Sears 1994.

Methods	Design: parallel‐group (2 arms) Country: USA Multisite: no Needle tip used: 24 G Sprotte vs 22 G Sprotte Needle diameter used: 24 vs 22 25 vs 27 Number of attempts (first attempt): unknown Procedure: spinal anaesthesia Site of the puncture: L2‐3 or L3‐4 Training level of those who administered the puncture: experienced anaesthesiologists Median or paramedian technique: midline Type of anaesthesia: hyperbaric bupivacaine 0.75% or hyperbaric 5% lidocaine, with or without fentanyl and/or morphine 12.5 mg to 17.5 mg Patient position: lateral position
Participants	1. 375 ASA physical status I and II caesarean section and postpartum tubal ligation patients at 4 hospitals participated in the study Exclusion criteria: unclear Patients randomized to: 24 G Sprotte group: 186 patients (49.6%. 22 G Sprotte group: 189 patients (50.4%) 2. No patients were excluded from further analysis 3. Main characteristics of patients: Age (mean, SD): 24 G Sprotte group: 29.5, 5; 22 G Sprotte group: 27.5, 4.8 Height (mean, SD): 24 G Sprotte group: 163.1, 6.5; 22 G Sprotte group: 160.8, 6.3 Weight (mean, SD): 24 G Sprotte group: 79.3, 11.9; 22 G Sprotte group: 79.7, 10.9
Interventions	1. 22 G Sprotte needle 2. 24 G Sprotte needle All patients received an infusion of at least 1000 mL of lactated Ringer's solution over 30 minutes prior to the block
Outcomes	Outcomes were not classified as primary or secondary 1. Complication: headache 2. PDPH 3. Severity of PDPH
Notes	Trial registration: not stated Funder: not stated Role of funder: not stated A priori sample size estimation: no Conducted: January 2008 and December 2009 Declared conflicts of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information to score this item as low or high risk of bias. Quote: "Patients were randomly assigned to receive" (page 43)
Allocation concealment (selection bias)	Unclear risk	Insufficient information to score this item as low or high risk of bias
Blinding of participants (performance bias)	Unclear risk	Insufficient information to score this item as low or high risk of bias
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "Patients were visited at least once by the anesthesiologist during the postoperative period, and nurses on the obstetrics floor were instructed to notify the anesthesiologist of any complication, including headache. In addition, patients were contacted by telephone 1 week or more after discharge by an investigator who was blinded to the type of needle used." (page 43)
Incomplete outcome data (attrition bias) All outcomes	Low risk	No patients were lost to follow‐up
Selective reporting (reporting bias)	High risk	Adverse events, additional to PDPH, were not reported
Other bias	Low risk	No other biases were identified