The effects of limb elevation and increased intramuscular pressure on nerve and muscle function in the human leg.

In this study we investigated the effects of increased intramuscular pressure (IMP) on nerve and muscle function in the leg and foot. In study A, muscle pressure was increased by inducing venous stasis in both legs, placed in plaster casts, of eight healthy subjects having a mean age of 29 years. The results from elevated and non-elevated limbs were compared. In study B, two different models for increasing IMP were studied in nine healthy subjects having a mean age of 32 years. The results of increased IMP and decreased blood perfusion pressure on local (= leg) and distal (= foot) function of muscle and nerve induced by venous stasis of a leg in a plaster cast and by external compression of the contralateral leg were compared. Contraction pressure of the tibialis anterior muscle in the leg was recorded. A biphasic compound muscle action potential was measured from the extensor hallucis brevis and the extensor digitorum muscles as an indication of foot muscle function. Muscle contraction pressure was 87 (SD 38) mm Hg in the vein-obstructed leg and 133 (SD 42) mm Hg in the externally compressed leg (P<0.05). In both studies the skin sensibility of the feet was significantly lower in the vein-obstructed elevated leg after 30 min (P<0.05). Vein stasis in an elevated human leg in a plaster cast defines a model for simulating imminent acute compartment syndrome with reversible neuromuscular dysfunction.