Effect of height versus height/weight-based spinal bupivacaine on maternal hemodynamics for elective cesarean in short stature patients: a randomized clinical trial.

Purpose: Doses of spinal bupivacaine adjusted to patient height or height/weight have been shown to provide hemodynamic stability during cesarean section. However, their effects in short stature parturients are unknown.
Methods: In this double-blind, randomized clinical trial, we randomly assigned short parturients (height < 150 cm) undergoing elective cesarean section, to receive doses of intrathecal hyperbaric bupivacaine either height or height/weight-adjusted, in a 1:1 ratio. The primary outcome was post-spinal hypotension (defined as systolic blood pressure [SBP] < 90% of baseline between spinal administration and delivery of the baby). Secondary outcomes included severe post-spinal hypotension (SBP < 80% of baseline), post-delivery hypotension (SBP < 90% and < 80% of baseline), intraoperative bradycardia, nausea and vomiting, shivering, rescue analgesic needed, and spinal block characteristics.
Results: A total of 112 patients underwent randomization. Post-spinal hypotension (SBP < 90% of baseline) occurred in 52% of the patients in the height/weight group and in 55% in the height group (difference - 3.5%: 95% confidence interval [CI] - 22 to 14.8, P = 0.705). There was no significant difference between the two groups in the occurrences of post-spinal severe hypotension (SBP < 80% of baseline), post-delivery hypotension, and spinal block characteristics. Six patients (11%) in the height/weight group needed intraoperative rescue analgesic compared to none in the height group (P = 0.027).
Conclusion: We found that height-based dosing in short parturients provides the optimal trade-off between intraoperative hemodynamic instability and provision of pain-free anesthesia.
Trial Registration: clinicaltrial.gov-NCT04082676. https://clinicaltrials.gov/ct2/show/NCT04082676 .
(© 2023. The Author(s) under exclusive licence to Japanese Society of Anesthesiologists.)