surgeries were mostly orthopedic (92%). The most common comorbidity was hypertension (52%), followed by diabetes (15%).


Out of the 242 who completed sleep studies preoperatively and on PON#1 and PON#3, 28% had an AHI ≤5 (non-OSA group), and 72% had an AHI ≥5 (OSA group). Of those with OSA, 27% were mild, 25% were moderate, and 20% were severe. The median preoperative apnea-hypopnea index was 12.5. No significant difference in morphine equivalents was found between patients with non-OSA vs. those with mild, moderate, or severe OSA. The percentage of patients who slept in the supine position was 40% preoperatively; however, it increased to 61% on PON#1 and 59% on PON#3 (editor’s note: OSA symptoms are worse in the supine position).


Postoperatively the apnea-hypopnea index increased in both non-OSA and in mild and moderate OSA patients on both PON#1 and PON#3 (P < 0.05). In non-OSA patients who received general anesthesia the apnea-hypopnea index was significantly increased on PON#1 and PON#3 (P < 0.003). In non-OSA patients who received regional anesthesia the apnea-hypopnea index only increased significantly on PON#3 compared to the preoperative night (P < 0.05; Figure 1).


In OSA patients, significant increases in the apnea-hypopnea index were seen on PON#3 compared to the preoperative night, irrespective of whether they received general or regional anesthesia (Figure 2). Patients with severe OSA had a slight decrease in their apnea-hypopnea index on PON#1, but then it increased by 44% on PON#3 compared to the preoperative sleep study (P < 0.05; Figure 3).



Figure 1. General vs. Regional and Apnea-Hypopnea Index

Figure 1

Note: AHI = apnea hypopnea index; PON = postoperative night.



Figure 2. Apnea-Hypopnea Index Changes in non-OSA Patients

Figure 2

Note: Exacerbations in AHI occurred equally in patients receiving GA and RA. GA = general anesthesia; RA = regional anesthesia; PON = postoperative night.



Figure 3. Apnea-Hypopnea Index Changes in OSA Patients

Figure 3


Note: Exacerbations in Apnea-Hypopnea Index occurred equally in patients receiving general anesthesia and regional anesthesia. AHI = Apnea-Hypopnea Index. PON = postoperative night.



Significant increases were seen in the central apnea index on PON#1 in both non-OSA and OSA patients receiving general anesthesia (P < 0.003). None of the patients had any central apnea events identified in the preoperative sleep study. The median central apnea index was less than 1 in both groups on PON#1. However, the number of events per hour ranged from 0 to 48 in both groups on PON#3. [Editor’s note: estimated from author’s figure; exact values not reported.]


A higher baseline apnea-hypopnea index, greater age, and greater 72-hour total morphine equivalents were each positively associated with a higher apnea-hypopnea index on PON#1 and PON#3. This indicated they were having more airway obstruction compared to the preoperative sleep study.


Predictors of postoperative central apnea included a higher preoperative central apnea index, male gender, and administration of general anesthesia. Each was positively associated with a higher central apnea index on PON#1.


Conclusion This study demonstrated that both non-OSA and OSA patients experienced increases in their apnea-hypopnea index postoperatively. Predictors of a higher postoperative apnea-hypopnea index included a higher preoperative apnea-hypopnea index, older age, and greater postoperative opioid use. A higher preoperative central apnea index, male gender, and administration of general anesthesia were associated with increased central apnea episodes postoperatively. Risk reduction strategies should be considered in patients with a higher preoperative apnea-hypopnea index, especially those with moderate to severe obstructive sleep apnea.



This study demonstrated that all patients, regardless of anesthesia type, have an increased apnea-hypopnea index up to three days after surgery. Non-OSA patients (based on a preoperative apnea-hypopnea index <5) had increased obstructive symptoms as evidenced by a progressively increasing apnea-hypopnea index which peaked on PON#3. Although these changes were still only in the mild OSA category, these changes in non-OSA patients may be of clinical significance. More dramatic results were seen in patients with mild to severe OSA, especially in those with severe OSA. The reason for these increases are multifactorial. A single preoperative polysomnography may have been falsely low in some patients. Additionally, opioids and pain are known to reduce REM sleep. It is during REM sleep when obstructive symptoms are the worst. Other factors that may influence obstructive symptoms may be older age, gender, severity of OSA, sleep position, administration of sedating medications, unit noise and frequent awakenings for vital signs or labs, and invasiveness of the surgical procedure. A combination of these factors most likely combined on PON#3 to contribute to the worsening postoperative apnea hypopnea index, especially in patients with severe OSA.


