Carbon dioxide narcosis: Influence of short-term high concentration carbon dioxide inhalation on EEG and cortical evoked responses in the rat

The effects of 1 min exposure to 80% CO₂ inhalation was studied in rats under light general anaesthesia with N₂O. It was found that 80% CO₂ gave a rapid slowing of the EEG as well as a rapid decrease of the amplitude of cortical somatosensory evoked potentials. Only minor influences upon the blood pressure and heart rate were seen. The changes were found to be transient and most of the EEG effects had disappeared about 2-3 min following the end of the CO₂ exposure. The findings are related to current procedures for preslaughter anaesthesia in swine using 80% CO₂. The present experiments show that 80% CO₂ rapidly induces an interruption of afferent sensory transmission to the cortex as well as slowing of the EEG. Both findings indicate that 80% CO₂ is an effective agent for inducing adequate anaesthesia for slaughter procedures. However, the transient nature of the CO₂ effects upon the central nervous system revealed here has to be taken into account to optimize the slaughter house procedures.