ISSN NUMBER: 1938-7172
Issue 4.3 VOLUME 4 | NUMBER 3

Editor:
Michael A. Fiedler, PhD, CRNA

Contributing Editors:
Penelope S. Benedik PhD, CRNA, RRT
Joseph F. Burkard, DNSc, CRNA
Mary A. Golinski, PhD, CRNA
Gerard T. Hogan, Jr., DNSc., CRNA
Alfred E. Lupien, PhD, CRNA
Lisa Osborne, PhD, CRNA
Dennis Spence, PhD, CRNA
Steven R. Wooden, MS, CRNA

Guest Editor:
Cassandra Taylor, DNP, DMP, CRNA, CNE

Assistant Editor
Jessica Floyd, BS

A Publication of Lifelong Learning, LLC © Copyright 2010

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

Table of Contents

EDITORIAL
  HOW LONG CAN YOU LAST?
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AIRWAY
USE OF MANOMETRY FOR LARYNGEAL MASK AIRWAY REDUCES POSTOPERATIVE PHARYNGEAL ADVERSE EVENTS
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OBSTETRIC ANESTHESIA
THE EPIDEMIOLOGY OF POSTPARTUM HEMORRHAGE IN A LARGE, NATIONWIDE SAMPLE OF DELIVERIES
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EPIDURAL ANALGESIA FOR LABOR AND DELIVERY
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PAIN
A MEDICAL-LEGAL REVIEW REGARDING THE STANDARDS OF CARE FOR EPIDURAL INJECTIONS, WITH PARTICULAR REFERENCE TO A CLOSED CASE
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PHARMACOLOGY
META-ANALYSIS OF AVERAGE AND VARIABILITY OF TIME TO EXTUBATION COMPARING ISOFLURANE WITH DESFLURANE OR ISOFLURANE AND SEVOFLURANE
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GABAPENTIN USE IN PEDIATRIC SPINAL FUSION PATIENTS: A RANDOMIZED, DOUBLE-BLIND, CONTROLLED TRIAL
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POLICY, PROCESS, & ECONOMICS
  SLEEP DEPRIVATION, PHYSICIAN PERFORMANCE, AND PATIENT SAFETY
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  EFFECTS OF EXTENDED WORK SHIFTS AND SHIFT WORK ON PATIENT SAFETY, PRODUCTIVITY, AND EMPLOYEE HEALTH
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RESPIRATION & VENTILATION
NONINVASIVE VENTILATION IMMEDIATELY AFTER EXTUBATION IMPROVES LUNG FUNCTION IN MORBIDLY OBESE PATIENTS WITH OBSTRUCTIVE SLEEP APNEA UNDERGOING LAPAROSCOPIC BARIATRIC SURGERY
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Editorial

How long can you last?


Editorial

When it comes to work hours, how long can you last? Twenty-four hours? Sixteen? Or are you maxed out after eight hours of giving anesthesia? How do you know where to draw the line when it comes to patient safety and your own health?

Extended work shifts are part of the culture of health care. Many have been reluctant to discard them, despite increasing evidence of the danger they pose to workers and patients alike. There is a belief that extended hours are a necessary rite of passage that promote professionalism and benefit patients through fewer provider transfers. In this era of evidence based practice, we cannot afford to cling to such beliefs based solely on tradition. While there are undoubtedly areas for continued study and debate, the data supporting the adverse effects of these old fashioned work schedules continues to accumulate. The comparison of sleep loss to alcohol consumption is a powerful call to action for even the most cynical among us. Continued use of extended work hour shifts for nurse anesthetists and other health care providers is becoming a difficult position to justify.

As individuals, we need to set realistic limits for ourselves for the maximum shift length we will work. Department managers should devise schedules that minimize the use of extended work hours and allow for adequate time off between long shifts. Undoubtedly, some managers are under pressure from administrators to use extended shifts to provide adequate coverage. Ample data exist, such as those in the two articles abstracted in this issue of Anesthesia Abstracts, to provide a risk management perspective that work hour limitation is a patient safety issue.  Our educational programs and professional organizations need to be agents of change to promote greater acceptance of a new culture that includes reasonable limits to the hours we work. All of us need to be part of the discussion that serves to increase awareness regarding this issue.

As nurse anesthetists, if we do not initiate positive change, we may well find a less thoughtful change forced upon us. Fifteen states have passed “mandatory overtime” legislation. These laws limit institutions from requiring nurses to work extended hours unless previously agreed upon but do not usually limit the number of hours to which a nurse can voluntarily agree. With mounting evidence that workers’ subjective assessment of their sleep deprived performance overestimates their actual ability, it is not difficult to foresee a future in which voluntary work hours are also restricted.

When health care policy is developed legislatively, there are bound to be unintended consequences. The proactive efforts of health professionals policing themselves could well come up with feasible real-world work hour guidelines, but only if we can shed the baggage of traditionally held beliefs. The tenets of evidence based practice must be applied to not only our clinical decision making, but also to the systems we use to deliver care. It is incumbent upon us to design systems to cover work place hours in a way that minimizes risk to ourselves while maximizing patient safety.

Cassandra Taylor, DNP, DMP, CRNA, CNE

Cassy Taylor  is an instructor at Charleston Area Medical Center School of Nurse Anesthesia, Charleston, West Virginia. She also is associate faculty, Lewis College of Business, Marshall University, South Charleston, West Virginia. She has three earned graduate degrees: a Doctor of Nursing Practice from the  Francis Payne Bolton School of Nursing, Case Western Reserve University, Cleveland, Ohio; a Doctor of Management Practice, Lewis College of Business, Marshall University, Huntington, West Virginia; and a Master of Science in Nursing, Case Western Reserve University, Cleveland, Ohio.

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 3, March 28, 2010




Airway

Seet E, Yousaf F, Gupta S, Subramanyam R, Wong DT, Chung F


 

 

Use of manometry for laryngeal mask airway reduces postoperative pharyngeal adverse events

Anesthesiology 2010;112:652-7

Seet E, Yousaf F, Gupta S, Subramanyam R, Wong DT, Chung F

 

 

Abstract

Purpose            The purpose of this study was to compare the difference in the incidence of pharyngolaryngeal complications in ambulatory surgical patients whose laryngeal mask airway (LMA) intracuff pressure was managed with manometry to limit inflation pressure to those who had routine cuff inflation without manometry.

