ISSN NUMBER: 1938-7172
Issue 4.7 VOLUME 4 | NUMBER 7

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 Editors:
Terri M. Cahoon, DNP, CRNA
Sandra L. Larson, PhD, CRNA, APN

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

PEDIATRIC ANESTHESIA
DEXAMETHASONE ADMINISTRATION AND POSTOPERATIVE BLEEDING RISK IN CHILDREN UNDERGOING TONSILLECTOMY
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PHARMACOLOGY
IHNALED FLUTICASONE PROPIONATE REDUCES POSTOPERATIVE SORE THROAT, COUGH, AND HOARSENESS
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NEOSTIGMINE INJECTED 5 MINUTES AFTER LOW-DOSE ROCURONIUM ACCELERATES THE RECOVERY OF NEUROMUSCULAR FUNCTION
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QUALITY IMPROVEMENT
EARLY POSTOPERATIVE SUBCUTANEOUS TISSUE OXYGEN PREDICTS SURGICAL SITE INFECTION
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ONGOING PROVISION OF INDIVIDUAL CLINICIAN PERFORMANCE DATA IMPROVES PRACTICE BEHAVIOR
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RESPIRATION & VENTILATION
THE EFFECT OF THORACIC EPIDURAL ANESTHESIA ON PULMONARY SHUNT FRACTION AND ARTERIAL OXYGENATION DURING ONE-LUNG VENTILATION
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Attention subscribers licensed in Alabama, Alaska, Idaho, Kentucky, Nevada, and New Mexico:

This issue contains 1 PHARMACOLOGY specific CE credit.


Pediatric Anesthesia

Brigger MT, Cunningham MJ, Hartnick CJ


 

Dexamethasone administration and postoperative bleeding risk in children undergoing tonsillectomy

Arch Otolaryngol Head Neck Surg 2010;136:766-772

Brigger MT, Cunningham MJ, Hartnick CJ

Abstract

Purpose            The purpose of this review was to evaluate the outcomes of pediatric tonsillectomy patients who received perioperative dexamethasone, looking specifically for postoperative hemorrhage.

Background            Tonsillectomy is the most common surgical procedure in the pediatric population. There are numerous studies in the literature that suggest the perioperative administration of dexamethasone to tonsillectomy patients is advantageous. The proposed benefits include decreased postoperative nausea and vomiting, earlier oral intake, decreased airway edema, and improved analgesia. Based on recommendations in the literature and verified via survey, dexamethasone is preferred by many surgeons for tonsillectomy patients. However, the early termination of a clinical trial by Czarnetzki et al. suggesting an increased incidence of postoperative hemorrhage for tonsillectomy patients who received dexamethasone caused the researchers to question their practice and the safety of their patients.

Methodology            This retrospective review looked at a database of all patients aged 2 years through 18 years who had a tonsillectomy performed by one of two surgeons during a seven year period. All patients received either dexamethasone 0.5 mg/kg or 1.0 mg/kg depending on the surgeon’s preference. Data gathered from the review were patient demographics, surgical procedure, surgeon, and primary diagnosis. The database was cross-referenced to determine those who might have had a subsequent diagnosis of postoperative hemorrhage. Postoperative bleeding was broken down into three levels of increasing severity. Level 1 included all children who were evaluated for a posttonsillectomy bleed, no matter where they were evaluated or what treatment they required (lowest level). Level 2 included all children who were readmitted due to the severity of their bleeding. Level 3 included all children who were reevaluated, readmitted, and returned to the OR for treatment of their bleeding (highest level of severity).

Result            Of the 2,788 patients identified in the database, 94 children experienced post tonsillectomy bleeding. Of those, 56 out of 1,237 (4.5%) of children receiving dexamethasone 0.5 mg/kg had postoperative hemorrhage. In children receiving 1.0 mg/kg dexamethasone, 38 of 1,551 (2.5%) had postoperative hemorrhage. In comparing the two groups, significant differences were noticed in surgical technique and primary diagnoses. The 0.5 mg/kg group included monopolar electrocautery more often and an intracapsular technique less often. In the 1.0 mg/kg group about 80% of patients had sleep-disordered breathing and 20% infectious tonsillitis as the primary diagnosis compared to 90% and 9% for the 0.5 mg/kg group. After adjusting for the variables of age, sex, primary diagnosis, and surgical technique; the odds ratio of a child hemorrhaging post tonsillectomy after receiving 1.0 mg/kg of dexamethasone is 0.66 (95% confidence intervalCI) compared with those receiving 0.5 mg/kg. Children who required treatment in the OR showed an adjusted odds ratio of 0.71 (95% CI).

Conclusion            The review of tonsillectomy cases done over a seven year period by two surgeons using three different techniques and two doses of dexamethasone revealed no association between increased dose and increased incidence of postoperative hemorrhage.

