Preexisting hypertension is the most common medical reason for postponing surgery . Hypertension is well known to be a risk factor for cardiovascular catastrophe, a risk that logically extends into the perioperative period [2,3]. In a case-control study of 76 patients who died of a cardiovascular cause within 30 days of elective surgery, a preoperative history of hypertension was four times more likely than among 76 matched controls . The issues regarding the perioperative management of the patient with hypertension are reviewed here.
BLOOD PRESSURE RESPONSE DURING ANESTHESIA
Sympathetic activation during the induction of anesthesia can cause the blood pressure to rise by 20 to 30 mmHg and the heart rate to increase by 15 to 20 beats per minute in normotensive individuals . These responses may be more pronounced in patients with untreated hypertension in whom the systolic blood pressure can increase by 90 mmHg and heart rate by 40 beats per minute.
The mean arterial pressure tends to fall as the period of anesthesia progresses due to a variety of factors, including direct effects of the anesthetic, inhibition of the sympathetic nervous system, and loss of the baroreceptor reflex control of arterial pressure. These changes can result in episodes of intraoperative hypotension. Patients with preexisting hypertension are more likely to experience intraoperative blood pressure lability (either hypotension or hypertension) , which may lead to myocardial ischemia .
Blood pressure and heart rate slowly increase as patients recover from the effects of anesthesia during the immediate postoperative period. Hypertensive individuals in particular may experience significant increases in these parameters .
PERIOPERATIVE RISKS ASSOCIATED WITH HYPERTENSION
Preexisting hypertension can induce a variety of cardiovascular responses that potentially increase the risk of surgery, including diastolic dysfunction from left ventricular hypertrophy, systolic dysfunction leading to congestive heart failure, renal impairment, and cerebrovascular and coronary occlusive disease. The level of risk is dependent upon the severity of hypertension.