Background            LMAs are routinely used for airway management. Serious complications are rare; however pharyngolaryngeal adverse events such as sore throat are common, with reported incidences as high as 42%. High intracuff pressures, > 60 cm H20 or 44 mm Hg have been associated with serious cranial nerve injuries secondary to LMA cuff over inflation. Unfortunately, routine monitoring of intracuff pressure with a manometer is not common practice.

Methodology            Ambulatory surgical patients, aged 18-60 years with ASA physical status I-III were recruited. Subjects were randomly assigned to routine care or pressure-limited to <60 cm H20 or 44 mm Hg. A standardized anesthetic technique was used for all patients. Anesthesia was induced with propofol and fentanyl and an LMA was inserted by an experienced clinician, followed by maintenance with desflurane and an air-oxygen mixture. Fentanyl was titrated as needed and patients were allowed to breathe spontaneously. Research assistants measured cuff pressure. Cuff pressure for subjects in the treatment group was kept < 60 cm H20 or 44 mm Hg. The incidence of sore throat, dysphagia, and dysphonia was evaluated by a blinded research assistant at 1, 2 and 24 hours postoperatively. The primary outcome of composite pharyngolaryngeal complications (sore throat + dysphagia + dysphonia) was compared between the two groups using a chi square test. Logistic regression was used to asses risk factors associated with pharyngolaryngeal complications.

Result            A total of 203 subjects completed the study (pressure limited group n = 97, routine care group n = 103). No differences in baseline demographics or perioperative data were found between groups. Immediately after LMA insertion, cuff pressure averaged 112 ± 59 mm Hg in the pressure-limited group compared to 114 ± 57 mm Hg in the routine care group. After adjustment of intracuff pressure in the pressure-limited group, cuff pressure was significantly lower than the control group (40 ± 6 vs. 114 ± 57 mm Hg, P < 0.001).

Composite pharyngolaryngeal adverse events were significantly less frequent in the pressure-limited group (13.4% vs. 45.6%, P < 0.001). Use of manometry decreased the relative risk of complications by 70.6% with a number needed to treat of 3 (95% CI 2.2-7.5) needed to prevent complications with the pressure-limited group. The incidence of sore throat was significantly less at 2 hours (2.1% vs. 8.7%, P <0.05) and 24 hours (3.1% vs. 13.6%, P < 0.05) in the pressure-limited group. Dysphagia was significantly less at all three time points (1 h: 1% vs. 12.6%; 2 h: 0% vs. 12.6%; 24 h: 2.1% vs. 8.7%, P < 0.05), whereas dysphonia was only significantly less at 1 hour (5.2% vs. 15.5%, P < 0.05). Logistic regression revealed that the only variable predictive of pharyngolaryngeal complications was intracuff pressure (P = 0.0001). Clinical experience, number of insertion attempts, ease of insertion, blood on LMA, duration of surgery, use of an oral airway, incidence of larygospasm, and suctioning were not associated with complications.

Conclusion            Use of a manometer to keep LMA intracuff pressure < 60 cm H20 or 44 mm Hg significantly decreased the incidence of sore throat, dysphagia and dysphonia in ambulatory surgical patients allowed to spontaneously breathe under general anesthesia with desflurane and air-oxygen mixture. The authors recommended the routine use of a pressure manometer to keep LMA intracuff pressures < 60 cm H20 or 44 mm Hg.

 

Comment

This was a well designed prospective, randomized trial which provides compelling evidence for keeping LMA intracuff pressures < 60 cm H20 or 44 mm Hg to limit the incidence of pharyngolaryngeal complications. I was amazed at how LMA intracuff pressures in both groups after placement were almost two times the manufactures’ recommendation for intracuff pressure (< 60 cm H20 or 44 mm Hg). In this day of increasing ambulatory surgery I think it is important that we continue to find ways to decrease complications and improve outcomes. I don’t think we will ever find a way to completely eliminate the incidence of sore throat after use of an LMA (or intubation); however anything we can do certainly may help. After reading this study I began using a manometer routinely with LMAs and found that my intracuff pressures were still higher than what is recommended, so I now use the manometer to keep the pressure less than 60 cm H20 or 44 mm Hg. Likewise, I teach my students to routinely use a manometer and to keep cuff pressures below recommended maximum pressure.

 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, Department of Defense or the United States Government.

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 3, March 28, 2010




Obstetric Anesthesia

Bateman BT, Berman MF, Riley LE, Leffert LR


The epidemiology of postpartum hemorrhage in a large, nationwide sample of deliveries

Anesth Analg 2010;110:1368-73

Bateman BT, Berman MF, Riley LE, Leffert LR

Abstract

Purpose            The purpose of this study was to describe the trends in the incidence and epidemiology of postpartum hemorrhage, with a focus on risk factors and maternal outcomes.

Background            Postpartum hemorrhage (PPH) is defined as > 500 mL of blood loss after a vaginal delivery and > 1000 mL after cesarean delivery. PPH is associated with significant morbidity and mortality, and recent trends in maternal demographics and obstetrical management may contribute to the increased incidence of PPH.

Methodology            Data was collected on PPH between 1995 and 2004 from the Nationwide Inpatient Sample (NIS), which is maintained by the Agency for Healthcare Research and Quality. It is a representative sample that includes approximately 20% of all discharges from non-Federal, acute-care hospitals in the U.S. The investigators used the International Classification of Diseases codes to identify cases of PPH and comorbid conditions that may be associated with PPH. Logistic regression was used to identify risk factors for uterine atony, a common cause of PPH.

