Deliberate+Hypotension

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 * =Definition=
 * A purposeful reduction in Systolic Blood pressure to 80-90mmHg, a reduction in MAP to 50-60mmHg, or a 30% reduction of MAP from baseline. Intended to reduce intra-operative blood loss, reduce blood transfusions, enhance visibility of the surgical field.
 * =Indications=
 * oromaxillofacial surgery (mandibular osteotomy, facial repair), endoscopic sinus or middle ear microsurgery, spinal surgery and other neurosurgery (aneurysm), major orthopaedic surgery (hip or knee replacement, spinal), prostatectomy, cardiovascular surgery (during cannulation of the great vessels) and liver transplant surgery.
 * =Contraindications=
 * Ischemic Cerebral Vascular Disease, Intracranial Hematoma, Coronary Artery Disease, Fever, Sepsis, Hypovolemia, Anemia, Severe Hypertension, Extremes of Age, Renal Dysfunction.Recent reports using control groups do not show significant differences in morbidity and mortality attributable to induced hypotension during anesthesia.
 * =Positioning=
 * The surgical site should be the highest point (i.e. non-dependent) allowing blood to drain easily and decreasing blood pressure to that particular site due to gravity. This is not always the optimal position for other reasons (Air embolism, Pt Comfort, etc)
 * =Inducing Hypotension =
 * ==Ventilation==
 * Hyperventilation leads to reduced PaCO2 and thus arteriolar vasoconstriction reducing blood flow to organs (this can be disatrous with already low MAP) The converse is true of hypoventilation which causes increased PaCO2 and thus vasodilation increasing blood flow.
 * ==Fluid Resuscitation==
 * Aggressive crystalloid administration can blunt baroreceptor response to the induced vasodilation and mitigate the need for compensatory tachycardia without subjecting the patient to blood transfusions which have been proven to increase mortality.
 * ==Opiates==
 * decrease SNS response to stimulation and blunt baroreceptor reflexes to maintain low-normal blood pressures in the face of painful stimulus and acute vasodilation. Propofol and Remifentanyl combinations are effective for inducing deliberate hypotension.
 * ==Vasodilators==

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