Calcium Homeostasis in Critical Illness

The regulation of calcium is fundamental to cellular function and systemic physiology. In critical illness, disturbances in calcium homeostasis are pervasive, reflecting complex interactions between organ dysfunction, inflammatory mediators and therapeutic interventions. Ionised calcium, the biologically active fraction, is tightly controlled by parathyroid hormone, vitamin D metabolites and renal excretion. However, sepsis, trauma and organ failure disrupt this balance through alterations in binding proteins, shifts in acid–base status and direct effects on cellular calcium channels. Hypocalcaemia occurs in the majority of intensive care patients and has been associated with impaired cardiovascular performance, coagulopathy and immune dysfunction. Conversely, hypercalcaemia, though less common, may exacerbate arrhythmias and neurologic complications. Emerging evidence highlights a U-shaped relationship between serum calcium levels and mortality, suggesting that both extremes can be deleterious. Understanding the mechanisms driving calcium derangements and their prognostic significance is essential for refining monitoring strategies and guiding potential interventions. This overview considers recent insights into the pathophysiology, prognostic implications and therapeutic challenges associated with calcium homeostasis in the critically ill.

Research from Nature Portfolio

Recent investigations have elucidated the prognostic value of admission calcium status in specific critical illness cohorts. A large retrospective cohort study of paediatric patients with severe pneumonia demonstrated that each 1 mmol/L increase in serum calcium upon intensive care admission was linked to a 24 per cent reduction in mortality risk. Patients in the highest calcium tertile exhibited a 63 per cent lower hazard of death compared with those in the lowest tertile. These findings held true across diverse subgroups, underscoring serum calcium as a robust early prognostic marker. The study further illustrated that cumulative hazard curves differed significantly according to baseline calcium levels, supporting the integration of calcium assessment into early risk stratification models for critically ill children.

Calcium Homeostasis in Critical Illness publication trend

The graph below shows the total number of articles in calcium homeostasis in critical illness across all publications each year (not limited to Nature Index journals).

Technical terms

Ionised calcium: The physiologically active fraction of serum calcium unbound to proteins or anions.

Total calcium: The sum of ionised, protein-bound and complexed calcium in plasma.

Hypocalcaemia: A decrease in serum ionised calcium below the normal reference range, often defined as <1.1 mmol/L.

Prognostic marker: A measurable clinical or laboratory parameter that forecasts patient outcomes.

U-shaped relationship: A pattern in which both low and high values of a variable are associated with increased risk, with an optimal mid-range.

References

1. Serum calcium and mortality in pediatric pneumonia patients admitted to the PICU: a retrospective cohort study. Scientific Reports (2024).
2. Management of hypocalcaemia in the critically ill. Current Opinion in Critical Care (2023).
3. The Prognostic Value of Serum Calcium Levels in Elderly Dilated Cardiomyopathy Patients. Global Heart (2024).
4. Assessment and clinical course of hypocalcemia in critical illness. Critical Care (2013).