Result            In 2004 there were 25,654 cases of PPH out of 876,641 deliveries, with uterine atony accounting for 79% of all cases of PPH (Table 1). From 1995 to 2004 the rate of PPH increased 27.5%; uterine atony accounted for the largest proportion of this increase, while the rates of other causes did not change significantly. Independent risk factors associated with PPH requiring a blood transfusion were age <20 or >40, cesarean delivery, hypertensive disorders of pregnancy, polyhydramnios, chorioamnionitis, multiple gestation, retained placenta, and antepartum hemorrhage.  After excluding age and cesarean delivery, 38.8% of patients had one or more of these risk factors. The five highest predictors (P<0.001) of PPH requiring transfusion were: (1) retained placenta (odds ratio 4.1, 95% CI 3.1-5.5), antepartum hemorrhage (odds ratio 3.8, 95% CI 3.0-4.8), multiple gestation (odds ratio 2.8, 95% CI 2.2-3.6), chorioamnionitis (odds ratio 2.5, 95% CI 1.9-3.3) and hypertensive disorders of pregnancy (odds ratio 2.5, 95% CI 2.1-2.8).

Table 1. Rate and Etiology of PPH

Causes

N (%)

Total deliveries

876,641

All causes

25,654 (2.93)

   Uterine atony

20,353 (2.32)

   Retained placenta (including accreta)

2466 (0.28)

   Delayed (>24 hours after delivery)

2007 (0.23)

   Coagulopathy

1349 (0.15)

   Resulting in transfusions

2312 (0.26)

   Resulting in hysterectomy

529 (0.06)

   Atony resulting in transfusion

1634 (0.19)

   Atony resulting in hysterectomy

265 (0.03)

 

The most frequent complication from PPH was hysterectomy (n = 529, 2.1%), with PPH increasing the odds of need for hysterectomy 89.1 times (95% CI, 75.7-104.9). The next three most common complications were: coagulopathy (n = 445, 1.8%; odds ratio 4.7, 95% CI 4.2-5.2), acute respiratory failure (n = 105, 0.4%; odds ratio 10.9 95% CI 8.7-13.6), and acute renal failure (n = 82, n = 0.3%; odds ratio 13.6, 95% CI 10.6-17.8). Parturients with PPH were 7.8 times more likely to have in-hospital mortality (95% CI 4.3-14.0) (n = 13, 0.1%), with PPH being associated with 19.1% of in-hospital deaths.

When compared to hospitals with the largest number of deliveries per year (> 1791), hospitals with the lowest delivery rates (< 272) deliveries had significantly higher rates of PPH and PPH from uterine atony, as well as PPH and PPH from uterine atony requiring transfusion (P <.005).

Conclusion            PPH, especially secondary to uterine atony, is a common complication of delivery that has steadily increased in frequency in the U.S. PPH is sometimes severe enough to require blood transfusions, and is associated with significant maternal morbidity and mortality. Unfortunately many parturients who experience PPH do not have identifiable antepartum risk factors.

 

Comment

This retrospective review of a large database is helpful to anesthesia providers because it provides us with some predictors of PPH and the associated complications. For me, it reinforces my belief that when I am faced with a patient who has uterine atony, especially with some of these identified risk factors, I need to be prepared to aggressively treat the atony with uterotonics (i.e., pitocin, methergine, hemobate, or cytotec) and be prepared to emergently transfuse blood products.

It is probably no surprise that when compared to hospitals with the highest delivery rates, hospitals with the lowest delivery rates had higher rates of PPH. The reason for this is most likely due to limited resources (i.e., interventional radiology capable of placing iliac balloon catheters, limited blood supply) and personnel with experience in managing PPH and subsequent complications. I think the take home message from this is that anesthesia providers that work in small rural facilities should be aware of what resources they have available and who they can identify to assist them in managing a hemorrhaging parturient. This might mean identifying a nurse who can be your second pair of hands to assist with blood transfusion and resuscitation or being familiar with your blood bank capabilities.

This was a well designed study; however because it is a retrospective review of a large database, with review of only one year of data (2004), it is prone to bias. Because it is a retrospective study, there is the possibility of coding errors when the data was originally entered. Also it does not include variables that may be important predictors of PPH, e.g., length of labor, tocolytic use, past obstetric history, type of anesthesia for cesarean delivery (regional vs. general anesthesia), and urgency of delivery. Nonetheless I still think it is an important study that provides us with a greater understanding of the epidemiology of PPH.

 

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, Department of Defense or the United States Government.

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 3, March 28, 2010





Hawkins J


 

Epidural analgesia for labor and delivery

N Engl J Med 362;16:1503-1510

Hawkins J

 

Abstract

Purpose            This article reviewed recommendations for pain management during labor and delivery using epidural analgesia.

Background            Obstetric labor often causes severe pain. It is unacceptable for an individual to experience untreated severe pain in any circumstance. Maternal request is a sufficient indication for pain relief during labor. Studies have shown that postnatal depression may be more common when sufficient pain relief is not provided to a laboring patient. It has also been shown that maternal cognitive function is improved with sufficient pain relief during labor and providing the labor patient with pain relief can even help the father focus on assisting the mother more effectively. Pain during labor is transmitted through nerves from T-10 through S-4 during labor. Stress and pain increased norepinephrine levels by 25% which, in turn, can decrease uterine blood flow by as much as 50%. Successful epidural analgesia can decrease endogenous catecholamine levels and return uterine blood flow to near normal levels.

Methodology            Most clinical trials compare epidural analgesia to narcotic pain control during labor. In one study of 992 nulliparous woman, epidural analgesia was compared to meperidine / nitrous oxide analgesia. Pain was rated from 0-100, with 100 being the worse pain imaginable. In another study of 2,703 nulliparous women, one group was assigned to epidural analgesia and the other to intravenous meperidine. The women were asked to rank their pain from 0-10, with 10 being the worst pain.

Result            In the first study the median pain score for the epidural group was 27, while the median pain score for the meperidine / nitrous oxide group was 75. In the second study, the women all ranked their pain score at 9 prior to intervention. After intervention, and during the first stage of labor, the epidural group ranked their pain score a 2 on average, while the meperidine grouped ranked their pain score a 4. During the second stage of labor, pain scores rose to 3 and 5 respectively. On the first postpartum day, the epidural group reported satisfaction with the analgesia at 95% while the meperidine group reported their satisfaction at 69%.

