P. Allan Klock

Three sudden postoperative respiratory arrests associated with epidural opioids in patients with sleep apnea

Current prominent textbooks on anesthesiology mention sleep apnea syndrome (SAS) only briefly. However, three patients in Illinois (two at one hospital) had sudden postoperative arrests associated with epidural opioids and sleep apnea. We therefore reevaluated the literature, which suggests that epidural opioids are the therapy of choice for patients with sleep apnea (1). Of the 15 patients with SAS reported in the literature, 10 had severe respiratory problems due to postoperative analgesia. Only one report was associated with epidural analgesia, to which we now add three. Based on the experiences we now describe (Case Reports l-3) and review of the literature (Case Reports 4-18), we believe that SAS patients are at particularly high risk of postoperative respiratory depression from any mode of analgesic therapy. Our theory is based on a review of a series of cases and not on mathematical estimates of relative risk. Because of our conclusion, we suggest guidelines for the anesthetic management of such patients.

Assessment of satisfaction with treatment for chronic pain

The purpose of this study was to develop an instrument to assess satisfaction with treatment of chronic pain, evaluate the reliability and validity of this instrument, and then examine predictors and consequences of satisfaction. The Pain Service Satisfaction Test (PSST) is the result of this effort. Fifty adult patients receiving services for chronic pain in a university pain clinic completed the PSST as part of a survey mailed to their homes. Findings supporting the validity of the PSST included significant positive correlations with a general measure of treatment satisfaction, patient ratings of global treatment satisfaction and effects of treatment, and physician ratings of patient satisfaction with treatment. Regression analyses of predictors of satisfaction highlighted significant contributions of confidence and trust in the provider, pain reduction, and waiting in the clinic. These predictors together accounted for 60% of satisfaction with treatment. Treatment satisfaction was negatively correlated with depression, reported number of physicians consulted, and number of physician visits for pain in the past 12 months; and there was a trend toward a negative correlation with disability. Results of the present study support the importance of satisfaction with treatment as a predictor and possible determinant of later health, function, and service utilization.

Subjective, psychomotor, cognitive, and analgesic effects of subanesthetic concentrations of Sevoflurane and nitrous oxide

Background: Sevoflurane is a volatile general anesthetic that differs in chemical nature from the gaseous anesthetic nitrous oxide. In a controlled laboratory setting, the authors characterized the subjective, psychomotor, and analgesic effects of sevoflurane and nitrous oxide at two equal minimum alveolar subanesthetic concentrations. Methods: A crossover design was used to test the effects of two end‐tidal concentrations of sevoflurane (0.3% and 0.6%), two end‐tidal concentrations of nitrous oxide (15% and 30%) that were equal in minimum alveolar concentration to that of sevoflurane, and placebo (100% oxygen) in 12 healthy volunteers. The volunteers inhaled one of these concentrations of sevoflurane, nitrous oxide, or placebo for 35 min. Dependent measures included subjective, psychomotor, and physiologic effects, and pain ratings measured during a cold‐water test. Results: Sevoflurane produced a greater degree of amnesia, psychomotor impairment, and drowsiness than did equal minimum alveolar concentrations of nitrous oxide. Recovery from sevoflurane and nitrous oxide effects was rapid. Nitrous oxide but not sevoflurane had analgesic effects. Conclusions: Sevoflurane and nitrous oxide produced different profiles of subjective, behavioral, and cognitive effects, with sevoflurane, in general, producing an overall greater magnitude of effect. The differences in effects between sevoflurane and nitrous oxide are consistent with the differences in their chemical nature and putative mechanisms of action.

Discovering Healthcare Cognition: The Use of Cognitive Artifacts to Reveal Cognitive Work

Healthcare systems, especially hospital operating room suites, have properties that make them ideal for the study of the cognitive work using the naturalistic decision-making (NDM) approach. This variable, complex, high-tempo setting provides a unique opportunity to examine the ways that clinicians plan, monitor, and cope with the irreducible uncertainty that underlies this work domain. As frontline managers, anesthesia coordinators plan and manage anesthesia assignments for surgical procedures. As frontline managers, coordinators develop and use cognitive artifacts to distribute cognition across time and among members of the acute care staff. Examination of these cognitive artifacts and their use reveals the hidden subtleties of the coordinators’ work. The use of NDM methods including cognitive artifact analysis to understand cognitive work generates insights that extend beyond the operator level to the study of team-level cognition. Results can be used to create computer-based artifacts that aid individual and team cognition.

Evolution of the extraglottic airway: a review of its history, applications, and practical tips for success.

