Comparing the effectiveness of phenylephrine infusion versus bolus regimen intreating hypotension during caesarean delivery under spinal anaesthesia

Abstract

Background: Phenylephrine is a preferred drug in preventing and treating hypotension during spinal anaesthesia for Caesarean section. Different techniques may be used to administer to get optimal blood pressure control.

Objective: To compare an infusion technique (group A) against a bolus regimen (group B) in maintaining blood pressure closer to baseline values in patients undergoing Caesarean section under spinal anaesthesia.

Patients and Methods: 96 patients were randomised to group Aand Bin a case-control study. The infusion was started at 100μg/minute immediately after administering spinal anaesthetic in Group A, and was maintained unless the patient developed hypertension (20% above baseline). In Group B, a 100μg bolus was given immediately after administration of spinal anaesthesia and additional 100μg boluses if hypotension occurred (20% below baseline). The primary outcome measure was degree of change in blood pressure from baseline level measured in mmHg.

Results: The infusion group had mean change in BPof +1.65mmHg (SD = ±6.88) and the bolus group had mean change in BP of -10.77mmHg (SD = ±9.16). There was a significant difference in mean blood pressure changes (p<0.01) between the groups. The infusion group had less incidences of hypotension (p< 0.05). Reactive hypertension and bradycardia were noted in Group Abut not in group B. The blood pressure was maintained within 20% of baseline using either technique of phenylephrine administration.

Conclusion: Phenylephrine infusion maintains BP closer to baseline with less hypotension, nausea and vomiting compared to bolus technique. However infusions at 100μg/minute may cause reactive hypertension and bradycardia.

Keywords: hypotension, caesarean section, spinal anaesthesia, phenylephrene