Effect of two different bypass techniques on the serum troponin-T levels in newborns and children: does pH-Stat provide better protection?

Cardiopulmonary bypass associated acute kidney injury: better understanding and better prevention

Cardiopulmonary bypass (CPB) is a common technique in cardiac surgery but is associated with acute kidney injury (AKI), which carries considerable morbidity and mortality. In this review, we explore the range and definition of CPB-associated AKI and discuss the possible impact of different disease recognition methods on research outcomes. Furthermore, we introduce the specialized equipment and procedural intricacies associated with CPB surgeries. Based on recent research, we discuss the potential pathogenesis of AKI that may result from CPB, including compromised perfusion and oxygenation, inflammatory activation, oxidative stress, coagulopathy, hemolysis, and endothelial damage. Finally, we explore current interventions aimed at preventing and attenuating renal impairment related to CPB, and presenting these measures from three perspectives: (1) avoiding CPB to eliminate the fundamental impact on renal function; (2) optimizing CPB by adjusting equipment parameters, optimizing surgical procedures, or using improved materials to mitigate kidney damage; (3) employing pharmacological or interventional measures targeting pathogenic factors.

Novel cfDNA Methylation Biomarkers Reveal Delayed Cardiac Cell Death after Open-heart Surgery

The use of cardiopulmonary bypass (CPB) is thought to cause delayed cardiac damage. DNA methylation-based liquid biopsies are novel biomarkers for monitoring acute cardiac cell death. We assessed cell-free DNA molecules as markers for cardiac damage after open-heart surgery. Novel cardiomyocyte-specific DNA methylation markers were applied to measure cardiac cfDNA in the plasma of 42 infants who underwent open-heart surgery. Cardiac cfDNA was elevated following surgery, reflecting direct surgery-related tissue damage, and declined thereafter in most patients. The concentration of cardiac cfDNA post-surgery correlated with the duration of CPB and aortic cross clamping. Strikingly, cardiac cfDNA at 6 h predicted duration of mechanical ventilation and maximal vasoactive-inotropic score better than did maximal troponin levels. Cardiac cfDNA reveals heart damage associated with CPB, and can be used to monitor cardiac cell death, to predict clinical outcome of surgery and to assess performance of cardioprotective interventions.

How to interpret cardiac biomarkers in children?

Cardiac biomarkers are used as first-line diagnostic tools in suspected myocardial injury and heart failure in adult patients. Their use in paediatric patients has been limited by variability caused by age, gender and the presence of an underlying congenital cardiac condition. There are established reference ranges for both NT-proBNP and troponin in healthy children, but these cannot be applied to all paediatric patients because of limited large studies focusing on children with congenital heart disease and/or cardiomyopathy.This article will focus on the pathophysiology of myocardial injury and heart failure in children and the subsequent cardiac biomarker correlation. It will explain how to interpret the biomarker assay levels obtained for both troponin and NT-proBNP and highlights the importance of a clear clinical question prior to requesting a cardiac biomarker assay level.Clinical cases outline scenarios that may prompt consideration of biomarker analysis in children and aims to equip the reader with an understanding of how to interpret the results.

Risk Factors for Cardiac Adverse Events in Infants and Children with Complex Heart Disease Scheduled for Bi-ventricular Repair: Prognostic Value of Pre-operative B-Type Natriuretic Peptide and High-Sensitivity Troponin T

Few reports have described the prognostic value of measuring both B-type natriuretic peptides (BNP) and high-sensitivity troponin T (hs-TnT) in pediatric patients with complex congenital heart disease (CHD) undergoing surgery. We assessed demographic, hemodynamic, and laboratory data, including BNP and hs-TnT levels, for the prediction of cardiac adverse events in 85 patients. Cardiac adverse events were defined as death, cardiac arrest, worsening heart failure requiring inotropic agents and/or respiratory support, and unscheduled surgery/intervention either within or after 12 months of surgery. There were 17 cardiac adverse events. Of the demographic variables, low birth weight (< 2500 g: Odds ratio [OR], 5.97; 95% confidential interval [CI] 1.48-24.0; p = 0.001) and Ross/New York Heart Association [NYHA] class (≥ 2.0) (OR 12.7; 95% CI 3.08-52.7; p = 0.0004) were strongly association with cardiac adverse events. Among hemodynamic and laboratory variables, preoperative BNP (OR 14.04; 95% CI 2.15-91.7; p = 0.001) and hs-TnT levels (OR 16.66; 95% CI 2.27-122; p = 0.002) were found to be independent risk factors. Receiver operating characteristic analysis determined BNP and hs-TnT levels of 60.9 pg/mL and 0.025 ng/mL, respectively, to be markers of high risk. Kaplan-Meier analysis demonstrated significant differences in the freedom from cardiac adverse events between Group A (BNP or hs-TnT elevated, n = 26) and Group B (both biomarkers elevated, n = 19; log-rank, p < 0.001). In conclusion, low birth weight (< 2500 g) and Ross/NYHA class ≥ 2.0 are strongly associated with cardiac adverse events. Preoperative BNP and hs-TnT also provide prognostic information in patients with complex CHD scheduled for surgery. Using both markers in combination predicts cardiac adverse events better than using either separately.

