Sia 2013.

Study characteristics
Methods	Parallel randomised controlled trial
Participants	Setting: recruited from KK Women's and Children's Hospital, Singapore Sample size: N = 102 Participants: age not provided Inclusion criteria: healthy (ASA 1) nulliparous parturients at term (> 36 weeks gestation) with a singleton fetus, who were in early labour (cervical dilation < 5 cm) and who had requested labour epidural analgesia with VAS > 3 cm
Interventions	AMB (n = 51): 0.1% ropivacaine + fentanyl 2 µg/mL. Automated bolus group: a PCEA algorithm was used, initiated immediately after the completion of CSE. The pump was designed to administer automated boluses of 5 mL in addition to the patient‐controlled boluses. The frequency of such automated boluses was dependent on the history of the participant's analgesic requirement over the past hour. The first automated bolus was programmed to be delivered 60 min from time 0 and every hour thereafter if no PCEA patient‐bolus was made (1 automated bolus of 5 mL every hour). At the first activation of a PCEA patient‐bolus, the timer would be reset with the subsequent automated bolus delivered 30 min following the PCEA patient‐bolus, and every hour thereafter if no further PCEA patient bolus was made (1 automated bolus of 5 mL every hour). If there was a second PCEA patient bolus in that same hour after the initial bolus, the time interval between 2 automated boluses would be shortened to 30 min (2 automated boluses of 5 mL every hour). If there was a third PCEA patient‐bolus within that hour, the automated bolus would be delivered at 20‐min intervals (3 automated boluses of 5 mL every hour). A fourth PCEA patient‐bolus within the same hour would further shorten the time interval between 2 automated boluses to 15 min (4 automated boluses of 5 mL every hour). On the other hand, if there were no patient‐bolus for 60 min, the frequency of automated boluses would step down in the reverse fashion. The lockout period for both PCEA and automated boluses was 10 min. If a PCEA demand was made within 10 min of an automated bolus, no patient bolus would be given and this would be recorded as an unsuccessful PCEA attempt. The PCEA demand bolus was set at 5 mL with a maximum hourly limit of 20 mL/h (inclusive of automated boluses). BI (n = 51): 0.1% ropivacaine + fentanyl 2 µg/mL. Infusion group: PCEA with basal infusion 5 mL/h initiated immediately following intrathecal drug administration (noted as time 0). The PCEA demand bolus was set at 5 mL, lockout interval at 10 min and maximum dose at 20 mL/h (inclusive of background infusion)
Outcomes	Rate of breakthrough pain with need for anaesthetic intervention Rate of caesarean delivery Rate of instrumental delivery Duration of labour Total LA/hour (time‐weighted mean hourly consumption of ropivacaine) Maternal satisfaction Apgar scores
Notes	Study dates not stated Funding sources: no external funding No conflict of interests declared
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation by computer‐generated random number tables: Quote: "The parturients were randomly allocated into two groups using sealed opaque envelopes and computer generated random number tables"
Allocation concealment (selection bias)	Low risk	Allocation concealment by sealed opaque envelopes: Quote: "The parturients were randomly allocated into two groups using sealed opaque envelopes and computer generated random number tables"
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants and monitoring clinical team were blinded: Quote: "The parturients were subsequently monitored by a second anaesthetist who was not involved in performing the block. Neither the parturient nor the anaesthetist who recorded the post‐block data was aware of the group assignment."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome assessors were blinded: Quote: "Neither the parturient nor the anaesthetist who recorded the post‐block data was aware of the group assignment."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Low attrition: no dropouts
Selective reporting (reporting bias)	Low risk	All a priori outcomes reported based on published protocol
Other bias	Low risk	Appears to be free of other sources of bias. Sample size calculation: sample size of 49 participants in each group was required to detect an 80% reduction in the incidence of breakthrough pain requiring physician top‐up (α = 0.05, ß = 0.2)