British Journal of Anaesthesia, 1985, Vol. 57, No. 9 896-899
© 1985 The Board of Management and Trustees of the British Journal of Anaesthesia
research-article |
EFFECT OF HALOTHANE ON SPINAL SOMATOSENSORY EVOKED POTENTIALS IN SHEEP
Departments of Anaesthesia and Neurosurgery, Royal Alexandra Hospital for Children Camperdown, NSW 2050, Australia.
Address for correspondence: Department of Anaesthesia, Royal Alexandra Hospital for Children, P.O. Box 34, Camperdown, NSW 2050, Australia.
The effects of increasing concentrations of halothane on the morphology of spinal somatosensory evoked potentials (SEP) were studied in seven anaesthetized sheep. Anaesthesia was induced with thiopentone and maintained with nitrousoxidein oxygen. Ventilation was controlled throughout. Arterial pressure, temperature and end-tidal carbon dioxide tension were monitored. A lumbar laminectomy was performed, the sciatic nerve exposed and a baseline spinal SEP was recorded from the surface of the lumbar spinal cord. Halothane was introduced in incremental steps of 1% up to 3% and further SEP were recorded. These recordings revealed that the spinal SEP peak latencies and general waveform configuration were stable under halothane anaesthesia. Baseline SEP amplitude was similar to that obtained with 1% halothane; however, at concentrations of 2% halothane or greater, there was a significant (P<0.005) attenuation of all components of the spinal SEP. These findings have important anaesthetic implications for patients undergoing spinal cord monitoring using SEP, although interspecies differences may occur.
*Present Address: Department of Nureology,Western Genral Hospital,Crew Road,Edinburgh,EH4 2XU