Two Norepinephrine Rescue Bolus Doses for Management of Severe Post-spinal Hypotension During Elective Cesarean Delivery

Upon arrival to the operating room, the patient will be in supine position with left uterine displacement using a wedge below the right buttock. Routine monitoring will be applied (electrocardiography, pulse oximetry, and non-invasive blood pressure monitor). An 18G-cannula will be inserted, and the patients will receive 10 mg metoclopramide. Baseline heart rate and systolic blood pressure will be recorded as the average of three consecutive readings with 2-minutes interval. Lactated Ringer's solution will be infused at rate of 15 mL/Kg over 10 minutes as a co-load; spinal anesthesia will be achieved by injecting 10 mg of hyperbaric bupivacaine and 20 mcg fentanyl into the subarachnoid space at L3-L4 or L4-L5 interspace using 25G spinal needle. After subarachnoid block, mothers will be placed in the supine position with left-lateral tilt. The decision to give prophylactic vasopressor infusion will be according to the attending anesthetist preferences. Block success will be assessed after 5 minutes from intrathecal injection of local anesthetic; and will be confirmed if sensory block level is at T4. The patient would receive the study drug only if she developed severe post-spinal hypotension (defined as systolic blood pressure ≤60% of the baseline reading) as her first hypotensive episode or after 10 minutes from the last successfully managed hypotensive episode and before the delivery. . The management of the hypotensive episode will be considered successful if the systolic blood pressure is \> 80% of the baseline within 2 mins of the bolus. If the bolus failed, NE bolus of 5 mcg will be given. Any other hypotensive episode (systolic blood pressure \<80% of baseline) will be managed with NE bolus of 5 mcg. Intraoperative bradycardia (defined as heart rate less than 55 bpm) will be managed by IV atropine bolus (0.5 mg) will be administered. Fluid administration will be continued up to a maximum of 1.5 liters. An oxytocin bolus (0.5 IU) will be delivered over five seconds after delivery then infused at a rate of 2.5 IU/hour.