Design: randomised, double-blind, non-inferiority trial; 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 to hold systolic pressure in the target range
Effect: median 3 (IQR 2–4) boluses vs 6 (5–8) infusion; difference of medians −3 (95% CI −4 to −2); phenylephrine 300 μg vs 630 μg

Spinal hypotension at caesarean is managed either by a variable-rate phenylephrine infusion, which needs a pump and constant titration, or by boluses, which have historically meant more work at the head end. A double-blind randomised non-inferiority trial in 80 healthy women having elective caesarean under spinal anaesthesia tested a modified bolus regimen against a variable-rate infusion, with the number of physician interventions as the primary outcome and a non-inferiority margin of two interventions.

The bolus arm received 100 μg immediately after the spinal and a further bolus whenever systolic pressure fell below 90% of baseline. The infusion started at 50 μg/min, titrated to hold systolic pressure at 90–99% of baseline. The bolus regimen needed a median of 3 interventions (IQR 2–4) against 6 (5–8) for the infusion, a difference of medians of −3 (95% CI −4 to −2), and used less drug overall — 300 μg (200–400) against 630 μg (426–765). Rates of hypotension, hypertension and bradycardia, umbilical cord gases, Apgar scores and maternal complications did not differ.

This matters most where an infusion pump is not a given for every elective list. The regimen is simple enough to write on a board, and the trial found no cost in blood pressure control for the reduced workload.

The regimen is specific: 100 μg at spinal, repeat at every systolic reading below 90% of baseline.
Baseline must be a real baseline — take it before the spinal, not after the woman is on the table and anxious.
Keep non-invasive blood pressure cycling at short intervals; the regimen depends on frequent readings.
Watch for bradycardia with repeated boluses even though rates did not differ here.
An infusion remains preferable where a pump is available and the case is not straightforward.

Why it matters

It removes the argument that bolus dosing costs you attention at the head end, in theatres where the pump is not always available.

The statistics, in plain English

Non-inferiority was tested against a margin of two interventions, meaning the bolus arm only had to avoid being worse by more than two. It was in fact better, with a confidence interval for the difference of −4 to −2 that never reaches zero. Eighty patients is enough to compare a frequent outcome like the number of interventions, but nowhere near enough to exclude differences in uncommon neonatal events — so "no difference in Apgar scores" here means "not detected", not "not present".