Heparin, low molecular weight heparin and physical methods for preventing deep vein thrombosis and pulmonary embolism following surgery for hip fractures.

BACKGROUND: Hip fracture patients have a high risk of thrombo-embolic complications following surgical management.
OBJECTIVES: To examine the effects of heparin (unfractionated (U), and low molecular weight (LMW) heparins), and physical methods (compression stockings, calf or foot pumps) for prevention of deep venous thrombosis (DVT) and pulmonary embolism after surgery for hip fracture in the elderly. SEARCH STRATEGY: We searched the Cochrane Musculoskeletal Injuries Group specialised register (up to March 2002), MEDLINE (1966 to March 2002), EMBASE (1980 to March 2002), CINAHL (1982 to February week 4 2002), Current Contents (1993 week 26 to 2002 week 12), reference lists of published articles and contacted trialists and other workers in the field. Date of most recent search: March 2002. SELECTION CRITERIA: Randomised and quasi-randomised trials evaluating the use of heparins and physical agents for prevention of DVT and pulmonary embolism in patients undergoing surgery for hip fracture. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed methodological quality and extracted data. Trials were grouped into five categories (heparin versus control, mechanical versus control, LMW heparin versus U heparin, heparin versus mechanical, and miscellaneous) and results pooled where possible. MAIN
RESULTS: The 31 included trials involved at least 2958 predominantly female and elderly patients. Overall, trial quality was disappointing. Ten trials involving 826 patients which compared U heparin with control, and five trials of 373 patients which compared LMW heparin with control, showed a reduction in the incidence of lower limb DVT (124/474 (26%) versus 219/519 (42%); relative risk (RR) 0.60; 95% confidence interval (CI) 0.50 to 0.71). There were insufficient data to confirm the efficacy of either agent in the prevention of pulmonary embolism. There was no statistically significant difference in overall mortality (42/356 (12%) versus 38/374 (10%); RR 1.16; 95%CI 0.77 to 1.74). Data were inadequate for all other outcomes including wound complications. There is insufficient evidence from five trials, involving 644 patients, to establish if LMW heparin was superior to U heparin. Most trials evaluating heparins had methodological defects. Five trials, involving 487 patients, testing mechanical pumping devices were also methodologically flawed, and so pooled results need to be viewed cautiously. Mechanical pumping devices may protect against DVT (16/221 (7%) versus 52/229 (22%); RR 0.31; 95%CI 0.19 to 0.51) and pulmonary embolism. Data were insufficient to establish any effect on the incidence of fatal pulmonary embolism and overall mortality. Problems with skin abrasion and compliance were reported. REVIEWER'S
CONCLUSIONS: U and LMW heparins protect against lower limb DVT. There is insufficient evidence to confirm either protection against pulmonary embolism or an overall benefit, or to distinguish between various applications of heparin. Foot and calf pumping devices appear to prevent DVT, may protect against pulmonary embolism, and reduce mortality, but compliance remains a problem. Good quality trials of mechanical methods as well as direct comparisons with heparin and low dose aspirin should be considered.