Scheingraber 1999.

Methods	Design: prospective randomized double‐blind controlled study Withdrawals: none Setting: single centre, USA Sample size: 24
Participants	Age (mean): 53/46 years Gender (M/F): all female ASA grade: I to II Surgery type: elective gynaecological surgery Surgery duration (mean): 2.3/2.3 hours Anaesthesia type: general
Interventions	Intervention n = 12 Buffered arm ‐ Ringer's lactate Control n = 12 Non‐buffered arm ‐ normal saline 30 mL/kg/h Co‐interventions: supplemental intravenous potassium administered according to intraoperative serum potassium levels During the study, no participants received colloids, plasma products, or blood transfusions.
Outcomes	Estimated intraoperative blood loss, urine output, pH, carbon dioxide, base excess, lactate, chloride, sodium
Notes	Funding source: not disclosed Declarations of interest: none disclosed
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomization details not available
Allocation concealment (selection bias)	Unclear risk	No details available
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Published data state that double‐blinding took place. No other details are available.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not disclosed
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No participants lost to follow‐up
Selective reporting (reporting bias)	Low risk	No evidence of selection bias. All proposed outcome measures adequately reported
Other bias	Low risk	No other information forthcoming