Conclusion            Pain management is an essential part of obstetric care. Epidural analgesia is an excellent method of providing pain management during labor. Some of the contraindications for epidural analgesia include uncorrected maternal hypovolemia, infection at the needle puncture site, increased intracranial pressure, and inadequate training on the part of the anesthesia provider. One of the benefits of establishing an epidural is that the catheter can be used to administer a surgical dose of anesthesia in the event a cesarean section is required.

Many physicians and nurses still believe that epidural analgesia contributes to an increased rate of cesarean section. The preponderance of evidence suggests otherwise. A Cochrane review of 20 trials involving more than 6,500 patients placed the increased risk of cesarean section attributed to epidural analgesia to be 0.07%. The studies also show that epidural analgesia increases the second stage of labor by 15 to 30 minutes and may increase the incidence of instrument delivery slightly.

Epidural analgesia is reasonably safe. The incidence of epidural hematoma and epidural abscess were estimated to occur  in 1 of every 168,000 cases and 1 of 145,000 cases respectively. Headaches associated with dural punctures are the most common complication estimated to occur in less than 1% of cases. Back pain associated with epidural placement is not increased after labor compared to no epidural intervention. Other rare complications associated with epidural analgesia include maternal fever and interference with post delivery breast feeding associated with epidural doses of fentanyl greater than 150 µg.

 

Comment

Epidural analgesia is a safe and effective method of pain control during labor. Its use is not associated with a significant risk of cesarean delivery no matter when it is initiated, and it is associated with less nausea and other complication compared to intravenous narcotic analgesia. Many anesthesia providers, physicians and nurses, still practice under the misconception that epidural analgesia should be delayed until a patient’s cervix is dilated to 5 cm or beyond to decrease the risk of an epidural slowing labor progress and increasing the risk of cesarean section. This misconception only delays appropriate pain relief, and in my opinion, contributes to a less satisfactory labor experience. Recent studies show that an epidural placed during active labor at any point during the labor process does not contribute to a negative outcome, and will most likely assist in a positive one. I am very aware that obstetric anesthesia is time consuming, often financially unrewarding, and frequently the cause of sleep deprivation. However, the experience for both the provider and the patient can be very rewarding, and the skills necessary to provide expert care in obstetric anesthesia are often beneficial in all other areas of anesthesia practice.

 

Steven R Wooden, MS CRNA

 

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 3, March 28, 2010




Pain

Helm S, Glaser S, Falco F, Henry B


 

 

A medical-legal review regarding the standards of care for epidural injections, with particular reference to a closed case

Pain Physician 2010;13:145-150

Helm S, Glaser S, Falco F, Henry B

 

 

Abstract

Purpose            This medical-legal review used a case study to demonstrate difficulties in determining the standard of care.

Background            The specialty of pain management rests on three pillars. They are, providing access to appropriate care, using techniques supported by scientific evidence, and providing these services safely. Even when these pillars of care are maintained, complications can still arise. The most serious complications occur in pain management when substances are injected into an artery or nerve. When these complications occur, experts for the plaintiff often argue that the provider was not following prescribed protocol or the standard of care.

Methodology            One such case involved a 67 year old woman with persistent back pain resulting from a compression fracture at T-12. After conservative therapy was not successful, a transforaminal epidural steroid injection was attempted at T12-L1. Under fluoroscopic guidance, a needle was placed in the ventral cranial aspect of the foramen followed by contrast dye. The contrast dye showed venous runoff, but no extravasation. The radiographic image also showed that there was a good outline pattern of the T-12 nerve root. After the dye was injected 4 times to determine proper needle placement, a local anesthetic and steroid were injected. Within 5 minutes, the patient developed paraplegia and incontinence.

Result            In the ensuing litigation, expert witnesses for the plaintiff provided contradictory statements regarding the standard of care and why they believed the provider had deviated from it. The first expert testified that the artery must be identified on the first injection before the contrast obscures the vessels. The second expert testified that the contrast was injected in the wrong position but found no problem with the location of the needle in the ventral aspect of the foramen when the steroid was injected. The third expert opinion was that the steroid was injected inappropriately in the ventral aspect of the foramen.

Conclusion            A standard of care might imply that there is a prescribed protocol, which when followed will avoid complications. The disagreements between these experts suggested that there is not one appropriate method when performing a procedure, and therefore failure to follow a particular set of guidelines does not automatically mean the standard of care was not met. Most states define the standard of care as what is reasonable under the circumstances presented, and care that would be provided by a well trained practitioner under similar circumstances.

Expert opinions are not supposed to be personal opinions, but unfortunately some so-called experts interject their own opinions and represent them as the standard of care, distorting the principles involved, to justify their expert status. This case study demonstrated the difficulty in defining the standard of care in some clinical situations. While protocol and guidelines are useful, there are often multiple reasonable ways of performing a procedure.

Comment

This particular case is interesting in itself, but the message behind the article is even more important. We often discuss the “standard of care” but many practitioners do not understand what it really means. We often mistake “standards” or guidelines developed by professional organizations as the standard of care. Those organizational standards are merely guidelines often established by consensus, literature review, or political mandate. Having served as a legal expert on several occasions, my “expert opinion” is often one of many. Just as in this case study, experts often differ in their opinion of what the standard is, even when considering the specific facts of a single procedure. What you must ask yourself when you consider what the standard of care is in any given situation is what an appropriately trained provider would do in a similar situation. Can you justify your actions by demonstrating that others in your field would have done the same thing given the circumstances? Can you identify peer reviewed clinical documents that demonstrate that what you do is safe and effective? I have always felt that the practice of anesthesia is as much an art is it is a science. Each and every situation is unique and sometimes requires creativity in order to successfully complete a task, but we need to make sure that “creative” techniques used in various situations do not stray from the foundations of scientific principles and safe patient care.

 

Steven R Wooden, MS, CRNA

 

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 3, March 28, 2010




Pharmacology

Agoliata A, Dexter F, Lok J, et al.


 

 

Meta-analysis of average and variability of time to extubation comparing isoflurane with desflurane or isoflurane and sevoflurane

Anesth Analg 2010;110:1433-9

Agoliata A, Dexter F, Lok J, et al.

