Comparison of two techniques of narcotic-induced anesthesia for use during recording of magnetic motor evoked potentials in dogs.

OBJECTIVE

To compare 2 types of narcotic-induced anesthesia for recording of transcranial magnetic motor evoked potentials (TMMEP) in dogs.

DESIGN

The effect of different doses of sufentanil and midazolam and of sufentanil and nitrous oxide on onset latencies and peak-to-peak, amplitudes of TMMEP was evaluated and compared.

ANIMALS

18 neurologically normal dogs.

PROCEDURE

Premedication with droperidol and fentanyl. Induction and maintenance of anesthesia either with sufentanil and midazolam or with sufentanil and nitrous oxide. Recording of TMMEP from the extensor carpi radialis muscle of the forelimb and from the cranial tibial muscle of the hind limb.

RESULTS

Both types of narcotic anesthesia induced dose-dependent suppression of TMMEP; compared with baseline recordings, latencies increased, amplitudes decreased, and reproducibility became poorer with increasing dose of the anesthetics. Using surgical-depth doses of the anesthetics, TMMEP could still be recorded in all dogs with sufentanil and nitrous oxide, but not with sufentanil and midazolam anesthesia.

CONCLUSIONS

Sufentanil and nitrous oxide anesthesia was superior to sufentanil and midazolam anesthesia for TMMEP recording.

CLINICAL RELEVANCE

In small animal medicine, and in dogs in particular, spinal cord diseases are among the most frequently encountered neurologic disorders. The development of techniques for recording TMMEP in anesthetized dogs allows noninvasive evaluation of transmission along descending motor pathways of the spinal cord.