Butwick 2010

Methods	5‐arm placebo‐controlled randomised trial.
Participants	Between July 2008 and April 2009, 75 parturients were randomised in a hospital setting in the USA. The population comprised women of unspecified parity, a singleton pregnancy, at high risk for PPH, who delivered by elective caesarean section. Exclusion criteria comprised parturients with active labour, ruptured membranes, drug allergy, multiple pregnancy, significant obstetric disease, risk factors for PPH (abnormal placentation, fibroids, previous PPH, previous classical uterine incision), coagulopathy or thrombocytopenia.
Interventions	Placebo or control (n = 15) versus 5, 3, 1, or 0.5 IU of oxytocin administered by an intravenous bolus (n = 60).
Outcomes	The study recorded the following outcomes: additional uterotonics, transfusion, blood loss (mL), nausea, vomiting, tachycardia, hypotension.
Notes	Contact with study authors for additional information: yes. Additional data from authors: no.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants were randomised using Microsoft Excel‐generated random number allocations.
Allocation concealment (selection bias)	Unclear risk	Investigators used opaque envelopes containing group assignments.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"The obstetrician and anaesthetist involved in each case were blinded to the oxytocin dose assignments."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Assessor blinding was not reported.
Objective assessment of blood loss	High risk	Investigators evaluated blood loss "by estimating blood collected by suction and by calculating the weight of blood on surgical swabs."
Incomplete outcome data (attrition bias) All outcomes	Low risk	"75 patients were enrolled, and 74 patients completed the study; 1 patient was excluded due to protocol violation (obstetrician request for supplemental oxytocin despite adequate uterine tone)."
Selective reporting (reporting bias)	Unclear risk	The protocol of the study was unavailable for verification.
Intention to treat analysis	High risk	Those who withdrew from the study after randomisation were not included in the analysis.
Funding source	Low risk	The study was supported by funding from the Department of Anaesthesia of the Stanford University School of Medicine (the institution of the authors).