Anesthesia alarms in context: An observational study

This paper surveys current work on the design of alarms for anesthesia environments and notes some of the problems arising from the need to interpret alarms in context. Anesthetists' responses to audible alarms in the operating room were observed across four types of surgical procedure (laparoscopic, arthroscopic, cardiac, and intracranial) and across three phases of a procedure (induction, maintenance, and emergence). Alarms were classified as (a) requiring a corrective response, (b) being the intended result of a decision, (c) being ignored as a nuisance alarm, or (d) functioning as a reminder. Results revealed strong effects of the type of procedure and phase of procedure on the number and rate of audible alarms. Some alarms were relatively confined to specific phases; others were seen across phases, and responses differed according to phase. These results were interpreted in light of their significance for the development of effective alarm systems. Actual or potential applications of this research include the design of alarm systems that are more informative and more sensitive to operative context than are current systems.

Sonification supports eyes-free respiratory monitoring and task time-sharing

Three experiments explored the effectiveness of continuous auditory displays, or sonifications, for conveying information about a simulated anesthetized patient's respiration. Experiment 1 established an effective respiratory sonification. Experiment 2 showed an effect of expertise in the use of respiratory sonification and revealed that some apparent differences in sonification effectiveness could be accounted for by response bias. Experiment 3 showed that sonification helps anesthesiologists to maintain high levels of awareness of the simulated patient's state while performing other tasks more effectively than when relying upon visual monitoring of the simulated patient state. Overall, sonification of patient physiology beyond traditional pulse oximetry appears to be a viable and useful adjunct to visual monitors. Actual and potential applications of this research include monitoring in a wide variety of busy critical care contexts.

Advanced patient monitoring displays: Tools or continuous informing

We reviewed the use of advanced display technologies for monitoring in anesthesia. Researchers are investigating displays that integrate information and that, in some cases, also deliver the results continuously to the anesthesiologist. Integrated visual displays reveal higher-order properties of patient state and speed in responding to events, but their benefits under an intensely timeshared load is unknown. Head-mounted displays seem to shorten the time to respond to changes, but their impact on peripheral awareness and attention is unknown. Continuous auditory displays extending pulse oximetry seem to shorten response times and improve the ability to time-share other tasks, but their integration into the already noisy operative environment still needs to be tested. We reviewed the advantages and disadvantages of the three approaches, drawing on findings from other fields, such as aviation, to suggest outcomes where there are still no results for the anesthesia context. Proving that advanced patient monitoring displays improve patient outcomes is difficult, and a more realistic goal is probably to prove that such displays lead to better situational awareness, earlier responding, and less workload, all of which keep anesthesia practice away from the outer boundaries of safe operation.

Learnability and discriminability of melodic medical equipment alarms

Melodic alarms proposed in the IEC 60601-1-8 standard for medical electrical equipment were tested for learnability and discriminability. Thirty-three non-anaesthetist participants learned the alarms over two sessions of practice, with or without mnemonics suggested in the standard. Fewer than 30% of participants could identify the alarms with 100% accuracy at the end of practice. Confusions persisted between pairs of alarms, especially if mnemonics were used during learning (p = 0.011). Participants responded faster (p < 0.00001) and more accurately (p = 0.002) to medium priority alarms than to high priority alarms, even though they rated the high priority alarms as sounding more urgent (p < 0.00001). Participants with at least 1 year of formal musical training identified the alarms more accurately (p = 0.0002) than musically untrained participants, and found the task easier overall (p < 0.00001). More intensive studies of the IEC 60601-1-8 alarms are needed for their effectiveness to be determined.

Design of the multicenter Australian study of epidural anesthesia and analgesia in major surgery: The MASTER Trial

The Multicenter Australian Study of Epidural Anesthesia and Analgesia in Major Surgery (The MASTER Trial) was designed to evaluate the possible benefit of epidural block in improving outcome in high-risk patients. The trial began in 1995 and is scheduled to reach the planned sample size of 900 during 2001. This paper describes the trial design and presents data comparing 455 patients randomized in 21 institutions in Australia, Hong Kong, and Malaysia, with 237 patients from the same hospitals who were eligible but not randomized. Nine categories of high-risk patients were defined as entry criteria for the trial. Protocols for ethical review, informed consent, randomization, clinical anesthesia and analgesia, and perioperative management were determined following extensive consultation with anesthesiologists throughout Australia. Clinical and research information was collected in participating hospitals by research staff who may not have been blind to allocation. Decisions about the presence or absence of endpoints were made primarily by a computer algorithm, supplemented by blinded clinical experts. Without unblinding the trial, comparison of eligibility criteria and incidence of endpoints between randomized and nonrandomized patients showed only small differences. We conclude that there is no strong evidence of important demographic or clinical differences between randomized and nonrandomized patients eligible for the MASTER Trial. Thus, the trial results are likely to be broadly generalizable. Control Clin Trials 2000;21:244-256 (C) Elsevier Science Inc. 2000.

