Closed‐loop double‐vasopressor automated system to treat hypotension during spinal anaesthesia for caesarean section: a preliminary study

Hypotension occurs in most caesarean sections under spinal anaesthesia, necessitating vasopressor administration. However, the optimal dosing regimen remains unclear. We have developed a novel vasopressor delivery system that automatically administers phenylephrine or ephedrine based on continuous non‐invasive blood pressure monitoring. This prospective cohort study recruited 55 healthy women under standardised spinal anaesthesia with 2.2 ml hyperbaric bupivacaine 0.5%, 15 μg fentanyl and 100 μg morphine. A 50‐μg phenylephrine bolus was given at 1‐min intervals when systolic blood pressure fell below 90% of baseline, and a 4‐mg ephedrine bolus was given when hypotension developed with bradycardia (heart rate <60 beats.min^?1). Systolic blood pressure was within 20% of baseline in 88% of all measurements. Six patients (11%) had one or more measurements above 120% of baseline (1% of all measurements), whereas 36 (65%) had at least one reading below 80% of baseline (11% of total measurements). The system maintained systolic blood pressure at a mean (SD) of ?9.1 (7.0)% below baseline, with 5.4 (2.5)% fluctuation. Two patients (4%) experienced pre‐delivery nausea. All 5‐min Apgar scores were 9.