Browsing by Author "Singh PM"

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    The Determination of the Minimum Anaesthetic Concentration of Halothane in the Rock Dove (Columba livia) Using an Electrical Stimulus
    (MDPI (Basel, Switzerland), 2021-03) Lehmann HS; Beausoleil NJ; Kongara K; Singh PM; Chambers JP; Musk GC; Johnson C; Jokimäki J
    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.
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    The Effect of Different Concentrations of Halothane Anaesthesia on the Electroencephalograph of Rock Doves (Columba livia)
    (MDPI (Basel, Switzerland), 2021-06-08) Lehmann HS; Beausoleil NJ; Kongara K; Singh PM; Musk GC; Johnson CB; Jokimäki J
    Anaesthetic agents and doses used can significantly impact cerebrocortical responsiveness as assessed by electroencephalography (EEG). The objective of this study was to evaluate the effect of three different halothane concentrations on the EEG of Rock Doves using measures of frequency distribution and burst suppression. Eight healthy Rock Doves (Columba livia) were anaesthetized with halothane in oxygen, their tracheas intubated and their lungs mechanically ventilated. Five minutes of EEG were recorded at three multiples of minimum anaesthetic concentration (MAC), 1× MAC (1.6%), 1.5× MAC (2.4%) and 2× MAC (3.2%), presented in ascending then descending order. Fast Fourier transformation of the raw EEG record gave the median frequency (F50), spectral edge frequency (F95) and the total power (Ptot). Burst suppression, expressed as inactive compared to active EEG (%), was calculated on a representative two-minute section of the raw EEG. Data were analysed using repeated-measures one-way ANOVA with Tukey post hoc correction for comparison of 1×, 1.5× and 2× MAC. Three of eight birds demonstrated negligible (<1%) burst suppression. No effect of halothane concentration on burst suppression incidence was seen. A significant decrease in all measured frequency variables (F50, p = 0.04; F95 p = 0.02; Ptot p < 0.0001) occurred between 1× and 2× MAC. Halothane anaesthesia at MAC multiples of 1×, 1.5× and 2× in the Rock Dove can be considered suitable where cortical responsiveness is desired.