Cardiopulmonary and isoflurane-sparing effects of epidural or intravenous infusion of dexmedetomidine in cats undergoing surgery with epidural lidocaine.

Objective: To compare the cardiorespiratory, anesthetic-sparing effects and quality of anesthetic recovery after epidural and constant rate intravenous (IV) infusion of dexmedetomidine (DEX) in cats given a low dose of epidural lidocaine under propofol-isoflurane anesthesia and submitted to elective ovariohysterectomy.

Study Design: Randomized, blinded clinical trial.

Animals: Twenty-one adult female cats (mean body weight: 3.1 +/- 0.4 kg).

Methods: Cats received DEX (4 microg kg(-1), IM). Fifteen minutes later, anesthesia was induced with propofol and maintained with isoflurane. Cats were divided into three groups. In GI cats received epidural lidocaine (1 mg kg(-1), n = 7), in GII cats were given epidural lidocaine (1 mg kg(-1)) + DEX (4 microg kg(-1), n = 7), and in GIII cats were given epidural lidocaine (1 mg kg(-1)) + IV constant rate infusion (CRI) of DEX (0.25 microg kg(-1) minute(-1), n = 7). Variables evaluated included heart rate (HR), respiratory rate (f(R)), systemic arterial pressures, rectal temperature (RT), end-tidal CO(2), end-tidal isoflurane concentration (e'ISO), arterial blood gases, and muscle tone. Anesthetic recovery was compared among groups by evaluation of times to recovery, HR, f(R), RT, and degree of analgesia. A paired t-test was used to evaluate pre-medication variables and blood gases within groups. anova was used to compare parametric data, whereas Friedman test was used to compare muscle relaxation.

Results: Epidural and CRI of DEX reduced HR during anesthesia maintenance. Mean +/- SD e'ISO ranged from 0.86 +/- 0.28% to 1.91 +/- 0.63% in GI, from 0.70 +/- 0.12% to 0.97 +/- 0.20% in GII, and from 0.69 +/- 0.12% to 1.17 +/- 0.25% in GIII. Cats in GII and GIII had longer recovery periods than in GI.

Conclusions And Clinical Relevance: Epidural and CRI of DEX significantly decreased isoflurane consumption and resulted in recovery of better quality and longer duration, despite bradycardia, without changes in systemic blood pressure.