Pregabalin Effects on Hypotensive Anesthesia During Spine Surgery.

Overview

Elective lumbar spine surgical procedures are commonly performed under controlled hypotension during general anesthesia. That is beneficial to limit the intraoperative blood loss and transfusions and improves surgical field. Deliberate hypotension could be achieved via various medications but mostly associated with significant side effects. Pregabalin effectively augmented hypotensive anesthesia. The hypothesis is that Pregabalin 150 mg single preoperative dose may augment intraoperative deliberate hypotension that will be reflected on blood loss and nitroglycerin consumption.

An arterial line will be established then general anesthesia will be conducted. After adequate preoxygenation, anesthesia induction by IV fentanyl 1.5µg/kg, propofol 2 mg/kg, and atracurium 0.5 mg/kg then appropriated size tracheal tube. The ventilator settings will be adjusted to maintain the end-tidal carbon dioxide tension (ETco2) at 30-35 mm Hg. Anesthesia will be maintained by isoflurane concentration 1.2%, with 40% oxygen in air then IV infusion of fentanyl 0.05 mcg/kg/min was started while atracurium 0.1 mg/kg incremental dose as required. Then patients will be turned into the prone position above pad support permitting free hanging of the abdomen. Intraoperatively, the target mean arterial arterial blood pressure (MBP) is 55-65 mm Hg. After surgical incision, if MBP exceeds 65 mm Hg (defined as hypertension) it will be managed by: increasing isoflurane MAC up to 2%, if no response after 5 min, Nitroglycerin infusion initiated at 0.5 mcg/kg/min to 40 mcg/kg/min. Hypotension (MBP \<55 mm Hg) will be treated by stopping nitroglycerin, proper compensation of losses, reducing Isoflurane MAC. If persisted; vasoactive drugs will be used. Bradycardia (HR \<50 beat/min.), treated with 0.01 mg/kg atropine IV increments. The nitroglycerin infusion will be stopped after the finial surgical hemostasis. Fentanyl infusion will be stopped before ligament sutures. Isoflurane will be closed after the last surgical suture. After dressing, patient will be turned to the supine position and morphine 0.025 mg/kg IV will be administered then 0.04 mg/kg neostigmine and 0.015 mg/kg atropine for reversal. Extubation will be done after establishment of acceptable spontaneous respiration.

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