[Controlled hypotension]

Induced hypotension is defined as a reduction in mean arterial blood pressure to 50-60 mm Hg in normotensive subjects. The aim of induced hypotension 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 loss by 50% in many surgical procedures; however, some studies report that blood loss is not significantly reduced. Current methods of induced hypotension are based on the use of rapid and short-acting vasodilators as primary agents (nitroprusside, nitroglycerine, urapidil), supplemented by volatile anesthetics (isoflurane) and/or beta-blockers (esmolol) 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 intracranial pressure in neurosurgical patients. Thus, major contraindications of induced hypotension are severe coronary artery disease, hypertension combined with arteriosclerosis of cerebral vessels and increased intracranial pressure in patients with cerebral disease. Complications are rare in otherwise healthy patients, but may be higher in elderly patients and those with underlying organ dysfunction. Therefore, careful assessment and selection of patients, together with consideration of the potential complications, appropriate choice of drugs and invasive beat-by-beat monitoring, are essential for the safe practice of induced hypotension.