Effect of medical thromboprophylaxis on mortality from pulmonary embolus and major bleedingy

BACKGROUND

Several studies have failed to discover a beneficial effect of medical thromboprophylaxis on mortality.

AIMS

To examine the relative influence of acute fatal pulmonary embolism (PE) and fatal major haemorrhage on overall mortality in medical patients treated with low molecular weight heparin (LMWP) for prophylaxis.

METHODS

The author compared deaths from the above factors using data from a recent Cochrane Collaboration meta-analysis. Data from trials satisfying the criteria of the Cochrane analysis plus additional exclusions to avoid bias were pooled to produce point estimates of mortality from PE and major bleeds to estimate net mortality benefit. Estimates were then subject to limited sensitivity analysis based on reported epidemiological data.

RESULTS

Reported PE and major bleeds were 0.44 per cent and 0.27 per cent, respectively. The corresponding case-specific mortality rates were 30.8 per cent and 12.8 per cent and the relative risk reduction (RRR) for PE was 23.2 per cent. Estimated deaths from major bleeds exceeded PE deaths avoided by a small margin (3/100,000 patients given prophylaxis). This excess increased to 30/100,000 when more plausible literature values for PE case fatality rates were applied.

CONCLUSION

Medical thromboprophylaxis has a finely balanced effect on mortality but may increase it. Such an effect would explain the failure to discover a mortality benefit from medical thromboprophylaxis. Further work, including a formal meta-analysis and additional clinical studies, is required to confirm this picture.

Current state of medical thromboprophylaxis in Australia

BACKGROUND

Australia has two published national guidelines for general medical thromboprophylaxis (MT), but the two differ in detail and the basis for patient selection remains uncertain. Several aspects of current guidelines are controversial, as is the proposed design of a dedicated prescribing box in the National Inpatient Medication Chart.

AIM

To discuss and comment on the current standing of medical thromboprophylaxis in Australia.

METHOD

We have marshalled literature known to us from our previous published research, and have applied this knowledge to discuss shortcomings, which, in our opinion, exist in current medical thromboprophylaxis practice, and to suggest solutions.

CONCLUSION

Australian guidelines are flawed because they are based on unsuitable evidence (incidence of subclinical thrombotic disease) and define eligibility broadly, such that about 80 per cent of patients are considered eligible. They urge that prescribers should "consider" prophylaxis without supplying an adequate basis for doing so. They do not provide grounds for assessing the balance between hazard (in the form of major bleeds) and benefit (thrombotic events avoided). Other clinical factors promoting unnecessary use of medical thromboprophylaxis include the use of age as a risk factor and proposed inclusion of a new DVT prophylaxis section in the National Inpatient Medication Chart (NIMC), which implicitly discourages non-prescription of prophylaxis.

The Australian arthroplasty thromboprophylaxis survey

Previous surveys of orthopedic surgeons have shown considerable variation in thromboprophylaxis for venous thromboembolism after joint arthroplasty. This survey aimed to determine the current practice among Australian orthopedic surgeons. A questionnaire regarding the duration, reasons, and methods of chemical and mechanical prophylaxis for hip and knee arthroplasty patients was sent to the 1082 surgeons identified; 593 (55%) members completed the questionnaire. The survey revealed that 98% of surgeons used chemical thromboprophylaxis, mainly low-molecular-weight heparin (84% hip and 79% knee). Those who use low-molecular-weight heparin were more likely to prescribe anticoagulants in fear of litigation (19.2% vs 10.1%, P = .04) and more likely to rely on protocols or guidelines (32.2% vs 17.2%, P = .004) instead of basing their decision on their own reading (52.4% vs 71.3%, P = .001). Most orthopedic surgeons in our survey have indicated that they would welcome guidelines from their association or college regarding thromboprophylaxis in arthroplasty.