Effect of epidural and intravenous use of the neurokinin-1 (NK-1) receptor antagonist maropitant on the sevoflurane minimum alveolar concentration (MAC) in dogs.

OBJECTIVE

To determine the effect of maropitant, an NK-1 receptor antagonist on the minimum alveolar concentration (MAC) of sevoflurane after intravenous and epidural administration to dogs.

STUDY DESIGN

Prospective experimental study.

ANIMALS

Seven, adult, spayed-female dogs (24.8 ± 1.9 kg).

METHODS

Each dog was anesthetized twice with sevoflurane in oxygen, with at least 10 days separating the anesthetic events. The minimum alveolar concentration (MAC) of sevoflurane was determined using the tail-clamp technique. During the first anesthetic event, the MAC of sevoflurane was determined initially and again after intravenous administration of maropitant (5 mg kg(-1)) and an infusion (150 μg kg(-1) hour(-1)). During the second anesthetic event, an epidural catheter was advanced to the 4th lumbar vertebra and MAC was determined after administration of saline and maropitant (1 mg kg(-1)) epidurally. All MAC determinations were done in duplicate. The MAC values were adjusted to sea level and compared using student's t-test.

RESULTS

The baseline MAC for sevoflurane was 2.08 ± 0.25%. Intravenous maropitant decreased (p < 0.05) MAC by 16% (1.74 ± 0.17%). In contrast, epidural administration of either saline or maropitant did not change (p > 0.05) the MAC (2.17 ± 0.34% and 1.92 ± 0.12%, respectively).

CONCLUSION AND CLINICAL RELEVANCE

Maropitant decreased the MAC of sevoflurane when administered intravenously to dogs but not after epidural administration.