So what do these results mean? Most providers think the most dangerous time for OSA patients is within the first 24 hours postoperatively; however, I think these results suggest we should be worried about obstructive symptoms worsening for at least 3 days after surgery. I think we should also be concerned about the increases in the central apnea index in both OSA and non-OSA patients.


A limitation of this study was that the investigators did not report complication rates, the lowest oxygen saturation, or duration of hypoxemia (SpO2 <90%), which would have helped us understand the clinical implications of these results. This study also did not tell us what happens in patients who have continuous peripheral nerve blocks postoperatively, who presumably require less opioid pain medicine.


To minimize risks, anesthesia providers should use multimodal analgesic techniques, minimize long-acting opioids (especially in those with moderate to severe OSA), encourage patients to sleep in a non-supine position when appropriate, and resume CPAP postoperatively if possible.

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 13, November 5, 2014

The impact of postoperative nausea and vomiting prophylaxis with dexamethasone on postoperative wound complications in patients undergoing laparotomy for endometrial cancer

Anesth Analg 2013;116:1041-1047

Bolac C, Wallace A, Broadwater G, Havrilesky L, Habib A



Purpose The purpose of this study was to discover if intravenous dexamethasone to prevent PONV played a role in the development or severity of postoperative wound complications in women undergoing laparotomy for endometrial cancer. A secondary objective was to identify perioperative factors that contributed to the development of postoperative wound complications.


Background Current evidence is conclusive - corticosteroids such as dexamethasone are efficacious in preventing PONV. Unfortunately, they may also delay the healing process by inhibiting the necessary inflammatory phase of wound healing and decreasing concentrations of intrinsic growth factors important for the reepitheliazation of wounds. The evidence is controversial and debates exist regarding the use of a single dose of intraoperative dexamethasone used for PONV prophylaxis. The question remains: does dexamethasone contribute to the development of postoperative wound infections? Those diagnosed with cancer are at significant risk for postoperative wound complications as well as PONV. It is critical that we identify whether or not corticosteroid administration has greater benefits than risks.


Methodology This study was a retrospective chart review. The medical records of women who had a laparotomy for endometrial cancer and received dexamethasone for PONV prophylaxis were compared to those who did not receive dexamethasone. The primary objective was to determine whether wound complications occurred within the first 30 days after surgery in women who received dexamethasone. Wound complications included: 

  • superficial surgical site infections
  • wound cellulitis
  • wound separation
  • fascial dehiscence

The time to complete wound healing were recorded, as was antibiotic use, wound care needs, and the time from diagnosis to complete healing. Serum glucose values for those with diabetes mellitus were also recorded on postoperative days 0 and 1. Baseline patient demographics and surgery-specific characteristics were compared between those given dexamethasone and those who did not receive dexamethasone. Demographics and surgical factors included:

  • age
  • BMI
  • diabetes
  • smoking status
  • preoperative immunosuppressive treatments
  • perioperative prophylactic antibiotic use
  • average inspired oxygen concentrations
  • intraoperative temperature
  • pelvic or periaortic lymph node dissection
  • suture type
  • surgery duration
  • estimated blood loss
  • blood transfusion
  • IV fluids
  • glucose levels

The correlation between dexamethasone administration and wound complication rates were tested statistically, and the dose of dexamethasone was compared in those with and without a wound complication.


Result Records revealed 192 women received dexamethasone and 239 did not, for a total sample size of 431. There were no statistically significant differences in patient demographics or surgery-specific characteristics. Overall, 99.6% of all patients received preoperative antibiotics. Smoking and BMI were significant predictors for the development of wound complications. Wound complications occurred in 31% of all patients; of these:

  1. 33.6% developed surgical site infection (45/134)
  2. 39.6% developed wound cellulitis (53/134)
  3. 21.6% had wound separation (9/134)
  4. 5.2% had fascial dehiscence (7/134)

There was no statistical difference in the number of wound complications between groups. The absolute rate of wound complications was actually lower in the dexamethasone group, 28% vs. 34% in the no dexamethasone group. There was also no relationship between the wound complication rate and the dose of dexamethasone. Relatively similar numbers of patients received dexamethasone doses of 4, 8, or 10 mg but only one patient received 12 mg. A total of 131 patients in either group had diabetes mellitus. There was no difference between groups in preoperative blood glucose levels. There was no association between the maximum glucose values on postoperative day 0 or 1 and change from baseline glucose in either group.


