Blood pressure and heart rate variability changes during cardiac surgery with cardiopulmonary bypass

This study investigated patients undergoing elective cardiac surgery to evaluate the effects of cardiopulmonary bypass (CPB) on the spontaneous variability of mean arterial pressure (MAP) and heart rate (HR). Forty-one adult patients receiving different cardiovascular system drugs were included in the study. Patients were divided into three groups: no preoperative pharmacological cardiovascular treatment (n = 12), beta-blocker (BB) (n = 13), and angiotensin-converting enzyme inhibition (ACEI) (n = 16). MAP was recorded before anaesthesia until the end of surgery. MAP and HR variability was analysed in very low- (VLF), low- (LF) and high-frequency bands. The LF spectral component of MAP was observed to decrease in patients under ACEI (-92%) or BB (-87%) following induction of anaesthesia. In addition, during CPB, VLF power decreased in BB group (-67%), and LF power decreased in ACEI group (-77%). Concerning HR, VLF spectral power decreased following anaesthesia in BB group (-74%). In addition, after CPB, VLF power reached lower value in ACEI group than in BB group (P < 0.05). LF spectral power of HR showed a large decrease after CPB in ACEI group (-89%). This study showed that MAP variability did not change during CPB in patients with no preoperative pharmacological cardiovascular treatment, suggesting an unaltered vascular control of MAP. Moreover, the change in LF spectral power of MAP in ACEI and BB groups, suggests that both the renin-angiotensin and sympathetic systems participate to the genesis of LF variability of MAP.