Experimental hyperthermia: protective effect of oxygen carrying fluorocarbon and crystalloids intraperitoneally.

The treatment of hyperthermia produced by passive warming was studied in anesthetized rats weighing 250-300 grams. In the first set of seven experiments, the authors found that venous blood oxygen fell as core temperature rose. Intraperitoneal injection of 20 ml of the oxygen carrying fluorocarbon (perfluorotributylamine, FC-43) emulsion in three of the animals shifted the curve to the right improving venous oxygen content (p less than 0.1). In the second series of experiments, a catheter was placed in the carotid artery. This catheter was attached to a pressure transducer for continuous recording of blood pressure and heart rate. Periodic blood samples were removed for measurement of blood gases, pH, and lactate. Four of the animals received 20 ml of isotonic saline, three received 20 ml of FC-43 emulsion both given intraperitoneally, and four served as controls. In the control group, there was an increase in systolic blood pressure and heart rate which peaked at a colon temperature of 42 degrees C, followed by cardiovascular collapse and death around 43 degrees C. Arterial PO2 (corrected for temperature) remained relatively constant up to 42 degrees C, and then fell. The arterial PCO2 rose sharply when the core temperature exceeded 43 degrees C. Arterial lactate content began to increase at 42 degrees C and above 43 degrees C was 2.5 fold elevated. Isotonic saline provided circulatory support but did not change the hypoxia or mixed acidosis from CO2 and lactate above 43 degrees C. FC-43 emulsion decreased hypoxia and improved circulatory performance but was associated with a mild respiratory alkalosis as arterial PCO2 fell.(ABSTRACT TRUNCATED AT 250 WORDS)