Conclusion This retrospective chart review study where researchers assessed the records of 431 females who had laparotomies for endometrial cancer revealed that a single dose of dexamethasone for the prevention of PONV did not influence the development of postoperative wound complications compared to those who did not receive dexamethasone. Additionally, smoking and a high BMI were the only predictors for the development of wound complications.



Providing anesthesia care for the patient with a cancer diagnosis has numerous implications and requires scrupulous consideration. This is often due not only to the pathology itself but existing comorbidities and the physiologic response to therapies given prior to the surgery and anesthetic. Healing is frequently altered for the same reasons. Anesthesia care should not potentiate altered healing processes, if at all possible. While the prevention of PONV in this population and all populations is extremely important, the pharmacologic treatments should not disrupt normal wound healing patterns. We have had great success with the use of dexamethasone in preventing PONV, and this study adds to the body of evidence that a single dose typically does not create problems for the cancer patient in terms of healing.


Mary A Golinski, PhD, CRNA

© Copyright 2014 Anesthesia Abstracts · Volume 8 Number 13, November 5, 2014

Pharyngeal function and breathing pattern during partial neuromuscular block in the elderly

Anesthesiology 2014;120:312-25

Hårdemark Cedborg AI, Sundman A, Bodén, K, Hedström HW, Kuylenstierna R, Ekberg O, Eriksson LI



Purpose The purpose of this study was to describe the effects of partial neuromuscular blockade on pharyngeal function, coordination of breathing and swallowing, and airway protection in patients >65 years old.


Background Residual neuromuscular blockade is associated with postoperative pulmonary complications, especially in elderly patients. Elderly patients are more likely to have impaired pharyngeal function, impaired coordination of breathing and swallowing, and reduced upper esophageal sphincter tone pressure. These impairments may place them at increased risk for aspiration and are worse when residual neuromuscular blockade is present. In this volunteer study, investigators used novel techniques to measure pharyngeal function, breathing and swallowing patterns, and upper esophageal sphincter function in elderly patients with partial neuromuscular blockade (train-of-four ratios of 0.7, 0.8, and 0.9).


Methodology Seventeen healthy elderly volunteers (mean age 73.5 years) participated in this laboratory study. Investigators evaluated pharyngeal function and coordination of breathing and swallowing with manometry and videoradiography. All study patients had control measurements taken, followed by measurements at train-of-4 (TOF) ratios of 0.7, 0.8, and 0.9. Rocuronium was infused to obtain the respective TOF ratios. Neuromuscular blockade was measured at the adductor pollicis with an isometric mechanomyography device. Investigators rated the degree of contrast aspiration into the airway using the 0-8 likert scale shown below:


No risk

1 = No airway invasion

2 = Bolus enters into airway with clearing

Risk of Aspiration

3 = Bolus enters into airway without clearing

4 = Bolus contacts vocal cords with airway clearing

5 = Bolus contacts vocal cords without airway clearing

Positive Aspiration

6 = Bolus enters trachea and is cleared into larynx or out of airway

7 = Bolus enters trachea and is not cleared despite attempts

8 = Bolus enters trachea and no attempt is made to clear

The investigators used a 0-3 scale to rate the amount of residual contrast in the valleculae and pyriform sinuses. Bolus clearance was rated as follows:

1 = no residual to mild bolus retention

2 = moderate residual with up to half the recess filled with material post-swallow

3 = severe residual with more than half the recess filled with material post-swallow. Other outcomes included the degree of swallowing and pharyngeal dysfunction, coordination of breathing and swallowing, and mean UES pressure.


Result There were 669 swallowing maneuvers evaluated in 17 subjects. At baseline, 37% of swallows showed pharyngeal dysfunction. Pharyngeal dysfunction, which was evaluated with videoradiography with contrast-medium swallows, worsened significantly with partial neuromuscular blockade. Disfunction occurred in 67% of the swallows at a TOF ratio of 0.7 and 71% at a TOF ratio of 0.8 (P < 0.05 vs control). The incidence of pharyngeal dysfunction remained 45% even at a TOF ratio of only 0.9; however, this was not significantly different compared to the control state. Likewise, the degree of pharyngeal dysfunction was significantly higher at a TOF ratio of 0.7 and 0.8 (P < 0.05; Figure 1). The median risk of aspiration score was 1.3 (range 1 to 4.7) at a TOF of 0.7 (P = 0.03). Disfunction rates were not significantly different at TOF ratios of 0.8 vs 0.9.


