Examination of nasopharyngeal and tracheal somatosensory evoked potential recordings in dogs

Objective—To investigate the value of nasopharyngeal and tracheal recordings of somatosensory evoked potentials (SSEP) in anesthetized dogs. Animals—10 healthy mixed-breed dogs (5 males and 5 females). Procedure—Square-ware electrical stimuli (50 microseconds duration, 4Hz) were delivered through bipolar surface electrodes to the median nerve of the right forelimb with 7 to 12 mA constant current. The SSEP were recorded with soft electrodes placed on the epipharynx and dorsal wall of the trachea, respectively. Traditional scalp and neck recordings of SSEP were also performed, using SC-inserted needle electrodes. The potentials recorded dorsally and ventrally from the neuraxis were compared to assess the application of these signals for intraoperative neurophysiologic monitoring. Results—Electrical stimulation of the median nerve resulted in multiphasic potentials recorded from all 4 recording sites. Latency and phase shifts were observed between the far-field potentials placed ventrally and dorsally from ...