Hyperosmolality and Intracranial Hemorrhage: Experimental Studies on Correlation between Hyperosmolality caused by 7% Sodium Bicarbonate Infusion and Brain Damage in Newborn and Young Rabbits

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  • 高浸透圧血症と頭蓋内出血:家兎新生仔および幼若家兎における7%重曹投与による高浸透圧血症と脳障害の実験的研究
  • コウ シントウアツ ケッショウ ト トウガイ ナイシュッケツ カト シンセイシ

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Studies on the correlation between hyperosmolality and brain damage, especially intracranial hemorrhage (ICH) were carried out on young and newborn rabbits following the infusion of a hypertonic solution ( 7 % sodium bicarbonate).<BR>1) All the young rabbits inject ed with 7 % sodium bicarbonate died of hyperosmolality over 380mOsm/L (mean was 462m0sm/L) after the drip infusion (18--60/d/kg/hr). Young rab bits under 10% hypoxic environment died even at 350mOsm/L level (mean was 397mOsm/L)during the infusion of 7 % sodium bicarbonate. Newborn rabbits injected with 7% sodium bicarbonate 10/d/kg intraperitoneally had ICH in half of the cases at 335mOsm/L. When hyperosmolality reached 392mOsm/L (50mi/kg), ICH could be observed in all cases.<BR>2) The main cause of death in young and newborn rabbits was subdural he morrhage (SDH)in the subtentorial region. Intraventricular hemorrhages (IVH) were observed in about 40% of the cases in the young and newborn rabbits.<BR>3) The blood pH was elevated by the drip infusion, but when hyperosmolality reached about 400mOsm/L, the blood pH began to fall. At the same osmolality, pCO2 showed a ma rked elevation. It is likely that the decrease of the blood pH was caused by the elevation of pCO2and the outflow of H+ from intracellular compartments resulting from hyperosmolality.<BR>4) Electron microscopic observation on the brain capillaries of the above animals revealed shrinkage of the endothelial cells, irregular swelling of the basement membrane and exudation of horseradish peroxidase (HRP) in the perivascular space (neuropil). HRP was detected neither in endfeet of astrocytes nor in nerve cells. This finding was corresponding to the figure of vasogenic edema. The increased permeability of the endothelial cells may depend on the opening of the tight junction caused by hyperosmolality and the pinocytotic vesicular transport in the cases of the hypoxic group.<BR>These results appar ently indicate that fatal ICH accompanied with brain edema was induced by hyperosmolality and was enhanced by the combination of hypoxia and immaturity.

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