Median residual and pyriform residue scores at a TOF ratio of 0.7 were significantly increased compared to the control state (P < 0.05). However, at TOF ratios of 0.8 and 0.9 no differences were found. This suggests that partial neuromuscular blockade at a TOF of 0.7 results in a significant amount of bolus residue at the level of the valleculae. However, there was no significant effect on bolus clearance at a TOF of 0.8, which indicates as the degree of neuromuscular blockade increases, so does the risk of impaired airway protection.



Figure 1. Pharyngeal Dysfunction in the Elderly 

Figure 1


Coordination of breathing and swallowing was not affected by partial neuromuscular blockade. Mean upper esophageal sphincter pressure was significantly lower at each TOF ratio (P < 0.05; Figure 2). Table 1 summarizes key factors for pharyngeal function and airway protection.



Figure 2. Changes in Upper Esophageal Pressure in Elderly 

Figure 2



Table 1. Key Factors of Pharyngeal Function & Airway Protection


No Neuromuscular Block

Partial Neuromuscular Block

Oral coordination



Coordination of pharyngeal contraction wave



Pharyngeal clearance



Upper esophageal sphincter pressure



Laryngeal protection



Coordination of breathing & swallowing



Notes: Oral coordination - prevents penetration of contents to the laryngeal inlet or aspiration;

Coordination of pharyngeal contraction wave - the propagation of contractions in the pharyngeal constrictor muscles into the upper esophageal sphincter;

Pharyngeal clearance- prevents retention of pharyngeal residue after completion of the pharyngeal contraction wave;

Upper Esophageal Sphincter pressure- resting pressure in the UES contributes to airway protection by preventing excessive air swallowing & regurgitation;

Laryngeal protection- prevents penetration of contents to the laryngeal inlet or aspiration;

Coordination of breathing & swallowing- swallowing during expiration and normal duration and timing of apnea in relation to the pharyngeal phase of swallowing prevents aspiration.


Conclusion In healthy elderly adults, partial neuromuscular blockade increased the incidence of pharyngeal dysfunction and reduced upper esophageal sphincter tone, which may impair the ability to protect the airway and increase the risk of aspiration. Avoiding residual blockade (TOF <0.9) is critical to minimizing these risks in elderly patients.



Recent publications suggest using a TOF ratio of >0.9 to reduce the risk of residual paralysis (see Anesthesia Abstracts, Volume 7, Number 6, June 2013). In that study the investigators reported 43% of patients arrived in the PACU with a TOF ratio <0.9 reported difficulty swallowing compared to 7% in patients with a TOF >0.9. Those results are consistent with the findings of this study that elderly patients with TOF <0.9 had significantly higher rates of pharyngeal dysfunction.


Given this evidence I think it is important that we ensure patients have a TOF ratio > 0.9 prior to extubation to ensure adequate neuromuscular function. However, the only accurate way to quantify neuromuscular function is with acceleromyography. However, if you don’t have a acceleromyography device you should monitor for a TOF of 4/4 twitches with sustained tetanus at the adductor pollicis rather than at the eye muscles. 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). These results reinforce my opinion that we should be using acceleromyography to measure the train-of-4 ratio.


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 13, November 5, 2014

Nitrous oxide–related postoperative nausea and vomiting depends on duration of exposure

Anesthesiology 2014;120:1137-45

Peyton P, Wu CY



Purpose  The purpose of this systematic review was to determine if prolonged exposure to nitrous oxide was associated with a higher incidence of postoperative nausea and vomiting (PONV).


Background  Nitrous oxide has been implicated as a causative agent for PONV. As a result, many anesthesia providers have stopped using nitrous oxide. A recent meta-analysis reported nitrous oxide was associated with a 20% increase in PONV. However, there was significant heterogeneity in the included studies. (Heterogeneity occurs in meta-analyses because there is excessive variation in study findings or inadequate sample size across multiple studies.) Additionally, most studies have not examined the effect of duration of nitrous oxide exposure on the incidence of PONV. This distinction may have important clinical implications on the future use of nitrous oxide.


