Cardiopulmonary bypass in infants and children: how is it different?

Safety and Effectiveness of Del Nido Cardioplegia in Comparison to Blood-Based St. Thomas Cardioplegia in Congenital Heart Surgeries: A Prospective Randomized Controlled Study

Background:

To compare the safety and effectiveness of del Nido cardioplegia with blood-based St Thomas Hospital (BSTH) cardioplegia in myocardial protection in congenital heart surgery.

Methods:

It is a prospective, open-labeled, randomized controlled study conducted at National Heart Institute, Kuala Lumpur from July 2018 to July 2019. All patients with simple and complex congenital heart diseases (CHD) with good left ventricular function (left ventricular ejection fraction [LVEF] >50%) were included while those with LVEF <50% were excluded. A total of 100 patients were randomized into two groups of 50 each receiving either del Nido or BSTH cardioplegia. Primary end points were the spontaneous return of activity following aortic cross-clamp release and ventricular function between two groups. Secondary end point was myocardial injury as assessed by troponin T levels.

Results:

Cardiopulmonary bypass and aortic cross-clamp time, return of spontaneous cardiac activity following the aortic cross-clamp release, the duration of mechanical ventilation, and intensive care unit stay were comparable between two groups. Statistically significant difference was seen in the amount and number of cardioplegia doses delivered ( P < .001). The hemodilution was significantly less in the del Nido complex CHD group compared to BSTH cardioplegia ( P = .001) but no difference in blood usage ( P = .36). The myocardial injury was lesser (lower troponin T release) with del Nido compared to BSTH cardioplegia ( P = .6).

Conclusion:

Our study showed that both del Nido and BSTH cardioplegia are comparable in terms of myocardial protection. However, single, less frequent, and lesser volume of del Nido cardioplegia makes it more suitable for complex repair.

Myocardial protection following del Nido cardioplegia in pediatric cardiac surgery

Background

This study was designed to compare myocardial protection with del Nido cardioplegia and conventional blood cardioplegia in children undergoing cardiac surgery in Risk Adjustment for Congenital Heart Surgery categories 1 and 2.

Methods

Sixty patients were randomized into 2 groups receiving del Nido cardioplegia solution or conventional blood cardioplegia. Myocardial injury was assessed using biochemical markers (troponin I and creatine kinase-MB). Vasoactive-inotropic scores were calculated to compare inotropic requirements.

Results

Demographic characteristics, cardiopulmonary bypass time, and aortic crossclamp time were comparable in the 2 groups. Time-related changes in troponin I and creatine kinase-MB were similar in both groups. Statistically significant differences were seen in total cardioplegia volume requirement ( p < 0.0001), number of cardioplegia doses given ( p < 0.0001), packed red cell volume usage during cardiopulmonary bypass ( p < 0.02), and time taken to restore spontaneous regular rhythm ( p < 0.0001). Vasoactive-inotropic scores on transfer to the intensive care unit ( p < 0.040) and at 24 h ( p < 0.030) were significantly lower in the del Nido group. Duration of mechanical ventilation, intensive care unit stay, and hospital stay were comparable in the 2 groups.

Conclusions

Our results show that del Nido cardioplegia solution is as safe as conventional blood cardioplegia. Moreover, it provides the benefits of reduced dose requirement, lower consumption of allogenic blood on cardiopulmonary bypass, quicker resumption of spontaneous regular cardiac rhythm, and less inotropic support requirement on transfer to the intensive care unit and at 24 h, compared to conventional blood cardioplegia.

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.

Hyperkalemic cardioplegia for adult and pediatric surgery: end of an era?

Despite surgical proficiency and innovation driving low mortality rates in cardiac surgery, the disease severity, comorbidity rate, and operative procedural difficulty have increased. Today's cardiac surgery patient is older, has a "sicker" heart and often presents with multiple comorbidities; a scenario that was relatively rare 20 years ago. The global challenge has been to find new ways to make surgery safer for the patient and more predictable for the surgeon. A confounding factor that may influence clinical outcome is high K(+) cardioplegia. For over 40 years, potassium depolarization has been linked to transmembrane ionic imbalances, arrhythmias and conduction disturbances, vasoconstriction, coronary spasm, contractile stunning, and low output syndrome. Other than inducing rapid electrochemical arrest, high K(+) cardioplegia offers little or no inherent protection to adult or pediatric patients. This review provides a brief history of high K(+) cardioplegia, five areas of increasing concern with prolonged membrane K(+) depolarization, and the basic science and clinical data underpinning a new normokalemic, "polarizing" cardioplegia comprising adenosine and lidocaine (AL) with magnesium (Mg(2+)) (ALM™). We argue that improved cardioprotection, better outcomes, faster recoveries and lower healthcare costs are achievable and, despite the early predictions from the stent industry and cardiology, the "cath lab" may not be the place where the new wave of high-risk morbid patients are best served.

