European Journal of Cardiovascular Medicine

Electrolyte disturbances are among the most frequently encountered laboratory abnormalities in hospitalized patients and represent a significant, often under-recognized, contributor to morbidity, prolonged hospitalization, and mortality across virtually all medical specialties.(1) Sodium, potassium, and calcium are the principal electrolytes routinely assessed in clinical practice, each governing fundamental physiological processes including cellular osmotic balance, neuromuscular excitability, and cardiac conduction; derangement of any of these parameters, even when mild, can precipitate serious clinical consequences ranging from confusion and seizures to life-threatening cardiac arrhythmias.(2)

The reported prevalence of electrolyte disturbances varies considerably depending on the population studied and the clinical setting. In a cohort of patients admitted to a general internal medicine department, electrolyte abnormalities were identified in 64% of patients, with hyponatremia the most frequent finding at 40.6% of abnormal cases, followed by hypokalemia at 28.1%.(3) Similarly, a study of hospitalized patients in Iraq spanning intensive care, cardiac care, and respiratory care units found hyponatremia and hypokalemia to be consistently the most prevalent disturbances across all three settings, with significant variation in prevalence according to the type of unit.(4) Among critically ill medical intensive care unit patients, hyponatremia was again the most common disturbance, occurring in 34.4% of patients, followed closely by hypokalemia (29.0%) and hypocalcemia (26.7%), with nearly 44% of patients exhibiting two or more concurrent electrolyte abnormalities.(5) A large emergency department cohort similarly reported a high prevalence of glucose-corrected hyponatremia (24.6%), although the prevalence of hyperkalemia and hypernatremia was comparatively lower in that less acutely unwell population, illustrating how case-mix and acuity influence the observed pattern of disturbance.(6)

The clinical determinants underlying electrolyte disturbances in hospitalized patients are well characterized and frequently overlapping. Diuretic therapy, particularly with thiazides, is a well-established cause of both hyponatremia and hypokalemia, while loop diuretics are more often implicated in hypernatremia and hypokalemia.(7) Chronic kidney disease independently predisposes patients to a broad spectrum of electrolyte and acid-base disturbances, including hyperkalemia, hyperphosphatemia, and impaired free water excretion leading to hyponatremia, as a consequence of progressively reduced nephron mass and impaired tubular regulatory capacity.(8) Sepsis and acute systemic illness can produce electrolyte derangement through a combination of mechanisms, including the syndrome of inappropriate antidiuretic hormone secretion, third-space fluid shifts, and impaired renal perfusion, while gastrointestinal fluid losses from vomiting or diarrhea commonly produce combined hypokalemia and metabolic derangement through direct electrolyte loss and secondary hyperaldosteronism.(9) Advanced age compounds these risks further, as older patients have reduced renal concentrating and diluting capacity, blunted thirst response, and a higher burden of comorbidity and polypharmacy, all of which increase susceptibility to electrolyte disturbance during acute illness.(10)

Importantly, electrolyte disturbances are not merely incidental laboratory findings but are independently associated with adverse clinical outcomes. A prospective study of acutely hospitalized elderly patients found that those with electrolyte imbalance at admission had significantly higher rates of acute kidney injury, longer hospital stays, and higher in-hospital mortality compared with those with normal electrolytes.(10) In a large cohort of medical intensive care unit patients, hypernatremia and hyperkalemia independently predicted mortality on multivariate analysis, and the presence of two or more concurrent electrolyte abnormalities was associated with significantly higher mortality and longer intensive care stay than the presence of a single abnormality.(5) These findings underscore that electrolyte disturbances, rather than representing a uniformly benign or easily reversible laboratory finding, may serve as an important marker of underlying disease severity and physiological reserve.

Given the considerable variation in reported prevalence across settings and the well-documented association between electrolyte disturbance and adverse outcomes, continued characterization of the pattern and determinants of electrolyte imbalance within specific hospital populations remains clinically valuable, both for guiding routine screening practices and for identifying patient subgroups warranting closer biochemical monitoring. The present study was therefore undertaken to determine the prevalence and pattern of electrolyte disturbances among patients admitted to a general medicine department and to identify the clinical determinants most strongly associated with their occurrence.

