COMPARATIVE TOLERABILITY PROFILE OF HYPERTENSIVE CRISIS TREATMENTS

Hypertensive crisis is defined as a severe elevation in BP and is clas sified as either urgency or emergency. In hypertensive urgency there i s no end-organ injury and no evidence that acute BP lowering is benefi cial. Indeed, rapid uncontrolled pressure reduction may be harmful. Th erefore, in hypertensive urgencies BP should be lowered gradually over 24 to 48 hours using oral antihypertensives. When the cause of transi ent BP elevations is easily identified, appropriate treatment should b e given. When the cause is unknown, an oral antihypertensive should be given. The efficacy of available treatments appear similar; however, the underlying pathophysiological and clinical findings, mechanism of action and potential for adverse effects should guide choice. Captopri l should be avoided in patients with bilateral renal artery stenosis o r unilateral renal artery stenosis in patients with a solitary kidney. Nifedipine and other dihydropyridines increase heart rate whereas clo nidine, beta-blockers and labetalol tend to decrease it. This is parti cularly important in patients with ischaemic heart disease. Labetalol and beta-blockers are contraindicated in patients with bronchospasm an d bradycardia or heart blocks. Clonidine should be avoided if mental a cuity is desired. In hypertensive emergency there is an immediate thre at to the integrity of the cardiovascular system. BP should be immedia tely reduced to avoid further end organ damage. Sodium nitroprusside i s the most popular agent. Nitroglycerin (glyceryl trinitrate) is prefe rred when there is acute coronary insufficiency. A beta-blocker may be added in some patients. Loop diuretics, nitroglycerin and sodium nitr oprusside are effective in patients with concomitant pulmonary oedema. Enalaprilat is also theoretically helpful, especially when the renin system might be activated. Initial treatment of aortic dissection invo lves rapid, controlled titration of arterial pressure to normal levels using intravenous sodium nitroprusside and a beta-blocker. If beta-bl ockers are contraindicated, urapidil or trimetaphan camsilate are alte rnatives. Hydralazine is the drug of choice for patients with eclampsi a. Labetalol, urapidil or calcium antagonists are possible alternative s if hydralazine fails or is contraindicated. For patients with catech olamine-induced crises, an alpha-blocker such as phentolamine should b e given; labetalol or sodium nitroprusside with beta-blockers are alte rnatives. There are few, if any, comparative or randomised trials prov iding definitive conclusions about the efficacy and safety of comparat ive agents. Some investigators recommend decreasing the diastolic BP t o no less than 100 to 110 mm Hg. A reasonable approach for most patien ts with hypertensive emergencies is to lower the mean arterial pressur e by 25% over the initial 2 to 4 hours with the most specific antihype rtensive regimen.