Hypertension artérielle et anesthésie

Abstract

Hypertension is one of the most important risk factors for cerebrovascular disease and ischaemic heart disease. Postoperative adverse outcomes of hypertension include cardiac death, left ventricular hypertrophy (with impaired diastolic function) leading to ventricular failure, myocardial ischaemia and infarction, renal damage and cerebrovascular accidents. The role of the anaesthetist for patients suffering from chronic hypertension goes beyond that in most other patient population since there is a unique opportunity to improve long-term survival and function by applying adequate preoperative evaluation and refined perioperative anaesthetic management. Maintenance of hemodynamic stability throughout the perioperative period is essential in these patients with cardiovascular risk, most of whom benefit from cardiac treatments designed to improve both their symptoms and life expectancy. Anesthetic agents development and improved delivery have reduced the importance of direct anaesthetic effects on heart versus effects of interactions with other cardio-vascular drugs. In patients with hypertensive disease undergoing anaesthesia and surgery, disease-drug-anaesthesia interaction may either increase or reduce the likelihood of perioperative morbidity and mortality. The blockade of the sympathetic system is well tolerated and has several beneficial effects including the prevention of hypertensive episodes and myocardial ischemia. By contrast, the blockade of the renin-angiotensin system markedly increases the lowering blood pressure effect of anesthesia. This is not surprising if one takes into account that this system is activated by any decrease in the loading conditions of the heart, especially preload. That leads to withdraw treatments, which interfere with the renin angiotensin system, the eve of surgery. Better knowledge of the physiopathological mechanisms involved in postoperative complications now enables to define perioperative managements for hypertensive patients undergoing non cardiac surgery and thus limit the risk of anesthesia. The main goal of the perioperative management is to limit postoperative stress by adequate intra and postoperative management and to control postoperatively increased sympathetic tone or its circulatory effects by administering preventive cardiovascular medications which interfere with the sympathic system. The prevention of intraoperative hypothermia and intensive postoperative analgesia significantly limit circulatory stress in the postoperative period. However, although diminished, these contraints have not been abolished. This is the reason why many authors have envisaged the administration of cardiovascular medication to effectively limit the sympathetic stimulation which persists several days after surgery. Two types of cardiovascular drugs have been recommended : beta-adrenergic blocking drugs and alpha-2 adrenoreceptor agonists. Postoperative hypertension episodes must be treated by vasodilatators (calcium channel blockers) and/or betablockers.