Response to The quality of epidural Anesthesia is crucial in the assessment of periciperative outcome

In their letter, Gogarten et al. question the effectiveness of the epidural regimens across the trial centers. In our original publication (1), we clearly demonstrated that patients in the epidural group had a working epidural block intraoperatively (evidenced by significantly more hypotension) and postoperatively (evidenced by significantly improved pain scores for 3 days).

Tailoring reveals information requirements: the case of anaesthesia alarms

We discuss the phenomenon of system tailoring in the context of data from an observational study of anaesthesia. We found that anaesthetists tailor their monitoring equipment so that the auditory alarms are more informative. However, the occurrence of tailoring by anaesthetists in the operating theatre was infrequent, even though the flexibility to tailor exists on many of the patient monitoring systems used in the study. We present an influence diagram to explain how alarm tailoring can increase situation awareness in the operating theatre but why factors inhibiting tailoring prevent widespread use. Extending the influence diagram, we discuss ways that more informative displays could achieve the results sought by anaesthetists when they tailor their alarm systems. In particular, we argue that we should improve our designs rather than simply provide more flexible tailoring systems. because users often find tailoring a complex task. We conclude that properly designed auditory displays may benefit anaesthetists in achieving greater patient situation awareness and that designers should consider carefully how factors promoting and inhibiting tailoring will affect the end-users' likelihood of conducting tailoring. (C) 2004 Elsevier B.V. All rights reserved.

Anesthesia of captive African wild dogs (Lycaon pictus) using a medetomidine-ketamine-atropine combination

Seven captive male African wild dogs (Lycaon pictus) weighing 25-32 kg each, were anesthetized by i.m. injection via hand syringe with a combination of 1.5 mg/kg ketamine, 40 mu g/kg medetomidine, and 0.05 mg/kg atropine. Following endotracheal intubation, each animal was connected to a bain closed-circuit system that delivered 1.5% isoflurane and 2 L/min oxygen. Atipamezole (0.1 mg/kg i.v.; 0.1 mg/kg i.m.) was given at the end of each procedure (60 min following injection of medetomidine/ketamine/atropine). Time to sternal recumbency was 5-8 min. Times to standing after atipamezole administration were 8-20 min. This anesthetic regimen was repeated on three separate occasions (September 2000, February 2002, and October 2002) on all males to perform electroejaculation procedures. Each procedure was < 80 min from injection to standing. Dogs showed excellent muscle relaxation during the procedures. Arterial blood samples were collected at 10-min intervals for blood gases in one procedure (September 2000). Separate venous samples were taken from each dog during each procedure for hematology and biochemistry. These values were within the normal range for this species. Arterial hemoglobin oxygen saturation (SpO2) and heart rate (HR) were monitored continuously in addition to other anesthesia monitoring procedures (body temperature, respiratory rate [RR], capillary refill time, blink response, pupil position, deep pain perception reflex). All dogs maintained relatively stable SpO2 profiles during monitoring, with a mean (+/- SD) SpO2 of 92% +/- 5.4%. All other physiological variables (HR, RR, body temperature, blood pressure) were within normal limits. Following each procedure, normal behavior was noted in all dogs. All the dogs were reunited into the pack at completion of their anesthetic procedures. An injectable medetomidine-ketamine-atropine combination with maintenance by gaseous isoflurane and oxygen provides an inexpensive, reliable anesthetic for captive African wild dogs.

The multimodal world of medical monitoring displays

A vision of the future of intraoperative monitoring for anesthesia is presented-a multimodal world based on advanced sensing capabilities. I explore progress towards this vision, outlining the general nature of the anesthetist's monitoring task and the dangers of attentional capture. Research in attention indicates different kinds of attentional control, such as endogenous and exogenous orienting, which are critical to how awareness of patient state is maintained, but which may work differently across different modalities. Four kinds of medical monitoring displays are surveyed: (1) integrated visual displays, (2) head-mounted displays, (3) advanced auditory displays and (4) auditory alarms. Achievements and challenges in each area are outlined. In future research, we should focus more clearly on identifying anesthetists' information needs and we should develop models of attention in different modalities and across different modalities that are more capable of guiding design. (c) 2006 Elsevier Ltd. All rights reserved.

Testing new alarms for medical electrical equipment

This paper reports the first of several tests of new auditory alarms originally proposed by Block et al. [1] and formalized in IEC 60601-1-8 for use in medical electrical equipment. We test whether participants who are supplied with the IEC-recommended mnemonics while learning label-alarm associations can more accurately identify the alarms after short periods of learning. Results for 18 participants strongly indicate that there is a mutual confusability between certain alarm pairs in both learning conditions, but that mnemonics may strengthen rather than diminish certain key confusions.