INDUCED HYPOTENSION BY SODIUM NITROPRUSSIDE, CLONIDINE OR ESMOLOL HYDROCHLORIDE IN MIDDLE EAR SURGERY. A COMPARATIVE STUDY

Abstract

Deliberate hypotension IS an acceptable intraoperative technique improving surgical conditions when a bloodless operative field is needed , together with reducing blood loss and the need for blood transfusion with its concomitant hazards . Normovolaemic hypotension can be produced by either, a reduction in cardiac output or a decrease in systemic vascular resistance . Drugs with different modes of action have been used alone or m combinations to induce hypotension . these drugs may be classified depending on their mode of action into : Ganglionic blockers (e.g. pentolinium & trimethaphan ) ; Direct - acting vasodilators (e.g. sod. Nitroprusside , nitroglycerin , hydralazine , adenosine , prostaglandin E1 ) ; a1 - adrenergic receptor blockers (e.g. phentolamine ) ; - adrenergic receptor blockers (e.g. propranolol , esmolol ) ; alpha2 adreoceptor agonists (e.g. clonidine ) ; Angiotensin - converting enzyme inhibitor (e.g. captopril )and calcium charmel blockers (e.g. veraparnil , nicardipme ) . Induced hypotension may result m hormonal and metabolic responses. However the major disadvantage of induced hypotension is that tissue oxygenation may be impaired if arterial pressure is reduced excessively to jeopardize the requirements of the vital organs. The aim of tlus study was to compare the effects of three different drugs (sodium nitroprusside , clonidine and esmolol hydrochloride) used to induce hypotension in middle ear surgery and the comparison includes their effects on haemodynamic parameters , some metabolic and endocrinal responses.