Ex vivo evaluation of a new neonatal/infant oxygenator: comparison of the Terumo CAPIOX® Baby RX with Dideco Lilliput 1 and Polystan Safe Micro in the piglet model

Objective: A newly developed neonatal and infant oxygenator with a nonheparin biocompatible polymer coating, low priming volume (43 mL), high oxygen transfer, wide operating range (<1.5 L/min) and low pressure drop represents a promising solution for cardiac surgery in neonates and infants. We compared the new CAPIOX® Baby RX, Terumo (BRX) with two commonly used neonatal oxygenators: Dideco Lilliput 1 (DL1) and Polystan Safe Micro (PSM) in a piglet model.

Methods: Fifteen piglets (5.6±1.3 kg) were placed on standardized cardiopulmonary bypass (CPB) for 6 hours using one of the three oxygenators ( n = 5 in each group). After 120 min, the system was cooled to 25°C for 60 min and then returned to normothermia. Arterial and venous blood gas data and temperature were recorded continuously by a CDI500 System (Terumo). Pressure drop, FiO2 and gas flow were recorded. Blood samples were taken before CBP, after 10 min, before and after cooling, and at the end. Total blood counts, thrombin-antithrombin complex and plasma-free haemoglobin (PfHb) were measured.

Results: All oxygenators showed acceptable performance for the duration of CPB. The BRX had lower mean gas flow (0.33±0.05 L/min) and FiO2 (0.43± 0.02%) throughout CPB than the DL1 (1.14±0.25 L/min, p = 0.006 and 0.60±0.02%, p = 0.009, respectively) or the PSM (1.47±0.87 L/min and 0.54±0.08%, p = ns). Pressure drop in the BRX group ranged from 12 to 22 mmHg. This was significantly lower than in the DL1 group (39-65 mmHg, p = 0.005). In the PSM group, values ranged between 24 and 33 mmHg (p = ns). The increase in PfHb at six hours was significantly lower in the BRX (11.3±4.2 ng/dL) versus the DL1 (42.2±6.1 ng/dL, p = 0.004) and the PSM (56.7±15.5 ng/dL, p = 0.045).

Conclusions: The BRX is as safe as the DL1 and the PSM, with superior performance in pressure drop, efficient blood gas management and lower haemolysis. The BRX exhibited the lowest prime, hold-up volume and breakthrough time.

Vasoactive-inotropic score is associated with outcome after infant cardiac surgery: an analysis from the Pediatric Cardiac Critical Care Consortium and Virtual PICU System Registries

OBJECTIVE

To empirically derive the optimal measure of pharmacologic cardiovascular support in infants undergoing cardiac surgery with bypass and to assess the association between this score and clinical outcomes in a multi-institutional cohort.

DESIGN

Prospective, multi-institutional cohort study.

SETTING

Cardiac ICUs at four academic children's hospitals participating in the Pediatric Cardiac Critical Care Consortium during the study period.

PATIENTS

Children younger than 1 year at the time of surgery treated postoperatively in the cardiac ICU.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Three hundred ninety-one infants undergoing surgery with bypass were enrolled consecutively from November 2011 to April 2012. Hourly doses of all vasoactive agents were recorded for the first 48 hours after cardiac ICU admission. Multiple derivations of an inotropic score were tested, and maximum vasoactive-inotropic score in the first 24 hours was further analyzed for association with clinical outcomes. The primary composite "poor outcome" variable included at least one of mortality, mechanical circulatory support, cardiac arrest, renal replacement therapy, or neurologic injury. High vasoactive-inotropic score was empirically defined as more than or equal to 20. Multivariable logistic regression was performed controlling for center and patient characteristics. Patients with high vasoactive-inotropic score had significantly greater odds of a poor outcome (odds ratio, 6.5; 95% CI, 2.9-14.6), mortality (odds ratio, 13.2; 95% CI, 3.7-47.6), and prolonged time to first extubation and cardiac ICU length of stay compared with patients with low vasoactive-inotropic score. Stratified analyses by age (neonate vs infant) and surgical complexity (low vs high) showed similar associations with increased morbidity and mortality for patients with high vasoactive-inotropic score.

