Less tends to go wrong for the patient during morning surgery, according to an analysis by Duke University Medical Center researchers, who studied the records of 90,159 surgeries to determine when most surgery patients experienced unexpected adverse events related to their anesthesia. Of these, they found 2,693 cases where error or harm occurred. Patients undergoing surgery in the afternoon most often had more trouble with postoperative pain, nausea and vomiting.

There might be several factors in these time-related problems, including afternoon fatigue among health care providers caused by swings in the circadian rhythms that influence normal biological ups and downs over the course of a day, and hospital work schedules.

According to the researcher's explanation regarding circadian rhythms -- a rhythm that serves as the body's internal clock that regulates sleep and brain wave activity -- the lows occur between 3 PM to 5 PM. These lows can affect human performance of complex tasks such as those required in anesthesia care.

The researchers note that end of day fatigue, a circadian low point, and changes in work shifts are all occurring around 3 PM to 6 PM and coincide with the block of time when some patients scheduled for surgery suffer more adverse reactions to surgery.

In addition, because patients who are scheduled for surgery in the afternoon spend most of the day without food and have more time to become stressed about the upcoming surgery, they speculate that patients might be more susceptible to pain or post operative nausea and vomiting by the time they are taken to surgery.

With this knowledge, new policies and procedures can be adopted to minimize the differences of experience now affecting patients who have surgery in the afternoon. More studies will be done to pinpoint exactly what is going on between the morning hours of 9 AM to 12 PM and then again from 3 PM to 6 PM.