The relationship between ischaemic conduction failure and conduction velocity in cat myelinated axons

Unitary action potentials have been recorded from cat spinal root filaments following electrical stimulation of hindlimb peripheral nerves. Potentials were monitored both before the ischaemia which follows the onset of cardiac arrest. The relationship between time to conduction failure (survival time) and initial conduction velocity was determined for 164 nerve fibres. This revealed that during ischaemia, slow myelinated axons tend to fail before fast myelinated axons. The average survival time was 24.6 min (range 11-39 min). The results are discussed in terms of (i) the possible mechanisms underlying ischaemic conduction block, (ii) their clinical implications for the role of ischaemia in peripheral neuropathies, and (iii) using ischaemia as an experimental technique to produce a differential nerve block.