The Relationship Between Preoperative Serum Ionized Calcium, Vitamin D, and Postoperative Bleeding After Major Cardiac Surgery

Objective: The role of calcium in coagulation homeostasis is well established, although the relationship between calcium levels and postoperative bleeding in major cardiac surgery remains largely unexplored. Methods: This retrospective, single-center study investigated the correlations between ionized calcium levels measured at several timepoints: preoperatively (after induction of anesthesia), immediately after cardiopulmonary bypass (CPB) weaning, on the first postoperative day measured three times at 8 h intervals, preoperative vitamin D values, and several significant bleeding outcomes. These outcomes included the volume of blood in the drainage bag (measured in milliliters on days 1 and 2), the need for surgical or medical hemostasis, the requirement for blood transfusion (red blood cells, fresh frozen plasma, or platelets), and the occurrence of extracardiac hemorrhagic complications. A multivariable logistic regression analysis was performed, with a two-sided p-value of <0.00625 considered significant after applying Bonferroni correction. Results: The study included 83 patients with a mean age of 64.9 ± 8.5 years, with 49 (59%) being male. The most common procedures were aortic valve replacement (26 patients, 31%) and coronary artery bypass grafting (26 patients, 31%). The multivariable regression analysis demonstrated a trend toward an association between low levels of preoperative calcium and increased bleeding volume immediately after CBP and on the first day after the intervention (r = 0.30; p = 0.08 for day 1 and r = 0.24; p = 0.03 for day 2). Similar trends were observed for the association between low levels of preoperative calcium, use of medical hemostasis (r = 0.30; p = 0.009), and red blood cell transfusion (r = 0.24; p = 0.03). Additionally, we observed a trend towards a positive correlation between lower serum vitamin D levels and increased postoperative blood loss on both day 1 (r = 0.32; p = 0.07) and day 2 (r = 0.29; p = 0.04). The subgroup analysis of valve procedures vs. coronary procedures showed no statistically difference between preoperative ionized calcium levels, postoperative bleeding (289 27 vs. 283 mL, p = 0.87), the need for surgical hemostasis (p = 0.5), or blood transfusion requirement (p = 0.57). Conclusions: In our study, preoperative calcium levels were consistently associated with increased bleeding after major cardiac surgery. Post-CPB ionized calcium levels did not influence bleeding outcomes. The role of calcium in coagulation homeostasis during major cardiac surgery warrants further research, ideally with more robust data, as our study’s small sample limits robust evidence. Further larger studies will conclude on the importance of calcium levels in cardiac surgery related to hemostasis and bleeding outcomes. Lower preoperative ionized calcium and vitamin D levels showed exploratory associations with increased bleeding-related outcomes following major cardiac surgery. These findings are hypothesis-generating, and larger prospective studies are needed to confirm these potential relationships and clarify their clinical implications.