10 Vs.15 mcg Norepinephrine Bolus in Severe Maternal Hypotension During 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.

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. 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, norepinephrine bolus of 5 mcg will be given.

Any other hypotensive episode (systolic blood pressure <80% of baseline) will be managed with norepinephrine 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 (1 IU) will be delivered over five seconds after delivery then infused at a rate of 2.5-7.5 IU/hour.

Inclusion criteria

• full-term singleton pregnant women
• American society of anesthesiologist II, scheduled for elective cesarean delivery,

Exclusion criteria

• Patients with uncontrolled cardiac morbidities (patients with tight valvular lesion, impaired contractility with ejection fraction < 50%, heart block, and arrhythmias),
• hypertensive disorders of pregnancy,
• peripartum bleeding,
• coagulation disorders (patients with INR >1.4 and or platelet count < 80000 /dL) or any contraindication to regional anesthesia,
• baseline systolic blood pressure (SBP) < 100 mmHg