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


Sílvia Renata Gaido Cortopassi, Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo, Universidade de São Paulo, São Paulo, SP, Brazil. E-mail:


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 μg 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 μg 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 μg kg−1 minute−1, n = 7). Variables evaluated included heart rate (HR), respiratory rate (fR), systemic arterial pressures, rectal temperature (RT), end-tidal CO2, 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, fR, 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.