 

Comment

Randomized clinical trial versus retrospective chart review? The higher level of evidence is usually produced by the former. However, the importance of examining the evidence closely is highlighted when the results of this review are compared to a previously reported study by Czarnetzki and associates (1). The study examined here produced different results than those previously reported. Although the first study intended to examine the effect of dexamethasone on nausea and vomiting, and analgesic requirements of children post tonsillectomy, the study was halted prematurely due to the incidence of postoperative bleeding. Wooden (2) correctly noted that the investigators did not control for variables that could affect bleeding, as that was not the focus or purpose of the research. Like Wooden, my clinical practice has included the use of dexamethasone in tonsillectomy patients without postoperative bleeding problems. This review of a larger patient group who underwent tonsillectomy and received dexamethasone is the additional examination of evidence that is needed.

The study abstracted here was different from the previous study in design and in the perioperative doses of dexamethasone. Postoperative bleeding was closely measured in 3 levels. In the previous study, only the occurrence of postoperative bleeding was recorded. Also, the dexamethasone doses given in this study were larger than previously studied, 0.5 mg/kg and 1.0 mg/kg. Although the dexamethasone doses given in the earlier Czarnetzki study were lower than those used here; 0.05 mg/kg, 0.15 mg/kg, or 0.5 mg/kg; the investigators suggested that delayed wound healing from steroids might have contributed to postoperative bleeding. That would also suggest a dose-dependent increase in post tonsillectomy hemorrhage. In this study, the clinical belief and antecdotal hunch that perioperative dexamethasone did not increase bleeding risk that outweighed the benefits was substantiated. Reasonable skepticism led to validation of their evidence-based practice.

 

Terri M. Cahoon, DNP, CRNA

 

1. Czarnetzki C, Elia N, Lysakowski C, Dumont L, Landis B, Giger R, Dulguerov P, Desmeules J, Tramer M. Dexamethasone and risk of nausea and vomiting and postoperative bleeding after tonsillectomy in children. JAMA. 2008;300:2621-2630.

2. Wooden S. Dexamethasone and risk of nausea and vomiting and postoperative bleeding after tonsillectomy in children. Anesthesia Abstracts. 2009;3:12-13.

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 7, July 31, 2010




Pharmacology

Tazeh-kand NF, Eslami B, Mohammadian K


 

 

Ihnaled fluticasone propionate reduces postoperative sore throat, cough, and hoarseness

Anesth Analg 2010;111:895-898

Tazeh-kand NF, Eslami B, Mohammadian K

 

 

Abstract

Purpose            The purpose of this study was to test whether or not a single dose of inhaled steroid prior to general anesthesia and endotracheal intubation would reduce the incidence of sore throat, cough, and hoarseness postoperatively.

Background            Sore throat and related, usually minor, complications are common after general anesthesia no matter what the method of airway management. The incidence of sore throat is highest following endotracheal intubation; reportedly as high as 90%. The incidence of sore throat following general anesthesia with a laryngeal mask airway is generally reported to be somewhat lower than endotracheal intubation, as is the use of a facemask during anesthesia maintenance. Female gender has been associated with an increased risk for, and severity of, post-general anesthesia sore throat.

Previous studies have reported that applying a topical steroid to the endotracheal tube (ETT) resulted in a decrease in the incidence of sore throat, cough, and hoarseness post-general anesthesia. An inhaled steroid would deliver a smaller total steroid dose compared to topical application, likely reducing systemic absorption of the steroid. Studies of the safety of intranasal steroids such as fluticasone have not identified systemic adverse events.

Methodology            This prospective, randomized study included ASA physical status I and II women undergoing elective cesarean section with general anesthesia. Women with a Mallampati assessment of grade III or IV and those who required more than two attempts at intubation were excluded. Also excluded were those with a history of recent NSAID use and those already receiving steroids.

Prior to induction of general anesthesia and while awake, women in the steroid group received 500 µg fluticasone propionate by inhalation (Editor’s Note: Flovent is the USA brand name for this drug). The control group received no treatment but were lead to believe that they had.

All patients received general anesthesia with pentothal, succinylcholine, halothane, 50% nitrous oxide, and atracurium. Rapid sequence intubation with cricoid pressure was used to place a 7.0 mm ETT. The ETT cuff was inflated until there was no leak at a peak airway pressure of 20 cm H2O.

Result            The 120 women enrolled in this study were randomized into two groups of 60 each. There were no statistically or clinically significant differences in age, height, weight, BMI, duration of anesthesia, or intubating conditions between groups.

