Cardiovascular tolerance of intravenous bupivacaine in broiler chickens (Gallus gallus domesticus) anesthetized with isoflurane

Peter M. DiGeronimo, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
Anderson F. da Cunha, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA. Electronic address: adacun1@lsu.edu.
Bruno Pypendop, Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA, USA.
João Brandão, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
Rhett Stout, Division of Laboratory Animal Medicine, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
Max Rinaldi, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
Thomas N. Tully, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.

Abstract

OBJECTIVE: To determine the median effective dose (ED) of intravenous (IV) bupivacaine associated with a 50% probability of causing clinically relevant cardiovascular effects [defined as 30% change in heart rate (HR) or mean arterial pressure (MAP)] in chickens anesthetized with isoflurane. STUDY DESIGN: Randomized up-and-down study. ANIMALS: A total of 14 Ross-708 broiler chickens (Gallus gallus domesticus) weighing 1.70-2.75 kg. METHODS: Anesthesia was induced and maintained with isoflurane. Monitoring included the electrocardiogram and invasive arterial pressures. Chickens were administered bupivacaine IV over 2 minutes using a dose based on the response of the previous animal. Dose was decreased when HR and/or MAP in the previous animal increased or decreased ≥30% after bupivacaine administration, or increased when HR or MAP changed <30%. The ED was defined as the dose resulting in ≥30% variation in HR or MAP in 50% of the population studied. RESULTS: The IV ED of bupivacaine was 1.94 mg kg using Dixon's up-and-down method and 1.96 mg kg by logistic regression. CONCLUSIONS AND CLINICAL RELEVANCE: These results suggest that 1.33 and 1.96 mg kg of IV bupivacaine are associated with a respective 1 or 50% probability of a clinically significant change in MAP in isoflurane-anesthetized chickens. Identification of the cardiovascular changes associated with different doses of bupivacaine can be used as the basis for studies of therapeutic applications in the domestic chicken. Further studies are required to determine interspecies variation.