Effect of Position-Based Dosing Strategy for Metaraminol on Neonatal Acid-Base Status During Elective Caesarean Delivery: A Noninferiority Randomised Controlled Trial.

BACKGROUND

The 15° left tilt position during caesarean delivery has been recommended by guidelines for many years, but recent studies have questioned the clinical benefit of left tilt position. We hypothesize that using a higher starting dose of metaraminol in the supine position will result in a non-inferior umbilical arterial pH, compared to the 15° left tilt position.

METHODS

Healthy women undergoing elective caesarean delivery were randomized to the supine position (n = 62) or 15° left tilt position (n = 62) after spinal anaesthesia (0.5% bupivacaine 9 mg). Different starting doses of metaraminol infusion were initiated at 2.7 μg kg min for the supine position group and 2.0 μg kg min for the tilt position group. The infusion rates were then adjusted using a fixed algorithm to maintain systolic blood pressure. The primary outcome was the pH of the umbilical artery.

RESULTS

Compared with tilt group, pH (supine group: 7.325 (7.29, 7.35) vs tilt group: 7.33 (7.3, 7.35), P = 0.76) and base excess (tilt group: -0.98 (2.59) mM vs supine group: -0.92 (2.77) mM, P = 0.9) of the umbilical artery are non-inferior. There was no difference in SBP (P = 0.16) or incidence of hypotension (P = 0.75) between the two groups. The incidence of reactive hypertension was greater in the supine position group (P < 0.001).

CONCLUSION

If maternal blood pressure is maintained using the higher starting dose of metaraminol, the left tilted position may not be necessary among healthy patients (BMI less than 35 kg/m) undergoing elective caesarean delivery with spinal anaesthesia.