精神科入院中の患者にみられる強迫的多飲および水中毒に関する研究—体重日内変動測定による予防を中心として

A Study of Compulsive Water Drinking and Water Intoxication in Psychiatric Inpatients: prevention by frequent body weighing

　【抄録】　対象は当院入院患者に対する病棟内日常行動観察の結果，中等度以上の多飲（松田の基準）を認めた患者のうち検査の説明を本人に行い，同意の得られた20例（男性18例，女性2例，平均年齢46.6歳）である。方法は21日間，午前と午後の2回，排尿後に体重測定を行った。また，週1回，計3回，午前と午後に血清Na濃度を測定した。初回の採血時にADH，ANP，尿比重，尿浸透圧なども測定した。その結果，水中毒の既往を有する群（水中毒危険群）と有しない群（良性多飲群）に分類すると，体重日内変動および血清Na変動はいずれも水中毒危険群で有意に大きかった。そして，血清Na低下と体重日内増加との間では両群ともに有意の相関がみられた（r＝－0.83，p＜0.001）。これらは，水中毒危険群では水中毒を反復する危険が大きく，体重日内変動が血清Naの変動をよく反映するため水中毒の危険を予測する有用な指標であることを示した。さらに，水中毒の発現頻度，発現機序，予防と対策などについても述べた。

　In order to examine the compulsive water drinking and water intoxication in patients undergoing long-term psychiatric treatment, a total of 21 patients with polydipsia (6.6%) were selected from the 318 inpatients in Miyagi Prefectural Natori Hospital according to the Matsuda's criteria for the assessment of polydipsia. Twenty patients (18 men, 2 women: mean age 46.6 years) who were capable of giving informed consent, were weighed everyday at 6:30 AM and 4:30 PM for three weeks, and were measured for serum sodium level one day a week at the same time during the observation period, and for levels of urine osmotic pressure, urine specific gravity, plasma ADH, ANP, and plasma osmotic pressure once.

　All 7 patients with a previous history of water intoxication (2.2%, named high risk patients here) belonged to the polydipsia group. The average diurnal change of body weight and serum sodium levels were much greater in the high risk patients than others within the polydipsia group, and serum sodium levels were significantly correlated with that of body weight (r = -0.83, p＜0.001) within the polydipsia group. The urine osmotic pressure levels of all 20 patients and the urine specific gravity levels of 17 patients were below normal values. Most patients had normal values for the other variables.