Cardiopulmonary bypass elicits a prominent innate immune response in children with congenital heart disease

Neutrophil extracellular traps formation is associated with postoperative complications in neonates and infants undergoing congenital cardiac surgery

Pediatric patients with congenital heart diseases (CHD) often undergo surgical repair on cardiopulmonary bypass (CPB). Despite a significant medical and surgical improvement, the mortality of neonates and infants remains high. Damage-associated molecular patterns (DAMPs) are endogenous molecules released from injured/damaged tissues as danger signals. We examined 101 pediatric patients who underwent congenital cardiac surgery on CPB. The mortality rate was 4.0%, and the complication rate was 31.6%. We found that neonates/infants experienced multiple complications most, consistent with the previous knowledge. Neonates and infants in the complication group had received more transfusion intraoperatively than the non-complication arm with lower maximum amplitude (MA) on rewarming CPB thromboelastography (TEG). Despite TEG profiles were comparable at ICU admission between the two groups, the complication arm had higher postoperative chest tube output, requiring more blood transfusion. The complication group showed greater neutrophil extracellular traps (NETs) formation at the end of CPB and postoperatively. Plasma histones and high mobility group box 1 (HMGB1) levels were significantly higher in the complication arm. Both induced NETs in vitro and in vivo . As histones and HMGB1 target Toll-like receptor (TLR)2 and TLR4, their mRNA expression in neutrophils was upregulated in the complication arm. Taken together, NETs play a major role in postoperative complication in pediatric cardiac surgery and would be considered a target for intervention.

Key points

Neonates and infants showed highest postoperative complications with more upregulation of inflammatory transcriptomes of neutrophils.Neonates and infants with organ dysfunction had more NETs formation with higher plasma histones and HMGB1 levels.

Biomarker-based risk model to predict persistent multiple organ dysfunctions after congenital heart surgery: a prospective observational cohort study

BACKGROUND

Multiple organ dysfunction syndrome (MODS) is an important cause of post-operative morbidity and mortality for children undergoing cardiac surgery requiring cardiopulmonary bypass (CPB). Dysregulated inflammation is widely regarded as a key contributor to bypass-related MODS pathobiology, with considerable overlap of pathways associated with septic shock. The pediatric sepsis biomarker risk model (PERSEVERE) is comprised of seven protein biomarkers of inflammation and reliably predicts baseline risk of mortality and organ dysfunction among critically ill children with septic shock. We aimed to determine if PERSEVERE biomarkers and clinical data could be combined to derive a new model to assess the risk of persistent CPB-related MODS in the early post-operative period.

METHODS

This study included 306 patients < 18 years old admitted to a pediatric cardiac ICU after surgery requiring cardiopulmonary bypass (CPB) for congenital heart disease. Persistent MODS, defined as dysfunction of two or more organ systems on postoperative day 5, was the primary outcome. PERSEVERE biomarkers were collected 4 and 12 h after CPB. Classification and regression tree methodology were used to derive a model to assess the risk of persistent MODS.

RESULTS

The optimal model containing interleukin-8 (IL-8), chemokine ligand 3 (CCL3), and age as predictor variables had an area under the receiver operating characteristic curve (AUROC) of 0.86 (0.81-0.91) for differentiating those with or without persistent MODS and a negative predictive value of 99% (95-100). Ten-fold cross-validation of the model yielded a corrected AUROC of 0.75 (0.68-0.84).

CONCLUSIONS

We present a novel risk prediction model to assess the risk for development of multiple organ dysfunction after pediatric cardiac surgery requiring CPB. Pending prospective validation, our model may facilitate identification of a high-risk cohort to direct interventions and studies aimed at improving outcomes via mitigation of post-operative organ dysfunction.

Lung injury following cardiopulmonary bypass: a clinical update

INTRODUCTION

Cardiopulmonary bypass (CPB) is an integral component of cardiac surgery; however, one of its most critical complications is acute lung injury induced by multiple factors including systemic inflammatory response.

AREAS COVERED

The objective of this review is to investigate the multiple factors that can lead to CPB-induced lung injury. These include contact of blood components with the artificial surface of the CPB circuit, local and systemic inflammatory response syndrome (SIRS), lung ischemia/re-perfusion injury, arrest of ventilation, and circulating endotoxins. We also focus on possible interventions to curtail the negative impact of CPB, such as off-pump surgery, impregnation of the circuit with less biologically active substances, leukocyte depletion filters and ultrafiltration, and pharmacological agents such as steroids and aprotinin.

EXPERT OPINION

Although many aspects of CPB are proposed to contribute to lung injury, its overall role is still not clear. Multiple interventions have been introduced to reduce the risk of pulmonary dysfunction, with many of these interventions having shown promising results, significantly attenuating inflammatory mediators and improving post-operative outcome. However, since lung injury is multifactorial and affected by inextricably linked components, multiple interventions tackling each of them is required.

