Acid-base status in dogs during long term anaesthesia

The acid-base status in dogs anaesthetized with chloralose or combinations of chloralose and barbiturates was studied. No surgical procedures were used to elucidate whether the anesthesia per se changes in the acid-base status. Irrespective of the anaesthetic used, a progressive metabolic acidosis developed after 2-3 hours. This progressed for several hours despite normal arterial blood pressure and pulse rate. A theoretical model, based on the results, is presented. Even the induction of anesthesia caused an impairment of the peripheral circulation. This impairment, in combination with rising body temperature, might be strong enough to cause a detectable metabolic acidosis. It is concluded that, as compared with blood pressure and pulse rate, the acid-base status of the blood is a reliable and early sign of the impairment of circulation during anesthesia.