Serum osmolarity in male patients with bipolar disorder manic episode

Abstract

Imbalance of water and electrolyte homeostasis has been suggested to be associated with the acute episodes of bipolar disorder. In this study we aimed to investigate, for the first time, the serum osmolarity in bipolar disorder manic episode. A total of 68 bipolar inpatients in manic episode and 60 age-gender matched healthy controls were included in the study. Serum osmolarity was calculated from Sodium (Na⁺), glucose and blood urea nitrogen (BUN) according to formula of (2 × Na⁺) + (BUN/2.8) + (Glucose/18). Significance level was accepted as P < 0.05. Serum osmolarity of manic patients was 295.34 ± 4.90 mOsm L⁻¹ and control group was 298.46 ± 5.33 mOsm L⁻¹. Serum osmolarity of manic group was significantly lower than controls (P  <  0.001). When we compare the components of serum osmolarity; statistically significant difference was also observed between groups in terms of glucose (85.85 ± 12.25 mg dl⁻¹ for manic, 92.95 ± 20.77 mg dl⁻¹ for controls, P = 0.019) and Na⁺ (140.73 ± 2.06 mmol L⁻¹ for manic, 142.06 ± 2.48 mmol L⁻¹ for controls, P = 0.001). For BUN levels; there was no statistically significant difference between manic (25.50 ± 9.85 mg dl⁻¹) and control (26.61 ± 6.64 mg dl⁻¹) groups (P = 0.461). Our results demonstrate a diminished serum osmolarity in manic episode compared with healthy controls. This finding supports the hypothesis of a fluid and electrolyte imbalance during acute episodes. Decreased serum osmolarity may be a reflection of a relative hemodilution in mania. However, exploring the role of fluid and electrolyte homeostasis and mechanisms of related hormones may contribute to better understanding the etiology of bipolar disorder.

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