抄録
The possible role of electrolytes in the induction of vasospasm has not been well evaluated. These electrolytes are known to have vasomotor effects, and this study especially investigated potasium ion, which is liberated in the process of blood clot hemolysis. Under pentobarbital anesthesia, the basilar arteries of adult rats were exposed by the transclival approach under the operating microscope. Subarachnoid hemorrhage was induced by puncture on a small branch artery. At 10 minutes, two hours, and 24 hours after subarachnoid bleeding, fresh arterial strips were removed and immediately frozen in liquid nitrogen, cryosectioned, and freeze-dried. Electron probe X-ray microanalysis of the dry cryosections was performed to determine the elemental compositions of the vascular smooth muscle, extravasated erythrocyte, and periarterial space. Cytoplasmic concentrations in normal vascular smooth muscle were-K: 133±5; Cl: 12±3; Na: 22±4 (mmol/kg wet weight±SEM). The potassium concentration increased in the extracellular space to up to 8 times above the baseline 24 hours after subarachnoid bleeding, and the cytoplasmic concentrations of Ca, Na, and Cl also increased. The potassium concentration of the extravasated erythrocyte decreased over 24 hours. The time course of potassium ion liberation from extravasated erythrocytes was also studied. Fresh rat and human arterial bloods were withdrawn in sterile test-tubes and stored at 37°C. Hypertensive intracerebral hematomas were also collected during surgery. With a flamephotometer, the potassium concentrations of the stored blood serum and of the hematoma supernatants were measured chronologically. The potassium ion level almost reached its peak valve within two days, although a gradual increase persisted in rat and human incubated blood. On the other hand, the potassium ion level peak of the intracerebral hematoma was reached around day 3 or 4 post hemorrhage, and the level gradually decreased back to normal in approximately three weeks. Potassium has been known to have potent vasomotor effects.
This study shows that the potassium environment is of critical importance in cerebral vasospasm caused by subarachnoid hemorrhage.
