AoS: Cardiac surgery outcomes unaffected by surgeons lack of sleep

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There is no evidence that consultant surgeon sleep hours had an effect on postoperative cardiac surgery patient outcomes, according to a prospective observational cohort study published May 16 in the Archives of Surgery.

Between January 2004 and December 2009, Michael W. A. Chu, MD, University Hospital, London Health Sciences Centre in London, Ontario, and colleagues prospectively collected sleep hours of six consultant surgeons, ranging in age from 32 to 55 years, working in a tertiary care academic institution.

The prospective study cohort included all patients undergoing CABG, valve, combined valve–CABG and aortic surgery. The researchers calculated the predicted risk of death and/or any of 10 major complications using an institutional multivariable model, which was then compared with observed values. Additional pre-specified analyses examined the interaction between surgeon age, sleep hours and postoperative outcomes.

This study had more than 90 percent power to detect a 4 percent (clinically important) difference in overall complication rates among groups, according to the study authors.

The primary objective was the complication and mortality rates in operations performed by surgeons with zero to three, three to six or more than six hours' sleep the evening prior to surgery.

Of the 4,047 consecutive surgical procedures, 83 were performed by a consultant with zero to three hours, 1,595 with three to six hours and 2,369 with more than six hours of sleep.

Chu et al reported that the rates of mortality (3.6 percent, 2.8 percent and 3.4 percent, respectively) were similar in the three groups, as were the observed versus expected ratios of major complications (1.20, 0.95 and 1.07, respectively). There was no significant interaction between surgeon age, hours of sleep and occurrence of death or any of 10 major complications.

The study authors wrote that the results of their study “may have important ramifications in restricting current trainee work hours when future practice may demand optimal performance during sleep-deprived conditions." It is almost seven years since the U.S. Accreditation Council for Graduate Medical Education (ACGME) imposed work-hour limits for postgraduate medical trainees. Similarly in Europe, more aggressive work-hour restrictions have been implemented that have improved trainee lifestyle satisfaction; however, again, there are few data demonstrating any reduction in medical errors or improved patient safety, they continued.

An analysis of the sleep characteristics of 180 attending physicians from varied specialties found that reduced sleep, not hours worked, was associated with increased sleepiness, highlighting the weak link between work hours and quantity of sleep. This finding “undermines the intuitive belief” that reduced work hours improve daytime fatigue, trainee performance and patient safety, which was a common tenet used to justify maximum-work-hour legislation, the researchers reported. 

Based on the study results, Chu and colleagues hypothesized that well-developed compensatory mechanisms must exist to combat the effects of sleep deprivation. Most attending cardiac surgeons could have developed physiologic adaptation to chronic sleep deprivation and, through conditional learning, practiced enough to reduce errors under these conditions. Most importantly, cardiac surgery is a "team sport" that involves multiple levels of trainee, surgical and nursing staff that collectively could potentially compensate for a consultant surgeon's fatigue-related impairment.

The investigators concluded that future studies should explore the compensatory mechanisms that individual healthcare practitioners and surgical teams use to maintain good patient outcomes when key members of the team are sleep deprived.