EFFECTS OF INTRAOPERATIVE HYPERTHERMIA ON PERIPHERAL-NERVES - NEUROLOGICAL AND ELECTROPHYSIOLOGICAL STUDIES

The tolerance of peripheral nerves to heat may limit the heat dose whi ch can be applied to tumours. This may be particularly important in in traoperative hyperthermia (IOHT) for pelvic and retroperitoneal tumour s. Furthermore the effects of hyperthermia alone must be known before its effects can be assessed in combination with irradiation. In this s tudy injury to sciatic nerves was evaluated in 30 beagle dogs for 1 ye ar following IOHT. IOHT was performed using a water circulating hypert hermia device with multichannel thermometry system. Neurological and e lectrophysiological examinations were done before, during and after IO HT treatment. Electrophysiological examinations showed a significant d ecrease in sciatic nerve conduction velocity and potential amplitude i mmediately after 60 min of heating for all temperatures. The greatest decrease in conduction velocity was observed for a temperature of 45-d egrees-C. Full recovery of nerve conduction velocity was observed 3 we eks following hyperthermia for all dogs except for those exposed to 45 -degrees-C. Neurological findings correlated with electrophysiological results. All five dogs which had nerve exposed to 45-degrees-C for 60 min had severe neurological changes, with recovery taking place betwe en 3 and 11 months after treatment. Based on these results it appears that temperatures to the peripheral nerve exceeding 44-degrees-C for 1 h are likely to cause significant, but not necessarily permanent, ner ve injury.