The overall incidence of sore throat, cough, and hoarseness was significantly lower in the steroid group than the control group at both 1 hour and 24 hours post-anesthesia. At 1 hour post-anesthesia only 2 patients in the steroid inhalation group (3.3%) reported sore throat, cough, and hoarseness (2 for each complication) compared to double digit incidences in the control group. Furthermore, the steroid group reported only “mild” symptoms while the control group included 3 to 5 patients who reported moderate or severe symptoms of sore throat, cough, and hoarseness.

 

Table 1            Airway Complications at 1 hour post-anesthesia

 

Steroid Group

Control Group

P values

Sore Throat

3.3 % (2)

36.7 % (22)

< 0.0001

Cough

3.3 % (2)

18.3 % (11)

 0.008

Hoarseness

3.3 % (2)

35.0 % (21)

< 0.0001

N = 60 per group. Numbers are % (n).

At 24 hours post-anesthesia, a few additional steroid group patients reported sore throat, cough, and hoarseness but only a third to a half as many as in the control group. Furthermore, none of the steroid group reported “severe” symptoms while the control group had a few patients who reported severe symptoms of sore throat, cough, and hoarseness. For sore throat and cough, over a third of the symptoms reported by control patients were “moderate” or “severe.”

 

Table 2            Airway Complications at 24 hour post-anesthesia

 

Steroid Group

Control Group

P values

Sore Throat

13.3 % (8)

40.0 % (24)

0.001

Cough

13.3 % (8)

41.67 % (25)

0.005

Hoarseness

25.0 % (15)

50.0 % (30)

0.005

N = 60 per group. Numbers are % (n).

Conclusion            A single 500 µg dose of inhaled fluticasone propionate prior to general anesthesia and endotracheal intubation reduced the incidence and severity of post-general anesthesia airway complaints.

 

Comment

It is encouraging that the incidence of major anesthetic related complications is low enough that we can afford to spend time on details like preventing sore throat. I find this information to be incredibly interesting and potentially quite valuable, especially for certain cases that almost always result in postoperative sore throat. This relatively well conducted study showed a highly clinically significant decrease in sore throat and other airway complaints overall. It also seemed to show that steroid inhalation before general anesthesia delayed the onset and reduced the severity of sore throat in those that experienced it. That said, I wish investigators in these types of studies would think a little more about clinical application while designing their studies. Applying this one may be a little challenging.

Flovent is administered from a handheld inhaler, usually reserved for a single individual, and it is currently available only as a brand name drug. If your administrative policy and procedure requires that these inhalers be used for only a single individual the cost will be high, since patients are only likely to need a single dose. As a worst cost scenario the Flowvent Diskus (powdered formula) is available at retail for between $90 and $140. Even in the total absence of complications from the steroid administration, it is difficult for me to imagine that we can spend even $90 per patient to reduce the incidence of sore throat and hoarseness. In a best cost scenario, the Flowvent HFA (chlorofluorocarbon free aerosol) costs much more, about $225, but if a cardboard spacer is used for the patient to put their lips around it may be safe to administer doses from a single inhaler to multiple patients. In that case the cost per administration is less than $4.00. I can easily imagine spending $4.00 to dramatically reduce the risk of sore throat and hoarseness postoperatively.

Of course, the trouble is that while patients may be significantly bothered by postoperative sore throat – it almost always gets better quickly and it doesn’t bother anesthesia. (I don’t mean to sound cold, I’m just trying to be realistic, the “squeaky wheel” and all that.) As a result, I wonder how many anesthesia providers will be motivated to try to fight the battle to use steroid inhalation in a cost effective way to prevent sore throat. In our current climate, a manufacturer may have to develop a single dose inhaler to make this treatment feasible on a widespread basis.

This study brings up one more area I need to comment upon. We are in a time of intense pressure to lower health care costs. But, at the same time, we have others forcing us to deliver health care in more and more expensive ways, and, too often, with little or no critical thought in the process. I’m not aware of any information that suggests that delivering doses from a metered dose aerosol inhaler to multiple patients through a disposable spacer results in cross contamination. (I’m not suggesting that we do so without checking for this information first.) Yet, I suspect that many, especially non-clinician administrators, would automatically assume it to be wrong. Probably somewhere a book says it is wrong based only upon theoretical concerns. Unexamined ideas like these add significant cost to our healthcare system at the very time we are desperate to reduce costs. We cannot afford (literally) to allow policy decisions like these to be driven by non-clinicians, especially lawyers. Clinicians must think about decisions such as these and be ready to change what we think as new, credible information becomes available. We must practice based upon evidence and solid clinical thinking.

 

Michael Fiedler, PhD, CRNA

 

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 7, July 31, 2010





Lederer W, Reiner T, Khuenl-Brady KS


 

Neostigmine injected 5 minutes after low-dose rocuronium accelerates the recovery of neuromuscular function

J Clin Anesth 2010;22:420-424

Lederer W, Reiner T, Khuenl-Brady KS

 

Abstract

Purpose            The purpose of this study was to compare the speed of recovery from neuromuscular blockade when neostigmine was administered soon after an intubating dose of rocuronium to spontaneous recovery without neostigmine administration.

