脳血管障害急性期に認められる低Na血症の発生機序

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To clarify the pathogenesis of hyponatremia in the acute phase of severe cerebrovascular disease, the authors studied 119 patients who had been too ill to eat by mouth for at least 2 weeks. In 38 patients the serum sodium (Na) level fell below 130 mEq/l. In these 38 patients, the serum Na, potassium (K), and creatinine (Cr) levels and osmolarity, blood urea nitrogen (BUN), and hematocrit, and urinary Na, K, and Cr were measured daily for 2 consecutive weeks. The balance of water, Na, and K, Cr clearance, free water clearance, and excreted fraction of filtered Na were calculated. Body weight and plasma levels of such hormones as antidiuretic hormone (ADH), aldosterone, and cortisol were measured. Ten of the 38 patients with hyponatremia were dehydrated, which is incompatible with the syndrome of inappropriate secretion of ADH (SIADH). The remaining 28 patients fulfilled the criteria for SIADH. Subsequently, special attention was directed to the serum K level in the hyponatremic stage. (The serum K level should be lowered due to the dilution mechanism in SIADH.) Based on the results, these 28 patients were divided into two groups: Group A (17 patients) had elevated serum K levels in the hyponatremic stage and Group B (11 patients) had no elevation of scrum K. In Group B, changes in ADH, BUN, and body weight, which are characteristic of SIADH, were observed, but no such changes were noted in Group A. In Group A the K balance showed a tendency for K out > K in and an increased serum K level despite profuse urinary excretion of K. These findings indicate an increased K level and hyponatremia due to extra-cellular K outflow and intracellular Na inflow, respectively, suggesting an Na-K pump disorder. The mechanism of hyponatremia in the acute phase of cerebrovascular disease may involve not only dehydration and SIADH but also "sick" cells responding to the apparent Na-K pump disorder. The group who tended to become dehydrated appeared to require a hypertonic Na solution to compensate for the loss of Na. Patients with SIADH were not considered to require water restriction, since they recovered spontaneously in a short period of time. Those with sick cells, a condition that is dependent on the underlying disease, were considered to require nutritional and glucose/in-sulin/K therapy to recover from the disease.
日本脳神経外科学会の論文
1987-11-15

脳血管障害急性期に認められる低Na血症の発生機序

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