Plasmin generation and fibrinolysis in pediatric patients undergoing cardiopulmonary bypass surgery

This prospective, single-centre cohort study aimed to evaluate plasmin generation and fibrinolysis during and after cardiopulmonary bypass (CPB) surgery in a cohort of children up to 6 years of age. Blood samples were drawn at eight time points: after induction of anesthesia, before unfractionated heparin (UFH), after UFH, after initiation of bypass, before protamine, after protamine, after chest closure, and 6 h after chest closure. The study identified an increase in fibrinolysis during CPB and particularly up to 6 h afterward in children. This could be the mechanism for the significant bleeding events observed in this young population after CPB. This study establishes the foundation for future studies in this area, particularly those focusing on clinical outcomes after CPB surgery.

Temperature-Related Differences in Mean Expired Pump and Arterial Carbon Dioxide in Patients Undergoing Cardiopulmonary Bypass

OBJECTIVE

To investigate the relationship between arterial carbon dioxide (PaCO(2)) and mean expired pump CO(2) during cardiopulmonary bypass (PeCPBCO(2)) in patients undergoing cardiac surgery with CPB during steady state, cooling, and rewarming phases of CPB.

DESIGN

Consenting patients, prospective study.

SETTING

University-affiliated hospital.

PARTICIPANTS

Twenty-nine patients.

INTERVENTIONS

Patients aged 22 to 81 years were enrolled. An alpha-stat acid-base regimen was performed during CPB. The PeCPBCO(2) was measured by an infrared multigas analyzer with the sampling line connected to the scavenging port of the oxygenator. Values for PaCPBCO(2) from the arterial outflow to the patient and PeCPBCO(2) during CPB at various oxygenator arterial temperatures were collected and compared. Data were analyzed by analysis of variance with 1-way repeated measures and post hoc pair-wise Tukey testing when appropriate. The differences between PaCPBCO(2) and PeCPBCO(2) were linearly regressed against temperature. A p value <0.05 was considered significant.

MEASUREMENTS AND MAIN RESULTS

Three to 5 data sets during CPB were collected from each patient. The mean gradient between PaCPBCO(2) and PeCPBCO(2) was positive 12.4 +/- 10.0 mmHg during the cooling phase and negative 9.3 +/- 9.9 mmHg during the rewarming phase, respectively. On regression of the data, the difference between PaCPBCO(2) and PeCPBCO(2) shows a good correlation with the change in temperature (r(2) = 0.79). The arterial CO(2) +/- x mmHg can be predicted by the formula PaCPBCO(2) = (-2.17x + 69.2) + PeCPBCO(2), where x is temperature in degrees C.

CONCLUSIONS

Monitoring the mean expired CO(2) value from the CPB oxygenator exhaust scavenging port with a capnography monitor provides a continuous and noninvasive data source to aid in sweep flow CPB circuit management during CPB.

Avoiding Transfusions in Children Undergoing Cardiac Surgery: A Meta-Analysis of Randomized Trials of Aprotinin

Aprotinin, a potent antifibrinolytic drug, reduces the proportion of adults who receive blood transfusions during cardiac surgery, although the effect in children remains unclear. We performed a systematic review of the literature to identify all English language, randomized controlled trials of aprotinin involving children undergoing corrective or palliative cardiac surgery with cardiopulmonary bypass. All studies were assessed for methodological quality, and sources of heterogeneity were examined. We measured the effect of aprotinin on the proportion of children transfused, the volume of blood transfused, and the volume of chest tube drainage. Twelve trials enrolling 626 eligible children met the inclusion criteria. Aprotinin reduced the proportion of children who received red blood cell or whole blood transfusions during cardiac surgery by 33% (relative risk = 0.67; 95% confidence interval, 0.51 to 0.89). Aprotinin did not have a significant effect on the volume of blood transfused or on the amount of postoperative chest tube drainage. Most of the studies were of poor methodological quality and predefined transfusion triggers were infrequently used. Overall, aprotinin reduced the proportion of children who received blood transfusion during cardiac surgery with cardiopulmonary bypass. Further high-quality trials with clinically important outcomes may be warranted before aprotinin can be routinely recommended in this population.