 

 

Abstract

Purpose            The purpose of this study was to use knowledge of how to model mean time to extubation from the Anesthesia Information Management system (AIMS) to conduct a meta-analysis of clinical trials comparing time to extubation between isoflurane and either desflurane or sevoflurane.

Background            Anesthesia Information Management Systems (AIMS) data can assist administrators in comparing extubation times across providers and agents with the goal of identifying ways of reducing cost. The authors of this study previously described how to use the AIMS to model time to extubation (quantified by calculating percent of AIMS cases with extubation times >15 minutes) They reported meta-analysis results suggesting desflurane reduced mean time to extubation by 25% and the variability in time to extubation by 21% when compared to sevoflurane.

Isoflurane is cheaper to purchase than newer inhaled anesthetics, however the benefit of this may be lost if there are delays in time to extubation. Prolonged time to extubation may increase labor and intangible costs in operating rooms with > 8 hours of cases, i.e., a frustrated surgeon waiting for the next case to start in the same room.

Methodology            A systematic review of the literature was completed using defined search terms on the Medline database. A total of 58 out of 116 articles identified met inclusion criteria. Meta-analysis techniques were used to analyze the results. Prolonged extubation times were defined as time to extubation >15 minutes. Additional data was presented on percentage reductions in time to extubation, percentage reductions in time to extubation with LMA, and percentage reductions in time to following commands for isoflurane compared to either desflurane or sevoflurane.

Result            Compared to isoflurane, desflurane reduced the mean time to extubation by 34% and reduced the variability in extubation times by 36%. This in turn would reduce the incidence of time to extubation >15 minutes by 95% and variability in extubation time by 97%, respectively. When an LMA was used, modeling indicated that desflurane would reduce the mean time to LMA removal by 18%. Similar results were found for sevoflurane when compared to isoflurane, however the percent reductions were smaller. Sevoflurane reduced the mean time to extubation by 17% and the variability in time to extubation by 8.4%, which would in turn reduce the incidence of prolonged extubations by 51% and variability by 35%. Mean percentage reductions in time to following commands were 34% for desflurane and 27% for sevoflurane, when compared to isoflurane.

Conclusion            Meta-analysis techniques allows for pooling of small time difference estimates across studies comparing time to extubation with various volatile anesthetics. This is important since cost reductions resulting from working faster and/or using a cheaper inhaled anesthetic depend on precise measurement of relatively small time differences. Facilities should use results from this study along with local data on mean extubation times when making evidence-based decisions on what inhaled anesthetics will be purchased and guidelines for how they will be used.

 

Comment

I must admit I had to read this study multiple times, and review the authors’ previous study, to understand the results. Essentially what the authors were attempting to do was use statistical modeling techniques (i.e., meta-analysis) to compare isoflurane with desflurane or sevoflurane with regard to mean time to extubation or following commands. Their results are not surprising given the solubility differences between isoflurane and desflurane or sevoflurane.

Clinically this is what we see in the OR; those patients who get isoflurane wake up a lot slower. I remember as a student that some staff would make me use isoflurane all the time because the other two agents were much more expensive, or they would allow me to use sevoflurane for induction then switch to isoflurane for maintenance. The belief was that this would save pharmaceutical costs, however at the expense for increased labor costs, for example, PACU staffing. The authors’ main argument in this study is that the newer inhaled anesthetics decrease both direct (time to extubation) and intangible costs. That is, it keeps the surgeon from running off to see patients in his clinic because it is taking a long time to wake-up the patient, which may delay the start of the next case because the surgeon is not present.

One thing I would like to point out to our readers is that the previous study1, which this report was based on, was funded by Baxter Pharmaceuticals, the maker of desflurane. The authors stated the company did not influence their results or assist in manuscript preparation with either study. However, the general theme of this and the previous manuscript seemed to place more emphasis on desflurane when compared to sevoflurane. Readers should consider this when interpreting the results.

 

Dennis Spence, PhD, CRNA

 

 

1. Dexter E, Bayman EO, Epstein RH. Statistical modeling of average and variability of time to extubation for meta-analysis comparing desflurane to sevoflurane. Anesth Analg 2010;110:570-80

 

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, Department of Defense or the United States Government.

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 3, March 28, 2010





Rusy LM, Hainsworth KR, Nelson TJ, et al


Gabapentin use in pediatric spinal fusion patients: a randomized, double-blind, controlled trial

Anesth Analg 2010;110:1393-8

Rusy LM, Hainsworth KR, Nelson TJ, et al

 

Abstract

Purpose            The purpose of this study was to evaluate the effect of preoperative and postoperative administration of gabapentin on acute postoperative pain in pediatric patients undergoing spinal fusion.

Background            Spinal fusion in pediatric patients is associated with significant postoperative pain and can result in peripheral and central sensitization of dorsal horn neurons secondary to tissue injury. Sensitization of these neurons may amplify postoperative pain and is implicated in the development of chronic pain. The anticonvulsant, gabapentin, has been shown to reduce neuronal firing and is effective in treating centrally mediated (central sensitization), chronic neuropathic pain, as well as acute postoperative pain. Studies in adults have found an opioid sparing effect with perioperative administration of gabapentin, however there are no reported studies in children or adolescents.

Methodology            This was a prospective, randomized, double blind, placebo controlled trial in patients aged 9 to 18 years. Subjects were administered either gabapentin 15 mg/kg or placebo preoperatively, followed by gabapentin 5 mg/kg or placebo 3 times a day for 5 days. The primary outcome measure was opioid consumption. Secondary outcomes included pain scores, opioid related side effects, and sedation scores. Descriptive and inferential statistics were used to analyze the results.

Result            Data collection was completed for 59 subjects in the study (gabapentin n = 29 and placebo n = 30). No differences were found between the groups on demographic variables. Subjects in both groups were approximately 14 years/old, weighed 56 kg, and were predominately female (75%).

