Impact of systemic hypertension on peri-operative morbidity and mortality

Chronic hypertension is associated with structural as well as functional changes of the vasculature, in particular of the coronary, cerebral and renal circulations. It is important to realize that (1) functional changes are often the result of structural changes, (2) the longer lasting the hypertension, the slower and less complete the regression of structural changes, and (3) acute ‘normalization’ of arterial pressure in longstanding hypertension may initially induce functionally subnormal smooth muscle and/or cardiac activity because the structure of the cardiovascular system is adapted to function at elevated pressures.

Despite a multitude of studies, the impact of hypertension on peri-operative morbidity and mortality remains controversal. There are as many studies seeming to suggest that pre-operative hypertension correlates with adverse outcome as there are studies that fail to establish such a relationship. When looking at the combined evidence, one is inclined to conclude that hypertension is a predictor of ‘soft’ outcomes (e.g. peri-operative myocardial ischaemia and transient post-operative neurologic deficit) rather than an independent predictor of “hard” outcomes (e.g. unstable angina, myocardial infarction and cardiac death).

In view of a lack of convincing outcome data, it is impossible to recommend a generally acceptable management strategy for the hypertensive patient. Although, in general, a gradual reduction of blood pressure over a period of weeks to months is the optimal therapeutic approach, we will be hard-pressed delaying surgery for the sole purpose of ‘better blood pressure control’. With full appreciation and detailed knowledge of the pathophysiology of hypertension, combined with sophisticated haemodynamic monitoring and interventions in the peri-operative period, acutely anaesthetizing an inadequately treated hypertensive patient will probably not adversely affect his outcome. Delaying surgery for additional work-up may possibly improve outcome in patients with target organ disease, evidence of secondary hypertension, in the most severe forms of hypertension or sudden-onset hypertension.