Diurnal variation in water homeostasis among schizophrenic patients subject to water intoxication

Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations

Hyponatremia is a serious, but often overlooked, electrolyte imbalance that has been independently associated with a wide range of deleterious changes involving many different body systems. Untreated acute hyponatremia can cause substantial morbidity and mortality as a result of osmotically induced cerebral edema, and excessively rapid correction of chronic hyponatremia can cause severe neurologic impairment and death as a result of osmotic demyelination. The diverse etiologies and comorbidities associated with hyponatremia pose substantial challenges in managing this disorder. In 2007, a panel of experts in hyponatremia convened to develop the Hyponatremia Treatment Guidelines 2007: Expert Panel Recommendations that defined strategies for clinicians caring for patients with hyponatremia. In the 6 years since the publication of that document, the field has seen several notable developments, including new evidence on morbidities and complications associated with hyponatremia, the importance of treating mild to moderate hyponatremia, and the efficacy and safety of vasopressin receptor antagonist therapy for hyponatremic patients. Therefore, additional guidance was deemed necessary and a panel of hyponatremia experts (which included all of the original panel members) was convened to update the previous recommendations for optimal current management of this disorder. The updated expert panel recommendations in this document represent recommended approaches for multiple etiologies of hyponatremia that are based on both consensus opinions of experts in hyponatremia and the most recent published data in this field.

Hyponatremia treatment guidelines 2007: expert panel recommendations

Although hyponatremia is a common, usually mild, and relatively asymptomatic disorder of electrolytes, acute severe hyponatremia can cause substantial morbidity and mortality, particularly in patients with concomitant disease. In addition, overly rapid correction of chronic hyponatremia can cause severe neurologic deficits and death, and optimal treatment strategies for such cases are not established. An expert panel assessed the potential contributions of aquaretic nonpeptide small-molecule arginine vasopressin receptor (AVPR) antagonists to hyponatremia therapies. This review presents their conclusions, including identification of appropriate treatment populations and possible future indications for aquaretic AVPR antagonists.

Effects of acute metabolic stress on the peripheral vasopressinergic system in schizophrenia

Although both vasopressin and stress have been implicated in the course of schizophrenia, it is unknown whether schizophrenic patients have altered stress-induced function of the vasopressinergic system. We examined the effects of acute metabolic stress induced by pharmacological doses (40 mg/kg) of 2-deoxyglucose (2DG) on plasma concentrations of vasopressin in 13 patients with schizophrenia (with no history of polydipsia and hyponatremia) and 12 healthy control subjects. Baseline vasopressin levels were lower in the schizophrenic patients and progressively increased in both groups throughout the 60 min following 2DG administration to a similar absolute amount, thus remaining lower in the schizophrenic group. Concomitantly, patients with schizophrenia had significantly higher 2DG-induced plasma homovanillic acid (HVA) and 5-hydroxyindoleacetic acid levels. Vasopressin responses correlated positively and significantly with the HVA responses in schizophrenics and with the pituitary-adrenal axis responses in controls. These results suggest two different patterns of neuroendocrine alterations in schizophrenia, namely a relatively normal vasopressin response to 2DG despite significantly decreased baseline levels and exaggerated responses of the peripheral dopaminegic and serotonergic systems in the face of normal baseline concentrations.

Hyper- and hyponatremia among geropsychiatric inpatients

We report our experience treating 14 elderly psychiatric patients with altered sodium states. Hypernatremia occurs more commonly among elderly psychiatric patients than among their younger counterparts, and elderly hypernatremic psychiatric patients suffer most commonly from dementia. Dilutional hyponatremia is less common and less severe among elderly schizophrenic patients compared with younger patients with schizophrenia. Central nervous system changes induced by altered sodium states among elderly psychiatric patients are sufficiently similar whether hyper- or hyponatremia is present; therefore, the clinician must not wait for specific features to develop, but must quickly measure serum sodium concentration in elderly psychiatric patients with altered mental states. Treatment of hypernatremia involves rehydration with normal saline or hypotonic solutions, and treatment of dilutional hyponatremia largely involves fluid restriction.

A review of disorders of water homeostasis in psychiatric patients

Disorders of water homeostasis are common in psychiatric patients and include compulsive water drinking, the syndrome of inappropriate antidiuretic hormone secretion (SIADH), and the syndrome of self-induced water intoxication (SIWI). Although water intoxication was recognized nearly 70 years ago, the physiological basis of these disorders of water metabolism still remains elusive. This review will provide a historical overview, critique current studies on compulsive water drinking and SIWI, discuss possible etiologies, and present current approaches to treatment of these disorders. Because of the complexity of the subject, a review of normal water homeostasis and the SIADH will be included.

