Depth of anesthesia monitors have been controversial in the United States. Do they help titrate inhaled anesthetics? Do they help titrate intravenous propofol? Can they be used in the intensive care unit? Do they measure brain function, and/or do they measure drug effect? And (most controversially) do they help prevent intraoperative awareness?
Several investigators from Australia have conducted large multicenter trials to determine whether depth of anesthesia monitors reduce the incidence of awareness, perhaps the most controversial claim. Drs. Erez Ben-Menachem and Dave Zalcberg, Department of Anesthesia, St. Vincent’s Hospital, Sydney, Australia, surveyed Australian anesthesiologists to determine whether the perceived effectiveness of these monitors promote their use and to see how much they are used to prevent intraoperative awareness. The authors review the results of their survey in the article titled “Depth of Anesthesia Monitoring: A Survey of Attitudes and Usage Patterns Among Australian Anesthesiologists,” which was published in this month’s issue of Anesthesia & Analgesia.
The authors emailed their 23-question survey to 963 randomly selected board-certified members of the Australia and New Zealand College of Anaesthetists (ANZCA), or about 30% of the members. Out of the 963 survey requests, 289 individuals completed the survey, which resulted in an overall response rate of 30%. The majority of respondents (66%) felt that depth of anesthesia monitors were useful in preventing awareness. Even in the absence of medicolegal protection in a case of awareness, most would still use a depth of anesthesia monitor. In individual practice, the majority (66%) used depth of anesthesia monitors in less than one-third of cases. As would be expected, the anesthesiologists who most frequently used depth of anesthesia monitoring also most strongly agreed that depth of anesthesia monitoring was useful in preventing awareness.
The majority of respondents (62%) felt that depth of anesthesia monitors allowed lower amounts of anesthesia to be used. A large proportion felt the monitors should be used for patients undergoing cardiac surgery (53%), cesarean delivery under general anesthesia (59%), major trauma (59%), total intravenous anesthesia (78%), particularly with paralysis, and in patients with a history of awareness under anesthesia (87%). When using the monitor, 48% found both the tracing and the number on the monitor to be equally useful.
This survey provides insight into how Australian anesthesiologists view and use currently available processed EEG based depth of anesthesia monitors. As Dr. Michael S. Avidan, Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, and Dr. George A. Mashour, Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan, write in the accompanying editorial titled “Mind the Gap: Attitudes Towards Intraoperative Brain Monitoring,” “Going forward, it is necessary to emphasize that monitoring the brain during general anesthesia is an evolving science, and it is likely that neurobiologically informed monitors will be developed and refined. These future monitors will hopefully have higher fidelity in discriminating brain states, with broader applicability to anesthetic practice. If brain monitoring is demonstrated convincingly to impact patient outcomes other than intraoperative awareness, the next major challenge for the field will be translating that evidence to standardized practice patterns. As the Australian and NAP-5 surveys suggest, we must ‘mind the gap’ between data and decision-making in order to understand better how to bridge evidence and changes in practice.”