Somatosensory evoked potentials and neuraxial blood flow in central nervous system decompression sickness

Seven adult, conditioned dogs were anesthetized with pentobarbital sodium and prepared for measurement of upper lumbar, mid-thoracic and lower cervical spinal evoked potentials (SEPs), cortical evoked potential (CEP), and aortic, right ventricular, and cerebrospinal fluid pressures. Following preparation, one animal was monitored by means of repeated evoked potentials for 2 h, at which time a [14C]iodoantipyrine autoradiographic blood flow study was performed. The 6 other animals were exposed to simulated dives in a compression chamber while anesthesia was maintained through a chamber penetration. These animals developed decompression sickness (DCS) of varying severity upon returning to the surface, and the corresponding decrements in neuronal function of the cord and the brain were measured by means of serial SEP and CEP recording. Following this evoked potential recording, [14C]iodoantipyrine autoradiographic blood flow studies were performed. The results indicated that clear reductions in SEP and CEP amplitude were associated with very low blood flows, which were in the 'neuron-disabling' range. Spinal and cortical somatosensory evoked potentials provide a valuable index with which to monitor and manage a model of spinal cord DCS.