Design: randomised, double-blind, non-inferiority trial with a margin of two interventions
Population: 80 healthy women with term uncomplicated singleton pregnancies for elective caesarean under spinal anaesthesia
Primary outcome: number of physician interventions needed to hold systolic blood pressure in the target range
Effect: median 3 (IQR 2–4) with boluses vs 6 (5–8) with infusion; difference of medians −3 (95% CI −4 to −2); total phenylephrine 300 µg vs 630 µg

The standard argument for a variable-rate phenylephrine infusion at elective caesarean under spinal anaesthesia is not that it controls blood pressure better — boluses do that too — but that it leaves the anaesthetist free. A randomised, double-blind non-inferiority trial in 80 healthy women tested whether a modified bolus regimen could match the infusion on that count.

It did more than match it. Women in the bolus group had a 100 µg dose immediately after the spinal and a further dose whenever systolic pressure fell below 90% of baseline. The median number of physician interventions needed was 3 (interquartile range 2–4) against 6 (5–8) with the infusion, a difference of medians of −3 (95% confidence interval −4 to −2). Total phenylephrine use was less than half: 300 µg against 630 µg. Rates of hypotension, hypertension and bradycardia, umbilical cord gases, Apgar scores and maternal complications did not differ.

That matters most where the syringe pump is the constraint rather than the drug. In a district-level theatre running several elective sections on a list, a regimen that needs fewer interventions and no pump is the more deliverable one, and this trial removes the usual reason for thinking otherwise.

Record baseline systolic pressure before the spinal — the whole regimen is defined against it.
Give the first 100 µg bolus immediately after the block rather than waiting for a fall.
Repeat whenever systolic pressure drops below 90% of baseline, not below an absolute threshold.
Keep the same monitoring interval you would use with an infusion; fewer interventions is not less observation.
This regimen was tested in healthy term singleton pregnancies only — do not carry it across to pre-eclampsia or emergency caesarean without thought.

Why it matters

The practical objection to bolus phenylephrine — that it ties you to the blood pressure cuff — did not survive testing.

The statistics, in plain English

Non-inferiority was declared against a margin of two interventions, and the bolus group was not merely non-inferior but better on the primary outcome — the confidence interval for the difference (−4 to −2) sits entirely on the bolus side. The neonatal and complication outcomes are a different matter: with 80 women in total the trial had no power to detect anything but a large difference, so 'no difference' on cord gases and maternal complications is an absence of evidence rather than evidence of safety equivalence.