CONCLUSIONS

Maximum vasoactive-inotropic score calculated in the first 24 hours after cardiac ICU admission was strongly and significantly associated with morbidity and mortality in this multi-institutional cohort of infants undergoing cardiac surgery. Maximum vasoactive-inotropic score more than or equal to 20 predicts an increased likelihood of a poor composite clinical outcome. The findings were consistent in stratified analyses by age and surgical complexity.

Effect of remote ischaemic preconditioning on ischaemic-reperfusion injury in pulmonary hypertensive infants receiving ventricular septal defect repair

BACKGROUND

Remote ischaemic preconditioning (RIPC) can reduce ischaemic-reperfusion injury in distant organs. The myocardial and pulmonary protective effect of RIPC in infants with pulmonary hypertension remains unclear. We conducted a randomized controlled trial to evaluate the effect of RIPC in infants receiving ventricular septal defect (VSD) repair.

METHODS

We studied 55 infants with pulmonary hypertension undergoing VSD repair (RIPC group, n=27; control group, n=28). RIPC consisted of four 5 min cycles of lower limb ischaemia and reperfusion. Serum troponin I (TnI) concentrations were measured after induction of anaesthesia and at 1, 6, 12, and 24 h after surgery. Other clinical data such as inotropic score, lung compliance, alveolar-arterial oxygen gradient, oxygen index, mechanical ventilation time, and length of intensive care unit stay were also recorded at each interval.

RESULTS

No differences in patient or surgical characteristics were observed between the two groups. There were no significant differences in postoperative TnI levels according to time (P=0.35) or the total amount of TnI release, expressed as the area under the curve over the 24 h after surgery [RIPC vs control: 207.6 (134.0) vs 274.6 (263.7) h ng ml(-1), P=0.24]. All other clinical data were also comparable.

CONCLUSIONS

RIPC does not reduce the postoperative TnI release after VSD repair in infants with pulmonary hypertension. Additionally, it is difficult to find significant clinical benefits of RIPC in this population. The effect of RIPC varies according to clinical situation and patient condition.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT01313832.

Biomonitors of cardiac injury and performance: B-type natriuretic peptide and troponin as monitors of hemodynamics and oxygen transport balance

Serum biomarkers, such as B-type natriuretic peptide and troponin, are frequently measured in the cardiac intensive care unit. A review of the evidence supporting monitoring of these biomarkers is presented.

DESIGN

A search of MEDLINE, PubMed, and the Cochrane Database was conducted to find literature regarding the use of B-type natriuretic peptide and troponin in the cardiac intensive care setting. Adult and pediatric data were considered.

RESULTS AND CONCLUSION

Both B-type natriuretic peptide and troponin have demonstrated utility in the intensive care setting but there is no conclusive evidence at this time that either biomarker can be used to guide inpatient management of children with cardiac disease. Although B-type natriuretic peptide and troponin concentrations can alert clinicians to myocardial stress, injury, or hemodynamic alterations, the levels can also be elevated in a variety of clinical scenarios, including sepsis. Observational studies have demonstrated that perioperative measurement of these biomarkers can predict postoperative mortality and complications.

RECOMMENDATION AND LEVEL OF EVIDENCE

(class IIb, level of evidence B): The use of B-type natriuretic peptide and/or troponin measurements in the evaluation of hemodynamics and postoperative outcome in pediatric cardiac patients may be beneficial.

Effect of deep hypothermic circulatory arrest followed by low-flow cardiopulmonary bypass on brain metabolism in newborn piglets: comparison of pH-stat and α-stat management

OBJECTIVE

To compare the effects of pH-stat and α-stat management before deep hypothermic circulatory arrest followed by a period of low-flow (two rates) cardiopulmonary bypass on cortical oxygenation and selected regulatory proteins: Bax, Bcl-2, Caspase-3, and phospho-Akt.

DESIGN

Piglets were placed on cardiopulmonary bypass, cooled with pH-stat or α-stat management to 18 °C over 30 mins, subjected to 30-min deep hypothermic circulatory arrest and 1-hr low flow at 20 mL/kg/min (LF-20) or 50 mL/kg/min (LF-50), rewarmed to 37 °C, separated from cardiopulmonary bypass, and recovered for 6 hrs.

