Hypomagnesemia: An Overlooked Cause of Delirium and Cardiac Complications in an Elderly Patient

Abstract 

Delirium is a frequent complication in elderly patients and is often multifactorial, with electrolyte imbalances representing a major contributor. While sodium, potassium, and calcium disorders are commonly evaluated, hypomagnesemia is an overlooked but clinically significant cause of both neurological and cardiac manifestations. Magnesium is essential for neuronal stability, neurotransmitter regulation, and calcium channel modulation. Its deficiency can lead to neuropsychiatric symptoms, arrhythmias, and myocardial injury. We report the case of an 81-year-old woman who presented with acute confusion following several days of diarrhea. Investigations revealed severe hypomagnesemia (serum magnesium: 0.3 mmol/L), ST-segment depression, prolonged QT interval, and elevated troponin levels. She was managed as a type 2 myocardial infarction in the context of sepsis and electrolyte imbalance. Prompt intravenous magnesium replacement resulted in rapid resolution of delirium and cognitive improvement. This case underscores the importance of routine assessment of magnesium levels in elderly patients presenting with delirium, especially in the presence of gastrointestinal losses or cardiovascular comorbidities, and highlights the reversibility of neurological and cardiac complications when deficiency is corrected. 

Introduction 

Delirium is an acute, fluctuating syndrome of encephalopathy causing disturbed consciousness, attention, cognition, and perception. It is a common and often multifactorial syndrome in older adults, associated with increased morbidity, prolonged hospitalization, and poor outcomes. The pathophysiology is complex, but delirium frequently arises from acute medical conditions such as infection, systemic inflammation, metabolic derangements, or electrolyte imbalance. While sodium, potassium, and calcium abnormalities are routinely evaluated, magnesium deficiency is frequently overlooked despite its profound neurological and cardiovascular effects. Magnesium is the second most abundant intracellular cation and plays a critical role in neuronal excitability, neurotransmitter release, synaptic plasticity, and ion channel modulation. Deficiency may result in a wide spectrum of neurological and cardiovascular manifestations, including confusion, seizures, arrhythmias, and myocardial injury. Recent evidence has shown that hypomagnesemia is independently associated with incident delirium in hospitalized older persons, suggesting it may be an under-recognized but clinically relevant risk factor. The interface between dementia and delirium adds diagnostic complexity, as acute cognitive fluctuations may be misattributed to the progression of baseline cognitive impairment. Magnesium deficiency is common in older adults, often due to poor intake, diarrheal loss, renal wasting, or the effect of medications such as diuretics and proton pump inhibitors. Despite its prevalence, magnesium is less frequently checked in standard panels, leading to missed diagnoses. Given its reversible nature, early recognition and treatment of hypomagnesemia can significantly improve outcomes in patients presenting with delirium and cardiovascular complications. We present the case of an elderly woman who developed delirium, sepsis, and myocardial injury in the context of profound hypomagnesemia, highlighting the importance of early recognition and correction of this reversible electrolyte disturbance. 

Discussion 

This case illustrates the under-recognized role of hypomagnesemia in precipitating delirium and myocardial injury in elderly patients. Electrolyte disturbances, particularly hypomagnesemia, are increasingly recognized as modifiable risk factors for delirium. In hospitalized older adults, low magnesium levels have been independently associated with incident delirium. Magnesium deficiency is often multifactorial, commonly resulting from gastrointestinal losses, renal wasting, or medications such as diuretics and proton pump inhibitors. In this patient, several days of diarrhea likely contributed to severe depletion. Neurologically, magnesium deficiency disrupts synaptic transmission, increases neuronal excitability, and manifests as confusion, agitation, or seizures. From a cardiovascular perspective, magnesium deficiency prolongs repolarization, predisposes to arrhythmias, and may exacerbate myocardial ischemia. Observational studies have linked low serum magnesium with adverse electrocardiographic changes, increased mortality, and coronary artery disease risk. In this patient, profound hypomagnesemia contributed to type 2 myocardial injury in the setting of sepsis. Vitamin D deficiency may have also contributed to delirium in this case. Evidence suggests that progressively lower vitamin D levels are associated with an increased risk of incident hospital-diagnosed delirium. This underscores the importance of monitoring both vitamin D status and electrolyte balance in older patients presenting with acute cognitive changes. Importantly, correction of hypomagnesemia leads to rapid improvement, as seen here. Clinicians should be aware that hypokalemia and hypocalcemia may be refractory to correction until magnesium is replaced. Despite its clinical importance, magnesium disturbance is frequently underappreciated as a potential contributor to delirium, particularly in frail older patients with multiple comorbidities. Its contribution to both cognitive disturbance and cardiovascular instability reinforces the need for routine assessment. Broader awareness among clinicians could support earlier intervention and improved patient outcomes. 

Conclusions 

Hypomagnesemia is a reversible but frequently overlooked cause of delirium and myocardial injury in elderly patients. This case highlights the unique presentation of severe hypomagnesemia with concurrent neuropsychiatric symptoms and cardiac abnormalities. Early recognition and correction can prevent complications, restore baseline cognitive function, and reduce cardiovascular risk. Magnesium assessment should be included in the routine evaluation of elderly patients presenting with delirium, especially in the presence of gastrointestinal disturbances, frailty, or cardiac comorbidities.