DURHAM, N.C. -- In a finding that has perplexed researchers, women appear to wake up almost twice as fast as men when general anesthesia is discontinued after surgery.
This may mean that women are less sensitive than men to anesthetic drugs that promote unconsciousness and could need more anesthesia during surgery, say researchers at Duke University Medical Center, who led the study, which was conducted at Duke, the University of North Carolina at Chapel Hill, Emory University and Massachusetts General Hospital in Boston. The finding may also help explain why three times more women than men have complained of being conscious during surgery, the investigators say. The research findings are published in the May issue of the journal Anesthesiology.
"This is the first time we have seen a difference in how men and women wake up after anesthesia is withdrawn, and that gender effect is both unexpected and strong," said Duke anesthesiologist Dr. Tong Gan, who co-authored the study. "It shows that women have a higher chance of being aware during surgery than men, and indicates women may need significantly more anesthesia than men to keep them asleep."
"No one ever thought gender would be a variable in delivering anesthetics to patients, but we now need to consider adding a patient's sex into the equation," added the other Duke co-author, anesthesiologist Dr. Peter Glass.
Currently, doses are based on body size, which means that women are typically given less anesthesia than men, although drug levels are often adjusted during the operation if a patient shows signs of returning consciousness. Anesthesiologists participating in this study, however, used a new standardized technique that delivered the same concentration of an anesthetic drug to patients -- enough to ensure they were asleep during the operation -- and then monitored their level of consciousness and how quickly they awoke after the drug was stopped.