Background            Muscle relaxation greatly aids in endotracheal intubation. Some short cases require rapid recovery from neuromuscular blockade. Succinylcholine, while having a short duration, is associated with cardiovascular side effects, myalgia, hyperkalemia, and, is a known trigger of malignant hyperthermia.

Historically, antagonism of neuromuscular block has been delayed until spontaneous return of neuromuscular function is pronounced. This is most likely because of a fear that long acting nondepolarizing relaxants might appear to be adequately antagonized, only to outlast the antagonist resulting in a return of significant muscle weakness with ensuing airway and ventilation risks.

Methodology            This prospective, randomized, non-blinded study included ASA physical status I and II patients 18 years to 65 years old undergoing elective surgery with general anesthesia. Those with preexisting renal, liver, or neuromuscular disease, and those taking medication that interfered with muscle relaxants were excluded.

Patients were randomized to one of three groups. Group 1 received neostigmine 0.03 mg/kg and glycopyrrolate 0.007 mg/kg five minutes after the intubating dose of rocuronium was administered. Group 2 received neostigmine 0.05 mg/kg and glycopyrrolate 0.01 mg/kg five minutes after the intubating dose of rocuronium was administered. In group 3 neuromuscular block was allowed to recover spontaneously (control group).

To assess neuromuscular blockade, the ulnar nerve was stimulated at the wrist and the response monitored with a Datex electromyograph (Relaxograph, GE Healthcare) at the adductor pollicis.

All patients were premedicated 30 to 60 minutes before arriving in the OR. Anesthesia was induced with fentanyl and propofol and maintained with propofol and 60% to 70% nitrous oxide. All patients were kept normothermic and normocarbic throughout the procedure. All patients received 0.4 mg/kg rocuronium prior to intubation. Five minutes after rocuronium was administered, neostigmine was administered to those not in the control group.

Result            A total of 60 patients were included; 20 in each of three groups. There were no statistically or clinically significant differences in age, height, weight, BMI, or gender between groups. Onset of skeletal muscle paralysis, maximum block, and block 5 minutes after rocuronium administration did not differ between the neostigmine and control groups. Rocuronium 0.4 mg/kg allowed intubation in between 2 minutes and 3 minutes after administration.

Time to 25% recovery of first twitch, recovery from 25% to 75% of the first twitch and complete recovery of neuromuscular block were all faster in the neostigmine groups than in the control group. Mean time to complete recovery, a Train-of-four ratio of 0.9, was 19.4 ± 5.1 min in the group given neostigmine 0.05 mg/kg five minutes after rocuronium injection compared to 39.0 ± 8.7 min in the control group (P = 0.001).

Conclusion            Early neostigmine antagonism of rocuronium neuromuscular block makes it possible to use rocuronium to facilitate intubation even in cases that last less than 30 minutes. Monitoring of neuromuscular blockade is still recommended.

 

Comment

I think this study is going to be more important than it may at first appear; especially to those working in outpatient surgery. Succinylcholine is an essential drug in anesthesia, but it has significant disadvantages and I’d rather not use it unless I have a specific reason to do so. Trouble is, for short cases even relatively short duration nondepolarizers are still too long. For a while sugammadex looked like it was going to allow us to use rocuronium even in very short cases, but since the US FDA rejected it in 2008 that will not be the case any time soon. Then comes our old friend neostigmine and, if the results of this study are verified in clinical use, it is almost as good as sugammadex. Way faster than waiting until twitches return to antagonize, though not as fast as sugammadex antagonism or succinylcholine. Still, the prospect of being able to use rocuronium to intubate in cases less than 30 minutes long is encouraging.

We must, however, be cautious when using this technique. I would not attempt it if more than one dose of rocuronium had been administered and I would carefully assess recovery with a nerve stimulator (sustained 100 Hz TET) or sustained head lift prior to extubation. I would not use this technique if other drugs, patient pathology, or electrolyte imbalance might increase the duration of a nondepolarizer. Lastly, patients in this study did not receive potent inhalation agents, which potentiate the effects of nondepolarizers. This technique may need fine tuning to allow for the increased duration of block when inhalation agents are used.

 

Michael Fiedler, PhD, CRNA

 

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 7, July 31, 2010




Quality Improvement

Govinda R, Kasuya Y, Bala E, Mahboobi R, Devarajan J, Sessler DI Ozan A


 

Early postoperative subcutaneous tissue oxygen predicts surgical site infection

Anesth Analg 2010;111:946-952

Govinda R, Kasuya Y, Bala E, Mahboobi R, Devarajan J, Sessler DI Ozan A

Abstract

Purpose            The purpose of this study was to test the hypothesis that tissue oxygen saturation measured by near-infrared spectroscopy in the early postoperative period could predict subsequent wound infection.