SUBJECTS

Newborn piglets, 2-5 days old, assigned randomly to experimental groups.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Cortical oxygen was measured by oxygen-dependent quenching of phosphorescence; proteins were measured by Western blots. The means from six experiments ± sem are presented as % of α-stat. Significance was determined by Student's t test. For LF-20, cortical oxygenation was similar for α-stat and pH-stat, whereas for LF-50, it was significantly better using pH-stat. For LF-20, the measured proteins were not different except for Bax in the cortex (214 ± 24%, p = .006) and hippocampus (118 ± 6%, p = .024) and Caspase 3 in striatum (126% ± 7%, p = .019). For LF-50, in pH-stat group: In cortex, Bax and Caspase-3 were lower (72 ± 8%, p = .001 and 72 ± 10%, p = .004, respectively) and pAkt was higher (138 ± 12%, p = .049). In hippocampus, Bcl-2 and Bax were not different but pAkt was higher (212 ± 37%, p = .005) and Caspase 3 was lower (84 ± 4%, p = .018). In striatum, Bax and pAkt did not differ, but Bcl-2 increased (146 ± 11%, p = .001) and Caspase-3 decreased (81 ± 11%, p = .042).

CONCLUSIONS

In this deep hypothermic circulatory arrest-LF model, when flow was 20 mL/kg/min, there was little difference between α-stat and pH-stat management. However, for LF-50, pH-stat management resulted in better cortical oxygenation during recovery and Bax, Bcl-2, pAk, and Caspase-3 changes were consistent with lesser activation of proapoptotic signaling with pH-stat than with α-stat.

Cardiac Troponin T Levels for Risk Stratification in Pediatric Open Heart Surgery

BACKGROUND

Cardiac troponin T has been found to be accurate predictor of complications and adverse clinical events after pediatric cardiac surgery. Contrary to adult cardiac surgery, the relationship of troponin T to patient survival after pediatric heart surgery has not been previously studied. The purpose of this study was to determine whether troponin T could predict death after pediatric open cardiac surgery.

METHODS

This was a retrospective cohort study in which data from 1001 consecutive children having cardiac surgery during a 5-year period were studied. Perioperative variables that could influence death at 30 postoperative days were evaluated.

RESULTS

Multivariate analysis, using a forward stepwise logistic regression, showed that troponin T measured on the first postoperative day was a strong independent predictor of death at 30 days. Level of troponin T greater than 5.9 microg/L on the first postoperative day predicted death (odds ratio, 10.7; 95% confidence interval: 5.2 to 22.1) as did admission lactate level greater than 5.2 mmol/L (odds ratio, 22.2; 95% confidence interval: 9.7 to 50.8) No other variable, including postoperative creatine kinase-MB mass concentration, age, diagnosis, surgical procedure, presence of cyanosis, chromosomal anomaly or ventriculotomy, duration of cardiopulmonary bypass, or aortic cross-clamp, had any independent effect on 30-day survival.

CONCLUSIONS

Cardiac troponin T level on the first postoperative day is a powerful independent risk marker of death in pediatric cardiac surgery.

Troponin-T levels in perinatally asphyxiated infants during the first 15 days of life

AIM

To measure serial cardiac troponin-T, creatine kinase, creatine kinase-MB, aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase levels in asphyxiated newborn infants during the first 15 d of life.

METHODS

Troponin-T, creatine kinase, creatine kinase-MB, aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase (LDH) concentrations were measured prospectively in blood samples obtained from 45 asphyxiated and 15 healthy term neonates within the first 2-4 h, third, seventh and 15th days.

RESULTS

Infants with severe asphyxia had significantly higher cardiac troponin-T levels than grade I and II asphyxiated and healthy neonates within the first 2-4 h of life (0.34+/-0.21 ag/ml vs 0.07+/-0.03 ag/ml, 0.12+/-0.07 ag/ml, 0.04+/-0.02 ag/ml, respectively). Troponin-T levels remained high on days 3 and 7 in severely asphyxiated neonates. The creatinine kinase-MB levels were significantly higher in grade II and III asphyxiated neonates than grade I asphyxiated and healthy neonates within the first 2-4 h. No difference was found in creatinine kinase-MB on day 3. There was cardiac involvement in 12 (80%) newborns of group III on B mode echocardiographic images on day 1. However, no echocardigraphic pathology was found in the seventh- and 15th-day echocardiographic analysis in any groups.

