Delayed decrement of the nerve impulse propagation during induced limb ischaemia in chronic hepatic failure

Sensory thresholds for vibrations and electrical shocks and the sensory nerve conduction velocity (median nerve) were measured during 30 minutes of induced limb ischaemia in 10 normal subjects and 15 patients with chronic hepatic failure. Sensory action potentials were recorded simultaneously at the wrist and elbow. Seven patients (group A) had a normal perception time for vibrations. As in normal subjects, the potential amplitude decreased from the onset of ischaemia, more pronounced at the elbow than at the wrist, and the conduction velocity became reduced more rapidly in the wrist-elbow than the first digit-wrist segment, indicating impulse propagation with decrement. Eight patients (group B) had a markedly prolonged perception time for vibrations. The reduction of potential amplitude and conduction velocity was considerably delayed, and the impulse propagation showed no evidence of decrement for 20-25 minutes of ischaemia. A rise of the threshold for electrical shocks was absent or very delayed. As in the two other groups, the rise was abrupt and occurred at the moment when the potential below the occluding cuff (elbow) was extinct. In both groups of patients there was an increasing temporal dispersion of action potentials and in patient group A a desynchronization of the late phase of the potential took place early in the course of ischaemia. Differences between groups A and B could not be predicted from the pre-ischaemic nerve conduction data.