THE EFFECT OF SURGICAL MEDICAMENTS ON PERIPHERAL-NERVE FUNCTION

Surgical medicaments are often placed in close proximity to peripheral nerves and may be responsible for some postoperative sensory disturba nces. In this study we investigated the effect of four medicaments - B IPP, (bismuth iodoform paraffin paste), Whitehead's varnish (compound iodoform paint), Surgicel (oxidized regenerated cellulose) and Carnoy' s solution (ethanol, chloroform and acetic acid) - on peripheral nerve function, The experiments were carried out on the saphenous nerve in anaesthetized adult rats. Electrical stimuli (30 V, 0.1 ms duration) w ere applied to the saphenous nerve through electrodes placed distally (at the ankle) to evoke a compound action potential (CAP) which was re corded proximally (in the thigh). The CAP was recorded before, and for 2 h after, the application of the medicament to a 1 cm length of nerv e between the electrodes, In other animals (n = 4 in each group) recor dings were made after the medicament had been placed in a connective t issue pocket immediately overlying the nerve for a 2-week period. BIPP (n = 4) had no immediate or delayed effect on neural function, wherea s Whitehead's varnish (n = 4) and Carnoy's (n = 4) solution both block ed neural conduction within 2 min of being placed adjacent to the nerv e, The effect of Surgicel (n = 8) was more variable; axonal conduction was blocked within 2 h in five of the eight experiments undertaken. A fter the application of Whitehead's varnish or Surgicel for 2 weeks, t he CAPs had regained characteristics which were similar to those of th e controls, but after the application of Carnoy's solution they remain ed significantly diminished (P < 0.004). These results suggest that, w ith the exception of BIPP, the medicaments tested could be responsible for some postoperative sensory disturbances, and the effects of Carno y's solution on neural function may be persistent.