Update in induced hypotension during surgery

induced hypotension is defined as a reduction of the systolic blood pressure to 80 mm Hg, a reduction of mean arterial pressure (MAP) to 50mm Hg or a 30% reduction of baseline MAP. For half a century, induced hypotension has been used to reduce bleeding and the need for blood transfusions, and provide a satisfactory bloodless surgical field.The aim of this study is to focus the light on the history of induced hypotension, methods of decreasing intra-operative blood loss, the physiology of blood pressure, the definition, the indications, the contraindications, techniques (especially the update), monitoring, complications and safety of induced hypotension, the effects on the functions of the various body organs and the anesthetic Management of surgical patient who scheduled for induced hypotension.In the past induced hypotension was used during anesthesia by using arteriotomy as the technique to induce hypotension and produce a relatively bloodless surgical field. Subsequently, ganglionic blocking was introduced, followed by other drugs, subsequently, deep anesthesia with volatile inhalation anesthesia.There are local and systemic methods to decrease intra-operative blood loss. The local methods are local vasoconstrictors, arterial compression, putting the patient with operative site above the heart level and Systemic methods; induced hypotension, normovolemic hemodilution and systemic coagulant drugs as: vitamin K, tranexamic acid, e-aminocaproic acid and desmopressin.Physiologically, normal arterial blood pressure is 120/80 mmHg. There are many factors which affect arterial blood pressure such as; peripheral resistance, vessel elasticity, blood volume and cardiac output. Arterial blood pressure is regulated by baroreceptor reflex, renin-angiotensin system, aldosterone release, neural and hormonal control.Most studies define induced hypotension as a reduction in systolic blood pressure to 80 to 90 mm Hg. According to another definition, induced hypotension is a decrease in MAP to 50 to 65 mm Hg in normotensive patients.