Comparison of cardiorespiratory variables in dorsally recumbent horses anesthetized with guaifenesin-ketamine-xylazine spontaneously breathing 50% or maximal oxygen concentrations.
Abstract: This study compared cardiorespiratory variables in dorsally recumbent horses anesthetized with guaifenesin-ketamine-xylazine and spontaneously breathing 50% or maximal (> 90%) oxygen (O2) concentrations. Twelve healthy mares were randomly assigned to breathe 50% or maximal O2 concentrations. Horses were sedated with xylazine, induced to recumbency with ketamine-diazepam, and anesthesia was maintained with guaifenesin-ketamine-xylazine to effect. Heart rate, arterial blood pressures, respiratory rate, lithium dilution cardiac output (CO), inspired and expired O2 and carbon dioxide partial pressures, and tidal volume were measured. Arterial and mixed-venous blood samples were collected prior to sedation (baseline), during 30 minutes of anesthesia, 10 minutes after disconnection from O2, and 30 minutes after standing. Shunt fraction, O2 delivery, and alveolar-arterial O2 partial pressures difference [P(A-a)O2] were calculated. Recovery times were recorded. There were no significant differences between groups in cardiorespiratory parameters or in P(A-a)O2 at baseline or 30 minutes after standing. Oxygen partial pressure difference in the 50% group was significantly less than in the maximal O2 group during anesthesia. Cette étude a comparé les variables cardiorespiratoires chez les chevaux en décubitus dorsal anesthésiés à l’aide de guaifénésine-kétamine-xylazine et respirant spontanément des concentrations de 50 % ou des concentrations maximales (> 90 %) d’oxygène (O). Douze juments en santé ont été assignées au hasard à la respiration de concentrations 50 % ou de concentrations maximales d’ O. Les chevaux ont été mis sous sédation avec de la xylazine, induits au décubitus à l’aide de kétamine-diazépam et l’anesthésie a été maintenue à l’aide de guaifénésine-kétamine-xylazine jusqu’à l’effet. Le rythme cardiaque, la pression artérielle, la fréquence respiratoire, le débit cardiaque par dilution au lithium, l’ O à l’inspiration et à l’expiration ainsi que les pressions partielles de gaz carbonique et le volume courant ont été mesurés. Des échantillons sanguins artériels et veineux mixtes ont été prélevés avant la sédation (données de référence), durant 30 minutes d’anesthésie, 10 minutes après le débranchement de l’oxygène et 30 minutes après s’être mis debout. La fraction du shunt, l’alimentation en O et la différence des pressions partielles d’ O alvéolaire-artérielle [P(A-a)O] ont été calculées. Les temps de réveil ont été consignés. Il n’y avait pas de différences significatives entre les groupes dans les paramètres cardiorespiratoires ou dans P(A-a)O aux données de référence ou 30 minutes après s’être mis debout. La différence entre la pression partielle de l’ O dans le groupe 50 % était significativement inférieure à celle du groupe avec des concentrations maximales d’ O durant l’anesthésie.(Traduit par Isabelle Vallières).
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This research paper is a detailed comparison study of the effects of two differing oxygen concentrations on the cardiorespiratory variables in horses during anesthesia.
Study Design and Process
Twelve healthy female horses (mares) were used for this study. These subjects were divided into two groups, each allocated to inhale different oxygen concentrations. One group was to breathe 50% oxygen concentration, and the other was to breathe oxygen concentrations above 90% (referred to as the ‘maximal O2’ group).
The horses were sedated using xylazine, put into a recumbent (lying down) position with ketamine-diazepam, and the anesthetic effect was maintained with a combination of guaifenesin-ketamine-xylazine until the desired effect was achieved.
Various cardiorespiratory variables such as heart rate, arterial blood pressures, respiratory rate, tidal volume, and lithium dilution cardiac output were measured throughout the procedure. Moreover, inspired and expired oxygen and carbon dioxide partial pressures were also monitored.
Blood samples were taken from the animals at different stages – prior to sedation, throughout 30 minutes of anesthesia, 10 minutes post disconnection of oxygen, and half an hour after the horses had stood up following the anesthesia.
Findings and Conclusion
Calculations of shunt fraction, oxygen delivery, and alveolar-arterial oxygen partial pressures difference were carried out. The recovery times were also recorded as a part of the study.
Results showed no significant difference in cardiorespiratory parameters or in oxygen partial pressure differences at baseline or after 30 minutes of returning to standing between the two study groups.
The group exposed to 50% oxygen showed significantly less difference in oxygen partial pressure during the anesthesia phase compared to the high oxygen group. This marks the key finding of the study and indicates potential alterations in respiratory responses based on oxygen concentration during anesthesia in horses.
Cite This Article
APA
Karrasch NM, Hubbell JA, Aarnes TK, Bednarski RM, Lerche P.
(2015).
Comparison of cardiorespiratory variables in dorsally recumbent horses anesthetized with guaifenesin-ketamine-xylazine spontaneously breathing 50% or maximal oxygen concentrations.
Can Vet J, 56(4), 387-392.
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, 601 Vernon L. Tharp Street, Columbus, Ohio 43210, USA.
Hubbell, John A E
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, 601 Vernon L. Tharp Street, Columbus, Ohio 43210, USA.
Aarnes, Turi K
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, 601 Vernon L. Tharp Street, Columbus, Ohio 43210, USA.
Bednarski, Richard M
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, 601 Vernon L. Tharp Street, Columbus, Ohio 43210, USA.
Lerche, Phillip
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, 601 Vernon L. Tharp Street, Columbus, Ohio 43210, USA.
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