Robert G. Loeb

The risk and outcomes of epidural hematomas after perioperative and obstetric epidural catheterization: a report from the Multicenter Perioperative Outcomes Group Research Consortium.

BACKGROUND:In this study, we sought to determine the frequency and outcomes of epidural hematomas after epidural catheterization. METHODS:Eleven centers participating in the Multicenter Perioperative Outcomes Group used electronic anesthesia information systems and quality assurance databases to identify patients who had epidural catheters inserted for either obstetrical or surgical indications. From this cohort, patients undergoing laminectomy for the evacuation of hematoma within 6 weeks of epidural placement were identified. RESULTS:Seven of 62,450 patients undergoing perioperative epidural catheterizations developed hematoma requiring surgical evacuation. The event rate was 11.2 × 10−5 (95% confidence interval [CI], 4.5 × 10−5 to 23.1 × 10−5). Four of the 7 had anticoagulation/antiplatelet therapy that deviated from American Society of Regional Anesthesia guidelines. None of 79,837 obstetric patients with epidural catheterizations developed hematoma (upper limit of the 95% CI, 4.6 × 10−5). The hematoma rate in obstetric epidural catheterizations was significantly lower than in perioperative epidural catheterizations (P = 0.003). CONCLUSIONS:In this series, the 95% CI for the frequency of epidural hematoma requiring laminectomy after epidural catheter placement for perioperative anesthesia/analgesia was 1 event per 22,189 placements to 1 event per 4330 placements. Risk was significantly lower in obstetric epidurals.

Development and Evaluation of a Graphical Anesthesia Drug Display

Background Usable real-time displays of intravenous anesthetic concentrations and effects could significantly enhance intraoperative clinical decision-making. Pharmacokinetic models are available to estimate past, present, and future drug effect-site concentrations, and pharmacodynamic models are available to predict the drugs associated physiologic effects. Methods An interdisciplinary research team (bioengineering, architecture, anesthesiology, computer engineering, and cognitive psychology) developed a graphic display that presents the real-time effect-site concentrations, normalized to the drugs’ EC95, of intravenous drugs. Graphical metaphors were created to show the drugs’ pharmacodynamics. To evaluate the effect of the display on the management of total intravenous anesthesia, 15 anesthesiologists participated in a computer-based simulation study. The participants cared for patients during two experimental conditions: with and without the drug display. Results With the drug display, clinicians administered more bolus doses of remifentanil during anesthesia maintenance. There was a significantly lower variation in the predicted effect-site concentrations for remifentanil and propofol, and effect-site concentrations were maintained closer to the drugs’ EC95. There was no significant difference in the simulated patient heart rate and blood pressure with respect to experimental condition. The perceived performance for the participants was increased with the drug display, whereas mental demand, effort, and frustration level were reduced. In a postsimulation questionnaire, participants rated the display to be a useful addition to anesthesia monitoring. Conclusions The drug display altered simulated clinical practice. These results, which will inform the next iteration of designs and evaluations, suggest promise for this approach to drug data visualization.

Effects of Integrated Graphical Displays on Situation Awareness in Anaesthesiology

Abstract: Anaesthetic information displays have been shown to influence anaesthesiologists’ situation awareness. In study 1 an object display was compared with the traditional display currently used. Twelve anaesthesiologists (residents and faculty members) participated in a simulator evaluation of the displays. Reaction times for detection of critical events and situation awareness were measured. The object display improved situation awareness for one of four test scenarios. Low-level situation awareness was higher with the traditional display, and medium-level situation awareness was higher with the new display. In study 2, an integrated 3D display was compared to the traditional display. Twelve students participated in the evaluation. The new 3D display helped the observers to see changes more rapidly. In one scenario, situation awareness was higher with the new display than with the traditional display. In summary, during 63% of the simulated scenarios, reliable differences were found in favour of the new displays. Thus, by introducing integrated graphical displays in the operating room, anaesthesiologists’ performance may be improved.

A laboratory evaluation of an auditory display designed to enhance intraoperative monitoring.

