Lack of recovery of baroreflex function in patients after heart surgery

Baroreflex sensitivity (BRS) and heart rate variability (HRV) have significant influence on the patients' prognosis after cardiovascular events. These parameters are supposed to be impaired in patients with essential hypertension. Heart surgery leads to a temporary reduction of BRS and HRV. The following study was performed to assess differences in the response of the autonomic regulation in hypertensive and normotensive patients undergoing cardiac surgery with heart-lung machine. 166 consecutive patients were enrolled in a prospective study; 102 of them were hypertensive according to the criteria of the WHO. Noninvasive blood pressure, ECG, peripheral oxygen saturation and respiratory rate were recorded the day before, 24h after surgery and one week after surgery. BRS was calculated according to the Dual Sequence Method, time and frequency parameters of HRV were calculated using standard methods. There were no major differences between Hypertensives and Controls in the preoperative values. SDNN steeply declined in Hypertensives 24h after the operation (46.5 vs. 24.5ms, p<10–7), the decline in normotensives was less pronounced, but still significant (52 vs. 30.8ms, p<0.01). After one week, SDNN was still significantly reduced in Hypertensives, but not in Normotensives. BRS decreased in both groups at 24h, recovery occurred normotensives only. While the response of the autonomic system to surgery is similar in normotensive and hypertensive patients, there obviously is a decreased ability to recover in Hypertensives, probably posing an increased risk of further cardiovascular events. Ongoing research is required for further carification of the pathophysiology of this phenomenon and to establish treatment strategies.