Doherty 2012.

Study characteristics
Methods	RCT
Participants	69 women Inclusion criteria: ASA physical status I/II; aged 18 years and older; weight 50‐100 kg; height between 150 and 180 cm Exclusion criteria: allergy or hypersensitivity to phenylephrine; hypertension; cardiovascular or cerebrovascular disease; fetal abnormalities; diabetes (excluding gestational diabetes); or contraindications to spinal anaesthesia Setting: Canada
Interventions	Phenylephrine infusion versus phenylephrine bolus Group 1: infusion: fixed rate phenylephrine infusion 120 μg/min; infusion was started immediately on completion of intrathecal injection, at a rate of 1 mL/min and continued for a minimum of 2 min, and continued if maternal SBP was equal to or lower than baseline. If maternal BP was higher than baseline, the infusion was discontinued and the BP reassessed after 2 min Group 2: bolus: intermittent phenylephrine bolus of 120 μg; women received 1 mL of bolus solution every time SBP was equal to or lower than baseline. A bolus was not administered when SBP was above baseline All women received an IV infusion of Ringer's lactate started at a minimal rate in the holding area, with subsequent standardised crystalloid coload on administration of spinal anaesthetic. No antiemetic premedication was given. All women received a standardised spinal anaesthetic technique, dose and positioning. Hypotension requiring intervention received rescue dose of 5 mg ephedrine. Bradycardia requiring intervention received 0.6 mg atropine if heart rate < 60 bpm for 2 consecutive readings and SBP equal to or lower than baseline (infusion was discontinued if bradycardia with SBP higher than baseline).
Outcomes	Maternal: BP; cardiac output; heart rate, hypotension; hypertension; nausea/vomiting; bradycardia; total dose of phenylephrine Neonatal: umbilical blood gases; neonatal weight; Apgar score at 1 min and 5 min
Notes	Hypotension was defined as SBP < 80% baseline. Hypertension was defined as SBP > 120% baseline. Bradycardia was defined as heart rate < 60 bpm.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random number table
Allocation concealment (selection bias)	Unclear risk	Sealed, opaque envelopes
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"Double blind": women and attending anaesthetists were blinded to the group allocation. 2 syringes, 1 20 mL bolus and 60 mL infusion were prepared for each woman. 1 syringe contained 120 μ/mL phenylephrine and the second syringe contained saline. Both syringes were labelled 'phenylephrine/placebo' and 'bolus syringe' and 'infusion syringe' respectively. The anaesthetist then received 1 syringe of infusion solution and 1 syringe of bolus solution (but did not know which syringe contained the phenylephrine). Each was administered according to the protocol for bolus and infusion as described above.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Not specifically stated, but probably done
Incomplete outcome data (attrition bias) All outcomes	Low risk	9/69 were lost to follow‐up: 4/35 from the intervention group (3 pump errors; 1 unable to calibrate properly) and 5/35 from the bolus group (2 required additional anaesthesia (ketamine), 2 pump errors and 1 unable to calibrate properly)
Selective reporting (reporting bias)	Unclear risk	Most expected outcomes were reported, although blood gases reported only as mean and SD, and not specified if maternal hypertension required intervention
Other bias	Low risk	Baseline characteristics were similar