To determine whether the time of day affects anesthesia adverse events related to surgery, researchers analyzed over 90,000 surgeries performed at Duke University Medical Center from 2000 to 2004. They found that patients whose surgeries started later in the day (between 3:00 p.m. and 4:00 p.m.) fared worse than those whose surgeries started early in the day.

Researchers divided anesthetic adverse events into three categories:

* error (31 events), such as improper dosing with anesthetic drugs

* harm (667 events), such as postop nausea and vomiting (the most common event in this category), prolonged sedation, and wound infection

* other adverse events (1,995 events). About half of events in this category were related to inadequate pain management. Other events in this category included potentially dangerous changes in blood pressure and problems with operating room equipment. The predicted probability of an adverse event in the "other" category increased from 1% at 9:00 A.M. to 4.2% at 4:00 P.M.

Possible reasons why more adverse events occur later in the day include patient-related factors, tired clinicians, physicians arriving late, fewer patient transporters, and delayed test results. While noting that most of the anesthesia adverse events associated with later-in-the-day surgery were "manageable," lead researcher Melanie Wright, PhD, suggested that looking more closely at the risks of late-day surgery could improve the quality of care.

Source: Time of day effects on the incidence of anesthetic adverse events, Quality and Safety in Health Care, MC Wright, et al., August 2006.