• Eduardo Gutierrez-Blanco, José M Victoria-Mora, Jose A Ibancovichi-Camarillo, Carlos H Sauri-Arceo, Manuel E Bolio-González, Carlos M Acevedo-Arcique, Gabriela Marin-Cano, and Paulo V M Steagall.
• Department of Animal Health and Preventive Medicine, Faculty of Veterinary Medicine, Yucatan Autonomous University, Merida, Mexico; Department of Veterinary Anesthesiology, Faculty of Veterinary Medicine, Mexico State Autonomous University, Toluca, Mexico.
• Vet Anaesth Analg. 2013 Nov 1;40(6):599-609.

ObjectiveTo evaluate the isoflurane-sparing effects of an intravenous (IV) constant rate infusion (CRI) of fentanyl, lidocaine, ketamine, dexmedetomidine, or lidocaine-ketamine-dexmedetomidine (LKD) in dogs undergoing ovariohysterectomy.Study DesignRandomized, prospective, blinded, clinical study.AnimalsFifty four dogs.MethodsAnesthesia was induced with propofol and maintained with isoflurane with one of the following IV treatments: butorphanol/saline (butorphanol 0.4 mg kg(-1), saline 0.9% CRI, CONTROL/BUT); fentanyl (5 μg kg(-1), 10 μg kg(-1) hour(-1), FENT); ketamine (1 mg kg(-1), 40 μg kg(-1) minute(-1), KET), lidocaine (2 mg kg(-1), 100 μg kg(-1) minute(-1), LIDO); dexmedetomidine (1 μg kg(-1), 3 μg kg(-1) hour(-1), DEX); or a LKD combination. Positive pressure ventilation maintained eucapnia. An anesthetist unaware of treatment and end-tidal isoflurane concentration (Fe'Iso) adjusted vaporizer settings to maintain surgical anesthetic depth. Cardiopulmonary variables and Fe'Iso concentrations were monitored. Data were analyzed using anova (p < 0.05).ResultsAt most time points, heart rate (HR) was lower in FENT than in other groups, except for DEX and LKD. Mean arterial blood pressure (MAP) was lower in FENT and CONTROL/BUT than in DEX. Overall mean ± SD Fe'Iso and % reduced isoflurane requirements were 1.01 ± 0.31/41.6% (range, 0.75 ± 0.31/56.6% to 1.12 ± 0.80/35.3%, FENT), 1.37 ± 0.19/20.8% (1.23 ± 0.14/28.9% to 1.51 ± 0.22/12.7%, KET), 1.34 ± 0.19/22.5% (1.24 ± 0.19/28.3% to 1.44 ± 0.21/16.8%, LIDO), 1.30 ± 0.28/24.8% (1.16 ± 0.18/32.9% to 1.43 ± 0.32/17.3%, DEX), 0.95 ± 0.19/54.9% (0.7 ± 0.16/59.5% to 1.12 ± 0.16/35.3%, LKD) and 1.73 ± 0.18/0.0% (1.64 ± 0.21 to 1.82 ± 0.14, CONTROL/BUT) during surgery. FENT and LKD significantly reduced Fe'Iso.Conclusions And Clinical RelevanceAt the doses administered, FENT and LKD had greater isoflurane-sparing effect than LIDO, KET or CONTROL/BUT, but not at all times. Low HR during FENT may limit improvement in MAP expected with reduced Fe'Iso.© 2013 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.

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