The Effect of Anesthetics on Somatosensorily Evoked Potentials during Surgery

Park, Young Joo; Ryu, Jin Yong; Youn, Jun Hum; Kim, Joung Won; Hong, Ki Hyouk

Abstract

BACKGROUND: Many methods are available for the monitoring of spinal cord injury during an operation. During anesthesia, somatosensily evoked potentials (SSEP) may undergo substantial changes in the latencies and amplitudes which may be interpreted as pathological. It is essential for the anesthesiologist to know the potential interactions between anesthetic drugs and neurophysiologic responses during operation. The depressant effect of inhalation agents on the central nervous system exceeds commonly used intravenous anesthetics. Therefore, intravenous anesthesia is preferred to inhalation agents. This study was designed to compare the effects of intravenous anesthetics (propofol and fentanyl) and inhalational anesthetics (enflurane and nitrous oxide) used in the operation room.
METHODS
According to the inclusion criteria of ASA I-II, 40 patients who were free of neurologic disease with electric abdominal operations were randomly selected. The baseline of the SSEPs were recorded with stimulation of the posterior tibial nerve at the ankle. After obtaining the baseline (preinduction) of the SSEPs, intravenous anesthetics (propofol 10 mg/kg/h, fentanyl 1 2 microgram/kg) and inhalational anesthetics (end tidal enflurane concentration 1.0 vol %, 50% nitrous oxide in oxygen) were administered. 30 minutes after induction (steady state), additional SSEPs were recorded. Mean arterial pressure, heart rate, temperature and arterial blood carbon dioxide tension were monitored.
RESULTS
There were no significant differences in the baseline of SSEPs between the intravenous anesthetics group and the inhalational anesthetics group. There were no significant differences in latencies and amplitudes between the preanesthesia state and the postanesthetia state in the intravenous anesthetics group. But the inhalational anesthetics group revealed prolonged latencies in the postanestesia state as compared with their preanesthesia state.
CONCLUSIONS
The above findings suggest that the use of intravenous anesthetics can be beneficial to intraoperative SSEP monitoring for possible damage to the central nervous system during operations.