CO<sub>2</sub> Stunning in Pigs: Physiological Deviations at Onset of Excitatory Behaviour

oleh: Bente Wabakken Hognestad, Nora Digranes, Vigdis Groven Opsund, Arild Espenes, Henning Andreas Haga

Format: Article
Diterbitkan: MDPI AG 2023-07-01

Deskripsi

Stunning by carbon dioxide (CO<sub>2</sub>) inhalation is controversial because it is associated with vigorous movements and behaviours which may or may not be conscious reactions. Furthermore, it is unknown whether some behaviours might indicate the transition into unconsciousness. Our study objective was to investigate the loss of consciousness during CO<sub>2</sub> stunning by linking physiological variables (in particular pH, PaO<sub>2</sub> and PaCO<sub>2</sub>) to the onset of observed behaviours. A total of 11 cross-bred pigs were studied. A tracheostomy tube, venous and arterial cannulae were placed under sevoflurane anaesthesia. After recovery from this, and a “wash out” period of at least 30 min, arterial blood samples were taken (and baseline values established) before 90–95% CO<sub>2</sub> in medical air was administered through the tracheostomy tube. Subsequent behaviours were video-recorded and key physiological variables were evaluated using an anaesthetic monitor and the frequent sampling of arterial blood (albeit with inconsistent inter-sample intervals). After the study, behaviours were classified in an ethogram. At the onset of behaviours categorised as “vigorous movement extremities”, “opisthotonos” and “agonal gasping” pH values (range) were: 6.74–7.34; 6.66–6.96 and 6.65–6.87, while PaCO<sub>2</sub> (kPa) was 4.6–42.2, 24.4–51.4 and 29.1–47.6. Based upon these values, we conclude that the pigs were probably unconscious at the onset of “opisthotonos” and “agonal gasping”, but some were probably conscious at the onset of “vigorous movements”.