Temporal stability of polydipsia–hyponatremia

Temporal stability of polydipsia–hyponatremia

Schizophrenia Research 26 (1997) 199–202 Temporal stability of polydipsia–hyponatremia David B. Schnur a,*, Susan Frick b, Scott Smith a a Mount Sina...

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Schizophrenia Research 26 (1997) 199–202

Temporal stability of polydipsia–hyponatremia David B. Schnur a,*, Susan Frick b, Scott Smith a a Mount Sinai Services of the Mount Sinai School of Medicine, Clinical Research Unit, Department of Psychiatry, Elmhurst Hospital Center, 79-01 Broadway, Elmhurst, NY 11373, USA b Pilgrim Psychiatric Center, West Brentwood, NY 11717, USA Received 20 August 1996; accepted 31 March 1997

Abstract We evaluated temporal stability and outcome predictors associated with polydipsia–hyponatremia (PH ). Severity of PH was measured on two occasions separated by at least 1 year in 25 chronic psychiatric inpatients (24 with schizophrenia). Three-quarters of the sample had clinically evident PH on follow-up. Follow-up PH severity was significantly related to intake severity and hospitalization length. Our findings suggest that PH may be a persistent condition with specific outcome predictors. © 1997 Elsevier Science B.V. Keywords: Polydipsia–hyponatremia syndrome; Water intoxication; Schizophrenia; Temporal stability

1. Introduction The polydipsia–hyponatremia syndrome (PH ) is characterized by excessive fluid intake and intermittent dilutional hyponatremia. Most commonly described in chronic schizophrenic patients, PH also is associated with other psychiatric conditions (Bremner and Regan, 1991; de Leon et al., 1994; Vieweg, 1996). PH presents with varying degrees of severity ranging from polydipsia with mild hyponatremia to life-threatening water intoxication ( WI; Illowsky and Kirch, 1988). This study evaluated the temporal stability of PH in a sample with varying degrees of severity, with the aim of broadening previous evidence that severe PH follows a chronic course (Peh et al., 1990; Koczapski and Millson, 1989; Vieweg et al., 1990) by including milder cases without histories * Corresponding author. 0920-9964/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII S 09 2 0 -9 9 6 4 ( 9 7 ) 0 0 0 41 - 8

of WI. We also report preliminary evidence on outcome predictors of PH, hypothesizing that poor outcome would be associated with severity of PH on initial evaluation and with protracted hospitalization. The latter prediction was based on the finding that PH patients had significantly longer inpatient treatment than inpatient controls with similar duration of illness (Schnur et al., 1993; Schnur and Smith, 1996).

2. Methods Our sample comprised 25 chronic inpatients at a state psychiatric facility, referred by clinicians to a consultant (D.B.S.) for the evaluation and management of PH. An additional patient underwent initial evaluation but was lost to follow-up due to discharge. As in a previous report (Schnur et al.,


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1993), patients included in this study either presented with, or had a history of, abnormally low serum sodium levels on at least one occasion (Na<135 mmol l−1) associated with polydipsia. Patients with excessive fluid intake or hyponatremia attributable to medical conditions or medication side eects (e.g., carbamazepine or thiazide diuretics) were not included. However, two patients in whom hyponatremia persisted after carbamazepine discontinuation remained in the study. Diagnostic assessments using DSM IIIR criteria were based on clinical interviews and chart reviews. All but one of the patients had schizophrenia, the exception having bipolar disorder, manic. The patients were all followed for at least one year. A 5-point scale to measure severity of PH (see Fig. 1) was carried out by the consultant after questioning sta regarding patients’ drinking behavior and signs of WI. Clinical charts also were reviewed and the patients were interviewed. Although the consultation service evaluated patients as often as necessary, ratings were carried out only at intake and study termination. The follow-up rating represented an overall assessment of PH for the final 6 months of the study.

3. Results Patients had a mean age (±SD) of 49.2±13 years, a mean education of 11.4±3 years, a mean duration of illness of 27.9±10 years, and mean length of hospitalization of 12.3±9 years. (Duration of hospitalization was not available for one patient.) Twelve patients (48%) were female. Histories of drug and alcohol abuse were evident in seven (28%) and 12 patients (48%) respectively. All were smokers. At intake it was impossible to determine with certainty which patients had past histories of WI. We did note histories of seizures in 16 patients (64%), but could not determine seizure history in one patient. All patients were treated with neuroleptics (mean dose 880 mg chlorpromazine equivalents; range 80–2000 mg chlorpromazine equivalents). Two also received levothyroxine and were euthyroid.

