Epinephrine Versus Norepinephrine Infusion for Prevention of Maternal Hypotension During Caesarean Delivery: a Randomized Clinical Trial

Upon arrival to the operating room, routine monitoring will be applied (electrocardiography, pulse oximetry, and non-invasive blood pressure monitor). An 18G-cannula will be inserted, and 10 mg metoclopramide, and 50 mg ranitidine will be delivered. Co-load infusion of lactated Ringer's solution will be infused at rate of 15 mL/Kg over 10 minutes; and 10 mg hyperbaric bupivacaine in addition to 20 mcg fentanyl will be injected in the subarachnoid space at L3-L4 or L4-L5 interspace using 25G spinal needle.

After subarachnoid block, mothers will be placed in supine position with left-lateral tilt and will receive the vasopressor infusion according to the allocated study group Block success will be assessed after 5 minutes from injecting local anesthetic into the subarachnoid space using pinprick; and will be confirmed if sensory block level is at T4. The vasopressor will be infused in the same line with intravenous fluids using a three-way stopcock. The baseline systolic blood pressure reading will be calculated as the average of 3 readings obtained in the supine position with left-uterine displacement at two-minute intervals with a difference of <10%.

Hemodynamic management in both groups will be as follow:

Post-spinal hypotension (defined as systolic blood pressure ≤80% of the baseline reading or systolic blood pressure <90 mmHg during the period from intrathecal injection to delivery of the fetus) will be managed by ephedrine 9 mg Severe post-spinal hypotension (defined as systolic blood pressure ≤60% of the baseline reading) will be managed by administration of ephedrine 15 mg Reactive hypertension (defined as systolic blood pressure ≥120% from the baseline reading) will be managed (if persisted > 1-reading) by stoppage of the infusion till the next systolic blood pressure reading.

Intraoperative bradycardia (defined as heart rate less than 55 bpm) will be managed by stoppage of the vasopressor infusion if not associated with hypotension. The infusion will be then re-started in a reduced rate (50%) when the heart rate is more than 55 bpm. IV atropine bolus (0.5 mg) will be administered if bradycardia persisted despite stoppage of the infusion. If accompanied with hypotension, bradycardia will be managed by IV bolus of ephedrine 9 mg.