Background            Surgical site infections cause significant morbidity, are expensive to treat, and occur regularly after surgery. The crucial period during which a contaminated wound becomes infected is thought to be only a few hours long immediately postoperatively, despite the fact that postoperative wound infections are often not apparent for a week or longer after surgery. A link has been established between tissue oxygenation and the probability of surgical wound infection. Previous measurement of tissue oxygen content has involved methods that are highly technical to employ, invasive, and not feasible for use in clinical practice. Near-infrared spectroscopy is a clinically practical, non-invasive technique that may allow bedside determination of tissue oxygenation.

Near-infrared spectroscopy can measure tissue oxygen saturation (StO2) of the arterial, capillary, and venous blood in the volume of tissue illuminated by the probe’s light source. The distance between the probe’s emitter and receiver determines how deeply the near-infrared light penetrates, and, thus, from how deep within the tissue the StO2 measurement is obtained.

Early prediction or detection of a developing surgical site infection is clinically important because there are a number of interventions available that can prevent or minimize the severity of a subsequent infection. Adequate analgesia reduces sympathetic nervous system mediated vasoconstriction and improves tissue oxygenation, as does warming, supplemental fluid administration, and administration of supplemental oxygen. Animal studies suggest that supplemental oxygen administered during at least the first six hours postoperatively may significantly reduce the risk of a postoperative wound infection.

Methodology            This prospective, observational study included colorectal surgery patients between 18 years and 80 years old with an ASA physical status of I to III. Those with a known or suspected abdominal abscess were excluded from the study. Patients were also excluded if they had preexisting problems with oxygenation or required supplemental oxygen preoperatively.

All patients received prophylactic antibiotics preoperatively according to normal practices. Patients received general anesthesia with between 30% and 80% oxygen intraoperatively. Normothermia was maintained with forced-air warming blankets and fluid warmers. Prior to incision the skin was prepared with a chlorhexidine-based antiseptic.

Postoperatively, patients received supplemental oxygen adequate to maintain their SpO2 ≥ 95%. Transcutaneous oxygen saturation (StO2) was measured 75 minutes postoperatively; 15 minutes after patients were no longer receiving supplemental oxygen. From that point on, oxygen was only administered if needed to keep SpO2 at or above 92%.

StO2 was measured at three points with an InSpectra model 650 tissue spectrometer (Hutchinson Technology Inc., Hutchinson, MN). StO2 was measured just lateral to the incision site, on the lateral aspect of the upper arm, and over a thenar muscle near the thumb. The upper arm site measured StO2 in the subcutaneous tissue while the thenar site measured StO2 in skeletal muscle.

Surgical site infection was diagnosed according to preexisting CDC guidelines.

Result            The study included 116 patients, 23 of whom (20%) developed a surgical site infection. All 23 patients developed superficial incisional infection. Three of these patients developed deep incisional infections and four others developed peritoneal infections. Infections were diagnosed an average of 9 (±5) days postoperatively. Almost all demographic variables and standard systems used to predict postoperative wound infections were the same in infected and infection-free patients. (Standard infection prediction systems included the Study on the Efficacy of Nosocomial Infection Control and the National Nosocomial Infection Surveillance System.) Body Mass Index (BMI) was significantly greater in patients who developed an infection than in those who did not, 32 kg/m2 vs. 27 kg/m2 (P < 0.001).

Tissue oxygen saturation (StO2) was only slightly lower at the surgical incision and the thenar (muscle) sites in patients who subsequently developed an infection than in those who did not, and the difference was not statistically significant. StO2 at the upper lateral arm site (subcutaneous tissue) was 52±22 % in those who subsequently developed an infection and 66±21 % in those who did not (P=0.033). Using 66% as the critical value, an StO2 in the upper arm of ≥ 66% had a negative predictive value of 90% for subsequent postoperative infection. The positive predictive value was only 29%. There was no correlation between the intraoperative FIO2 used and the postoperative StO2 (r2 = 0.007). Median visual analogue pain scores were higher 75 minutes postoperatively in patients who subsequently developed an infection than in those who did not (8 vs. 6, P = 0.043).

Conclusion            Tissue oxygen saturation (StO2) measured in the upper, lateral forearm of colorectal surgery patients 75 minutes postoperatively predicted the development of a surgical site infection an average of 9 days later.

