Closed-loop Double-vasopressor Automated System to Treat Hypotension During Spinal Anaesthesia for Caesarean Section

Closed-loop Double-vasopressor Automated System vs Manual Bolus Vasopressor to Treat Hypotension During Spinal Anaesthesia for Caesarean Section

Hypotension occurs commonly during spinal anesthesia for caesarean section with maternal and fetal adverse effects. The investigators developed a double-vasopressor automated system incorporating continuous non-invasive arterial pressure monitoring (CNAP, CNSystems, Austria).

Hypotension occurs commonly during spinal anesthesia for cesarean section with maternal and fetal adverse effects. The investigators developed a double-vasopressor automated system incorporating continuous non-invasive arterial pressure (CNAP, CNSystems, Austria) monitoring feeding hemodynamic data to a laptop computer, which triggers syringe pumps to deliver phenylephrine 50mcg or ephedrine 4mg (if heart rate<60 beats.min-1) every 30 seconds when systolic blood pressure fell to below 90% of baseline.

A randomised controlled trial was done to compare with manual bolus technique. With the manual bolus technique, phenylephrine 100mcg or ephedrine 8mg (if heart rate<60 beats.min-1) was given every 60 seconds by the attending anesthesiologist when systolic blood pressure was below 90% of baseline as measured by conventional intermittent non-invasive blood pressure monitoring.

Inclusion Criteria:

• age 21-45 years old,
• weight 40-90 kg,
• height 145-170 cm

Exclusion Criteria:

• contraindications to spinal anaesthesia,
• allergy to drugs used in the study, and
• those with uncontrolled medical conditions such as hypertension, diabetes mellitus, and cardiovascular disease