158 EFFECTS OF ACUTE VOLUME EXPANSION IN HYPOXIC NEWBORN DOGS

Abstract

Volume expansion is used frequently in hypoxic newborn infants. The effect on cardiac output (CO) of hypoxia alone (n=7) and hypoxia plus volume expansion (n=7) was studied in newborn dogs (age 1-12 days), using radioactive microspheres. Both groups of animals were made hypoxic by breathing 12% O₂ throughout the experiment (PO₂< 40 torr). In both groups period I was baseline and periods II and III were measurements made 20′ and 40′ post hypoxia. In the hypoxic group period III consisted of hypoxia alone, while the animals in the hypoxia plus volume expansion group received in addition a volume expansion of 30ml/kg of adult dog plasma. In the hypoxic group CO was 264.7±29.2ml/kg/min (SEM) and 198.3±15.7ml/kg/min during periods I and II respectively. In the hypoxia plus volume expansion group CO was 262.2±35.Oml/kg/min and 233.6±39.9ml/kg/min during periods I and II respectively. During period III CO decreased further from baseline in hypoxic group to 214.3±19.5 ml/kg/min (p<0.05) and vascular resistance (R) increased from .276±.06mmHg/ml/kg/min during period I to .326±.02mmHg/ml/kg/min (p<0.05) during period III. On the other hand in the hypoxia plus volume expansion group CO increased to 295.8±36.lml/kg/min (p<0.05) and R decreased from .193±.02 mmHg/ml/kg/min during period I to .147±.02mmHg/ml/kg/min during period III (p<0.05). Thus acute volume expansion prevents the fall in CO seen in hypoxic newborn animals.

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