Decremental Conduction, in Normal Human Nerves Subjected to Ischemia?

Abstract

Abstract The effect of ischemia on the maximal orthodromic sensory and motor nerve conduction was studied in the digit 1‐elbow segment of the median nerve in 24 normal subjects. Action potentials were recorded at 2, 3 or 4 sites along the nerve. The latency of the potentials increased as a function of the duration of ischemia and of the distance from the point of stimulation. The earliest indication of an impaired nerve function was a decrease in the sensory action potential amplitude. During ischemia the length of the nerve segment, through which the potential was propagated, gradually became shortened. This was seen in sensory as well as in motor nerves. The sensory threshold to electrical stimuli (digit 3) had a two‐phasic course: During 15 min of ischemia it was almost stationary despite a severe reduction of the conduction velocity and of the potential amplitude. Then a rapid increase took place, coincicling with the extinction of the potential recorded at the elbow just below the occlucling cuff. The conduction parameters were normalized shortly after reestablishment of the circulation in the arm. The results indicate that action potentials become conducted with decrement during ischemia.