The Effect of Body Position on the Respiratory System of Anesthetized Red-Tail Hawks (Buteo jamaicensis)
American Association of Zoo Veterinarians Conference 2007
Shachar Malka1, DVM; Michelle G. Hawkins2, VMD, DABVP (Avian); Adrian M. Solano1, DVM; James H. Jones3, DVM, PhD; Peter J. Pascoe3, BVSc, DACVA; Philip H. Kass4, DVM, PhD; Hajime Ohmura5, DVM, PhD; Erik R. Wisner3, DVM, DACVR
1Veterinary Medical Teaching Hospital, University of California-Davis, Davis, CA, USA; 2Department of Medicine and Epidemiology, University of California-Davis, Davis, CA, USA; 3Department of Surgical and Radiological Science, University of California-Davis, Davis, CA, USA; 4Department of Population Health Reproduction, University of California-Davis, Davis, CA, USA; 5Equine Research Institute, Japan Racing Association, Utsunomiya, Japan
Abstract
It has been hypothesized that when birds are anesthetized in dorsal recumbency, it may cause the lungs and air sacs to be compressed by visceral organs and that sternal recumbency can restrict the movement of the keel which is essential for respiration, therefore resulting in hypoventilation and hypoxemia.
This study tested the hypothesis that different patient positions would differentially affect air sac volume, lung volume and density and physiologic parameters during anesthesia. Six adult, gender unknown red-tailed hawks (Buteo jamaicensis) were evaluated under isoflurane anesthesia while spontaneously breathing in three different positions: dorsal, right lateral, and sternal recumbency. Lung volume, lung density, and air sac volume were calculated from helical computed tomography (CT) images using software designed for volumetric analysis of CT data. ANOVA was used to compare the effect of position while controlling for replicates. When differences were significant (p≤0.05), a paired Student’s t-test was used to compare the results.
Out of the three body positions commonly used during avian anesthesia, sternal recumbency allowed for significantly greater lung and air sac volume and significantly lower lung density in red-tailed hawks.
In a second phase of the study, the birds were anesthetized in right lateral and dorsal recumbency in similar manner for 75 minutes. Tidal volume, end tidal CO2, heart rate, respiratory rate, direct and indirect blood pressure were measured every 5 minutes. Blood was drawn every 15 minutes for gas analysis. There was no significant difference between the two groups for most of the variables and at the time of writing this abstract, it is inconclusive whether the trends are physiologically significant. Our results provide clinically important insight into the potential for respiratory compromise associated with patient positioning during avian anesthesia.
Acknowledgments
This study was funded by the Center for Companion Animal Health, Veterinary Medical Teaching Hospital, School of Veterinary Medicine, UC-Davis.