Kairaluoma 2006.

Methods	Triple‐blinded (participant, providers, outcome assessor), sham‐ and placebo‐controlled, randomized clinical trial Sequence generation was not described Follow‐up: 12 months
Participants	Participants: 60 adults in a university setting in Helsinki, Finland Operation: conservative breast surgery with sentinel lymph node biopsy for cancer 2 groups, size: 30/30 Age: not reported Men/women: 0/60
Interventions	Group 1 (preincision PVB): single shot PVB at T3 with bupivacaine (0.5%, 1.5 mL/kg), GA, post‐op: oral ibuprofen (10 mg/kg) and paracetamol (1 g, 3 x daily ) rescue analgesia: paracetamol (500 mg with codeine 30 mg) or tramadol (50‐100 mg) Group 2 (sham PVB): sham PVB at T3 with normal saline, GA, post‐op: oral ibuprofen (10 mg/kg) and paracetamol (1 g, 3 x daily) rescue analgesia: paracetamol (500 mg with codeine 30 mg) or tramadol (50‐100 mg) Adjuvants: none Immediate post‐op pain control: significantly improved
Outcomes	Dichotomous: NRS larger 3 at 6 and at 12 months, use of pain medication at 6 and 12 months Continuous: pain at rest and in motion reported as NRS, number of pain descriptors, all at 6 and 12 months Effective regional anaesthesia not reported, but treatment reduced the severity of postoperative pain and oxycodone consumption, postoperatively
Notes	We acknowledge the study author's response regarding randomization and allocation concealment Funding sources: source of funding not reported Conflicts of interest: conflict of interest statement not provided
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants "were randomly assigned." Sequence generation was "randomized", "performed in a randomized fashion", but the exact method of randomization was not explained. The study author responded "The randomization was done using the opaque sealed envelope method."
Allocation concealment (selection bias)	Unclear risk	Allocation concealment not described in the original report
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "the patients and the study anaesthesiologists who performed the analysis remained blinded to the use of PVB with bupivacaine or a sham block throughout the entire study period." "Procedure behind a drape curtain" The study author responded, also that "the patient, the anaesthesiologist providing anaesthesia and the staff taking care of the patient were blinded to the study group. The curtains and drapes were hung so that the block was performed behind the curtains on the back side of the patient while the patient's head and front side and her nurse were on the other side of the curtains. The anaesthesiologist and nursing staff giving general anaesthesia were blinded to the study group..."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "the patients and the study anaesthesiologists who performed the analysis remained blinded to the use of PVB with bupivacaine or a sham block throughout the entire study period.", "telephone interviews by a blinded interviewer." "A group‐blinded study assistant conducted all telephone interviews." The study author responded also that "A non‐medical study assistant blinded to the study group performed the follow‐up telephone interviews at predestined time points up to 12 months postoperatively".
Incomplete outcome data (attrition bias) All outcomes	Low risk	Attrition explained in detail, ITT analysis performed
Selective reporting (reporting bias)	Unclear risk	Primary outcomes fully reported
Null bias	Low risk	Quote: "the patients given PVB with bupivacaine had less postoperative pain, as indicated by longer times to first analgesic dose, lower VAS scores, and 40% smaller oxycodone consumption in the PACU... On the first postoperative day, the number of patients who experienced continuous aching pain and pain at rest was significantly smaller in the PVB group"