Singh 2013

Methods	Double‐blinded (participant/outcome assessor), randomized clinical trial Sequence generation by a computer‐based, random numbers generator Follow‐up: 3 months
Participants	Participants: 60 women at a university hospital in Ontario, Canada Operation: caesarean section Groups, size: 20/20/20 Age (± SD), group 1, 2, 3: 33 (± 3), 32 (± 7), 33 (± 4) All female participants Comorbidities: previous caesarean delivery, groups 1, 2, 3 (16, 14, 15) Remarks: ASA I, II, and III
Interventions	All participants received SA with 0.75% bupivacaine 10 mg‐12 mg, fentanyl 10 µg and morphine 150 µg Group 1 (high‐ropivacaine): post‐op: a 22‐G, 50 mm or 80mm Pajunk Uniplex nanoline needle was introduced into the fascia between the internal oblique and transversus abdominis muscles. After confirmation of needle placement, the study solution was injected in 5 mL increments after negative aspiration. Study solution for high‐ropivacaine group consisted of 0.5% ropivacaine 3 mg/kg (up to a maximum of 300 mg) plus saline to total 60 mL of fluid. TAP blocks were performed bilaterally. Group 2 (low‐ropivacaine): post‐op: same method as group 1, but study solution consisted of 0.25% ropivacaine 1.5 mg/kg (up to a maximum of 150 mg) plus saline to total 60 mL.TAP blocks were performed bilaterally. Group 3 (placebo): post‐op: TAP blocks consisting of 60 mL of saline were administered bilaterally using same method as groups 1 and 2. Adjuvants: none Immediate post‐op pain control: no difference
Outcomes	Dichotomus: none Continuous: NRS at 3 months Other reported: the time to first request for additional analgesia, the total consumption of opioids, antiemetics and anti‐pruritics 72 h postoperatively Adverse events: none reported
Notes	Funding sources: "this study was supported in part by a grant from the Lawson Health Research Institute." Conflicts of interest: "the authors have no conflicts of interest to declare."
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "patients were randomly assigned using a computer generated table of random numbers to one of three groups."
Allocation concealment (selection bias)	Low risk	Quote: "group allocations were concealed in sealed opaque envelopes that were opened only after patient consent was obtained.."
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "the patients, anesthesiologists, and nursing staff involved in direct patient care were unaware of the study group allocations."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "patients were interviewed at regular intervals by an investigator unaware of group allocation..."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Of the 60 participants enrolled, 59 completed the study.
Selective reporting (reporting bias)	Low risk	No subgroup analysis or selective reporting was noted.
Null bias	High risk	Quote: "neither high‐ or low‐dose TAP blocks as part of a multimodal analgesia regimen including intrathecal morphine improved pain scores."