Development of tissue hypoxia during progressive hyperthermia in dogs

Abstract

Heart rate, mean arterial pressure, respiratory rate, minute volume, arterial blood, Po 2 , Pco 2 , pH, hemoglobin saturation, lactic acid, and pyruvic acid were determined on anesthetized dogs during progressive hyperthermia. Heart rate increased as rectal temperature ( T r ) increased. Mean arterial pressure began to decline at T r between 41 and 42 C. Respiratory rate and minute volume reached maximum values at temperatures around 42 C. Arterial Po 2 and hemoglobin saturation did not decrease until rectal temperature exceeded 42 C. Pco 2 decreased and pH increased from control values as minute volume increased. Arterial excess lactate showed the most marked rise at T r s between 41 and 42 C. Failure of external respiration is not the primary physiological failure during progressive hypothermia but the development of tissue hypoxia may be.