Gender differences in baroreflex response and heart rate variability in anaesthetized humans.
BACKGROUND
In conscious humans, men have a greater cardiovagal baroreflex gain than women. We studied gender-related differences in baroreflex function during general anaesthesia.


METHODS
Sixty healthy patients (30 male and 30 female) were anaesthetized with sevoflurane 2% end-tidal in air and oxygen, and their lungs were mechanically ventilated. We recorded the ECG and invasive arterial pressure. Baroreflex gain was measured as the linear relationship of R-R interval with systolic arterial pressure changes caused by doses of phenylephrine i.v., and also the spontaneous changes in R-R interval and arterial pressure. In addition, consecutive R-R intervals were analysed using a fast Fourier transformation.


RESULTS
Baroreflex gains (mean (sd)) assessed by the pharmacological method in men (7.98 (5.12) ms x mm x Hg(-1)) was significantly greater than that in women (4.89 (3.87) ms x mm x Hg(-1)). Similarly, spontaneous baroreflex gains were significantly greater in men than in women, and correlated well with high-frequency power, but not with low-frequency power or low/high ratio, of heart rate variability in both genders.


CONCLUSIONS
Our results extend findings in conscious humans to sevoflurane anaesthesia. Men have greater cardiovagal reflex gains than women, which may reflect differences in parasympathetic action on heart rate.
Tanaka
M
M
Department of Anaesthesia, Akita University School of Medicine, Akita-city 010-8543, Japan. mtanaka@mes.akita-u.ac.jp
Kimura
T
T
Goyagi
T
T
Nishikawa
T
T
D000328:Adult; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D017704:Baroreflex / Q000187:drug effects* / Q000502:physiology; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D010656:Phenylephrine; D000077149:Sevoflurane; D012737:Sex Factors; D012815:Signal Processing, Computer-Assisted
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D010656:Phenylephrine; D000077149:Sevoflurane