(CNN) -- It's 3 p.m. You're checked into the hospital for a routine surgery, scheduled to begin in 15 minutes. This is the first operation you've had.
Lying on a small gurney, covered only by a thin patient gown, you begin to shiver. Your heart pounds. Four words race through your head: "Am I gonna die?"
Then you meet the operating room team. The anesthesiologist, nurse anesthetist and operating room nurse all exude a combination of compassion and confidence. This is just what you need.
Your pulse slows, and the shakes disappear. The surgeon and OR nurse hold each of your hands. The anesthesiologist then injects a powerful sedative. The last thing you hear prior to drifting off is, "We'll take good care of you."
Suddenly, you're jolted awake. Intense, blinding lights glare into your face. You find yourself gagging on a thick plastic tube stuck down your throat. The lights turn away. Your eyes begin to adjust, and you see four faces you've never seen before.
The time of day you have surgery can affect your outcome.
That was the finding of a 2006 Duke University study published in the journal Quality and Safety in Healthcare. Researchers found operations starting between 3 and 4 p.m. had a higher rate of nausea, vomiting and postoperative pain.
Why is this? I suspect there are two major factors.
Our bodies follow natural circadian rhythms, which regulate our sleep/wake cycle, brain wave activity and certain bodily functions. These circadian rhythms dip between 3 and 5 p.m. each day, causing many of us to feel sleepy.
The Spaniards apparently discovered this long ago when they instituted the afternoon siesta. And George Costanza of "Seinfeld" fame isn't the only one who naps on the job. Nike and Google have reportedly instituted official sleeping rooms so their employees can deal with the afternoon circadian dip. It's also the reason why I put a couch in my office.
Unfortunately, there is no napping in the operating room. So it's definitely possible that getting a case of the sleepies plays a role in the higher rate of adverse events in midafternoon surgeries.
But there's another factor that's probably more important.
Most members of surgical teams arrive for work between 6:30 and 7 a.m. That means, when accounting for a 30-minute lunch break, the eight-hour shifts of most anesthesiologists, OR nurses and surgical technologists end at 3 p.m. This is when a new team takes over, sometimes right in the middle of surgery.
So who puts you to sleep won't necessarily be who wakes you up.
I see this routinely. Although the team members being replaced are typically very complete in the information transfer during handoff, key details about the patient may not be conveyed to the next provider. These details usually aren't life threatening, but can still have an impact on a patient's outcome.
For example, the original anesthetist might forget to inform her replacement that the patient doesn't respond well to a certain nausea medication. The replacement anesthetist (and the patient) then learns this the hard way.
So is there anything that can be done to prevent shift changes in the operating room? Not really.
We're all human. Health care providers can't work endless hours or be expected to be completely mistake-free. And there are no signs that workplace regulations are going to be lightened.
But one fact typically remains that should give patients comfort. Anesthesiologists and nurses may come and go, but when you have surgery, whatever time of day, there is one constant. Your surgeon should be with you the whole time.
But if he or she gives you a choice between having surgery at 7:30 a.m. or 3 p.m., think long and hard.
Then choose 7:30 a.m.