Quantitative and functional changes in platelets and fibrinogen following cardiopulmonary by-pass in children

Abstract

Introduction: Cardiopulmonary bypass (CPB) causes coagulopathy, increasing the risk of postoperative bleeding and mortality. The underlying causes of post-CPB coagulopathy and the factors associated with its occurrence are not yet fully understood. This study assesses platelet and fibrinogen concentration and function following CPB in children with congenital heart diseases (CHD).

Methods: We analyzed prospective data from 104 patients aged 0-16 years who underwent CPB surgery for CHD. Blood samples were collected before surgery and within 30 min of CPB completion. In addition to usual coagulation tests, functional analyses were performed using point of care systems with thromboelastometry and impedance aggregometry.

Results: Platelet count, fibrinogen concentration, and platelet and fibrinogen activities significantly decreased after CPB. The duration of CPB was directly associated with a reduction in platelet count and fibrinogen level (r = -0.38, p < 0.001; r = -0.21, p = 0.03, respectively), but not with their measured activity. Postoperative percentages of baseline values for platelet count (58.36% [43.34-74.44] vs. 37.44% [29.81-54.17], p < 0.001) and fibrinogen concentration (73.68% [66.67-82.35] vs. 65.22% [57.89-70.83], p < 0.001) were significantly higher in patients who did not experience hypothermia during surgery. Age was inversely associated with the decrease in platelet count (r = 0.63, p < 0.001), TRAPTEM AUC (r = 0.43, p < 0.001), fibrinogen concentration (r = 0.44, p < 0.001) and FIBTEM MCF (r = 0.57, p < 0.001).

Conclusion: Post-CPB coagulopathy is multifactorial and not solely attributed to hemodilution. It also involves functional changes in coagulation cascade components, which can be demonstrated by thromboelastometry and impedance aggregometry. Young children, patients requiring prolonged CPB surgery, or those experiencing hypothermia are particularly affected.

Keywords: ROTEM; cardiopulmonary bypass; children; coagulopathy; congenital heart disease; fibrinogen; platelet.

Figure 1

Patients inclusion flow diagram.

Figure 2

Linear regression (95% CI) and Spearman's correlations between CPB duration and platelet count (A) and fibrinogen level (B) after CPB. Post-CPB fibrinogen level and platelet count are expressed in percentage of baseline values. R, rho; CPB, cardiopulmonary bypass.

Figure 3

Platelet count, fibrinogen level, FIBTEM MCF and TRAPTEM AUC after cardiopulmonary bypass with normothermia or hypothermia (<35°C). Post-CPB values are expressed in percentage of baseline values. TRAPTEM, impedance aggregometry test, platelets activated with thrombin receptor activating peptide (TRAP); AUC, area under the curve; FIBTEM, thromboelastometry test, coagulation is activated by tissue factor and platelets are blocked with cytochalasin; MCF, maximum clot firmness.

Figure 4

Linear regression (95% CI) and Spearman's correlations between patients’ age and platelet count (A), TRAPTEM AUC (B) fibrinogen level (C) and FIBTEM MCF (D) after CPB. Post-CPB values are expressed in percentage of baseline values. R, rho; TRAPTEM, impedance aggregometry test, platelets activated with thrombin receptor activating peptide (TRAP); AUC, area under the curve; FIBTEM, thromboelastometry test, coagulation is activated by tissue factor and platelets are blocked with cytochalasin; MCF, maximum clot firmness.