 

Comment

I would have thought that the best place to assess tissue oxygenation as it related to whether or not a wound infection was going to develop would have been in the tissue near the wound. Thus, I was surprised that the wound edge StO2s did not correlate with later development of a wound infection. The investigators believed that this was likely due to swelling and inflammation near the incision site impeding the ability of the spectrometer to measure tissue oxygenation. The upper, lateral arm site where tissue oxygenation did correlate with later development of a wound infection was simply a good proxy for subcutaneous tissue oxygenation – and it worked.

We are beginning to understand that there are a lot of things anesthesia can do to reduce the incidence of wound infections; things that go way beyond keeping everything clean. Anything that results in vasoconstriction reduces tissue oxygenation at the surgical site and increases the likelihood of a wound infection. When we keep the patient warm, well hydrated, anxiety free, and as pain free as possible we reduce their sympathetic vasoconstriction and improve their tissue oxygenation. If we can use regional anesthesia, so much the better because the chemical sympathectomy prevents sympathetic vasoconstriction in the area of the wound. It is not enough to make sure the antibiotics get in on time. We need to pay attention to the details of patient warming, anxiety, and maximum pain relief – something that still doesn’t get enough of our attention (in my opinion).

It may be that in the near future it will become routine to measure tissue oxygenation in order to allow surgeons to aggressively prevent wound infections in those whose StO2 suggests they are at risk of developing one. In the mean time, understanding that tissue oxygenation plays a crucial role in wound infection risk, there is much we can do for every patient to reduce their risk. Things that are consistent with great patient care even if they are not at risk for an infection.

On a technical note, the investigator’s conclusion may be a little misleading. StO2 measurements didn’t actually predict surgical site infections all that well; the positive predictive value was only 29% - fairly low. This says that if the StO2 was below 66%, there was a 29% probability that the patient would develop a wound infection. A better conclusion might be that if the StO2 was 66% or higher the patient was unlikely to develop a wound infection. The high negative predictive value says that, in this case, there was a 90% probability that the patient would not develop a wound infection.

If there is an overall lesson to be learned here, I suggest that it is this. Complications are both deleterious to patients and expensive to the health care system. Our continuing work to reduce the incidence and patient impact of complications not only improves the lives of our patients, it benefits the healthcare system overall. This benefit reduces our workload and is likely to increase access to care.

 

Michael Fiedler, PhD, CRNA

 

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 7, July 31, 2010





Frenzel JC, Kee SS, Ensor JE, Riedel BJ, Ruiz JR


 

Ongoing provision of individual clinician performance data improves practice behavior

Anesth Analg 2010;111:515-9

Frenzel JC, Kee SS, Ensor JE, Riedel BJ, Ruiz JR

 

Abstract

Purpose            The purpose of this study was to evaluate whether or not giving anesthesia providers information on their compliance could improve adherence to clinical practice guidelines for postoperative nausea and vomiting (PONV).

Background            The Agency for Healthcare Research and Quality has concluded that continuing medical education efforts aimed at improving provider knowledge only modestly sustains incorporation of new consensus guidelines into clinical practice. To sustain change in clinical practice, continuous feedback may be needed. In recent years consensus guidelines for PONV prophylaxis have been published; however provider compliance with these guidelines is variable.

Methodology            A retrospective review of 23,279 anesthetics administered over four 6 month periods was completed to evaluate PONV consensus guideline compliance. Data were retrieved using a commercial anesthesia information management system (AIMS). Patients less than 18 years or age and those without risk factors for PONV were excluded.

Baseline data were collected and analyzed, and then three interventions were implemented every 6 months with the goal of sustaining provider practice behavior change. The interventions were: (1) a single information session reviewing PONV literature and risk factors; (2) an information session with a single retrospective report on personal compliance with PONV consensus guidelines; (3) quarterly reports on compliance with PONV guidelines.

A modification of Apfel’s simplified risk score for PONV was used to define the risk factors. The risk factors included: gender, smoking status, and history of PONV or motion sickness. Planned postoperative opioid use for this study was not used as a risk factor. Compliance was defined as administration of at least one antiemetic of a different class for each risk factor. Nitrous oxide was not used at the facility. Overtreatment was defined as administration of more antiemetics than patient risk factors. Providers were not given feedback on their overtreatment of PONV.

Result            Figure 1 presents adjusted compliance rates over time. Overall, there were modest increases in PONV guideline compliance over time, especially in patients with more risk factors. In the all risk factors group, compliance was significantly different between time 1 and 2 (P = 0.0002) and between time 2 and 3 (P < 0.0001). In the 1 risk factor group, compliance rates were only significantly different between times 1 and 2 (P = 0.0049). In the 2 risk factor group, compliance was significantly different between time 1 and 2 (P = 0.0056) and between time 2 and 3 (P <0.0001). In the 3 risk factors group the only significant difference was between time period 2 and 3 (P = 0.0002). Overtreatment rates increased from a baseline 13.1% to 25.4%.

