Hypertensive episodes during and after open heart surgery
Since our initial description of hypertension following myocardial revascularization in 1973,1 hypertension has been recognized more frequently as a complication before, during, and after surgery for myocardial revascularization and heart valve replacement. A classification based upon the timing of occurrence of the hypertension in relation to surgery is more feasible than a classification based on a specific mechanism2(Table).
Systemic arterial pressure is determined by several variables, cardiac output, peripheral resistance, blood volume, aortic compliance, autonomic activity, and other humoral factors. All of these are affected by premedication, anesthesia, surgery on the heart itself, cannulation of the big vessels, cardiopulmonary bypass, and the postoperative setup.
Preoperative stress, discomfort, and inadequate premedication can cause a sudden rise in blood pressure more pronounced in preoperatively hypertensive patients, particularly if antihypertensive treatment and beta blockers were discontinued. A sudden rise in blood pressure at this stage increases myocardial oxygen consumption, can cause anginal pain and vice versa, therefore, a vicious circle of hypertension and myocardial ischemia. Reflex sympathetic activity due to endotracheal intubation, nasopharyngeal, rectal, or urethral manipulation causes tachycardia and a rise in blood pressure, which can be complicated by acute impairment of left ventricular function as well as electrocardiographic signs of ischemia.
Not infrequently, acute hypertension develops during median sternotomy possibly due to reflex sympathetic stimulation, despite the expected decrease in venous return and cardiac output due to loss of negative intrapleural pressure.
On initiation of cardiopulmonary bypass, arterial mean pressure drops due to the nonpulsatile flow and the effect of . . .