Calcium Homeostasis Disturbances After Cardiac Surgery: Revisiting Hypocalcaemia and Its Clinical Consequences

Abstract

Background: Calcium homeostasis is an important factor in myocardial contractility, vascular tone, electrophysiological stability and coagulation. Hypocalcaemia is an underexplored disruption of taking place after cardiac surgery, especially cardiopulmonary bypass (CPB), despite routine perioperative biochemical monitoring. There has been an emerging evidence that postoperative calcium imbalance is evidence of complex regulatory derailment, and not of dilutional effects. It is an integrative review of biochemical, endocrine, and clinical pathways that cause post-cardiac-surgery hypocalcaemia.

Methods: Systematic search PRISMA 2020 was used to conduct a search in PubMed, Scopus, Web of Science and Embase (2000-2025). A total of 62 eligible studies were involved. Appraisal was done based on the Newcastle Ottawa Scale, Cochrane RoB-2 and CASP. They were mapped by developing a three-layer integrative synthesis to measure the biochemical-regulatory disturbances, clinical manifestations and therapeutic responses.

Findings: The findings reveal that CPB triggers a multifactorial impairment of Ca–PTH-vitamin D axis by haemodilution, citrate chelation, parathyroid inhibition by hypothermia, inflammation cytokine storm, and magnesium-dependent PTH loss of control. The peak of ionized calcium is generally attained after 1224 hours after surgery, with inconsistent and usually attenuated rise of PTH. The hypocalcaemic condition is enhanced by concomitant magnesium depletion and hyperphosphataemia. At the clinical level, the disturbances are observed as reduced myocardial contractility, vasoplegia, QT prolongation, arrhythmogenesis, neuromuscular irritability, and increased ICU-length of stay. The presence of a distinct postoperative phenotype was determined, and the cluster of hypocalcaemia, hypomagnesemia, and suppressed PTH is the most dangerous.

Conclusion: Post-cardiac-surgery hypocalcaemia is not a biochemical abnormality but a hormone-electrolyte imbalance. A combination of ionized calcium and magnesium as well as PTH courses and electrophysiology measures like QT intervals are used to give a predictive model of early detection of vulnerable patients. Magnesium-first correction, PTH-responsive regimens of supplementation, and real-time calcium assessment can be possible ways to enhance the recovery of haemodynamics and reduce the number of postoperative complications. The next generation of research should consider endocrine-guided guidelines and machine-learning algorithms to handle calcium individually.