Variability of plasma aprotinin concentrations in pediatric patients undergoing cardiac surgery

OBJECTIVES

Infants and children undergoing cardiopulmonary bypass for repair of congenital heart defects are at substantial risk for excessive bleeding, contributing greatly to morbidity and mortality. Aprotinin significantly reduces bleeding and transfusion requirements in adults but is of indeterminate value for pediatric patients. The aim of this study was to determine plasma aprotinin concentrations in these patients with a functional aprotinin assay.

METHODS

Thirty patients less than 16 years of age scheduled for cardiac surgery with aprotinin were enrolled. Aprotinin was administered as a 25,000 KIU/kg bolus, 35,000 KIU/kg cardiopulmonary bypass prime, and 12,500 KIU.kg(-1).h(-1) continuous infusion. Blood samples for aprotinin concentrations (kallikrein-inhibiting units/milliliter) were obtained before aprotinin; 5 minutes post-bolus; 5 minutes after cardiopulmonary bypass initiation; 30 and 60 minutes on cardiopulmonary bypass; on discontinuation of aprotinin; 1 hour after aprotinin discontinuation; and 4 hours after permanent separation from cardiopulmonary bypass. For analysis, patients were grouped according to weight (<10 kg, 10-20 kg, >20 kg). Differences between weight groups were assessed using an exact test for categoric variables and 1-way analysis of variance for continuous variables.

RESULTS

Aprotinin concentrations differed significantly across weight groups. Five minutes after aprotinin bolus and initiation of cardiopulmonary bypass, there was significant correlation between weight and aprotinin concentration (r =.57, P =.003; r =.69, P =.001, respectively).

CONCLUSION

A functional assay reveals significant variability in aprotinin concentration for pediatric patients using current weight-based aprotinin dosing. Additional investigation is necessary to determine target aprotinin concentration dosing regimens to provide better efficacy.

Significant merits of a fibrin sealant in the presence of coagulopathy following paediatric cardiac surgery: randomised controlled trial

OBJECTIVES

The efficacy of a fibrin sealant in paediatric cardiac surgery has been demonstrated. However, its effectiveness in the presence of significant untreated coagulopathy has not been addressed. This study was designed to investigate the role of the topical application of a fibrin sealant, Beriplast P (BP), in the presence of coagulopathy following paediatric cardiac surgery.

METHODS

After confirming the presence of significant post-bypass coagulopathy, patients undergoing repair of congenital heart defects using cardiopulmonary bypass were randomised to the use of BP (group BP) or no intervention (group C). BP was applied over suture lines and microvascular bleeding sites. Criteria for transfusion of blood and blood products were standardised for both groups. Outcome variables were: (1) post-operative bleeding; (2) transfusion of blood and blood products; (3) theatre time to achieve haemostasis; (4) ventilation time, intensive therapy unit (ITU) and hospital stay.

RESULTS

Fifty-two patients (n=26 in each group), aged 3 days to 17.4 years were recruited. There were no hospital deaths and no significant differences in demographic or intraoperative variables that might have affected the chosen endpoints. After protamine, all patients in both groups had significant coagulopathy (P< or = 0.05 versus baseline). There were fewer patients receiving transfusions of fresh frozen plasma (FPP) in the intervention group, when compared to the control group (P< or = 0.05). Patients receiving BP spent less time in theatre to achieve haemostasis (P< or = 0.05), had a lesser amount of bleeding intraoperatively (P< or = 0.01), at 4h (P< or = 0.05) and at 24h (P< or = 0.05), required a lower amount of transfusions of red cells (P< or = 0.01), FPP (P< or = 0.05) and platelets (P< or = 0.05). There were no differences in ventilation time, length of stay in ITU or in hospital.

CONCLUSIONS

Even in the presence of significant coagulopathy, intraoperative use of fibrin sealant in paediatric cardiac surgery reduces the amount of bleeding and need for transfusions of blood and blood products. The theatre time necessary to achieve haemostasis is also significantly reduced. These findings have a potential to improve clinical outcomes and enhance cost benefits.