The "safest" time to have an operation was at 9 a.m., while the worst was from 3-4 p.m. Interestingly, scientists speculate problems during late afternoon procedures may be attributed to health care workers administering anesthesia during the low point of their own natural circadian cycles (and their patients' too).

The lion's share of the problems, relegated to the "other" category, included operating equipment problems and coordinating anesthesia and pain medications before and after surgery. Also, scientists discovered some 9,500 administrative delays -- many of them in the afternoon -- that weren't categorized as problems, but could have influenced them.

Makes you wonder if the high number of errors was exacerbated by the number of patients receiving unnecessary procedures, surgeries or drugs.