Methodology  The investigators conducted a systematic review and meta-analysis. PubMed was searched using the terms “nitrous oxide” and “nausea,” “vomiting,” or “PONV.” The references in each article were hand searched to identify additional relevant studies. Only randomized controlled trials that compared the incidence of PONV in patients who received or did not receive nitrous oxide as part of their anesthetic were included. PONV was defined as the need for antiemetic rescue treatment or the reported incidence of nausea. Meta-regression was used to determine the relative risk (RR) of PONV associated with different durations of nitrous oxide exposure. The authors stratified findings by duration of anesthesia:

  • <1 hour
  • 1 to 2 hours
  • >2 hours.

They also examined whether age or gender influenced the results. A P < 0.05 was significant.


Result The authors identified 27 studies including 10,317 patients (N2O group = 5,179 vs. no-N2O = 5,138). The pooled incidence of PONV in the N2O group was 29.4% versus 24.5% in the no-N2O group. The mean duration of anesthesia was 99 minutes (range = 10 to 266 minutes). Across all studies, nitrous oxide exposure increased the risk of PONV by 21% (RR = 1.21, P = 0.014). The risk of PONV increased by 20% for every hour of exposure to nitrous oxide beyond 45 minutes.


The risk of PONV with N2O exposure was positively correlated with duration of anesthesia (r = 0.7, P = 0.002) and patient age (r = 0.5, P = 0.023) but not associated with female gender (P = 0.09). When the duration of anesthesia was less than 1 hour, the number needed to treat to prevent one case of PONV by avoiding nitrous oxide was 128 (Figure 1). (In this case the “treatment” was not using nitrous oxide.) When the duration of anesthesia was 1 to 2 hours the number needed to treat to prevent one case of PONV was 24 (P < 0.05). When the duration of nitrous exposure was >2 hours the number needed to treat to prevent one case of PONV decreased to 9. These results suggest that avoiding nitrous oxide administration in cases less than 1 hour in duration did not reduce the incidence of PONV; however, avoiding its use in longer cases did. Substantial heterogeneity was identified across the studies.


Conclusion Administration of nitrous oxide for less than 1 hour has no clinically significant effect on the incidence of PONV. Therefore, nitrous oxide is appropriate to use in minor or ambulatory surgery.



I must admit I am one of the many anesthesia providers who stopped using nitrous oxide after guidelines came out suggesting it was associated with higher rates of PONV. Nitrous oxide is a great agent for reducing the MAC of volatile agents needed. This can help minimize the hypotensive effects of volatile anesthetics, hasten emergence from anesthesia, and smooth out the wake-up after administration of desflurane. These factors are especially important in short procedures where fast patient recovery and room turn-over are essential; cases less than 1 hour long. Anything we can do to reduce costs and improve the patient experience will improve our bottom line. These results tell us nothing about the best concentration of nitrous oxide to avoid PONV. I would use the lowest concentration possible.


Based on these results I may start using nitrous oxide again for short procedures. If I use nitrous oxide I would administer PONV prophylaxis based on the patient's risk factors and current guidelines.

Dennis Spence, PhD, CRNA

The number needed to treat (NNT) is the number of patients needed to be treated to prevent one bad outcome. The higher the NNT the less effective the treatment. In this study the "treatment" was avoiding nitrous oxide administration. For example, in procedures between 1 and 2 hours in duration, you would need to not administer nitrous oxide to 24 patients to prevent one patient from experiencing PONV. For procedures over 2 hours in duration if you avoid its use in 9 cases then you would prevent one case of PONV. 


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 13, November 5, 2014

Anesthetic Induction with Etomidate, Rather than Propofol, Is Associated with Increased 30-day Mortality and Cardiovascular Morbidity After Noncardiac Surgery

Anesth Analg 2013;117:1329-1337

Komatsu R, You J, Mascha E, Sessler D, Kasuya Y, Turan A



Purpose The purpose of this study was to see if an association existed between etomidate induction and the incidence of adverse outcomes in ASA physical status III and IV adults having noncardiac surgery.


Background Etomidate is frequently chosen as an induction agent for high acuity individuals because it does not cause hypotension and therefore prevents end organ hypoperfusion and related sequelae. It does however suppress adrenocortical function by blocking the enzyme 11B-hydroxylase. Studies have demonstrated that even induction doses of etomidate can suppress the increase in plasma cortisol normally seen in response to surgical stimulation. It has been suggested that cortical suppression in high acuity individuals may lead to poor outcomes. The association between etomidate, used as an induction agent for ASA III and IV adults having non cardiac surgery, and poor post operative outcomes has not been established. [See editor’s note at the end of this abstract and comment.]


