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

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.

hypotension, spinal anesthesia, cesarean section, phenylephrine, ephedrine, closed-loop system, continuous non-invasive monitor

vasopressor delivery automated system that administered phenylephrine and ephedrine based on data from continuous non-invasive hemodynamic monitor

manual bolus that delivered phenylephrine and ephedrine based on data from non-invasive intermitted blood pressure monitor

Novel closed-loop system incorporating: Continuous non-invasive arterial pressure (CNAP) monitor that measured and recorded hemodynamic data in real time. Controller algorithm loaded onto a laptop computer that monitored the hemodynamic data from CNAP and determined if vasopressors should be administered. Two syringe pumps loaded with phenylephrine and ephedrine that was activated by the controller algorithm.

Phenylephrine is a vasopressor drug that was administered when the participant's systolic blood pressure fell below 90% of baseline systolic blood pressure, with heart rate of at least 60bpm.

Ephedrine is a vasopressor drug that was administered when the participant's systolic blood pressure fell below 90% of baseline systolic blood pressure, with heart rate of less than 60bpm.

Manual dosing system consisting: Non-invasive intermittent blood pressure monitor that measured and recorded blood pressure at 1-minute intervals. Attending anesthesiologist that noted the blood pressure readings and manually administered phenylephrine or ephedrine according to the algorithm.

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

Ngan Kee WD. Prevention of maternal hypotension after regional anaesthesia for caesarean section. Curr Opin Anaesthesiol. 2010 Jun;23(3):304-9. doi: 10.1097/ACO.0b013e328337ffc6.

Sia AT, Tan HS, Sng BL. Closed-loop double-vasopressor automated system to treat hypotension during spinal anaesthesia for caesarean section: a preliminary study. Anaesthesia. 2012 Dec;67(12):1348-55. doi: 10.1111/anae.12000. Epub 2012 Sep 28.

Sng BL, Tan HS, Sia AT. Closed-loop double-vasopressor automated system vs manual bolus vasopressor to treat hypotension during spinal anaesthesia for caesarean section: a randomised controlled trial. Anaesthesia. 2014 Jan;69(1):37-45. doi: 10.1111/anae.12460. Epub 2013 Nov 20.