Intracranial hemorrhage following administration of sodium bicarbonate in rabbits

Studies on the correlation between hyperosmolality and brain damage, especially intracranial hemorrhage, were carried out on young and newborn rabbits following infusion with 7% sodium bicarbonate. 1) All the young rabbits injected with 7% sodium bicarbonate died of hyperosmolality at over 380 mOsm/L (the mean was 462 mOsm/L) after drip infusion at the rate of 20-60 ml/kg/hr. Young rabbits under a 10% hypoxic environment died even at the 350 mOsm/L level (the mean was 392 mOsm/L) during infusion of 7% sodium bicarbonate. Half of the case of newborn rabbits injected with 7% sodium bicarbonate at 10 ml/kg, intraperitoneally, had intracranial hemorrhage at 335 mOsm/L. When the hyperosmolality reached 392 mOsm/L (50 ml/kg), intracranial hemorrhage was observed in all cases. 2) The main cause of death in young and newborn rabbits was subdural hemorrhage in the subtentorial region. Intraventricular hemorrhage was observed in about 40% of the cases of young and newborn rabbits. 3) The blood pH was elevated by the drip infusion, but when the hyperosmolality reached about 400 mOsm/L, the blood pH began to fall. At the same osmolality, pCO2 showed a marked elevation. It is likely that the decrease of the blood pH was caused by the elevation of pCO2 and the outflow of H+ from intracellular compartments resulting from the hyperosmolality. These results apparently indicate that fatal intracranial hemorrhage was induced by hyperosmolality and was enhanced by the combination of hypoxia and immaturity.