UNLABELLED Encouraged by the popularity of the pulse oximeter pulse-tone, we developed and tested an auditory display of six physiologic variables. The display consisted of a cardiovascular sound triggered by every heartbeat (conveying heart rate) and a respiratory sound triggered by every breath (conveying respiratory rate). Attributes of the cardiovascular sound were modulated to convey hemoglobin saturation and blood pressure, and those of the respiratory sound were modulated to denote end-tidal CO(2) and tidal volume. Three display formats (auditory, visual, and combined) were compared. Fourteen anesthesia residents monitored dynamic displays of 6 variables to detect and identify 6 predefined events during 21 trials. An event occurred during each trial and the subjects task was to detect when it started and then identify the type of event. Subjects detected every event. They detected events more rapidly with the combined display (10.4 s) than with the visual (12.8 s) or auditory (13.0 s) displays. Subjects correctly identified events least often with the auditory display (60% versus visual 88% and combined 80%). They correctly identified events more quickly with the combined display than with the visual display. We conclude that, with little training, clinicians can successfully detect and identify simulated clinical events using an auditory display of six variables. IMPLICATIONS We developed and tested an auditory display of multivariable clinical data. With little training, clinicians successfully used the display to detect and diagnose simulated critical events. This suggests that a multivariable auditory display could enhance intraoperative monitoring.

Clinical information displays to improve ICU outcomes

PURPOSE In a previous study, we compared a prototype ecological display (ED) that represented physiological data in a structured pictorial format with two bar graph displays [J.A. Effken, Improving clinical decision making through ecological interfaces, Ecol. Psych. 18 (2006) 283-318]. In ED and the first bar graph display, data were grouped hierarchically based on a cognitive work analysis (CWA); in the second bar graph display they were grouped as usually collected. Treatment efficiency (i.e., percentage of time seven variables in the CWA model were in target range) improved similarly with the two displays incorporating the CWA order for intensive care unit (ICU) residents, but not for novice ICU nurses. Hypothesized reasons for this result included: insufficient practice with novel displays; use of identical histories across displays; insufficient clinical knowledge; and the variables used in the efficiency analysis, which included only one of EDs four integrated design elements. In the current study we tested these hypotheses. METHODS We asked ICU nurses assigned to three knowledge groups based on intensive care and hemodynamic monitoring pretests to identify and treat oxygenation problems presented via ED and the first bar graph display (BGD) in an experimental laboratory simulation. We measured the impact of display, clinical scenario, data level, knowledge, presentation order, and practice extent on event recognition, treatment efficiency, cognitive workload, and user satisfaction. RESULTS The two displays produced little difference in recognition speed or overall cognitive workload, but user satisfaction was greater with ED. When 12 variables were included in the analysis, treatment efficiency improved with ED; when only 7 were measured, BGD prevailed. The results suggest benefits for the kind of synthesis provided in ED, but also a potential limitation. If too many different pictorial formats are used in a display, detecting critical events may be more difficult.

Pain perception in sequential cataract surgery: Comparison of first and second procedures

PURPOSE: To compare pain and anxiety between first and second cataract extractions under topical anesthesia with monitored anesthesia care. SETTING: University ophthalmology clinic. DESIGN: Cohort study. METHODS: Consecutive adults having bilateral sequential clear corneal cataract extraction using phacoemulsification under topical anesthesia with monitored anesthesia care were recruited. Exclusion criteria included baseline eye pain, poor comprehension, and complicated cataract extraction. Patients completed 4 short perioperative surveys with each cataract extraction as follows: the Amsterdam Preoperative Anxiety and Information Scale (APAIS) and the State‐Trait Anxiety Scale (STAI) preoperatively and a 0‐to‐10 visual analog scale pain survey twice after surgery. Pain and difference in pain were the primary outcomes. RESULTS: Of the 65 patients who completed the study, 26 (40%) reported higher visual analog scale pain scores for the second cataract extraction. Overall, the median pain score was 0 (range 0 to 6) for the first cataract extraction and 1 (range 0 to 9) for the second (P=.004). By 1 day postoperatively, the pain scores were similar (median 0; range 0 to 9; P=.58). Both APAIS and STAI anxiety scores decreased between surgeries (P=.003 and P<.001, respectively). CONCLUSIONS: Although cataract extraction remained relatively painless under topical anesthesia with monitored anesthesia care, there was a subtle increase in pain in the second surgery relative to the first. This appears to be associated with decreased preoperative anxiety and may be related to the amnestic effects of intravenous sedation. These data may explain a common operative observation. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Recognition accuracy of current operating room alarms.

