Gallus 1973.

Methods	RCT
Participants	Patients (n = 350) over 40 years old admitted for elective surgery, or for emergency surgery after fracture of the femoral neck and medical patients suspected of having myocardial infarction. Mean age and gender were not reported separately for thoracic surgery patients, which represented less than 3% of the study population
Interventions	‐ UFH 5000 IU sc 2 hours before surgery and then tid starting 8 to 10 hours after the preoperative dose. Treatment was continued until the participant was fully mobile ‐ Control: no UFH
Outcomes	DVT and bleeding. DVT was objectively verified by 125I‐fibrinogen scanning performed before surgery, within 4 hours of the end of surgery, and then daily until fully mobile or discharge. Venography was performed if the 125I‐fibrinogen scanning suggested the presence of thrombosis of the popliteal or femoral veins
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of random sequence generation not reported: "...were randomized separately"
Allocation concealment (selection bias)	Unclear risk	Numbered, sealed envelopes. It remained unclear whether envelopes were opaque
Blinding of participants and personnel (performance bias) All outcomes	High risk	Surgeons were unaware of study treatment. Participants were not blinded and it is not reported if the other study personnel were blinded
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported if outcome assessment was blinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants included were considered in the analysis
Selective reporting (reporting bias)	Low risk	Study not registered. No published protocol. All outcomes mentioned in the methods section were addressed in the results section
Other bias	Unclear risk	Participant characteristics are not reported. Unclear if participants were consecutively included