A Novel Closed-loop Integrated System for the Maintenance of Haemodynamic Stability

A Novel Closed-loop Integrated System for the Maintenance of Haemodynamic Stability to Improve Perioperative Outcome During Spinal Anaesthesia for Caesarean Section

Hypotension occurs commonly during spinal anaesthesia for caesarean section with maternal and fetal adverse effects. The investigators developed a double-vasopressor automated system incorporating continuous non-invasive haemodynamic monitoring using NexfinTM with a two-step algorithm.

Hypotension occurs commonly during spinal anaesthesia for caesarean section with maternal and fetal adverse effects. We developed a double-vasopressor automated system incorporating continuous non-invasive haemodynamic monitoring using Nexfin cardiac output monitor with a two-step algorithm. The system delivered phenylephrine 25 mcg or ephedrine 2 mg (if heart rate<60 beats.min-1) every 30 seconds when systolic blood pressure was between 90-100% of baseline. The system delivered phenylephrine 50 mcg or ephedrine 4 mg (if heart rate<60 beats.min-1) every 30 seconds when systolic blood pressure was <90% of baseline.

A randomised controlled trial will be done to compare with manual bolus technique. With the manual bolus technique, phenylephrine 50mcg or ephedrine 4mg (if heart rate<60 beats.min-1) every 60 seconds when systolic blood pressure was between 90-100% of baseline. The system delivered phenylephrine 100mcg or ephedrine 8mg (if heart rate<60 beats.min-1) every 60 seconds when systolic blood pressure was <90% of baseline.

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