Disorders of calcium in the critically ill
Calcium is vitally important for normal cellular signalling and function. However, its toxicity necessitates that intracellular calcium concentration [Ca2+] be tightly regulated and compartmentalized. Evolutionary pressures have yielded several regulatory mechanisms to maintain intracellular and extracellular ionized calcium concentrations compatible with life. During periods of critical illness these process are commonly overwhelmed, and disorders of calcium homeostasis are highly prevalent among intensive care unit (ICU) patients. Indeed, hypocalcaemia occurs in up to 88% of critically-ill ICU patients suffering from trauma, sepsis, and burns. Contemporary evidence suggests that although hypocalcaemia may be associated with ICU mortality, it is not in the causal pathway. A systematic review concluded there are no data to support the routine parenteral administration of calcium in the management of asymptomatic critical illness-related hypocalcaemia. Asymptomatic hypocalcaemia of critical illness does not necessitate replacement. However, acute, symptomatic hypocalcaemia necessitates parenteral supplementation to prevent tetany, seizures, and cardiac arrhythmias