Effects of limb elevation on abnormally increased intramuscular pressure, blood perfusion pressure, and foot sensation: an experimental study in humans.

Abstract

To study the effects of limb elevation on abnormally increased intramuscular pressure (IMP) and blood perfusion pressure in the anterior compartment of the leg. An experimental cross-over design. The test leg was elevated and the control leg was kept at heart level. Eight healthy subjects with a mean age of twenty-nine years. IMP was measured in the anterior compartment of the leg, and blood pressures were taken in the left arm and both legs. Four variables were recorded (with or without venous stasis, with or without plaster cast). All measurements were made simultaneously in both legs. When the leg was obstructed by venous stasis and elevated to between thirty-three and thirty-five centimeters, IMP decreased from 16.5 to 9.8 millimeters of mercury. When venous stasis was simulated in a level casted leg, the IMP was thirty-eight (SD = 6.4) millimeters of mercury but showed only a slight decline to thirty-five (SD = 7.8) millimeters of mercury after the leg was elevated. Blood perfusion pressure fell significantly once the leg was elevated, decreasing 53 percent from forty-seven (SD = 7.8) to twenty-five (SD = 8.0) millimeters of mercury (p < 0.001). All subjects experienced loss of foot sensation in the elevated limb. In those cases in which venous stasis increased IMP levels in the anterior compartment of the leg, elevating the limb produced a 40 percent reduction in IMP. However, limb elevation did not significantly reduce increased IMP levels when the venous stasis occurred in a casted leg. Therefore, we believe casted legs in which abnormally increased IMP is attributable to venous stasis should not be elevated above heart level because elevation induces low perfusion pressure and sensory dysfunction.