Peri-operative hypertension and its treatment with intravenous agents

Several pathophysiological mechanisms are involved in the occurrence of hypertension during the peri-operative period. The effective management of blood pressure requires knowledge of the presence of concomitant diseases (e.g. coronary and peripheral atherosclerosis, renal dysfunction and cerebral disease). The patient who is undergoing an aortic or cerebral aneurysm repair will need a different therapeutic approach from someone scheduled for a peripheral procedure. Tailoring of anti-hypertensive therapy requires a detailed understanding of the effects on organ circulation (myocardial, cerebral and renal) as well as the pharmacokinetic and pharmacodynamic effects of the various anti-hypertensive drugs. The complexity of the pathogenesis of peri-operative hypertension offers a large number of opportunities for pharmacological intervention, including direct vasodilators or substances acting via blocking or stimulating various peripheral or central receptors. It is impossible to give definite dose recommendations for the different drugs. Many factors may influence the ‘ideal’ dose—pre-existing anti-hypertensive therapy, concomitant diseases, age, gender, extent of hypertension, time for lowering blood pressure (emergency/urgency), the kind of surgery and other factors—which may markedly affect the dose-response relationship of the different anti-hypertensive substances.

Treating hypertension has its benefits and risks. The complications result either from the nature of therapy (e.g. severe bradycardia after beta-blocker therapy) or from hypotension. Substances with a short duration of action appear to be of advantage in the peri-operative period. Undoubtedly, sudden increase in blood pressure should be urgently avoided; however, a rapid and marked reduction of blood pressure should also be prevented. The cerebral-or cardiac-compromised hypertensive patient particularly requires close monitoring, both during the operation and during recovery from surgery and anaesthesia. Blood pressure in these patients should be controlled only under the precise control of haemodynamics, probably using invasive blood pressure measurement and pulmonary artery catheter monitoring. For example, in patients with an aortic dissection, careful intraarterial monitoring is a prerequisite for optimal peri-operative management.

Financial consequences are becoming more and more important. The climate of cost-consciousness and cost-containment will also influence the treatment of peri-operative hypertension. Thus, although very sophisticated substances for controlling blood pressure (e.g. endothelin antagonists) will enter the market, cost-benefit analyses will more and more influence the choice of anti-hypertensive substance. However, we should always bear in mind that the fundamental step is to minimize the patients' peri-operative risk. Primum nil nocere is of highest importance when tailoring the therapeutic concept of the hypertensive patient in the peri-operative period.