Association Between Ionized Calcium Concentrations During Weaning From Cardiopulmonary Bypass and Postoperative Low Cardiac Output Syndrome: A Retrospective Cohort Study
Abstract
BACKGROUND:
Weaning from cardiopulmonary bypass (CPB) is a critical step in cardiovascular surgery. Although ionized calcium (iCa) plays a crucial role in myocardial contractility, and hypocalcemia commonly occurs during CPB, only a few studies have examined the association between iCa levels and clinical outcomes following CPB. This study aimed to evaluate whether iCa levels during CPB weaning were associated with clinical outcomes.
METHODS:
This multicenter retrospective study was conducted in three Japanese hospitals. Adult patients (aged ≥ 18 years) who underwent cardiovascular surgery with CPB were included. Exposure was defined as iCa concentration during CPB weaning. The primary outcome was low cardiac output syndrome (LCOS) on ICU admission, which was determined when at least one of the following three criteria was met: (i) postoperative MCS use, (ii) cardiac index <2.0 L min-1 m-2, (iii) use of two or more inotropes (dopamine, dobutamine, adrenaline, and milrinone) at 1 hour following the end of the surgery. The patients were divided into four groups based on iCa quartile: low iCa group (iCa ≤ 1.05 mmol L-1), standard iCa group (1.05 < iCa ≤ 1.13 mmol L-1), moderate-high iCa group (1.13 < iCa ≤1.24 mmol L-1), and high iCa group (iCa > 1.24 mmol L-1). Multivariate logistic regression analyses were performed to calculate adjusted odds ratios (ORs) with 95% confidence intervals (CIs).
RESULTS:
In total, 2,382 patients were included between September 2012 and December 2022. The median age was 70 years (IQR: 60–76 years), and 1,464 patients (61%) were men. The overall LCOS incidence was 501 cases (21%). Compared to the standard iCa group, the adjusted ORs for LCOS were 1.45 (95% CI, 1.06 to 1.99, P = .020) in the low iCa group, 1.42 (95% CI, 1.01 to 2.00, P = .046) in the moderate-high iCa group, and 1.36 (95% CI, 0.95 to 1.94, P = .094) in the high iCa group.
CONCLUSIONS:
Both low and high iCa levels at CPB weaning were associated with an increased risk of postoperative LCOS in patients undergoing cardiovascular surgery.