Subjects in the gabapentin group required significantly less morphine when compared to the placebo group both in the PACU (0.044 ± 0.017 mg/kg/hr vs. 0.064 0.031 mg/kg/hr, P = 0.003) and on postoperative day 2 (0.036 ± 0.016 mg/kg/hr vs. 0.047 ± 0.019 mg/kg/hr, P = 0.018). Subjects in the gabapentin group had lower opioid consumption on postoperative day 1 (0.046 ± 0.016 mg/kg/hr) when compared to the placebo group (0.055 ± 0.017 mg/kg/hr), however the difference was not statistically significant (P = 0.051). Cumulative morphine consumption through day 2 was significantly less in the gabapentin group (0.126 ± 0.038 mg/kg/hr) compared to the placebo group (0.165 ± 0.061 mg/kg/hr, P = 0.005).

Pain scores in the gabapentin group were significantly less in the PACU (2.5 ± 2.8 vs. 6.0 ± 2.4, P < 0.001) and on the morning of day 1(3.2 ± 2.6 vs. 5.0 ± 2.2, P = 0.005), then were similar through postoperative day 4. There were no statistically significant differences in opioid related side effects or mean number of doses of medications, although subjects in the gabapentin group did require less odansetron, diphenhydramine, and diazepam.

Conclusion            Perioperative gabapentin decreased initial postoperative pain and opioid consumption after spinal fusion surgery without significantly impacting opioid related side effects. Gabapentin is effective in reducing early postoperative pain for up to 2 days in children and adolescents. No benefit was seen beyond 48 hours of treatment.

 

Comment

There is a growing body of evidence suggesting that perioperative administration of gabepentin in a multimodal approach significantly reduces postoperative pain (decreasing pain scores by 27-39%) and opioid consumption (decreasing opioid consumption by 35%) in adults within the first 24 hours after surgery.1 The exact mechanism is unknown, but it is believed that gabapentin blocks or reduces the development of hyperalgesia surrounding the surgical incision by selectively blocking the nociceptive process involved in central sensitization. Most studies in adults have evaluated the efficacy of large single doses of gabapentin (e.g., 1200 mg). This is the first study in adolescents having major back surgery that evaluated the efficacy of preoperative and postoperative gabapentin administration. I believe it provides further support for gabapentin use as part of a pre-emptive and multi-modal analgesia plan.

When administering adjunctive medications such as gabapentin it is important to understand the side effects so that they can be conveyed to the patient or family member. The most common side effect of gabapentin is dizziness (relative risk = 1.4) and sedation (relative risk 1.65). The severity of these side effects is dose dependent.1 In this current study, the authors did not measure dizziness, but did measure sedation scores. However I could not find the sedation score results in the manuscript. Not reporting on these two side effects is a weakness of this study, especially given these are the two most common side effects. It is important to note that two subjects in the gabapentin group withdrew from the study secondary to side effects; one for excessive feeling of sedation and 1 for a rash. In my clinical experience, sedation is fairly common with larger doses of gabapentin, and the withdrawal of one patient is not surprising given the large preoperative dose of 15 mg/kg, which equated to 840 mg of gabapentin. Future research studies should report on the incidence and severity of these side effects of gabapentin since this allows anesthesia providers to weigh the risks and benefits when recommending its use.

A limitation of this study was that the patient population was predominately female, ranged from 9-15 years of age, and had a single surgical procedure (posterior spinal fusion), which may limit the generalizability of the results. Nonetheless, I still believe it is an important study that adds to the growing body of knowledge on perioperative administration of gabapentin.

 

Dennis Spence PhD, CRNA

 

1. Peng P, Wijeysundera DN, Li C. Use of gabapentin for perioperative pain control- a meta-analysis. Pain Res Manage 2007;12:85-92

 

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, Department of Defense or the United States Government.

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 3, March 28, 2010




Policy, Process, & Economics

Olson EJ, Drage LA, Auger RR


 

 

Sleep deprivation, physician performance, and patient safety

Chest 2009;136:1389-1396

Olson EJ, Drage LA, Auger RR

 

 

Abstract

Problem            While extended work hours have historically been routine in healthcare settings, there is increasing debate regarding the risks and benefits of such schedules.

Background            This review summarized sleep/wakefulness physiological processes as they apply to health care workers in general, and specifically to physicians in training.

Sleep/wake Regulation            Activities of the hypothalamus and brainstem serve as a switch that determines cycles of sleep and wakefulness, with transitions primarily regulated by the interaction of two mechanisms. One mechanism is a homeostatic process that is dependent on hours spent asleep or awake. The other mechanism of influence is the well known circadian rhythm, which is tied to environmental light, and is independent of sleep.

Sleep and work             Most of the studies included in this review were grounded in the homeostatic process, examining the effect of sleep deprivation. Few studies of circadian rhythm, relating to non-daylight work hours, were included. Studies of psychomotor skills after extended wakefulness have compared the resulting effects to be similar to that of alcohol. Like alcohol, sleep deprivation increases the likelihood of motor vehicle accidents. Sleep deprived participants subjectively experience a plateau in loss of psychomotor skills, while observation confirms that the effects are in fact dose dependent and continue to worsen with increasing hours of wakefulness. Most studies documenting adverse effects of sleep deprivation on physicians and their patients have involved physicians in training. Anesthesia residents demonstrated slower response times when sleep deprived. When the schedule of internal medicine residents was rearranged to allow for increased sleep time, the frequency of errors was significantly reduced. Interestingly, there was no effect on adverse patient outcomes, attributed to the positive effect of multidisciplinary support from other health care providers. While there is some evidence that naps may offset some of the effects of sleep deprivation, the effect of “sleep inertia” impairs performance during the time immediately following awakening.

Although the complexity of factors makes the study of sleep quite challenging, the data collected have prompted limits on the duty hours of physician residents. Tracking of these limits since their adoption in 2003 has shown multiple areas of non-compliance, most commonly in the time limit of continuous duty (30 hours).

Conclusion            The processes regulating sleep and wakefulness are challenged by multiple factors common in physician residents and other health care workers. Six years after the change to limit resident work hours there are still those saying the limits are unnecessary, while others are calling for stronger restrictions.

