INDUCED HYPOTENSION

Induced hypotension is defined as a reduction in mean arterial blood p ressure to 50-60 mm Hg in normotensive subjects. The aim of induced hy potension is to decrease intraoperative blood loss, decrease the need for blood transfusions and improve operating conditions. Most studies indicate that induced hypotension can decrease intraoperative blood lo ss by 50% in many surgical procedures; however, some studies report th at blood loss is not significantly reduced. Current methods of induced hypotension are based on the use of rapid and short-acting vasodilato rs as primary agents (nitroprusside, nitroglycerine, urapidil), supple mented by volatile anesthetics (isoflurane) and/or beta-blockers (esmo lol) to improve effect, reduce dosage and prevent side effects (reflex tachycardia, tachyphylaxis, rebound hypertension). Proper positioning of the patient and controlled ventilation aid in reducing blood loss. Major risks of induced hypotension are a reduction in blood flow (i.e . ischaemia) of vital organs (brain, myocardium) and elevation of intr acranial pressure in neurosurgical patients. Thus, major contraindicat ions of induced hypotension are severe coronary artery disease, hypert ension combined with arteriosclerosis of cerebral vessels and increase d intracranial pressure in patients with cerebral disease. Complicatio ns are rare in otherwise healthy patients, but may be higher in elderl y patients and those with underlying organ dysfunction. Therefore, car eful assessment and selection of patients, together with consideration of the potential complications, appropriate choice of drugs and invas ive beat-by-beat monitoring, are essential for the safe practice of in duced hypotension.