What do systematic reviews say?

Heparin vs placebo

Heparin showed no clear difference in major bleeding events: all heparin compared with placebo (low certainty).

• Interventions for preventing thrombosis in solid organ transplant recipients 2021 · Cochrane Headline outcomes only
  RR 2.7 [0.89, 8.19]
  3 studies · 180 participants
  Low

Heparin vs placebo

Heparin showed no clear difference in major bleeding events: unfractionated heparin compared with placebo (low certainty).

• Interventions for preventing thrombosis in solid organ transplant recipients 2021 · Cochrane Headline outcomes only
  RR 2.92 [0.89, 9.56]
  3 studies · 155 participants
  Low

Heparin vs pentasaccharide

It is very uncertain whether heparin changes major bleeding compared with pentasaccharide (very low certainty).

• Pharmacological interventions for preventing venous thromboembolism in people undergoing bariatric surgery 2022 · Cochrane Headline outcomes only
  RR 1.7 [0.42, 6.92]
  1 study · 198 participants
  Very low

Higher‐dose heparin vs standard‐dose heparin

Higher‐dose heparin showed no clear difference in major bleeding compared with standard‐dose heparin (low certainty).

• Pharmacological interventions for preventing venous thromboembolism in people undergoing bariatric surgery 2022 · Cochrane Headline outcomes only
  RR 1.19 [0.48, 2.96]
  4 studies · 597 participants
  Low

Unfractionated heparin vs low molecular weight heparin

Unfractionated heparin showed no clear difference in major bleeding compared with low molecular weight heparin (low certainty).

• Pharmacological interventions for preventing clotting of extracorporeal circuits during continuous renal replacement… 2020 · Cochrane Headline outcomes only
  RR 0.58 [0.13, 2.58]
  5 studies · 153 participants
  Low

Heparin vs placebo

Heparin showed no clear difference in bleeding ‐ major Treatment duration 28 ‐ 42 days compared with placebo (moderate certainty).

• Anticoagulants (extended duration) for prevention of venous thromboembolism following total hip or knee replacement or… 2016 · Cochrane Headline outcomes only
  OR 0.59 [0.14, 2.46]
  5 studies · 2500 participants
  Moderate

Heparin vs placebo

The review found no eligible studies for this question.

• Anticoagulants (extended duration) for prevention of venous thromboembolism following total hip or knee replacement or… 2016 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Subcutaneous unfractionated heparin vs low molecular weight heparin

Subcutaneous unfractionated heparin showed no clear difference in major bleedingd (3 months) compared with low molecular weight heparin (low certainty).

• Subcutaneous unfractionated heparin for the initial treatment of venous thromboembolism 2017 · Cochrane Headline outcomes only
  OR 0.72 [0.43, 1.2]
  5 studies · 2300 participants
  Low

Subcutaneous unfractionated heparin vs unfractionated heparin

Subcutaneous unfractionated heparin showed no clear difference in major bleedingd (7 days ‐ 12 months) compared with intravenous unfractionated heparin (low certainty).

• Subcutaneous unfractionated heparin for the initial treatment of venous thromboembolism 2017 · Cochrane Headline outcomes only
  OR 0.91 [0.42, 1.97]
  4 studies · 583 participants
  Low

Low molecular weight heparin vs unfractionated heparin

The review found no eligible studies for this question.

• Anticoagulation for people receiving long‐term haemodialysis 2024 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Heparin prophylaxis vs no prophylaxis

Heparin prophylaxis showed no clear difference in major bleeding compared with no prophylaxis (moderate certainty).

• Parenteral anticoagulation in ambulatory patients with cancer 2017 · Cochrane Headline outcomes only
  RR 1.3 [0.94, 1.79]
  18 studies · 9592 participants
  Moderate

Low molecular weight heparin vs unfractionated heparin

The review found no eligible studies for this question.

• Anticoagulation for the initial treatment of venous thromboembolism in people with cancer 2021 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Combined NMES and low‐dose heparin vs low‐dose heparin

• Neuromuscular electrical stimulation for the prevention of venous thromboembolism 2017 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 31 participants
  GRADE not reported

Heparin started before vs after the surgical procedure

It is very uncertain whether heparin started before changes major bleeding compared with after the surgical procedure (very low certainty).

• Pharmacological interventions for preventing venous thromboembolism in people undergoing bariatric surgery 2022 · Cochrane Headline outcomes only
  RR 3 [0.13, 71.92]
  1 study · 100 participants
  Very low

Unfractionated heparin vs no thromboprophylaxis

The review found no eligible studies for this question.

• Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy 2020 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Unfractionated heparin vs no pharmacological anticoagulation

It is very uncertain whether unfractionated heparin changes major bleeding compared with no pharmacological anticoagulation (very low certainty).

• Pharmacological interventions for preventing clotting of extracorporeal circuits during continuous renal replacement… 2020 · Cochrane Headline outcomes only
  RR 0.5 [0.05, 4.67]
  1 study · 10 participants
  Very low

Low molecular weight heparin vs control

Does low molecular weight heparin prevent central venous… showed no clear difference in major bleeding ( compared with control (low certainty).

• Low molecular weight heparin for prevention of central venous catheter‐related thrombosis in children 2020 · Cochrane Headline outcomes only
  RR 0.27 [0.05, 1.67]
  2 studies · 813 participants
  Low

Low molecular weight heparin vs active control

The review found no eligible studies for this question.

• Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy 2020 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found
• Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy 2020 · Cochrane Headline outcomes only
  RR 0.14 [0.01, 2.76]
  2 studies · 781 participants
  Low
• Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy 2020 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Low molecular weight heparin vs no thromboprophylaxis

Low‐molecular‐weight heparin probably leads to higher major bleeding compared with no thromboprophylaxis (moderate certainty).

• Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy 2020 · Cochrane Headline outcomes only
  RR 1.63 [1.12, 2.35]
  15 studies · 7282 participants
  Moderate

Ultra‐low‐molecular‐weight heparin vs placebo

Ultra‐low‐molecular‐weight heparin showed no clear difference in major bleeding compared with placebo (moderate certainty).

• Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy 2020 · Cochrane Headline outcomes only
  RR 1.05 [0.55, 2]
  1 study · 3172 participants
  Moderate