Recovery from general anesthesia has long been known to be affected by many factors. However, gender has never been recognized as one of the factors that influences the time a patient takes to emerge from general anesthesia.
The conclusion that women wake faster from anesthesia seems quite convincing for the following reasons:
- This discovery was made in a study designed for a different purpose (to measure how quickly patients recover from their anesthetic when using a special monitor of the depth of anesthesia).
- The study was conducted not just at one, but four separate medical centers -- at Duke University (Durham, NC), Emory University (Atlanta, GA), the University of North Carolina (Chapel Hill) and the Massachusetts General Hospital (Harvard Medical School in Boston, MA) -- and at all four centers, women awakened significantly faster than men.
- The patients (274 in number) were randomly assigned to different treatment groups but received the same anesthesia and in all treatment groups, women woke up significantly faster than did men.
The lead author of the report, Dr. Tong J. Gan from Duke, told MedicineNet that he and his fellow investigators found that women wake up faster from general anesthesia by serendipity -- purely by accident!
The times from the end of anesthesia to eye opening and to a response to a verbal command were significantly different between men and women, meaning these differences were unlikely to be due to chance.
Men consistently had prolonged recovery times from anesthesia compared to women, supporting the principle that men and women differ in their sensitivity to anesthesia.
Although the anesthesia used in this study involved 3 agents -- propofol, alfentanil, and nitrous oxide -- the sedative propofol seems to be the agent responsible for the gender difference.
The molecular basis for this new difference between the sexes is still unknown. This type of difference between the sexes (termed a sexual dimorphism) appears to be a matter of pharmacogenetics -- genetic factors influencing the sensitivity to a drug.
The discovery that women awaken faster from general anesthesia than men may also explain why the incidence of awareness during surgery is reportedly higher in women. Women may awaken during surgery at higher concentrations of propofol and perhaps other anesthetic agents than men.
Source: Women emerge from propofol/alfentanil/nitrous oxide anesthesia faster than men. Gan TJ, Glass PS, Sigl J, Sebel P, Payne F, Rosow C, Embree P. Anesthesiology 90: 1283-87, 1999.