Acid-Base Balance and Arterial Ion Concentrations in Rat Under Three Types of General Anaesthesia: Chronobiological Study

The design and development of experimental, in vivo , chronobiological animal models may help reveal some of the relationships between circadian rhythms and biological functions. In vivo experiments require the use of appropriate anaesthesia, which should be selected according to their particular effect on the organism. The aim of study was to review the status of acid-base balance and ion concentration in arterial blood under common used general anaesthesias in experiments in dependence on the light-dark (LD) cycle in spontaneously breathing rats. The experiments were performed using three- to four-month-old pentobarbital (P)-, ketamine/xylazine (K/X)- and zoletil (Z)-aneasthetized female Wistar rats after a four-week adaptation to an LD cycle (12h light:12h dark). It was concluded that P anaesthesia disturbs LD dependence of acid-base balance compared to K/X and Z anaesthesia, but LD differences in plasma ion concentrations are disturbed under all type of general anaesthesia. P anaesthesia is not the most appropriate type of anaesthesia in rat chronobiological experiments. It eliminated LD differences, and also produces a more acidic environment, more pronounced hypercapnia and hypoxia than K/X and Z anaesthesias. This should be taken into account because the altered internal environment may affect the activity of systems whose functions are primarily dependent on acid-base balance or/and ion concentrations.