cardiopulmonary bypass in man Neuronal and adrenomedullary catecholamine release in response to (original) (raw)
Cardiopulmonary bypass (CPB) alters systemic hemodynamics and affects several biochemical systems involved in cardiovascular regulation. We investigated the changes in levels of circulating epinephrine (E) and norepinephrine (NE) and related them to events during CPB. Twenty-eight patients undergoing various surgical procedures were studied. Plasma E and NE were determined by radioenzymatic assay at eight stages of the operation. A ninefold increase in arterial E (from 75 + 13 to 708 ± 117.3 pg/mI) occurred from prebypass (stage 1) measurements to the end of aortic cross-clamping (stage 4). The values at stage 4 were signific'antly higher (p < 0.05) than at all other stages. E decreased rapidly, to 360 84.3 pg/ml, rafter myocardial and pulmonary reperfusion (stage 5). Arterial NE increased twofold from stage 1 to stage 4 (from 426 66.9 to 825 84.2, p < 0.05). The increase in NE from initial CPB values (stage 2) to 30 minutes of aortic cross-clamping (stage 3) was associated with an increase in mean blood pressure (r 0.51, p = 0.02). The peak increases in catecholamines occurred when the heart and lungs were'excluded from the circulation, which suggests that either or both contributed to the increase. Because the increase in E was markedly greater than that in NE, the predominant humoral response to CPB appears to be adrenomedullary release of E. This significant increase in catecholamines could jeopardize myocardial protective measures during'CPB. MARKED INCREASES in norepinephrine (NE) and epinephrine (E) concentrations in arterial blood during cardiopulmonary bypass (CPB) have been demonstrated. '-' However, no report describes the temporal increase in NE and E in relation to the abnormal hemodynamic and biochemical events during CPB. Methods Patients Twenty-eight adult patients, 10 female and 18 male, scheduled for elective cardiac surgery were studied using a protocol approved by the institutional review board of'the University of Alabama. The operations performed are shown in table 1. All patients continued to take their usual medications, including propranolol, until the time of surgery. Patients taking a methyldopa were excluded from the study. Table 2 contains demographic variables describing the patient population. Comparison of catecholamines and hemodynamic data from patients with ischemic heart disease (20 patients) and those with combined ischemic and valvular or congenital heart disease revealed no significant alterations in'the response to CPB. Likewise, whether or not patients were taking particular medications (e.g., propranolol or antihypertensive drugs) did not alter the catecholamine or hemodynamic response. Therefore, data from all patients are considered together. Anesthesia All patients were anesthetized by the same physician to ensure a consistent anesthetic approach. Anesthetic
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