Methodology This was a retrospective electronic medical record/database review. The health documentation system registry at the Cleveland Clinic was queried for adults having noncardiac surgery between 2005 and 2009. Cases that met the following criteria were included in the review:

  1. ASA physical status III & IV adults having noncardiac surgery with general anesthesia requiring ≥ 1 night of postoperative hospital admission
  2. Anesthesia induction drugs used: etomidate, propofol, thiopental, or ketamine & not repeatedly administered after induction dose
  3. Anesthesia maintained with volatile agent with or without opioid

Each patient who received etomidate and met the other criteria was matched to a maximum of 3 patients who received propofol for anesthesia induction. The medical record was comprehensively reviewed. The primary outcomes documented for those who received etomidate or propofol included:

  • 30 day mortality
  • in-hospital cardiovascular morbidity
  • in-hospital infectious morbidity

Additionally, for those who received etomidate, the relationship between the dose of etomidate and the primary outcomes was assessed. Data was collected for all patients and comparisons were made between the etomidate and matched propofol groups for intraoperative vasopressor use and duration of hospitalization. Lastly, blood pressures during each major intraoperative period were compared.


Result A total of 2,144 “etomidate only” patients were compared with 5,233 “propofol only” patients . A total of 7,377 electronic records were analyzed. The average dose of etomidate was 0.22 mg/kg. The average dose of propofol was 1.8 mg/kg.


Patients who received etomidate were generally older, had a higher acuity status, and were more likely male. They also had cardiovascular and/or cerebrovascular disease and a lower BMI. Etomidate patients were more likely to have undergone urgent or emergency surgery. Etomidate patients were also more likely to have received regional anesthesia as an adjunct to general anesthesia. They were less likely to have cancer or to have been on steroids.


Compared to patients who received propofol, etomidate patients had significantly higher 30-day mortality and major cardiovascular morbidity after adjusting for ASA status, co-morbidities, and emergency surgery (P< 0.001). Other ways in which etomidate patients differed from patients who received propofol induction included:

  • Duration of hospital stay was longer in the etomidate group (P< 0.001)
  • Intraoperative blood pressure was higher in the etomidate group at all time periods
  • Intraoperative vasopressor use was similar between groups
  • There was no correlation between the dose of etomidate and the incidence of mortality, cardiovascular morbidity, or infectious morbidity
  • Etomidate was not associated with major infectious morbidity.


Conclusion Induction with etomidate was associated with greater 30 day mortality, cardiovascular morbidity, and prolonged length of hospital stay compared to propofol induction in ASA III and IV patients having noncardiac surgery. Etomidate was not associated with infectious morbidity, use of vasopressors to support blood pressure, or perioperative hypotension. While statistical associations were observed, a cause-effect relationships between etomidate and adverse outcomes has not been established.



The great debate continues regarding cortisol suppression following etomidate administration and how this influences outcomes of care. I refer the readers to Critical Care Medicine Feb 2013. In this retrospective cohort study that included a mixed diagnosis group of critically ill patients with sepsis, severe sepsis, and septic shock, single dose etomidate for ICU intubation was not associated with higher mortality or other adverse clinical outcomes. While these studies are not similar in terms of subjects (high acuity surgical patients versus ICU patients with infectious morbidities), they are similar in terms of generalized high acuity status, and both studies measured morbidity and mortality following etomidate administration. Routinely I choose etomidate over propofol either due to presenting hemodynamics, which are typically very poor in a level one acute care and trauma setting, or pre-existing comorbidities. I simply believe that the myocardial depressant effects of propofol, on average 17% reduction in cardiac output, cannot be tolerated by the higher acuity folks. The often-seen resulting hypotension can create more damage and untoward outcomes than a brief period of cortisol suppression. Until I see more evidence emerge, I will continue to use my best clinical judgment and of course as much information as I can glean from the patient and the medical record, and continue the use of etomidate over propofol when appropriate.


Mary A Golinski, PhD, CRNA

Editor’s Note: The literature on this topic has not reached a consensus. For the other side of the “Etomidate is associated with greater morbidity and mortality” debate see “Single-dose Etomidate is not associated with increased mortality in ICU patients with sepsis: Analysis of a Large Electronic ICU Database” in the December 2012 issue of Anesthesia Abstracts (from Crit Care Med. 2013;41:774-783).


© Copyright 2014 Anesthesia Abstracts · Volume 8 Number 13, November 5, 2014