The development of the laryngeal mask airway in 1981 was an important first step toward widespread use and acceptance of the extraglottic airway (EGA). The term extraglottic is used in this review to encompass those airways that do not violate the larynx, in addition to those with a supraglottic position. Although the term extraglottic may be broad and include airways such as tracheostomy tubes, the term supraglottic does not describe a large number of devices with subglottic components and is too narrow for a discussion of modern devices. EGAs have flourished in practice, and now a wide variety of devices are available for an ever-expanding array of applications. In this review we attempt to clarify the current state of EGA devices new and old, and to illustrate their use in numerous settings. Particular attention is paid to the use of EGAs in special situations such as obstetric, pediatric, prehospital, and nontraditional “out of the operating room” settings. The role of the EGA in difficult airway management is discussed. EGA devices have saved countless lives because they facilitate ventilation when facemask ventilation and tracheal intubation were not possible. Traditionally, difficult airway management focused on successful tracheal intubation. The EGA has allowed a paradigm shift, changing the emphasis of difficult airway management from tracheal intubation to ventilation and oxygenation. EGA devices have proved to be useful adjuncts to tracheal intubation; in particular, the combination of EGA devices and fiberoptic guidance is a powerful technique for difficult airway management. Despite their utility, EGAs do have disadvantages. For example, they typically do not provide the same protection from pulmonary aspiration of regurgitated gastric material as a cuffed tracheal tube. The risk of aspiration of gastric contents persists despite advances in EGA design that have sought to address the issue. The association between excessive EGA cuff pressure and potential morbidity is becoming increasingly recognized. The widespread success and adoption of the EGA into clinical practice has revolutionized airway management and anesthetic care. Although the role of EGAs is well established, the user must know each devices particular strengths and limitations and understand that limited data are available for guidance until a new device has been well studied.

Effects of naloxone on nitrous oxide actions in healthy volunteers

A number of studies have examined the effects of naloxone on nitrous oxide-induced analgesia with conflicting results. In the present study the effects of a relatively high dose of naloxone was examined to determine its effects on nitrous oxide-induced analgesia, as well as on the subjective and psychomotor effects of nitrous oxide. Fourteen subjects participated in a four-session crossover trial in which they received intravenous injections of either saline or 30mg/70kg naloxone 10min into a 35min period in which they were inhaling either 100% oxygen or 30% nitrous oxide in oxygen. Ten minutes after the naloxone administration, subjects were tested on the cold pressor test. Mood and psychomotor performance were also assessed before, during and after the inhalation period. Subjects reported higher pain ratings after the naloxone injection than the saline injection, but there was no evidence of naloxone reversing the analgesic effects of nitrous oxide. Similarly while naloxone also affected mood and impaired psychomotor performance, there was no evidence of naloxone reversing the effect of nitrous oxide on these measures. The results of this study call into question the role of the opioidergic system in mediating various effects of nitrous oxide in humans.

The effect of sevoflurane and desflurane on upper airway reactivity

Background Although bronchial reactivity can be assessed by changes in airway resistance, there is no well-accepted measure of upper airway reactivity during anesthesia. The authors used the stimulus of endotracheal tube cuff inflation and deflation to assess changes in airway reactivity in patients anesthetized with sevoflurane and desflurane. Methods Sixty-four patients classified as American Society of Anesthesiologists physical status I or II participated in this randomized, double-blind study. Patients were anesthetized with either sevoflurane or desflurane at 1.0 and 1.8 minimum alveolar concentration (MAC). The trachea was stimulated by inflating the endotracheal tube cuff. A blinded observer assessed the severity of patient response to the stimulus and changes in hemodynamic variables. The process was repeated at the second MAC treatment condition. Results At 1.0 MAC, patients anesthetized with desflurane had a more intense response and a greater likelihood of significant coughing and associated hemodynamic changes (both at P < 0.05). At 1.8 MAC, sevoflurane and desflurane both suppressed clinically significant responses to tracheal stimulation. Interrater reliability was excellent for this measure of upper airway reactivity (P < 0.001). Conclusions The assessment of the cough response to tracheal stimulation by endotracheal tube cuff inflation is a reliable and clinically meaningful measure of upper airway reactivity. At 1.0 MAC, sevoflurane is superior to desflurane for suppressing moderate and severe responses to this stimulus.

