The ideal time for surgeries among menstruating women could be right after their periods because changes in heart rate and blood pressure during various phases of menstruation can affect breathing tube ventilation during anesthesia, say Turkish researchers.

Ventilation tubes are usually placed after a patient has received general anesthesia and are unconscious. But a woman's heart rate and blood pressure response to receiving a ventilation tube when undergoing surgery varies at different times of the menstrual cycle, researchers have found.

These changes in heart rate and blood pressure occur as the body responds to the unpleasant stimulation of being placed by ventilation tubes.

Dr. Volkan Hanci, of Zonguldak Karaelmas University in Turkey, and colleagues studied the effect of the menstrual cycle on heart rate and blood pressure response to tube ventilation (tracheal intubation) in 62 healthy women.

About 50 percent of the women were in the follicular phase of the menstrual cycle - one to 12 days after the start of their last period, when hormone levels are lower, while the other half were in the luteal phase or the phase after ovulation.

The researchers found the heart rate and blood pressure response to be 30 percent greater among women in the luteal phase of their menstrual cycle even though both groups showed a significant increase in heart rate and blood pressure after tracheal intubation.

The investigators could not, however, pinpoint the reasons for this difference. They hypothesize that the changes may be due to increased sympathetic nervous system responsiveness. The results of the study were published in the August issue of the journal Anesthesia & Analgesia.

"The hormones that govern the menstrual cycle, estradiol and progesterone, have significant analgesic properties. It is not surprising that fluctuations in these hormones might be associated with different responses to tracheal intubation, depending on the phase of the menstrual cycle," journal editor-in-chief Dr. Steven L. Shafer of Columbia University said in a press release.