Study Design and Setting This cross-sectional observational study was conducted in the Department of General Medicine at a tertiary care teaching hospital over a period of twelve months. Institutional Ethics Committee approval was obtained prior to commencement of the study, and the study was conducted in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from all participants, or from their legally authorized representative where the patient was unable to consent due to clinical condition. Study Population A total of 350 consecutive adult patients aged 18 years and above admitted to the Department of General Medicine were enrolled. Inclusion criteria comprised all adult patients admitted under general medicine for whom a serum electrolyte panel (sodium, potassium, and calcium) was obtained within 24 hours of admission. Exclusion criteria included patients admitted primarily for elective procedures, patients transferred from another inpatient department after more than 48 hours of hospitalization (to avoid capturing hospital-acquired rather than admission electrolyte status), patients with known hemolyzed or otherwise technically inadequate admission samples, and patients who were discharged or who died within six hours of admission, precluding adequate clinical data collection. Data Collection and Operational Definitions Demographic data, primary admitting diagnosis, comorbidities, current medications (with particular attention to diuretic use), and clinical course were recorded using a structured proforma. Admission serum sodium, potassium, and total calcium (corrected for serum albumin using standard formulae) were obtained from the central clinical laboratory, which uses ion-selective electrode methodology for sodium and potassium and a colorimetric method for calcium, with the same analyzer and reference ranges used throughout the study period. Electrolyte imbalance was defined as the presence of any sodium, potassium, or calcium value outside the institutional reference range at admission (sodium 135–145 mmol/L; potassium 3.5–5.0 mmol/L; corrected calcium 8.5–10.5 mg/dL). Hyponatremia and hypernatremia, hypokalemia and hyperkalemia, and hypocalcemia and hypercalcemia were defined using these respective cut-offs. Determinants of interest, namely diuretic therapy at admission, documented chronic kidney disease, sepsis or severe infection, and gastrointestinal fluid loss (vomiting and/or diarrhea), were identified from admission clinical notes and medication charts. Length of stay was recorded in days, and in-hospital mortality was recorded as a binary outcome. Statistical Analysis Continuous variables were expressed as mean ± standard deviation, and categorical variables as frequencies and percentages. The prevalence of each electrolyte abnormality was calculated both as a percentage of the total study population and as a percentage of patients with any electrolyte abnormality. The association between electrolyte imbalance and each clinical determinant was assessed using the chi-square test. A two-tailed p-value of less than 0.05 was considered statistically significant. All statistical analyses were performed using standard statistical software.

A total of 350 patients admitted to the Department of General Medicine were enrolled during the study period. Baseline demographic and clinical characteristics of the study population are summarized in Table 1.

The study population had a mean age in the mid-fifties, with a slight male predominance, and two-fifths of patients were aged 65 years or older. Approximately one-quarter of patients were receiving diuretic therapy at the time of admission, and nearly one in five had known underlying chronic kidney disease.

Table 1. Baseline demographic and clinical characteristics of the study population

Values are expressed as mean ± standard deviation or number (percentage).

The distribution of primary admitting diagnoses among the study population is presented in Table 2.

Table 2. Primary admitting diagnosis of the study population

Diagnoses reflect the principal admitting condition as documented at the time of admission.

Cardiac disease, predominantly congestive heart failure, was the leading admitting diagnosis, followed closely by sepsis or severe infection and chronic kidney disease or renal failure. Gastrointestinal illness with vomiting or diarrhea accounted for a further notable proportion of admissions, consistent with its recognized role as a precipitant of acute electrolyte derangement.

The overall prevalence and pattern of specific electrolyte disturbances identified at admission are shown in Table 3.

Table 3. Pattern and prevalence of electrolyte disturbances at admission

Percentages in the third column are calculated as a proportion of the total study population (n = 350); percentages in the fourth column are calculated as a proportion of patients with any electrolyte abnormality (n = 224).

Almost two-thirds of the study population had at least one electrolyte abnormality at admission. Hyponatremia was the single most common disturbance, accounting for over a quarter of the entire cohort and affecting two-fifths of all patients with an electrolyte abnormality. Hypokalemia was the second most frequent disturbance. Hyperkalemia, hypernatremia, and calcium disturbances were each considerably less common. A substantial minority of patients exhibited two or more concurrent electrolyte abnormalities, most frequently the combination of hyponatremia with hypokalemia.

The association between electrolyte imbalance and key clinical determinants, including comorbidities and outcomes, is summarized in Table 4.

Table 4. Clinical determinants and outcomes associated with electrolyte imbalance

Percentages are row percentages, expressing the proportion of patients with each determinant who did or did not have electrolyte imbalance. p-values calculated using chi-square test.

Diuretic therapy, chronic kidney disease, age 65 years or older, sepsis or severe infection, and gastrointestinal fluid loss were each significantly more common among patients with electrolyte imbalance than among those with normal electrolytes. Patients with electrolyte imbalance also had a significantly higher proportion of prolonged hospital stay exceeding ten days and a significantly higher in-hospital mortality rate compared with patients with normal electrolyte status, supporting the clinical relevance of electrolyte disturbance as a marker of adverse outcome in this population.