 

Comment

See comment following the next abstract, “Effects of extended work shifts and shift work on patient safety, productivity, and employee health.”

 

Cassandra Taylor, DNP, DMP, CRNA, CNE

 

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 3, March 28, 2010





Keller SM


 

Effects of extended work shifts and shift work on patient safety, productivity, and employee health

AAOHN Journal 2009;57:497-502

Keller SM

 

Abstract

Problem            Non-traditional work hours may adversely affect the health of workers and their work results.

Background            The need for highly qualified staff, combined with provider shortages, often force managers to look for creative staffing patterns to maintain adequate coverage. These factors combine to potentially impact worker health and safety in environments such as factories and the maritime industry. In work environments such as law enforcement and health care, the safety of non-workers must be examined as well. This review is targeted toward occupational health nurses’ efforts to prevent adverse events in work place environments. Literature relating to shifts outside of conventional daytime and those with extended hours designed to compress the work week were included in this review.

Negative Effects            Working extended hours has been shown to have negative effects on workers. The effect of sleep deprivation on driving has been compared to that of alcohol. Studies outside of health care have demonstrated an association of non-traditional work hours with increased worker fatigue and chronic illness, and that this effect is stronger in older workers. Hours for health care workers are longer than in other professions, which may expose them to additional increases in the risk to their own health.

Extended work hours for health care workers can also affect the patients under their care. In health care settings, non-traditional work hours have been linked to increased errors and patient injuries. In 2003, concern about the adverse effects of prolonged work hours prompted initiation of limits to the hours physicians work during residency. Nurses working extended hours self report impaired critical thinking and a greater tendency toward medication errors. Increasing number of days worked consecutively and fewer number of hours between shifts may add to the negative effects of non traditional work hours.

Positive Effects            Some workers value the additional time off that extended work hours create, while others may spend the entire time off recovering from work. Younger workers are especially likely to accept the trade off because they are less prone to fatigue and adapt more quickly to non-daylight working hours.

Compensatory Behaviors            Non-traditional work hours are a powerful tool to help with staffing needs, prompting the search for alternatives to eliminating these shifts.  Naps during work have been shown to have beneficial effects during non traditional work hours. Flexible hours, job sharing, and limits to consecutive extended shifts may offset the negative affects of non-traditional work hours. Some additional strategies suggested are adequate workplace lighting, recreational facilities, and breaks. Healthy eating and sleeping patterns outside of work become even more important for the wellness of those working non-traditional schedules.

Conclusion            This author concludes that there is no one size fits all approach to work hours and suggests an individualized approach to determining best practices regarding work hours.

 

Comment

Studies of extended work hours of nurses and physicians are reviewed in these two articles. Continued research from both fields will be useful to advanced practice nurses, such as nurse anesthetists. Studies of experienced physicians and non-physicians need to be done to investigate if the findings with trainees hold true with experienced workers. While restricted resident work hours have not translated into improved patient outcomes, it is noteworthy that the amount of non-compliance to the new resident guidelines is significant, meaning future trends could change. The role of the anesthesia provider shortage cannot be ignored in these discussions, as efforts to limit work hours will only exacerbate the shortage. Strategies that allow work places to continue to use non-traditional hours will help alleviate the shortage, but most have not yet been tested. Even if the effects of sleep deprivation could be thoroughly documented and managed, the need for anesthesia coverage during non-daylight hours would remain. Anesthesia providers, and all healthcare workers, could benefit from an improved understanding of non-daylight work hours that further study might bring.

The emerging body of knowledge regarding non-traditional work hours and sleep deprivation has direct implications on the practice of nurse anesthesia. Many nurse anesthetists have worked extended hours, since we are highly qualified workers whose services are required 24 hours a day in most work environments. The anesthesia provider shortage contributes to the need for non-traditional hours in order to maintain adequate coverage. Historically, nurse anesthetists have done whatever it takes to cover their work environments. There is now considerable evidence that this attitude contributes to a previously unrecognized risk to their health. Since nurse anesthetists are an aging work force, we are even more susceptible to the health risks associated with non-traditional hours. Nurse anesthetist may not always be comfortable with putting their own health needs ahead of the needs of their work place. However, the needs of our patients will always come first, making the clear association between sleep deprivation and increased risk to patients profoundly important. It may be that the first element of anesthesia patient safety is a well rested provider.

 

Cassandra Taylor, DNP, DMP, CRNA, CNE

 

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 3, March 28, 2010




Respiration & Ventilation

Neligan PJ, Malhotra G, Fraser M, Williams N, Greenblatt EP, Cereda M, Ochroch EA


Noninvasive ventilation immediately after extubation improves lung function in morbidly obese patients with obstructive sleep apnea undergoing laparoscopic bariatric surgery

Anesth Analg 2010;110:1360-5

Neligan PJ, Malhotra G, Fraser M, Williams N, Greenblatt EP, Cereda M, Ochroch EA

Abstract

Purpose            This study compared noninvasive positive pressure ventilation (NIPPV) initiated immediately after extubation with delayed initiation (30 minutes after extubation) on postoperative lung function in morbidly obese patients with obstructive sleep apnea (OSA) undergoing laparoscopic bariatric surgery.

Background            Morbid obesity is associated with increased morbidity and mortality related to pulmonary complications during the perioperative period. Atelectasis is a common problem that results from decreased functional residual capacity secondary to anesthesia, surgery, and opioids. Furthermore, airway obstruction secondary to OSA is a significant problem in bariatric patients that is also compounded by the above factors. A variety of intraoperative and postoperative measures have been reported to improve postoperative lung function after bariatric surgery. NIPPV has been shown to improve outcomes, however it is unclear when is the best time to begin NIPPV after bariatric surgery.

Methodology            This was a single-blind, randomized controlled trial of 40 patients with sleep study confirmed OSA treated with CPAP (continuous positive airway pressure) undergoing laparoscopic bariatric surgery by a single surgeon. Subjects were randomized to receive NIPPV immediately after extubation (Immediate group) or to have NIPPV delayed for 30 minutes after surgery (Delayed group). Both the Immediate and Delayed groups included 20 patients. Randomization was stratified so that both groups included 10 subjects who underwent a laparoscopic roux-en-Y gastric bypass and 10 subjects who underwent laparoscopic gastric banding. A standardized anesthetic approach was used for all patients (Table 1).