MORE OR BETTER : EDUCATING THE PATIENT ABOUT THE ANESTHESIOLOGIST'S ROLE AS PERIOPERATIVE PHYSICIAN

I n this issue of Anesthesia & Analgesia, Zvara et al. (1) report on their study to discover whether patient satisfaction with perioperative care is improved by multiple postoperative visits from the anesthesiologist. In addition to surveying patients for satisfaction with care, the authors asked them to give the gender and name of their anesthesiologists. Name recognition was seen as the patient’s acknowledgment of the role of the anesthesiologist in perioperative care. That there was no correlation between number of postoperative visits by the anesthesiologist and name recognition or satisfaction with care should not surprise us. The quality of the postoperative visits with patients was difficult to determine from the description by Zvara et al. First, quality may have been limited by the constraints of the five rules governing interaction during the visits. For example, not sitting during the visit may have been perceived by the patient as the equivalent of “I just popped in for a bit; I’m not staying long.” A handshake was permitted, but because touching was not, the anesthesiologist may not have been perceived as acting “like a physician.” It is doubtful whether 10 such seemingly perfunctory visits with patients postoperatively, much less the three in this study, would have affected patient perception of care. In other words, what the anesthesiologist does during a visit with the patient may be more important than the number of times the patient is visited. It is also possible that simply increasing the number of postoperative visits is not an intervention sufficiently powerful to affect the outcomes of name retention and patient satisfaction. More powerful interventions may have included a physical examination, discussion of pain management effectiveness, recapping significant parts of the intraoperative course, or even leaving the attending anesthesiologist’s business card. Such interventions may have had a more profound effect on the perceived degree of the anesthesiologist’s caring or on the patient’s understanding of the anesthesiologist’s role during surgery.n this issue of Anesthesia & Analgesia, Zvara et al. (1) report on their study to discover whether patient satisfaction with perioperative care is improved by multiple postoperative visits from the anesthesiolo- gist. In addition to surveying patients for satisfaction with care, the authors asked them to give the gender and name of their anesthesiologists. Name recognition was seen as the patient’s acknowledgment of the role of the anesthesiologist in perioperative care. That there was no correlation between number of postoperative visits by the anesthesiologist and name recognition or satisfaction with care should not sur- prise us. The quality of the postoperative visits with patients was difficult to determine from the descrip- tion by Zvara et al. First, quality may have been lim- ited by the constraints of the five rules governing interaction during the visits. For example, not sitting during the visit may have been perceived by the pa- tient as the equivalent of “I just popped in for a bit; I’m not staying long.” A handshake was permitted, but because touching was not, the anesthesiologist may not have been perceived as acting “like a physician.” It is doubtful whether 10 such seemingly perfunctory visits with patients postoperatively, much less the three in this study, would have affected patient per- ception of care. In other words, what the anesthesiologist does during a visit with the patient may be more important than the number of times the patient is visited. It is also possible that simply increasing the number of postoperative visits is not an intervention suffi- ciently powerful to affect the outcomes of name reten- tion and patient satisfaction. More powerful interven- tions may have included a physical examination, discussion of pain management effectiveness, recap- ping significant parts of the intraoperative course, or even leaving the attending anesthesiologist’s business card. Such interventions may have had a more pro- found effect on the perceived degree of the anesthesi- ologist’s caring or on the patient’s understanding of the anesthesiologist’s role during surgery.

The effects of subanesthetic concentrations of sevoflurane and nitrous oxide, alone and in combination, on analgesia, mood, and psychomotor performance in healthy volunteers.

UNLABELLED We studied the effects of subanesthetic concentrations of sevoflurane and nitrous oxide, alone and in combination, on analgesia, mood, and psychomotor performance in human volunteers. We hypothesized that nitrous oxide and sevoflurane would produce both opposing and potentiating effects within the same study. Over the course of three sessions, 20 subjects inhaled 0%, 0.2%, or 0.4% end-tidal sevoflurane for a 68-min period that was divided into four 17-min blocks. During either the second or fourth block, 30% end-tidal nitrous oxide was added to the concentration of sevoflurane being inhaled. Pain response, psychomotor performance, and mood were evaluated during the second and fourth blocks. Pain ratings were higher when sevoflurane and nitrous oxide were administered together than when nitrous oxide was administered alone, which indicates that sevoflurane attenuated the analgesic effects of nitrous oxide. Sevoflurane increased self-reported ratings of sleepiness, and the addition of nitrous oxide decreased these ratings. Nitrous oxide potentiated psychomotor impairment that was induced by sevoflurane. The combination of sevoflurane and nitrous oxide produced both opposing and potentiating effects within the same study. The results suggest that nitrous oxide and sevoflurane may act through different neurochemical mechanisms on some end points, such as analgesia and sleepiness. IMPLICATIONS Healthy volunteers inhaled subanesthetic concentrations of sevoflurane and nitrous oxide. Sevoflurane made nitrous oxide less effective as an analgesic, and nitrous oxide made sevoflurane less effective as a sedative. The two drugs may work at cross purposes on different end points of anesthesia.

The effects of alcohol history on the reinforcing, subjective and psychomotor effects of nitrous oxide in healthy volunteers

The purpose of this study was to characterize the reinforcing, subjective and psychomotor effects of nitrous oxide in healthy volunteers with different alcohol histories. Subjects were divided into two groups: light drinkers (n = 9) and moderate drinkers (n = 10). A choice procedure was used in which subjects first sampled placebo and a given concentration of nitrous oxide, and then chose between the two. Nitrous oxide concentration varied across the four-session experiment from 10-40%. Besides choice, subjective and psychomotor effects served as dependent measures. The majority of subjective effects of nitrous oxide, and its psychomotor-impairing effects, did not vary as a function of drinking group. However, a Wilcoxon rank sum test showed that the median number of times moderate drinkers chose nitrous oxide (three) was significantly higher than the median number of times light drinkers chose nitrous oxide (one). This study provides suggestive evidence that the reinforcing effects of nitrous oxide are modulated by alcohol history.