Article Text

Time of day effects on the incidence of anesthetic adverse events
  1. M C Wright,
  2. B Phillips-Bute,
  3. J B Mark,
  4. M Stafford-Smith,
  5. K P Grichnik,
  6. B C Andregg,
  7. J M Taekman
  1. Department of Anesthesiology and the Duke University Human Simulation and Patient Safety Center, Duke University Medical Center, Durham, North Carolina, USA
  1. Correspondence to:
 MC Wright PhD
 Department of Anesthesiology, Box 3094, Duke University Medical Center, Durham, NC 27710, USA; melanie.wright{at}


Background: We hypothesized that time of day of surgery would influence the incidence of anesthetic adverse events (AEs).

Methods: Clinical observations reported in a quality improvement database were categorized into different AEs that reflected (1) error, (2) harm, and (3) other AEs (error or harm could not be determined) and were analyzed for effects related to start hour of care.

Results: As expected, there were differences in the rate of AEs depending on start hour of care. Compared with a reference start hour of 7 am, other AEs were more frequent for cases starting during the 3 pm and 4 pm hours (p<0.0001). Post hoc inspection of data revealed that the predicted probability increased from a low of 1.0% at 9 am to a high of 4.2% at 4 pm. The two most common event types (pain management and postoperative nausea and vomiting) may be primary determinants of these effects.

Conclusions: Our results indicate that clinical outcomes may be different for patients anesthetized at the end of the work day compared with the beginning of the day. Although this may result from patient related factors, medical care delivery factors such as case load, fatigue, and care transitions may also be influencing the rate of anesthetic AEs for cases that start in the late afternoon.

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  • This research was funded by a grant from the Anesthesia Patient Safety Foundation (APSF), Indianapolis, IN, USA.

  • Competing interests: none declared.

  • Preliminary results of this project were presented at the Healthcare Systems Ergonomics and Patient Safety Conference in Florence, Italy on 1 April 2005 ( Wright MC, Andregg BC, Mark JB, et al. Effects of time of day and surgery duration on adverse events in anaesthesia. In: Tartaglia R, Bagnara S, Bellandi T, eds. International Conference on Healthcare Systems Ergonomics and Patient Safety. Taylor & Francis, 2005, 377–80) .

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