Can knee position save blood following total knee replacement?
Introduction
Blood loss following total knee replacement (TKR) can be substantial. Allogenic blood transfusion has associated risks; these include infection, allergic reaction and immunosuppression [1], [2]. In order to minimise transfusion-related risks, post-operative blood loss should be minimised.
Previous research showed knee flexion at 70° for 6 h following TKR reduced wound drainage by 33% [3]. In the previous study, 48-h wound drainage was the only outcome measure and blood transfusion rate was not assessed. Popliteal vein compression when the knee was extended was proposed as an explanation for the decreased drainage with flexion. However, drain obstruction or relative elevation of the knee joint during knee flexion could also explain their findings. Sehat et al. demonstrated that the volume of blood in the suction drain 48 h following TKR was not an accurate measure of total blood loss, which was roughly double the drainage [4].
The purpose of this study was firstly to confirm that the simple, cheap method of flexing the knee not only reduced wound drainage but also total haemoglobin loss and secondly was to determine whether the reduction in wound drainage identified by Speck et al. [3] could be explained by elevation of the limb or obstruction of the drain.
Section snippets
Materials and methods
This study was approved by the local ethical committee and all patients in the trial were formally consented. Sixty consecutive patients undergoing primary unilateral total knee replacements for osteoarthritis between February and December 2000 were randomly allocated into three groups of 20 patients by sealed envelopes opened immediately after the operation. The number in each group was twice the number in each group reported by Speck et al. [3] to reduce the likelihood of a Type-II
Results
Patients’ age, sex and thromboprophylaxis were similar in all three groups (Table 1). The distribution of prosthesis type between the groups is summarised in Table 2. Groups 1 and 3 each had a single case of lateral release of the patella.
Discussion
The present study was unable to confirm the 33% reduction in wound drainage for the knee flexion group as reported by Speck et al. [3]. The knee flexion group showed only a 6% reduction in wound drainage, which was not statistically significant.
However, this study did show a reduction in total haemoglobin loss in the flexion and the elevation in extension groups compared with the extension only group. Both knee flexion and knee elevation in extension showed similar reduction in total
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