The present study found that electrolyte disturbances were highly prevalent among hospitalized medical patients, affecting nearly two-thirds of the study population, with hyponatremia and hypokalemia emerging as the dominant abnormalities. This overall prevalence and pattern closely mirrors the findings of a recent observational study in an internal medicine department, which similarly reported electrolyte abnormalities in 64% of patients, with hyponatremia accounting for 40.6% of abnormal cases and hypokalemia for 28.1%, figures that are remarkably concordant with our own findings of 40.6% and 28.1% of abnormal cases, respectively.(3) This consistency across independent cohorts lends considerable support to the generalizability of hyponatremia and hypokalemia as the predominant electrolyte disturbances encountered in general medical inpatient populations.

Our finding that hyponatremia was the single most common electrolyte disturbance is consistent with a substantial body of literature spanning diverse clinical settings. Studies of intensive care, cardiac care, and respiratory care unit patients have similarly identified hyponatremia as the most prevalent sodium disturbance across all unit types, despite significant variation in prevalence between settings.(4) Likewise, a large cohort of medical intensive care unit patients found hyponatremia in over a third of patients, again establishing it as the leading individual electrolyte abnormality, ahead of hypokalemia and hypocalcemia.(5) The consistency of this finding across emergency department, general ward, and intensive care populations suggests that the pathophysiological drivers of hyponatremia in hospitalized patients—including diuretic use, heart failure, the syndrome of inappropriate antidiuretic hormone secretion, and hypovolemia—operate broadly across the spectrum of acute medical illness rather than being confined to any single disease process.(9)

The significant associations we observed between electrolyte imbalance and diuretic therapy, chronic kidney disease, advanced age, and sepsis are well supported by the existing literature on the determinants of electrolyte disturbance. Diuretic therapy has long been recognized as a major precipitant of both hyponatremia and hypokalemia, with thiazide diuretics particularly implicated in hyponatremia and both thiazide and loop diuretics contributing to hypokalemia.(7) Our finding that chronic kidney disease was strongly associated with electrolyte imbalance similarly aligns with the well-established pathophysiology of CKD, in which progressive loss of nephron mass impairs the kidney's capacity to regulate sodium, potassium, and calcium homeostasis, predisposing patients to a broad spectrum of disturbances including hyperkalemia and impaired free water excretion.(8) The strong association we found between advanced age and electrolyte imbalance is similarly consistent with a prospective study of acutely hospitalized elderly patients, which reported dysnatremia and dyskalemia prevalence of 28.4% and 14.7% respectively, with combined dysnatremia and dyskalemia occurring in a further 32.4% of patients, and demonstrated that affected patients had significantly higher rates of acute kidney injury, longer hospital stays, and higher in-hospital mortality.(10)

Our observation that electrolyte imbalance was significantly associated with both prolonged hospital stay and increased in-hospital mortality reinforces the growing recognition that electrolyte disturbances are not merely incidental biochemical findings but meaningful prognostic markers. This is consistent with data from a large emergency department cohort, in which increasing severity of electrolyte imbalance was associated with longer length of stay and increased in-hospital, 30-day, and one-year mortality, and with findings from medical intensive care unit patients, where the presence of two or more concurrent electrolyte abnormalities was independently associated with significantly higher mortality than the presence of a single abnormality.(5,6) It is worth noting, however, that not all studies have found electrolyte imbalance to be a robust independent predictor of outcome; a study of dengue-infected patients found that hyponatremia and hypokalemia at admission were not significantly associated with length of stay or mortality once other factors such as renal injury and diabetes were accounted for, suggesting that the prognostic significance of electrolyte disturbance may vary depending on the underlying acute illness and the extent to which the electrolyte abnormality reflects an independent pathological process versus a marker of overall disease severity.(11)

This study has several limitations. The cross-sectional design captures electrolyte status only at admission and does not characterize the evolution of disturbances or correction patterns during hospitalization. The single-centre design may limit generalizability to settings with different case-mix, prescribing patterns, or laboratory reference ranges. Magnesium and phosphate, both clinically relevant electrolytes, were not systematically assessed in this study and their inclusion may have altered the overall prevalence of detected abnormalities. Additionally, the determination of underlying etiology for each electrolyte disturbance relied on clinical documentation rather than a systematic diagnostic protocol, which may have introduced some degree of misclassification. Future prospective studies incorporating serial electrolyte measurements, a broader electrolyte panel, and systematic etiological work-up would help to further characterize the trajectory and clinical significance of electrolyte disturbances in this population.

Electrolyte disturbances are highly prevalent among hospitalized medical patients, affecting nearly two-thirds of the study population, with hyponatremia and hypokalemia emerging as the predominant abnormalities. Diuretic therapy, chronic kidney disease, advanced age, sepsis, and gastrointestinal fluid loss were each significantly associated with electrolyte imbalance, which was in turn associated with prolonged hospital stay and higher in-hospital mortality. These findings support the routine assessment of serum electrolytes at admission for all medical inpatients, with particular vigilance warranted in elderly patients, those on diuretic therapy, and those with underlying renal impairment or acute systemic illness, to enable timely identification and correction of these clinically significant abnormalities.

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