Sir,
I read this paper with interest. This article declares that
guidelines should, in theory, benefit patient care by ensuring that every
patient routinely receives the best prophylaxis; lack of it may expose
patients to danger and yet the first line of the article states that thromboprophylaxis
remains a controversial subject. It gives reasons for the
surgeons' cynical response to guidelines but in the same breath raises doubt about
the clinical significance of randomised trials that recommend the use of
thromboprophylaxis. The already very low death rates following major joint
arthroplasty have not reduced any further with increasing use of
thromboprophylaxis.1-3 Warwick et al have previously stated that death
rates are now so low, even without prophylaxis, that a randomised study
would require about 90 000 patients in order to study death as an endpoint.4 The
absence of evidence for a reduction of mortality with increasing and
extended use of thromboprophylaxis would suggest a need to carry out such
a trial rather than supporting and advocating guidelines based on
surrogate endpoints. The authors also state that most patients die from
vascular events caused by thrombin-driven processes such as fat embolism,
myocardial infarction, stroke and venous thromboembolism, therefore
prophylaxis should ideally cover all thrombin-generated events but the
main effects of using low-molecular-weight-heparin (LMWH) and other heparin-type chemoprophylaxis have
been shown to reduce venous thromboembolism, not the other vascular
events.
The authors acknowledge that the data may be under-powered with
respect to surgical-site bleeding but then accuse the cynical surgeon of
relying on any study that showed potentially increased bleeding with
thromboprophylaxis. The surgeon is accused of having a tendency to place a
relatively low value on the prevention of venous thrombosis and a
relatively high value on minimising bleeding complications. The reasons
for this attitude need to be addressed perhaps but it does not contribute
to the debate by suggesting surgeons lack clinical balance or are cynical.
The reduction in mortality and venous thrombosis rates has been ascribed
to modern anaesthetic and surgical techniques, and in particular to earlier
post-operative mobilisation.5 While the effects of early mobilisation
have been recognised in the NICE guidelines, they are
undervalued because there is a lack of controlled randomised data on
this. We would need a very large trial involving thousands to prove the
benefits of very early mobilisation, which may have a very large effect on
reducing venous thromboembolism.5
K.C. Kong,
Consultant Orthopaedic Surgeon,
King George Hospital,
Ilford, Essex, UK.
1. Howie C, Hughes H, Watts AC. Venous thromboembolism associated
with hip and knee replacement over a ten-year period. J Bone Joint Surg
[Br] 2005;87-B:1675–80.
2. Freedman KB, Brookenthal KR, Fitzgerald RH,
Williams S, Lonner JH. A meta-analysis of thromboembolic
prophylaxis following elective total hip arthroplasty. J Bone Joint Surg
[Am] 2000;82-A:929-38.
3. Lie SA, Engesaeter LB, Havelin LI, Furnes O, Vollset SE. Early postoperative mortality after 67,548
total hip replacements: causes of death and thromboprophylaxis in 68
hospitals in Norway from 1987 to 1999. Acta Orthop Scand 2002;73:392–9.
4. Warwick D. New concepts in orthopaedic thromboprophylaxis. J Bone
Joint Surg [Br] 2004;86-B:788–92.
5. Pearse EO, Caldwell BF, Lockwood RJ, Hollard J.
Early mobilisation after conventional knee replacement may reduce the risk
of post-operative venous thromboembolism. J Bone Joint Surg [Br] 2007;89-B:316-22.
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