Hyponatremia, defined as a serum sodium concentration of less than 135 mEq/L, is the most common electrolyte disorder encountered in hospitalized patients, particularly in intensive care settings [1]. It reflects a disturbance in water balance rather than sodium deficiency and is primarily mediated by inappropriate secretion or action of antidiuretic hormone (ADH) [2]. The prevalence of hyponatremia ranges from 15–30% among hospitalized patients and may reach up to 25% in ICU settings [3,4]. Moderate to severe hyponatremia is associated with significant neurological complications including cerebral edema, seizures, coma, and death [5]. The severity of symptoms depends on both the degree and rapidity of sodium decline [6].

Critically ill patients are particularly vulnerable due to multiple contributing factors such as sepsis, renal dysfunction, medications, and inappropriate fluid administration [7]. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is one of the most common etiologies, especially in association with pulmonary infections, CNS disorders, and malignancies [8]. In developing countries like India, infections such as tuberculosis play a significant role in the pathogenesis of hyponatremia through mechanisms including SIADH, adrenal insufficiency, and CNS involvement [9,10,11]. Despite it’s clinical importance, distinguishing the etiology of hyponatremia remains challenging due to overlapping clinical presentations and multifactorial causes [12].

Hence, this study was undertaken to evaluate the clinical features, etiology, and severity of hyponatremia in critically ill patients admitted to MICU.

OBJECTIVE

To assess the clinical features, etiology and severity of hyponatremia in critically ill patients admitted to MICU.

MATERIALS AND METHODS

This study was a cross-sectional observational study conducted over a period of two years (October 2015–October 2017) in the Medical Intensive Care Unit of a tertiary care hospital.

Study Population

• Total sample size was 100 patients.
• Adult patients (≥18 years) with moderate to severe hyponatremia (Serum sodium ≤125 mEq/L) admitted to MICU were included.
• Patients having hyperglycemia, hyperlipidemia, paraproteinemia, and on mannitol therapy were excluded.

Data Collection and analysis: Demographic data (age, sex); Clinical presentation; Physical examination including hydration status; Laboratory investigations like Serum sodium, Serum and urine osmolality, Urine sodium, Renal function tests were noted. Hyponatremia was classified based on Volume status (euvolemic, hypovolemic, hypervolemic), and Osmolality. Statistical Analysis was computed using SPSS software. Categorical variables were expressed in the form of percentages; continuous variables in the form of mean ± SD. Appropriate statistical tests of significance (Chi-square / Fisher’s exact test) were applied. P value of ≤ 0.05 was considered as statistically significant.

RESULTS

In the present study of 100 adult patients with hyponatremia, 59% were males and 41% were females. The male to female ratio was 1.43:1. In the present study no association was found between sex and severity of hyponatremia (p=0.642). The mean age of population under study was 58.94 ± 16.10 years. Most affected age group was 61–70 years (29%). In this study the severity of hyponatremia was comparable in all the age groups (p=0.098). In the present study no association was found between sex and severity of hyponatremia (p=0.642).

CNS symptoms present in 61% patients. In this study, confusion was observed to be significantly high in patients with severe hyponatremia as compared to moderate hyponatremia (84.62 vs 15.38%; p<0.001). No statistically significant association was observed in cases of other clinical features (p>0.05). High urine sodium significantly associated with SIADH (p<0.001). SIADH strongly associated with euvolemic hypoosmolar hyponatremia (p<0.001). However, no association was found between severity and causes of hyponatremia (p=0.328).

Table 1. Demographic Profile

Table 2. Clinical Presentation

Table 3. Severity and Type of Hyponatremia

Table 4. Etiology of Hyponatremia

Table 5. Outcome

DISCUSSION

Hyponatremia remains a complex clinical entity with diverse etiologies and presentations. In the present study, a male predominance (59%) was observed, which is consistent with findings reported by Rahil et al. [13]. However, no significant association between sex and severity was observed, suggesting that gender may not influence disease progression. The majority of patients were elderly, with a mean age of 58.94 years. Aging is known to impair water and electrolyte homeostasis, increasing susceptibility to hyponatremia [14]. Similar findings have been reported in previous studies [15,16]. Vomiting (28%) and confusion (26%) were the most common presenting symptoms. Notably, confusion was significantly associated with severe hyponatremia (p<0.001), consistent with the known neurological manifestations of acute sodium decline [5,6]. CNS involvement was observed in 61% of patients, similar to findings reported by Rao et al. [17]. Euvolemic hyponatremia was the most common type observed, accounting for 50% of cases. SIADH was identified as the leading cause (46%), consistent with earlier studies [8,18]. The strong association between SIADH and euvolemic hyponatremia was statistically significant (p<0.001).

Chart 1: Causes of SIADH in the Study Group (n = 46)

A key finding of this study is the predominance of infection-related SIADH, particularly tuberculosis (57.7%). Tuberculosis is a well-recognized cause of hyponatremia through mechanisms such as ectopic ADH secretion, adrenal involvement, and CNS infection [9,19,20]. Previous studies have also highlighted the association between tuberculosis and SIADH [21]. Other causes included renal dysfunction (13%), gastrointestinal losses (11%), cirrhosis (10%), drug-induced causes (10%), and cardiac failure (10%), reflecting the multifactorial nature of hyponatremia in critically ill patients [7,12]. The mortality in this study was 6%, which is comparable to other ICU-based studies like Padhi et al. [22]. Early recognition and targeted management may have contributed to improved outcomes.

CONCLUSION

Hyponatremia is a common and clinically significant electrolyte disorder in critically ill patients. It is not merely a biochemical abnormality but a marker of underlying disease severity and systemic dysfunction. It predominantly presents with neurological manifestations and is most commonly euvolemic in nature. SIADH is the leading cause, with infections—especially tuberculosis—playing a major role in developing countries. Early diagnosis, careful evaluation of etiology, and appropriate management are essential to reduce morbidity and mortality.

ACKNOWLEDGEMENT

The authors acknowledge the support of the Department of Medicine and MICU staff of our institution. The authors also wish to thank the VAssist Research team (www.thevassist,com) for their contribution in manuscript editing and submission process.

Conflict of Interest: None

Source of Funding: Nil

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