Body clock may speed surgical recovery

Patients could recover more quickly after surgery if hospitals pay closer attention to the body's internal clock, a new review finds.

The Chronobiology Research Group at Waipapa Taumata Rau, University of Auckland, has published a review on the importance of circadian rhythms for anaesthesia, pain and postoperative recovery.

When anaesthetic drugs are administered can influence how long they last, how effectively they work and how people experience pain, the review has found. Anaesthetic medicines can also disrupt the body's circadian clock, affecting sleep, immune function and recovery after surgery.

Some local anaesthetics used for dental work, epidurals and other procedures can last two to three times longer when administered at around 3pm than in the morning, says lead author Guy Warman, an associate professor of anaesthesiology at the University.

The review points to substantial differences in how patients respond to certain anaesthetic medicines throughout the day.

“The effect of time of day on the action of these drugs is really quite remarkable, and holds clinical relevance,” says Warman.

The findings highlight a two-way relationship between anaesthesia and the body's circadian clock. Biological rhythms influence how anaesthetic drugs act, while anaesthetic drugs can also shift the body's internal timing system.

Some of the after-effects of surgery may be linked to disruption of the body’s natural rhythms, he says.

“Very much like jet lag, some of these medicines that are essential for anaesthesia can shift our biological clock to a different time zone,” he says. “If we can help treat that anaesthesia-induced jet lag, then we can speed up postoperative recovery and send patients home quicker.”

Factors beyond anaesthesia can also disrupt patients' circadian rhythms. Hospital stays often involve reduced exposure to natural light, changes to eating patterns, limited physical activity and overnight interruptions, all of which can affect the body's normal sleep-wake cycle, he says.

The review identified light exposure as one of the most promising ways of supporting the body’s natural rhythms after surgery.

“Morning light is key in keeping our clocks adjusted to a 24-hour day,” he says.

“In a hospital environment, if we can maximise that morning light, then we can keep patients' biological rhythms and their sleep-wake cycles well-adjusted to a 24-hour day.”

Protecting patients' circadian rhythms after surgery could offer broader benefits beyond improved sleep, including support for immune function and wound healing.

Patients can also take steps themselves to help restore normal sleep patterns after an operation.

Researchers are now working to better understand exactly how anaesthetic medicines affect the circadian clock and how that knowledge could be used to improve patient care and recovery, he says.

Public interest in the science of the body clock is growing, with the Chronobiology Research Group appearing in a TVNZ documentary on sleep and circadian rhythms, airing later this month.

‘Circadian rhythms, anaesthesia and peri-operative circadian disruption’, by Dr Warman, Dr James Cheeseman and Dr David Cumin from the Chronobiology Research Group at the Department of Anaesthesiology and consultant anaesthetist Dr Rebecca de Souza from Te Toka Tumai, was published in BJA Education.