 

Table 1. Standard Anesthetic Plan and Outcome Measures

Induction

Emergence

     Ramped position

     Reversal of neuromuscular blockade

     Preoxygenated with Pressure Support of

     7-10 cm H20 / PEEP 10 cm H2O

     Extubation in semirecumbant position. No

     spontaneous ventilation while intubated

     Induction w/ fentanyl/propofol/vecuronium

 PACU

     Direct laryngoscopy

     NIPPV w/ BiPAP at subjects prescribed

     settings

Maintenance

     Hydromorphone PCA

    Recruitment maneuver: maintain 40 cm

    H2O vital capacity breath for 30-40 sec

     PACU stay for 2 h then sent to bariatric unit

     Reverse trendelenburg

    NIPPV for minimum of 8 h overnight

     Tidal Volume 6 ml/kg ideal body weight

Spirometric Measurements

     PEEP 7 cm H2O if BMI<50 kg/m2, 10 cm

     H2O if BMI> 50 kg/m2

    FVC, FEV1, PEFR @ preop (baseline), 1 h

     postop, and on postop day 1 (24 h after

     extubation).

     50:50 Air : O2 + Desflurane

Primary outcome

     Intraop: vecuronium/morphine/ketorolac

     Change in FVC (FVC baseline – FVC 24 h)

Note. Forced vital capacity (FVC), forced vital capacity in 1 second (FEV1), and peak expiratory flow rate (PEFR).

 

Subjects in the Delayed group received 4-6 lpm oxygen via nasal cannula immediately after extubation. Subjects in the Immediate group were placed on NIPPV immediately after extubation with FiO2 0.50, CPAP as prescribed from their sleep study, and inspiratory positive pressure support to maintain a tidal volume of 400-500 mL via a portable ventilator and full mask.

Outcome measures are listed at the bottom of Table 1. Descriptive and inferential statistics were used to analyze the results. Analysis of covariance (ANCOVA) was used to control for significant covariates in spirometric results.

Result            Groups were similar for all demographic and baseline spirometric measurements except weight and BMI. Subjects in the Immediate group weighed more and had a greater BMI (Immediate group: 145 ± 23.4 kg vs. Delayed group: 127 ± 20.0 kg) and (Immediate group: 50 ± 8.20 kg/m2 vs. Delayed group: 46 ± 5.14 kg/m2) (P = 0.03). The majority of subjects in both groups were female (80%). Mean postoperative CPAP was 9.9 cm H2O in the Delayed group (range 2-17 cm H2O) and 11.3 cm H2O in the Immediate group (range 4-19 cm H2O) (P = 0.34). Type of surgery was not associated with spirometric results in either group.

At 1 hour after surgery, subjects in the Immediate group had significantly less reduction in FEV1, FVC, and PEFR compared to the Delayed group (P = 0.0001). On average, there was a 55% reduction in spirometric measurements in the Delayed group compared to only a 24% reduction in the Immediate group at 1 hour postoperatively. For the primary outcome (FVC baseline – FVC 24 h) subjects in the Immediate group had significantly less reduction in FVC at 24 hours (Immediate group: 0.66 L (-23%) vs. Delayed group: 1.3 L (-44%), P = 0.0005). The Delayed group had statistically significant improvement in all spirometric measurements at 24 hours when compared to the 1 hour measurement; however the Immediate group showed only mild improvement in PEFR.

The ANCOVA model indicated age and height were the only significant covariates related to spirometric measurements, with age being important for PEFR and height for FVC. Weight and BMI did not affect the relationship between group and any spirometry measurements. No adverse events occurred in either group.

Conclusion            In morbidly obese patients with OSA, Noninvasive Positive Pressure Ventilation (NIPPV) started immediately after extubation significantly improved pulmonary function at both 1 hour and 24 hours after laparoscopic bariatric surgery compared to CPAP delayed to the PACU.

 

Comment

The investigators evaluated a very aggressive perioperative management program aimed at preventing postoperative atelectasis and pulmonary complications in morbidly obese patients with OSA undergoing laparoscopic bariatric surgery. They found they could reduce, but not eliminate, the decrease in lung function as measured by spirometry in the intermediate postoperative period. The findings of this study are important because it demonstrates despite using a standardized anesthetic and postoperative management plan that includes early initiation of CPAP, patients still experience over a 50% reduction in lung function. I think the findings in the control group are important, and it makes me wonder how much greater is the reduction in lung function in morbidly obese patients with OSA when an aggressive approach to intraoperative (i.e., use of preinduction CPAP/PS + recruitment maneuvers + no spontaneous breathing while under anesthesia) and postoperative management (CPAP initiated within 30 minutes after surgery) is not used.  The question for me is, in the control group, is it all or just one of these interventions that is beneficial?

There are some limitations to this study. The biggest was the baseline difference in weight and BMI between the groups, with the Immediate group weighing almost 18 kg more. However, the ANCOVA model did not find these variables to influence the results. Subjects in the Immediate group may have been the ones most likely to benefit from immediate NIPPV initiation, and thus this could partially explain the dramatic differences between groups. Also a majority of the patients were female, and the facility where the study was completed had dedicated staff and protocols in place for managing bariatric patients.

Despite these limitations, I think the findings that immediate use of NIPPV after extubation, along with an aggressive postoperative management plan, are important. The question becomes how can other facilities apply these findings to practice. Trying to coordinate immediate use of NIPPV may be challenging in some facilities, but could be accomplished, especially if a multi-disciplinary team is brought together to develop a guideline for managing bariatric patients. One concern I have heard from surgeons is that they are hesitant to start CPAP in OSA patients postoperatively out of concern it increases anastomotic leaks. I believe using an evidence-based approach along with a multi-disciplinary team and dedicated staff is the best way to tackle the latter issue as well as the broader issue of trying to improve outcomes after bariatric surgery.

 

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, Department of Defense or the United States Government.

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 3, March 28, 2010