Evaluating optimal superficial limb perfusion at different angles using non-invasive micro-lightguide spectrophotometry.

Background: It is common practice to elevate the limbs postoperatively to reduce oedema and hence optimise perfusion and facilitate rehabilitation. However, elevation may be counterproductive as it reduces the mean perfusion pressure. There are no clear data on the optimal position of the limbs even in normal subjects.

Methods: The optimal position of limbs was investigated in 25 healthy subjects using a non-invasive micro-lightguide spectrophotometry system "O2C", which indirectly measures skin and superficial tissue perfusion through blood flow, oxygen saturation and relative haemoglobin concentration.

Results: We found a reduction in skin and superficial tissue blood flow of 17% (p=0.0001) on arm elevation (180° shoulder flexion) as compared to heart level and an increase in skin and superficial tissue blood flow of 25% (p=0.02) on forearm elevation of 45°. Lower limb skin and superficial tissue blood flow decreased by 15% (p=0.004) on elevation to 47 cm and by 70% on dependency (p=0.0001) compared to heart level. However, on elevation of the lower limb there was also a 28% reduction in superficial venous pooling (p=0.0001) compared to heart level.

Conclusions: In the normal limb, the position for optimal superficial perfusion of the upper limb is with the arm placed at heart level and forearm at 45°. In the lower limb the optimal position for superficial perfusion would be at heart level. However, some degree of elevation may be useful if there is an element of venous congestion.