Comparison of medetomidine and dexmedetomidine as premedicants in dogs undergoing propofol-isoflurane anesthesia.

OBJECTIVE

To compare 3 dose levels of medetomidine and dexmedetomidine for use as premedicants in dogs undergoing propofol-isoflurane anesthesia.

ANIMALS

6 healthy Beagles.

PROCEDURE

Dogs received medetomidine or dexmedetomidine intravenously at the following dose levels: 0.4 microg of medetomidine or 0.2 microg of dexmedetomidine/kg of body weight (M0.4/D0.2), 4.0 microg of medetomidine or 2.0 microg of dexmedetomidine/kg (M4/D2), and 40 microg of medetomidine or 20 microg of dexmedetomidine/kg (M40/D20). Sedation and analgesia were scored before induction. Anesthesia was induced with propofol and maintained with isoflurane. End-tidal isoflurane concentration, heart rate, and arterial blood pressures and gases were measured.

RESULTS

Degrees of sedation and analgesia were significantly affected by dose level but not drug. Combined mean end-tidal isoflurane concentration for all dose levels was higher in dogs that received medetomidine, compared with dexmedetomidine. Recovery time was significantly prolonged in dogs treated at the M40/D20 dose level, compared with the other dose levels. After induction, blood pressure decreased below reference range and heart rate increased in dogs treated at the M0.4/D0.2 dose level, whereas blood pressure was preserved in dogs treated at the M40/D20 dose level. However, dogs in these latter groups developed profound bradycardia and mild metabolic acidosis during anesthesia. Treatment at the M4/D2 dose level resulted in more stable cardiovascular effects, compared with the other dose levels. In addition, PaCO2 was similar among dose levels.

CONCLUSIONS AND CLINICAL RELEVANCE

Dexmedetomidine is at least as safe and effective as medetomidine for use as a premedicant in dogs undergoing propofol-isoflurane anesthesia.