Abstract
This study aims to determine the minimum anaesthetic concentration (MAC) of halothane in the Rock Dove using electrical stimulus. Seven Rock Doves are anaesthetised with halothane, and the MAC is determined using the bracketing method. An electrical stimulus (two single pulses and two five-second stimuli, all separated by five-second pauses; 30 Hz, 30 V, 7.5 ms) is applied to the legs via subcutaneous electrodes. A maximum of eight periods of electrical stimulation, each with a preceding 15 min stable phase, is applied to each bird. If the non-reflexive movement occurred following stimulation, the end-tidal halothane (Fe’Hal) is increased by 10% before the next stimulus delivery. If no movement occurred, Fe’Hal is decreased by 10%. The MAC is the average of the highest concentration that allowed movement and the lowest that prevented movement. Physiological variables and ventilatory settings are recorded every five minutes. The current delivered is calculated offline. The mean ± SD MAC of halothane is 1.62 ± 0.29%, calculated from five birds. During the entire anaesthesia, all birds had cardiac arrhythmias —with three having sporadic recurrent periods of prolonged ventricular standstill followed by marked sinus tachycardia. The mean recorded voltage and calculated current and resistance are 27.6 ± 2.7 V, 20.3 ± 7.3 mAmp and 1.6 ± 0.9 kΩ, respectively. The advantage of halothane for prolonged anaesthesia in Rock Doves may be limited when noxious stimulation is used, due to the development of severe ventricular arrhythmias.
Highlights
Ornithological research in the field and laboratory may often require the use of anaesthesia
During anaesthesia a number of cardiac arrhythmias were detected; second-degree atrioventricular block, atrioventricular dissociation and prolonged ventricular standstill followed by sinus tachycardia
Arrhythmias were detected through the remainder of the anaesthesia when not apparent during the pre-stimulation stabilisation period
Summary
Ornithological research in the field and laboratory may often require the use of anaesthesia. Birds 2021, 2 is considered when standardising research techniques [1]. This is relevant for variables related to the central nervous system, the target of general anaesthesia. This standardisation of anaesthesia originates with species, drug and dose considerations. Halothane is an inhalant anaesthetic agent recommended for anaesthesia in some electrophysiological studies, those exploring brain and cortical responses to noxious stimuli. In this context, halothane is superior to the newer commonly used inhalant agents, such as isoflurane and sevoflurane, as it preserves cortical responses to a much greater degree, at least in chickens and various mammals [4,5]. The MAC of halothane in Rock Dove has not yet been reported
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