Vasopressin in chronic psychiatric patients with primary polydipsia

Twelve chronic in-patients with primary polydipsia were studied, during free drinking and after fasting, by concurrent measurements of plasma AVP, serum sodium and osmolality, and urine volume, AVP, osmolality, and creatinine. A majority of the patients showed inappropriately high levels of AVP: plasma AVP estimations demonstrated that seven had Type I SIADH and two had Type II SIADH. Urinary AVP estimations confirmed inappropriately raised AVP in seven of the subjects tested, and there was a significant agreement between the plasma and urine diagnoses. Although able to concentrate their urine in response to fluid deprivation, the patients showed a decreased renal sensitivity to AVP. Despite the mitigating effect of decreased renal sensitivity to AVP, the SIADH seen in these patients appears to contribute to the development of water intoxication caused by polydipsia.

Seasonal stability of water balance among schizophrenic patients subject to water intoxication

1. Diurnal weight gain, afternoon hyponatremia, and polyuria were assessed for one year among eight male schizophrenics subject to water intoxication. 2. The authors normalized the diurnal weight gain (NDWG) as a percentage by subtracting the 7 a.m. weight from the 4 p.m. Weight, multiplying the difference by 100, and then dividing the result by the 7 a.m. weight. 3. NDWG ranged between 2.69 +/- .99 and 3.34 +/- 1.32 percent (F [3, 5] = .885, p = .509) during the four seasons of the year. 4. The seasonal decrease in afternoon serum sodium compared to its morning counterpart ranged between 4.23 +/- 1.96 and 6.14 +/- 2.82 mmol/l (F [3, 5] = 2.212, p = .205). 5. Seasonal polyuria ranged between 8.2 +/- 3.5 and 8.8 +/- 3.2 liters (F [3, 5] = .228, p = .873). 6. Among schizophrenics subject to water intoxication, the seasonal stability in our three parameters of water imbalance suggest they may be used to follow patients with altered water homeostasis over time. This finding has both clinical and research implications.

Survey of diurnal weight gain and urine volume in chronic schizophrenia

We found diurnal weight gain to be abnormal among 39 chronic schizophrenic patients. The patients were weighed and urine samples obtained weekly for three weeks at 7 a.m. and 4 p.m. We normalized the dirunal weight gain (NDWG) as a percentage by subtracting the 7 a.m. weight from the 4 p.m. weight, multiplying the difference by 100, and then dividing the result by the 7 a.m. weight. NDWG was 2.075 +/- 1.331% for the 38 study patients, .631 +/- .405% for 16 acutely psychotic controls and .511 +/- .351% for 29 normals. Seventy-seven percent of the study patients had abnormal NDWG values and 62% were polyuric. NDWG related to urine volume (n = 39, r = .356, p = .026) with the variability in urine excretion explaining 13% of the variability in NDWG. We discuss factors that may have contributed to our findings.

Failure of antipsychotic drug dose to explain abnormal diurnal weight gain among 129 chronically psychotic inpatients

1. The diurnal weight gain was found to be abnormal among 129 chronically psychotic inpatients. 2. The patients were weighed at 7 a.m. and 4 p.m. weekly for three weeks. We normalized the diurnal weight gain (NDWG) as a percentage by subtracting the 7 a.m. weight from the 4 p.m. weight, multiplying the difference by 100, and then dividing the result by the 7 a.m. weight. 3. NDWG was 2.2 +/- 1.5 percent for 87 male patients compared (p less than .0001) with .53 +/- .41 for 14 male controls. 4. NDWG was 1.8 +/- 1.0 percent for 42 female patients compared (p less than .0001) with .49 +/- .30 for 15 female controls. 5. Seventy percent of male and female patients had NDWG values greater than two standard deviations above the mean values of controls. 6. Differences in age, sex, morning weight, antipsychotic drugs, lithium, carbamazepine, phenytoin, blood pressure, and pulse did not explain these findings.

Diurnal weight gain as a predictor of serum sodium concentration in patients with psychosis, intermittent hyponatremia, and polydipsia (PIP syndrome)

Ten male patients (mean age 37.3 +/- 6.4 years) with psychosis, intermittent hyponatremia, and polydipsia (PIP syndrome) underwent measurement of weight, sitting and standing blood pressure, and serum sodium concentration at 7 a.m. and 4 p.m. weekly for 8 consecutive weeks. Blood pressure was higher in the afternoon than in the morning. The diurnal decrease in serum sodium (141.4 +/- 2.8 to 134.2 +/- 4.8 mEq/l) was associated with a diurnal increase in weight (78.4 +/- 9.7 to 80.0 +/- 10.3 kg). When the weight increase was normalized by dividing by 7 a.m. weight (NDWG), the following relationship evolved: diurnal serum sodium decrease = 3.060 + [201.728 x NDWG]. Therefore, NDWG accounted for 63.1% of the variability of serum sodium. Using the known relationship of plasma water, total body water, and total body weight, we calculated that antidiuresis (afternoon weight gain) accounted for 62.5% of afternoon hyponatremia. Thus, two separate methods of calculating the relationship between antidiuresis and hyponatremia provided remarkably similar findings. We derived a table to predict 4 p.m. serum sodium values based on 7 a.m. weight, 7 a.m. serum sodium, and 4 p.m. weight.