 

Conclusion            Providing ongoing personal performance feedback resulted in improved compliance with PONV guidelines. This feedback gave providers insight into their actual practice patterns and may be a useful tool for sustaining practice change. However, the feedback may also result in overtreatment. Monitoring may be required to minimize adverse events.

Comment

I thought this was an interesting study because it brought up several important issues. First, I think it demonstrated the versatility of AIMS and the ability to easily retrieve data for both research and quality improvement projects. Second, I believe the researchers showed how it takes more than just giving a lecture to sustain a practice change. Old habits are hard to change, and I would be curious to see what their compliance rates are in a year or two to see if the change was sustained. I think that would provide more support for their intervention, providing written feedback, to increase compliance with PONV guidelines.

I believe this study demonstrates what a colleague of mine called the “band wagon effect.” One of the unexpected findings the authors found was that their overtreatment rate for PONV almost doubled. A quarter of all patients with at least one risk factor received at least one or more antiemetics than the guidelines which were adopted by this department recommended. Over the last several years there has been a shift towards ambulatory surgery and a focus on minimizing PONV.  I think the pendulum has shifted to almost pretreating everyone with an antiemetic. Many times my students ask me if they can give a patient odansetron and/or decadron for PONV prophylaxis, and my first question is “what are the patient’s risk factors” and “what do current PONV guidelines recommend?” They often then ponder this, and then review the evidence and discover that maybe the patient does not need to be given PONV prophylaxis or multiple antiemetic medications. I am not saying that PONV is not a significant problem, just that providers base their clinical decisions on the best evidence with consideration of the risks and benefits, and patient preferences. This is the essence of evidence based practice.

 Dennis Spence, PhD, CRNA

 

EDITOR’S NOTE: Unfortunately, other studies have taught us that Dr. Spence’s observation that “old habits are hard to change” is well founded. To quote an abstract from Dr. Burkard in a previous issue of Anesthesia Abstracts (Anesthesia Abstracts · Volume 3 Number 9, September 30, 2009), “The increase in guideline adherence was immediate and complete after introduction of the automated reminders. After discontinuation, guideline adherence returned to control levels immediately.” Perhaps we need to make reminders about practice guidelines a permanent part of our process?

 

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 7, July 31, 2010




Respiration & Ventilation

Jung SM, Cho CK, Kim YJ, Cho HM, Kim C-W, Kwon HU, Kim EK, Park JM


 

The effect of thoracic epidural anesthesia on pulmonary shunt fraction and arterial oxygenation during one-lung ventilation

J Cardiothorac Vasc Anesth 2010;24:456-462

Jung SM, Cho CK, Kim YJ, Cho HM, Kim C-W, Kwon HU, Kim EK, Park JM

Abstract

Purpose            This study compared the effects of thoracic epidural bupivacaine, thoracic epidural sufentanil, or intravenous remifentanil on pulmonary shunt fraction, arterial oxygenation, and hemodynamic changes during one-lung ventilation in patients undergoing thoracic surgery.

Background            Hypoxic pulmonary vasoconstriction (HPV) is a vasomotor response to alveolar hypoxia in smooth muscle cells of resistance pulmonary arteries. HPV mediates ventilation-perfusion matching, reduces shunt fraction, and optimizes systemic arterial oxygenation. Despite years of study, the numerous mechanisms that mediate and modulate HPV have yet to be clearly described.

Understanding how anesthetic techniques affect HPV is an important consideration during thoracic surgery where optimizing arterial oxygenation can be challenging. Thoracic epidural anesthesia is frequently used in thoracic surgery because of its superior ability to provide effective postoperative pain relief and decrease postoperative respiratory complications. However, the literature is equivocal about the effect of epidural sympathetic blockade and epidural opioid analgesia on HPV.

Methodology            This prospective study randomized 39 patients undergoing pulmonary resection with one lung ventilation to 1 of 3 groups based on anesthetic technique:  thoracic epidural anesthesia with bupivacaine (TEA-B group, n=13), thoracic epidural anesthesia with sufentanil (TEA-S group, n=13), or continuous intravenous infusion of remifentanil (IV-R group, n=13). Exclusion criteria were creatinine concentration > 1.5 mg/dl, elevated liver enzymes, significant coronary artery disease on coronary angiography, and anyone in whom regional anesthesia was contraindicated. During one lung ventilation, inoperability and severe hypoxemia that necessitated two-lung ventilation resulted in withdrawal from the study.