This prospective study was performed to determine whether anesthesia clinicians (i.e., both anesthesiologists and nurse anesthetists) can identify operating room alarms by their distinctive sounds and to identify factors related to alarm recognition accuracy. Nineteen alarms from 15 commonly used devices were recorded. These sounds were played, in a quiet room, to 44 anesthesia clinicians. The clinicians were asked to choose from a list the device that produced the alarm. After this recognition test, the clinicians rated the importance of each alarm and the frequency with which they heard it in the clinical situation. Clinicians correctly identified the alarm source 34% of the time. The recognition rate was higher for alarms rated as heard more frequently; however, alarms that were rated as more important were less likely to be correctly identified. Complexity of the sound did not influence accuracy of recognition. Most errors were attributed to similarities in sound or function, or both, among alarms. We conclude that anesthetists cannot reliably identify current operating room alarms by their distinctive sounds.

Manual record keeping is not necessary for anesthesia vigilance

Objective. The goal of this study was to determine whether the intraoperative vigilance of anesthesia residents is different when they keep a manual record than when an assistant performs the charting.Methods. A total of 9 anesthesia residents were studied during 36 general anesthesia cases on ASA class 1 or 2 patients. In half of the cases, the resident performed all record keeping. In the other half, the anesthesia record was kept by a human assistant. Vigilance was measured as detection rate and response time for the resident to detect a simulated abnormal value displayed on the physiologic monitor. For analysis, anesthesia cases were divided into stages of induction, maintenance, and emergence.Results. Response times and detection rates were not different when record keeping was performed by an assistant, rather than by the clinician. Shorter cases were associated with longer median response times (i.e., lower vigilance) during the maintenance phase, but only when record keeping was done manually.Conclusions. The results demonstrate that anesthesia residents are equally attentive to an experimental signal displayed on an electronic monitor while manually charting as they are when an assistant keeps the record. This brings into question the contention that eliminating the record-keeping task will result in a reduced level of vigilance.

The Utah Anesthesia Workstation

A prototype anesthesia workstation has been developed to demonstrate the feasibility of a computer-assisted anesthesia workplace. The workstation provides a central display of information and aids the user in controlling and monitoring the anesthesia delivery system. The anesthesiologist interacts with the workstation through a Macintosh computer, which is easy for the clinician to understand and to use. Seventeen sensors and monitors transmit information from the anesthesia delivery system to the computer. The computer monitors this information using a set of rules, evaluated once each breath, to detect changes in the delivery system. If an event is detected, the computer alerts the anesthesiologist with a diagram, a text message, and an audible warning. A laboratory test of the monitoring system was performed to see if it properly identified 26 different critical events during simulated low flow and closed circuit anesthesia. Five hundred and eight-three of 660 simulated critical events (88%) were identified with the unique and correct message. On 35 occasions, multiple messages were displayed, including the correct one. Critical events were misidentified or not detected 42 times. Eight false positive alarms occurred during the 20 h of testing; all occurred as a result of baseline drift in a single transducer. These results demonstrate that a sophisticated monitoring system can reliably diagnose specific anesthesia machine failures.

A simulation-based evaluation of a graphic cardiovascular display.

INTRODUCTION:A graphic presentation of complex information can facilitate early detection and management of adverse events. Prior work found that graphical presentation of selected cardiovascular variables led to earlier detection of a simulated ischemic event. Based on these findings, a second evaluation explored the utility of a graphical cardiovascular display (GCD) in a variety of simulated adverse cardiopulmonary events for two different display configurations. In this evaluation, we revised the GCD to present hemodynamic variables with or without a pulmonary artery catheter. Our hypotheses were that the revised GCD would improve detection of adverse cardiopulmonary events and add no additional perceived workload. METHODS:Sixteen anesthesiologists and anesthesia residents were enrolled in a simulation-based evaluation of the GCD. Participants were randomly split into two groups balanced for expertise and asked to manage six simulated adverse cardiopulmonary events. The GCD was present in half of the simulations, balanced across scenarios and groups. Participants’ verbalizations and actions during each scenario were recorded and transcribed. Transcripts of treatment interventions were subsequently rated by two blinded expert anesthesiologists. Perceived workload, time to detection, and proper treatment of the adverse event were compared between groups. RESULTS:Experts ranked anesthesiologists using the GCD as being more effective overall and individually in three of six scenarios. Use of the GCD was demonstrated to influence the time to detection and the time to treatment of some critical events. There were no workload differences between display groups. DISCUSSION:Treatment intervention by participants using the GCD was rated superior by two blinded experts. The presence of the GCD resulted in a modest improvement in the time to detect myocardial ischemia and increased pulmonary capillary wedge pressure. The GCD may be a useful adjunct to monitor patients during adverse cardiopulmonary events.