Annexin A2 Loss After Cardiopulmonary Bypass and Development of Acute Postoperative Respiratory Dysfunction in Children

Abstract

The primary objective of this study was to determine whether expression of the multifunctional and adherens junction-regulating protein, annexin A2 (A2), is altered following cardiopulmonary bypass (CPB). A secondary objective was to determine whether depletion of A2 is associated with post-CPB organ dysfunction in children.

Design: In a prospective, observational study conducted over a 1-year period in children undergoing cardiac surgery requiring CPB, we analyzed A2 expression in peripheral blood mononuclear cells at different time points. We then assessed the relationship of A2 expression with organ function at each time point in the early postoperative period.

Setting: Twenty-three-bed mixed PICU in a tertiary academic center.

Participants: Patients 1 month to 18 years old undergoing cardiac surgery requiring CPB.

Mean outcome measurements and results: We analyzed A2 expression in 22 enrolled subjects (n = 9, 1-23 mo old; n = 13, 2-18 yr old) and found a proteolysis-mediated decline in intact A2 immediately after bypass (p = 0.0009), reaching a median of 4% of baseline at 6 hours after bypass (p < 0.0001), and recovery by postoperative day 1. The degree of A2 depletion immediately after bypass in 1-23-month-olds correlated strongly with the extent of organ dysfunction, as measured by PICU admission Vasoactive-Ventilation-Renal (p = 0.004) and PEdiatric Logistic Organ Dysfunction-2 (p = 0.039) scores on postoperative day 1. A2 depletion immediately after bypass also correlated with more protracted requirement for both respiratory support (p = 0.007) and invasive ventilation (p = 0.013) in the 1-23-month-olds.

Conclusions and relevance: The degree of depletion of A2 following CPB correlates with more severe organ dysfunction, especially acute respiratory compromise in children under 2 years. These findings suggest that loss of A2 may contribute to pulmonary microvascular leak in young children following CPB.

Keywords: annexin A2; cardiopulmonary bypass; endothelium; hypoxia; inflammation; pulmonary edema.

Figure 1.

Proteolytic degradation of annexin A2 (A2) following cardiopulmonary bypass (CPB). A, Representative immunoblots of peripheral blood mononuclear cell (PBMC) A2, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and annexin A5 (A5) over a range of time points in two different subjects (left and right). PBMC lysates were probed with immunoglobulin G directed against A2, GAPDH, and A5. B, Levels of intact A2 following CPB as quantified by densitometry. A2 levels (n = 22) are shown relative to each subject’s baseline value, set at 1. The data were analyzed using a one-sampled two-tailed Wilcoxon signed-rank test comparing median (median with interquartile range) ratios of intact A2 to baseline for statistical significance (GraphPad Prism v. 9.0.2 Software for Windows, San Diego, CA). 6hr p CPB = 6 hr post-cardiopulmonary bypass, Imm p CPB = immediately post-cardiopulmonary bypass, NS = not significant, POD1 = postoperative day 1.

Figure 2.

Annexin A2 (A2) levels post-cardiopulmonary bypass and organ dysfunction scores in subjects 1–23 mo old. A, PEdiatric Logistic Organ Dysfunction-2 (PELOD-2) score (16) on postoperative day 1 (POD 1) as a function of A2 level (n = 9). B, Postoperative Vasoactive-Ventilation-Renal (VVR) score (15) upon admission to the PICU as a function of A2 level (n = 9). Statistical significance was evaluated using the two-tailed Spearman (Rho, p) test (GraphPad Prism v. 9.0.2 Software for Windows, San Diego, CA). GAPDH = glyceraldehyde-3-phosphate dehydrogenase, Imm p CPB = immediately post-cardiopulmonary bypass.

Figure 3.

Annexin A2 (A2) levels and indices of respiratory dysfunction immediately after cardiopulmonary bypass in 1–23-mo-old subjects. Total duration of respiratory support (n = 9) (A), duration of mechanical ventilation (n = 9) (B), worst oxygenation index (OI) (20) on the ventilator (n = 5) (C), and oxygen saturation/Fio₂ (SF) ratio (21) off positive pressure ventilation (PPV) (n = 7) (D) were compared with intact A2. Two-tailed Spearman correlation analysis (Rho, p) was used to evaluate statistical significance (GraphPad Prism v. 9.0.2 Software for Windows, San Diego, CA). GAPDH = glyceraldehyde-3-phosphate dehydrogenase, Imm p CPB = immediately post-cardiopulmonary bypass.