CONCLUSION

Our results suggest that asphyxia-related cardiac changes were significant but reversible in severely asphyxiated neonates, and troponin T is a good determinant of the degree of injury to the heart within the first week of life. Cardiac troponin T also has a wider diagnostic frame than other diagnostic markers of myocardial damage.

Effect of dexamethasone on postoperative cardiac troponin T production in pediatric cardiac surgery

OBJECTIVE

Pediatric cardiac surgery is associated with a temporary rise in cardiac troponin T (cTnT) during the postoperative period. We examined whether dexamethasone given before cardiopulmonary bypass has myocardial protective effects as assessed by the postoperative production of cTnT.

DESIGN AND SETTING

Prospective randomized interventional study in the pediatric intensive care unit in a university hospital.

INTERVENTIONS

Patients were randomly allocated to act as controls or receive a single dose of dexamethasone (1 mg/kg) during induction of anesthesia.

MEASUREMENTS AND RESULTS

cTnT was measured four times postoperatively: immediately after admission to the pediatric intensive care unit (PICU) and 8, 15, and 24 h thereafter. The two groups had similar mean cTnT concentrations on PICU admission: those receiving dexamethasone 1.85 ng/ml (1.55-2.15) and those not receiving it 2 ng/ml (95% confidence interval 1.56-2.51). Concentrations of cTnT 8 h after admission to the PICU differed significantly after 8 h: 1.99 ng/ml (1.53-2.45) in those receiving dexamethasone and 3.08 ng/ml (2.46-3.69) in those not receiving it. After subgroup statistical analysis differences between the two groups remained significant only at 8 h, not those after 15 or 24 h.

CONCLUSIONS

The use of dexamethasone (1 mg/kg) before cardiopulmonary bypass is associated with a brief but significant reduction in postoperative cTnT production. The clinical significance of this effect is unclear.

Blood Gas Strategies and Management during Pediatric Cardiopulmonary Bypass

Blood gas management during hypothermic cardiopulmonary bypass may be corrected by pH stat or alpha stat strategy. The pH stat philosophy is to maintain the blood pH constant at any temperature. Carbon dioxide must be introduced to the oxygenator in order to maintain the pH and pCO2 during hypothermic cardiopulmonary bypass. Conversely, during alpha stat blood gas management pH is maintained according to 37 degrees C despite the patient temperature. Alpha stat management preserves intracellular pH and autoregulation of cerebral vasculature by following the natural shift of the oxyhemoglobin dissociation curve. In-line blood gas analysis is a practical tool in assessing adequate blood gas management, because this technology provides immediate detection for modification of air/oxygen/carbon dioxide parameters. Results from several studies favor the pH stat strategy during neonatal cardiopulmonary bypass. This strategy increases tissue oxygenation and cerebral blood flow while cooling. Data also suggest that pH stat management results in better outcomes with shorter ventilation times and intensive care unit stays after pediatric cardiac surgery.

Effect of three different anaesthetic agents on the postoperative production of cardiac troponin T in paediatric cardiac surgery

BACKGROUND

Paediatric cardiac surgery is associated with some degree of myocardial injury. Ischaemic preconditioning (IP) has been investigated widely in the adult population. Volatile agents have been shown to simulate IP providing extra protection to the myocardium during adult cardiopulmonary bypass (CPB) while propofol seems to act through different mechanisms. IP has not been investigated in the paediatric population to the same extent. Cardiac troponin T (cTnT) is a reliable marker of myocardial injury in neonates and children. We have investigated the relationship between three anaesthetic agents, midazolam, propofol, and sevoflurane, and postoperative production of cTnT.

METHODS

Ninety patients undergoing repair of congenital heart defect with CPB were investigated in a prospective randomized study. cTnT was measured four times during the first 24 h following admission to the paediatric intensive care unit. Other variables measured included arterial blood gases, lactate, fluid balance, use of inotropic drugs, PaO2/FiO2 ratio and ventilator hours.

RESULTS

cTnT was elevated in all three groups throughout the study period. The differences between the three groups were not statistically significant. Eight hours after admission to the intensive care unit cTnT concentrations tended to be higher in the midazolam group [mean (95% confidence intervals)]; 2.7 (1.9-3.5) ng ml(-1). Patients receiving a propofol-based anaesthesia had similar concentrations 2.6 (1.7-3.5) ng ml(-1) while those receiving sevoflurane tended to have a lower cTnT production 1.7 (1.3-2.2) ng ml(-1).

CONCLUSIONS

Midazolam, propofol, and sevoflurane appear to provide equal myocardial protection in paediatric cardiac surgery when using cTnT as a marker of myocardial damage.