Serum TNF-α levels in children with congenital heart disease undergoing cardiopulmonary bypass: A cohort study in China and a meta-analysis of the published literature

OBJECTIVE

To investigate the changes in tumor necrosis factor alpha (TNF-α) serum levels after cardiopulmonary bypass (CPB) in children with congenital heart disease (CHD), followed by a meta-analysis to analyze the clinical value of TNF-α in CPB.

METHODS

Our cohort study enrolled 67 CHD children, assigned into off-pump group (n=32) and CPB group (n=35). The TNF-α serum levels in two groups were detected by ELISA before the operation (T1), at the end of the operation (0 hour, T2), and after 24 hours of the operation (T3). For meta-analysis, literature search was conducted to identify published case-control articles about the changes of TNF-α serum levels with CPB of CHD.

RESULTS

The TNF-α levels in CPB group were lower than that in the off-pump group at T3 (P=.006). TNF-α level at T3 was significantly lower than that at T1 and T2 (all P<.05). Meta-analysis results further confirmed that the TNF-α levels of CHD children were dramatically decreased at T3 as compared to that at T1 and T2 (both P<.001).

CONCLUSION

The TNF-α serum levels showed a transient and dramatic decline after 24 hours of CPB, and it may act as an important biological indicator for monitoring the efficacy of CPB in CHD children.

Inflammatory response after neonatal cardiac surgery and its relationship to clinical outcomes

BACKGROUND

Cardiac surgery in infants results in a profound inflammatory response secondary to cardiopulmonary bypass (CPB) and the need for blood products. It is not clear how this inflammatory response modulates postoperative course or whether quantification of proinflammatory cytokines can aid with risk stratification. In this study, we prospectively assessed a panel of candidate markers to determine the time course for inflammation and the association of specific markers with clinical outcomes defined as intensive care unit length of stay (LOS).

METHODS

We obtained preoperative blood samples from 92 neonates undergoing surgery with CPB and then serially for 5 days after surgery. Numerous interleukins were assayed along with tumor necrosis factor (TNF)-alpha and interferon (INF)-gamma. The most common surgical procedures were arterial switch procedure (n = 35) and Norwood operation (n = 34). Multivariate analysis was performed to determine if inflammatory mediators could independently predict prolonged intensive care unit LOS.

RESULTS

Compared with the presurgery level, there were statistically significant increases (p < 0.005) for 8 out of 11 inflammatory markers: INF-gamma, interleukin (IL)-10, IL-13, IL-2, IL-5, IL-8, TNF-alpha, and IL-6 after surgery. The only cytokine on the first postoperative day that was independently associated with prolonged length of stay was IL-8 (p = 0.002). Cytokine values measured on postoperative day 3 were most valuable in predicting prolonged LOS. A model that included use of circulatory arrest, and day 3 measures of IL-6 and IL-8 yielded an area under of the curve of 0.88 (95% confidence interval 0.79 to 0.96) for predicting a prolonged LOS.

CONCLUSIONS

In summary, neonatal heart surgery for complex lesions elicits a broad inflammatory response. This early inflammatory response appears nonspecific and did not predict clinical course. Persistence of specific inflammatory mediators on the third day after surgery, however, provided important prognostic information. As such, select cytokines may serve as valuable biomarkers in this population. Whether strategies targeting specific cytokines can alter clinical course is not known.

Triiodothyronine supplementation and cytokines during cardiopulmonary bypass in infants and children

OBJECTIVE

The Triiodothyronine Supplementation in Infants and Children Undergoing Cardiopulmonary Bypass (TRICC) study demonstrated a shortened time to extubation in children younger than 5 months old undergoing cardiopulmonary bypass for congenital heart surgery with triiodothyronine supplementation. Cardiopulmonary bypass precipitates a systemic inflammatory response that affects recovery, and triiodothyronine is related to cytokine mediators of inflammation. We sought to investigate the preoperative cytokine levels by age and relationship to the triiodothyronine levels and to examine the effect of the cytokine levels on the time to extubation.

METHODS

We measured 6 cytokines at preoperative time 0 and 6 and 24 hours after crossclamp removal in 76 subjects.

RESULTS

The preoperative cytokine levels were related to both the triiodothyronine levels and the patient age. The postoperative cytokine levels were predictive of the triiodothyronine levels at 6, 12, 24, and 72 hours. Preoperative CCL4 was associated with an increased chance of early extubation. Inclusion of the cytokines did not change the relationship of triiodothyronine to the time to extubation, and the postoperative course of interleukin-6 was independently associated with a decreased chance of early extubation.

CONCLUSIONS

The preoperative and postoperative cytokine levels, in particular, interleukin-1β, showed complex time-dependent relationships with triiodothyronine. The data suggest that cytokine-mediated suppression of triiodothyronine plays an important role in determining the clinical outcome after cardiopulmonary bypass.