Blood gas and plasma ion concentrations of asphyxiated hypothermic and normothermic rats

• 1.1. Cardiac punctures were made in four groups of rats during and after the time they were subjected to the procedures described for the induction of hypothermia with subsequent cardiac arrest.
• 2.2. The absolute amounts of oxygen were low and the carbon dioxide was high in the arterial and mixed venous blood. Even under these situations a large A-V oxygen and carbon-dioxide difference remained.
• 3.3. Although animals in all groups were acidotic, fibrillation was not observed on the electrocardiographic recordings during immersion of the animals of Groups AAH (ambient asphyxiation followed by hypothermia) and HAH (hypothermic asphyxiation followed by hypothermia) in the ice baths.
• 4.4. A decreased buffering capacity of the blood, as evidenced by the BHCO₃/H₂CO₃ ratio, was prominent especially in those groups ambiently asphyxiated.
• 5.5. Plasma K⁺ increased at least 80 per cent in all groups. However, plasma sodium exhibited a significant decrease only in Groups HA (hypothermic asphyxiation) and HAH.
• 6.6. It is suggested that one of the limiting factors for the induction of hypothermia with cardiac arrest is the absolute amount of oxygen available to the animal after respiratory arrest.