Higher Calcium Repletion After Neonatal Cardiac Surgery Is Associated With Worse Clinical Outcomes

Introduction: Calcium is essential for cardiac function and hypocalcemia is common in neonates undergoing cardiac surgery (CS). Repletion strategies vary across institutions; our protocol boluses calcium chloride (CaCl) for ionized calcium (iCal) < 4.8 mg/dL. We hypothesize that greater CaCl repletion mitigates low cardiac output syndrome (LCOS), reduces fluid resuscitation, improves fluid balance and clinical outcomes. Our aim is to evaluate relationships of CaCl, fluid status, and outcomes.


Methods: We retrospectively reviewed neonates ( < 30 days) undergoing CS with CPB July 2022-Sept 2024 at our university hospital. Exclusion criteria: death, ECMO, or CaCl infusion. Data collected 0-72 hours post-op: demographics, cardiac diagnosis, procedures, STAT category, iCal levels, total CaCl administered, transfusions, daily fluid balance/boluses, vasoactive infusion scores (VIS), diuretic use. Clinical outcomes included: infection, thrombosis, acute kidney injury [AKI], duration of ventilation, ICU stay, and hospitalization. Subjects were grouped into quartiles based on total CaCl (mg/kg) received and net fluid status (positive v. negative) at 72 hours.


Results: Of 82 neonates, 8 were excluded (2 deaths, 6 ECMO), 74 were analyzed (median 11 days [IQR 7–15.75], weight 3.3 ± 0.6 kg). 2 (2.7%) had VCFS; 71.6% were STAT category ≤3. CaCl totals (mg/kg): 199.5 [140.1–246.1], 120.5 [66.4–163.9], and 1.9 [0–3.6] by 24-hr interval. Cell saver was used in 86% (median 10.9 ml/kg), and 4.1% received RBC transfusion/day. Fluid boluses were median 0 [0–10] ml/kg. Peak VIS scores were:10, 8.5, and 7.5. Fluid balance by CaCl quartile ranged from –39.3 to +116.2 ml/kg (p=0.09). CaCl dose correlated with longer ventilation, ICU stay, and higher VIS (all p< 0.01). No differences were seen in thrombosis, CLABSI, AKI, or survival. At 72 hrs 57% had net positive fluid balance, which was associated with higher CaCl (p=0.01) and worse clinical outcomes (p < 0.01).


Conclusions: Contrary to our hypothesis, greater CaCl administration was associated with worse fluid balance, prolonged ventilation, vasoactive use and ICU stay, without observed benefit reducing LCOS or complications. These findings suggest lowering replacement thresholds may improve fluid status and clinical outcomes. Prospective studies are needed to confirm these results.