Effects of tourniquet ischemia on current perception thresholds in healthy volunteers.

The neuroselective effects of tourniquet ischemia/compression in healthy volunteers were evaluated using the automated electrodiagnostic sensory Nerve Conduction Threshold (sNCT) test. The sNCT evaluation generates reliable, painless Current Perception Threshold (CPT) measures. Standardized CPT measures using constant alternating current sinusoid waveform stimulus at 3 different frequencies 5 Hz, 250 Hz, and 2 kHz (NeurometerEG CPT/C Neurotron, Inc. Baltimore, MD) were obtained from 10 individuals at baseline and after 5, 10, 15, and 20 minutes of tourniquet ischemia and 30 minutes post-tourniquet release. The data were analyzed to determine the significance of any changes in CPTs. Increases in CPTs after 15 and 20 minutes of tourniquet ischemia at 2000 Hz and 250 Hz reached statistical significance. There were no significant changes in 5 Hz CPT measures. The results of this study demonstrate the ability of the sNCT test to quantify previously described differential neuroselective effects of tourniquet ischemia on sensory nerve function. Demonstration of statistically significant increases in CPT values at 2000 Hz and 250 Hz secondary to tourniquet ischemia, with no change in 5 Hz CPT values, is consistent with the understanding that 2000 Hz sine wave stimuli activate the large myelinated sensory fibers, 250 Hz sine wave stimuli activate small myelinated sensory fibers, and 5 Hz sine wave stimuli activate small unmyelinated sensory fibers.