Aouad 2001.

Methods	Randomization: yes Participant blinding: yes Provider blinding: no Assessor blinding: yes Dropouts: 0
Participants	Country: Lebanon ASA: I and II Gender: women Mean age: 31 (SD 5) years Caesarean section Surgical positioning: supine Number of participants: 200
Interventions	Drug 1: 5% lido, hyperbaric, fixed dose (1.5 mL) Drug 2: 0.75% bupi, hyperbaric, fixed dose (1.6 mL) Needle: 25 G, pencil‐point
Outcomes	TNS at 1 day Back pain
Notes	Follow‐up duration: 1.3 days Follow‐up method: telephone contact
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "patients were allocated randomly by sealed envelope…" Comment: did not specify the method of randomization (referring to a random number table, computer‐generated random number sequence, tossing coin, etc.).
Allocation concealment (selection bias)	Unclear risk	Quote: "patients were allocated randomly by sealed envelope…" Comment: did not specify allocation by sequentially numbered, sealed, opaque envelopes.
Participant blinding (performance bias and detection bias)	Low risk	Quote: "patients were blinded as to the spinal anesthetic used."
Provider blinding (performance bias)	High risk	Quote: "the anesthesiologist who administered the spinal anesthetic and collected the data on sensory and motor blockade was not blinded as to the study groups."
Assessor blinding (detection bias)	Low risk	Quote: "all patients were interviewed… by an anesthesiologist who was unaware of the local anesthetic given."
Incomplete outcome data (attrition bias) All outcomes	Low risk	200 participants enrolled. Results reported for 200 participants.
Selective reporting (reporting bias)	Unclear risk	Study protocol not available.