クモ膜下出血および高血圧性脳内出血急性期における低酸素血症

抄録

We evaluated a relationship between hypoxemia and urinary catecholamine excretion in 34 patients with cerebrovascular diseases. Hypoxemia was induced by an increase in alveolar-arterial oxygen difference (AaDO₂). And AaDO₂ positively correlated with urinary catecholamine excretion. The patients with increased AaDO₂ had an increased intrapulmonary shunt. The maximum diameter of hematoma on CT scan in 20 patients with supratentorial hemorrhage had a significantly positive correlation with AaDO₂. Administration of phentolamine and propranolol decreased the intrapulmonary shunt followed by a decrease in AaDO₂ in patients with intracranial hemorrhage through reducing pulmonary vascular resistance and cardiac output, respectively. Trimethaphan camsilate also decreased these two values without any change in pulmonary vascular resistance or cardiac output.
From these facts, we can speculate that an overactivity of sympathetic nervous system plays an important role in increasing the intrapulmonary shunt through acting on the pulmonary vascular bed directly, through acting on the efferent sympathetic nerves to the pulmonary vascular bed, and/or through increasing cardiac output.