Preoperative assessment, premedication, placement of a thoracic epidural catheter, and test dosing of the thoracic epidural using 3 mL of 1% lidocaine without epinephrine was identically managed across all three groups. Anesthetic induction, invasive monitoring, left-sided double-lumen tube intubation, double-lumen tube positioning, mechanical ventilation, blood pressure adjustment, fluid infusions and transfusion criteria were identically managed across all three groups. At no time was an inhalation anesthetic agent administered in any group. Anesthesia was maintained in all groups using a continuous infusion of propofol. Muscle relaxation was maintained using a continuous infusion of vecuronium.

The TEA-B group received a 10 mL bolus of bupivacaine over 10 minutes followed by a continuous infusion of 0.25% bupivacaine via the epidural catheter at a rate of 0.1 mL/kg/hr. The TEA-S group received a 50 µg bolus of sufentanil in 10 mL volume over 10 minutes followed by a continuous infusion of epidural sufentanil 1 µg/mL at a rate of 0.1 mL/kg/hr. The IV-R group received a continuous intravenous infusion of remifentanil at a rate of 4 µg/kg/hr.

A blinded observer recorded four sets of hemodynamic and blood gas measurements with the patient in the lateral position prior to clamping the pulmonary bronchi or vessels:  one set during two lung ventilation, and then at 15, 30, and 60 minutes after initiation of one lung ventilation. A fifth set of measurements was recorded after the reinstitution of two lung ventilation. Hemodynamic measurements consisted of heart rate, mean arterial pressure, central venous pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, and cardiac output. Calculated measurements included systemic vascular resistance, pulmonary vascular resistance, and pulmonary shunt fraction.

Result            Demographic characteristics, preoperative lung function, baseline arterial blood gas analysis, and surgical procedures were similar among groups. There were no statistically significant differences among the groups in CVP, MPAP, HR, CO, SVR, PVR, or peak airway pressure in any of the 5 sets of measurements. The shunt fraction in all groups increased significantly after the initiation of one lung ventilation and decreased significantly after return to two lung ventilation, but these changes were not statistically significantly different between the three groups. During one lung ventilation, there were no statistically significant differences in arterial or mixed venous oxygenation variables between groups. The TEA-S and TEA-B groups required statistically significantly more ephedrine to maintain blood pressure within 30% of baseline.

Conclusion            The effect of local anesthetic or opioid administered into the thoracic epidural space on the HPV response was indistinguishable from that produced by opioid administered intravenously. Furthermore, the observation that changes in shunt fraction and oxygenation following initiation of one lung ventilation were similar despite different magnitudes of sympathetic blockade in the three groups suggested that HPV during one lung ventilation was not influenced by sympathetic blockade.

 

Comment

When one considers these research findings within the broader body of literature on HPV and hypoxemia during one-lung ventilation, the use of thoracic epidural analgesia as an adjunct to general anesthesia is supported. The bottom line seems to be that while numerous studies show that inhalation, intravenous, and epidural anesthetic agents either attenuate or potentiate HPV in dose dependent fashion, these effects are clinically minimal. Patient and surgical variables and not anesthetic technique predicts hypoxemia during one-lung ventilation (assuming hemodynamic stability and appropriate endobronchial tube position). For example, a low PaO2 during two-lung ventilation in the lateral position, a lower proportion of perfusion or ventilation to the nonoperated lung on the preoperative V/Q scan, and surgery on the right lung (left lung is 10% smaller than right lung) increase the risk for hypoxemia during one-lung ventilation. The degree of obstructive lung disease on the preoperative pulmonary function test also predicts hypoxemia but in an inverse fashion. Patients with more severe airflow limitation will tend to have a better PaO2 during one-lung ventilation. This is probably related to the development of auto-positive end-expiratory pressure in the ventilated lung.

Management of hypoxemia during one-lung ventilation should consider alveolar recruitment strategies such as routine use of low levels of positive end-expiratory pressure to the ventilated lung to decrease shunt caused by compression atelectatasis (1), and routine use of continuous positive airway pressure to the operative lung 3. I have found the latter to be poorly tolerated by the surgeon, and not an option if the surgery is video assisted. Intermittent two-lung ventilation and occlusion of the ipsilateral pulmonary artery are also options when all else fails. Finally, while previous research showed that larger tidal volumes (8-12 mL/kg) produced the highest PaO2 during one-lung ventilation, the current literature cautions against ventilator induced lung injury associated with large tidal volumes and high peak airway pressures. Pressure-controlled ventilation is preferred to volume-mode ventilation because it requires less inspiratory pressure to obtain the same tidal volume (2).

 

Sandra L Larson, PhD, CRNA, APN

 

1. Tusman G, Bohm SH, Sipmann FS, & Maisch S. Lung recruitment improves the efficiency of ventilation and gas exchange during one-lung ventilation anesthesia. Anesth Analg 2004;98:1604-9

2. Senturk M. New concepts of the management of one-lung ventilation. Curr Opin Anaesthesiol 2006;19:1-4

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 7, July 31, 2010