Venous thromboembolism: prophylaxis: LMWH was more effective than unfractionated heparin in general surgical patients

Clinical bottom line (level 1a)

  1. Patients undergoing general surgery who receive LMWH compared with placebo are less likely to have a DVT or PE, but more likely to have a major haemorrhage.
  2. There is no clear difference in mortality between the two groups.
  3. Patients who received LMWH compared with unfractionated heparin are less likely to have a clinical venous thromboembolism, but not clearly more likely to have a major haemorrhage.
Mismetti et al: Br J Surg 2001; 88 : 913-930
Expires May 2004

The study

Systematic review of all randomised controlled trials of
  • Patients: undergoing general surgery (abdominothoracic excluding vascular, urological, gynaecological and surgery for malignant disease)
  • Intervention: low molecular weight heparin compared with untreated or placebo; or unfractionated heparin
  • Outcome: deep vein thrombosis, pulmonary embolism, major haemorrhage, death

Articles found in all languages using Medline, Current Contents, to 2000 (search terms: detailed in text )

Selection criteria: by ?3 independent reviewers
Appraisal criteria: by 3 independent reviewers with disagreements resolved by consensus: based on randomisation; blinding; intention-to-treat
Articles excluded if:
  • patients undergoing orthopaedic surgery, non-cancer thoracic surgery, laporoscopic surgery
  • dose-ranging studies
  • heparinoids
59 RCTs found - 8 comparing LMWH with placebo involving 5520 patients; and 51 comparing LMWH with unfractionated heparin involving 48624 patients
Study outcomes reported below were not significantly heterogeneous.

The evidence

LMWH v. placebo
Outcome Time to outcome CER RR
(95% CI)		 NN?
(% CI)
DVT weeks /
(%)		 0.28
(0.14 to 0.54)
PE weeks /
(%)		 0.25
(0.08 to 0.79)
major haemorrhage weeks /
(%)		 2.03
(1.37 to 3.01)
death weeks /
(%)		 0.54
(0.21 to 1.10)

LMWH v. unfractionated heparin
Outcome Time to outcome CER RR
(95% CI)		 NN?
(% CI)
clinical venous thromboembolism weeks /
(%)		 0.71
(0.51 to 0.99)
major haemorrhage weeks /
(%)		 0.89
(0.75 to 1.05)

Comments

  1. Control rates were not reported, so NNTs could not be calculated.

Citation

  1. Mismetti P, Laporte S, Darmon J-Y, et al: meta-analysis of low molecular weight heparin in the prevention of venous thromboembolism in general surgery. Br J Surg 2001; 88 : 913-930
Search Terms: from ACP Journal Club other articles noted
Contributor: Chris Ball, May 2002
Reviewer:

Clinical Question.
Patient general surgery
Intervention or Exposure low molecular weight heparin (LMWH)
Comparison control, unfractionated heparin
Outcome DVT, PE, major haemorrrhage, death