Management of PH was not standardized but, if indicated, diurnal weights were monitored and temporary water restriction was instituted. Serum sodium levels were obtained according to clinical need, usually in the morning. At intake, 22 patients had active PH (ratings of 2 or more) and the other three had PH by history (see Fig. 1). The mean follow-up duration was 15.9±4 months. Temporal stability was assessed by determining the proportion of patients with active PH at follow-up. Seventy-six percent met this criterion (see Fig. 1). PH at follow-up was severe enough in 12 patients (48%) to require specialized treatment (see Fig. 1). Severity of PH on intake was significantly related to severity on follow-up (r=0.46; p=0.04). Moreover, two of the three patients with WI during the follow-up period had been referred with recent histories of WI. Conversely, none of the three patients without active PH at intake had active PH on follow-up. Duration of hospitalization also was associated with PH severity at follow-up. Patients hospitalized 10 years or more had significantly poorer outcome than patients with shorter lengths of hospitalization (t[23]= −2.3; p=0.04). Finally, to determine patient characteristics that independently predicted PH severity at follow-up, a stepwise multiple regression analysis was carried out using a stepwise selection of predictor variables. PH severity at intake, duration of hospitalization, gender, age, education, duration of illness, history of alcohol or drug abuse, and seizure history served as predictor variables and PH severity at follow-up served as the outcome variable. Relations between smoking and outcome could not be measured as all patients were smokers. The rating of PH severity at intake was entered in the first step, accounting for approximately 26% of outcome variance (R=0.55, adjusted R2=0.26; F=7.8) and length of hospitalization made a nontrivial incremental contribution to outcome variance (R=0.7, adjusted R2=0.43, adjusted R2 increase=0.17; F=6.3). Outcome variance was not significantly increased by the remaining seven predictor variables (F≤2.5)

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Fig. 1. Severity of polydipsia–hyponatremia on initial and follow-up evaluations rated on a 5-point scale: 1=No active polydipsia–hyponatremia (PH by history only). 2=Polydipsia is noted by sta; serum sodium concentration is normal. 3=Polydipsia and hyponatremia are both evident; one to one monitoring is not required. 4=Patient must be maintained in a restricted environment to monitor fluid intake; or serum sodium concentration on at least one occasion ≤125 mmol/l. 5=There have been episodes of acute water intoxication.

4. Discussion PH appeared to be temporally stable in this study with roughly three-quarters of the sample showing evidence of this condition a year or more after an initial evaluation. These results confirm and broaden previous research. For example, Koczapski and Millson (1989) reported persistent polydipsia and stable morning sodium concentration in eight schizophrenic men with histories of WI followed for 1 year. Similarly, Vieweg et al. (1990) found normalized diurnal weight gain to be seasonally stable in eight schizophrenic men with PH of unspecified severity also studied for 1 year. Our evidence extends these findings to a larger sample of patients in whom PH varied widely in severity and also suggests that severity

of PH at follow-up may be associated with severity on intake as well as length of hospitalization. The latter relation is consistent with a recent crosssectional survey (de Leon et al., 1996). Certain methodological shortcomings may be pertinent to the interpretation of our findings. First, failure to find relations between outcome and most predictor variables may have been due to small sample size. Secondly, severity of PH was not continuously assessed and relied on interviews with clinical sta and chart reviews instead of direct observation of drinking behavior by the investigators. In addition, neither treatments nor evaluations were standardized. These limitations may have impacted on relations between patient characteristics and outcome, but likely do not weaken the conclusion that PH is


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temporally stable in chronically hospitalized psychiatric patients.

Acknowledgment The authors thank Barbara Cornblatt, PhD, Pritish Shah, MD and Michael Obuchowski, PhD for their comments on previous versions of this manuscript

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Illowsky, B.P., Kirch, D.G., 1988. Polydipsia and hyponatremia in psychiatric patients. American Journal of Psychiatry 145, 675–683. Koczapski, A.B., Millson, R.C., 1989. Individual dierences in serum sodium levels in schizophrenic men with self-induced water intoxication. American Journal of Psychiatry 146, 1614–1615. Peh, L.H., Devan, G.S., Eu, P.W., 1990. Water intoxication in psychiatric patients in Singapore. Singapore Medical Journal 31, 238–241. Schnur, D.B., Smith, S., 1996. Polydipsia–hyponatremia and cognitive impairment: pathophysiological implications for schizophrenia. In: Schnur D.B., Kirch D.G. (Eds.), Water Balance and Schizophrenia. American Psychiatric Press, Washington. Schnur, D.B., Wirkowski, E., Reddy, R., Decina, P., Mukhergee, S., 1993. Cognitive impairments in schizophrenic patients with hyponatremia. Biological Psychiatry 33, 836–838. Vieweg, W.V.R., 1996. Overview. In: Schnur, D.B., Kirch, D.G. ( Eds.), Water Balance and Schizophrenia. American Psychiatric Press, Washington. Vieweg, W.V.R., Harrington, D.P., Westerman, P.S., McKelway, R.B., Hundley, P.L., Yank, G.R., 1990. Seasonal stability of water balance among schizophrenic patients subject to water intoxication. Progress in Neuropsychopharmacology and Biological Psychiatry 14, 215–222.