Effects of CO₂ anaesthesia on central nervous system activity in swine

Abstract

SummaryT he objective of the study was to exam ine the changes in central nervous system (CNS) activity and physical behaviour during induction and awakening from CO 2 anaesthesia. Two studies, each using pigs immersed into 90% CO 2 gas for a period of 60 s were performed. In study 1, we monitored middle latency auditory evoked potentials (changes in latencies, amplitudes and a depth of anaesthesia index), electroencephalographic parameters (delta, theta, alpha and beta electroencephalographic power and 95% spectral edge frequency) and heart rate; and in study 2, we monitored body movements and arterial and venous partial pressure of CO 2 and O 2 . No behavioural signs of distress were observed during the early part of the induction. T he swine exhibited muscular activity from 13±30 s after induction-start as well as during awak ening from anaesthesia, possibly because of a transitory weaker suppression of the brain stem than of the cortex. T he CNS and blood gas param eters started to change from the very start of induction. T he CNS suppression lasted only approxim ately one minute after the end of the induction period. T he two studies indicated a good tem poral relationship between changes in amplitude, depth of anaesthesia index, spectral edge frequency, and arterial P CO 2 during the induction period.

Response to the Letter to the Editor on the surgical castration of piglets

“…There were also no vocalisations. This absence of indicators of distress was also reported by Martoft et al (2002). We agree that the induction of anaesthesia with CO 2 induces stress; this is not different from induction of anaesthesia with other volatile anaesthetics.…”

Pre-slaughter conditions, animal stress and welfare: current status and possible future research

“…Deiss et al, 2006). There is currently no consensus on the question whether pigs lose consciousness before or after the behavioural signs (Hoenderken et al, 1979;Martoft et al, 2002).…”

“…The effects of physical activity and psychological stress on the secretion of hormones, measured in blood, urine or saliva and heart rate are well known and can be used to assess stress at slaughter (Foury et al, 2005;Hambrecht et al, 2005;Terlouw and Rybarczyk, 2008). Stimulus-induced electro-encephalocortical responses allow one to assess whether unconsciousness has been correctly induced by the stunning technique (Raj et al, 1992;Robb et al, 2000;Martoft et al, 2002). If genetic and environmental (rearing/carcass handling) aspects are controlled for, post-mortem muscle metabolism reflects partly pre-slaughter stress and physical effort (Debut et al, 2005;Terlouw, 2005).…”

Efectividad de Dos Métodos de Aturdimiento de Cerdos: Electronarcosis de Tres Puntos y Narcosis con CO2

“…A pesar de que los patrones técnicos del equipo de aturdimiento con CO 2 fueron los ideales (Martoft et al, 2002), el 45.3% de los cerdos exhibieron respiración rítmica inmediatamente después de salir de la gón-dola, porque el método no causó una apnea profunda como producto de la exposición insuficiente a las concentraciones de CO 2 (Atkinson et al, 2012;EFSA, 2013). Pese a que el intervalo entre el aturdimiento y el desangrado fueron óptimos en una alta proporción de los cerdos (89.3%), el 63.7% recobró la consciencia, posiblemente por problemas del desangrado como el corte insuficiente de los vasos sanguíneos (WSPA, 2010; Romero y Sánchez, 2015).…”