Routine use of mechanical ventricular assist following the Norwood procedure

A Review of Physiologic Considerations and Challenges in Pediatric Patients With Failing Single- Ventricle Physiology Undergoing Ventricular Assist Device Placement

Advances in surgical techniques and outpatient cardiac care have led to a growing population of pediatric patients surviving well into adulthood with previous single-ventricle palliation. Continued improvement in survival has resulted in subsequent increases in the number of patients with single-ventricle physiology listed for heart transplantations. Some of these patients require mechanical circulatory support as a bridge to transplantation, although establishing successful mechanical circulatory support in these complex patients remains challenging. Only limited published data exist describing the perioperative anesthetic management and key considerations dedicated to patients with failing single-ventricle physiology presenting for ventricular assist devices. This clinical review aims to provide a focused evaluation of the vital perioperative considerations encountered in this novel population.

Pediatric Mechanical Circulatory Support

Over the past two decades clinicians and researchers have sought to bring mechanical circulatory support (MCS) to pediatric patients with heart failure. ECMO, IABPs, and VADs have all been used in infants and children as a bridge to myocardial recovery or as a bridge to transplant. However, until recently, a commitment by industry, government, and researchers towards the development of pediatric MCS has not been present, especially in the United States. Advancements in adult VAD design to smaller, quieter, and fully implantable pumps capable of complete outpatient support have sparked curiosity in the application of this technology to children. Also, the increasing success of palliating congenital heart disease is creating an ever-growing cohort of children and adolescents with heart failure. These changing demographics and technological advances have caused a refocus of attention. This is most clearly demonstrated by the international use of several established MCS pediatric and neonatal systems, by the FDA's increasing proclivity to allow the use of international pediatric VADs in the USA, and by the recent National Heart, Lung, and Blood Institute funding of several institutions to develop pediatric VADs. This review describes the different aspects of pediatric MCS including indications, the features of the various VADs, and their current application in children worldwide.

Impact of Timing of ECMO Initiation on Outcomes After Pediatric Heart Surgery: A Multi-Institutional Analysis

Little is known about the relationship of timing of extracorporeal membrane oxygenation (ECMO) initiation on patient outcomes after pediatric heart surgery. We hypothesized that increasing timing of ECMO initiation after heart surgery will be associated with worsening study outcomes. Patients aged ≤18 years receiving ECMO after pediatric cardiac surgery at a Pediatric Health Information System-participating hospital (2004-2013) were included. Outcomes evaluated included in-hospital mortality, composite poor outcome, prolonged length of ECMO, prolonged length of mechanical ventilation, prolonged length of ICU stay, and prolonged length of hospital stay. Multivariable logistic regression models were fitted to study the probability of study outcomes as a function of timing from cardiac surgery to ECMO initiation. A total of 2908 patients from 42 hospitals qualified for inclusion. The median timing of ECMO initiation after cardiac surgery was 0 days (IQR 0-1 day; range 0-294 days). After adjusting for patient and center characteristics, increasing duration of time from surgery to ECMO initiation was not associated with higher mortality or worsening composite poor outcome. However, increasing duration of time from surgery to ECMO initiation was associated with prolonged length of ECMO, prolonged length of ventilation, prolonged length of ICU stay, and prolonged length of hospital stay. Although this relationship was statistically significant, the odds for prolonged length of ECMO, prolonged length of ventilation, prolonged length of ICU stay, and prolonged length of hospital stay increased by only 1-3 % for every 1-day increase in ECMO that may be clinically insignificant. We did not demonstrate any relationship between timing of ECMO initiation and mortality among the patients of varying age groups, and patients undergoing cardiac surgery of varying complexity. We concluded that increasing duration of time from surgery to ECMO initiation is not associated with worsening mortality. Our results suggest that ECMO is initiated at the appropriate time when dictated by clinical situation among patients of all age groups, and among patients undergoing heart operations of varying complexity.

Delayed extracorporeal membrane oxygenation in children after cardiac surgery: two-institution experience

OBJECTIVE

There are limited data on the outcomes of children receiving delayed (≥7 days) extracorporeal membrane oxygenation after cardiac surgery. The primary aim of this project is to identify the aetiology and outcomes of extracorporeal membrane oxygenation in children receiving delayed (≥7 days) extracorporeal membrane oxygenation after cardiac surgery.

PATIENTS AND METHODS

We conducted a retrospective review of all children ≤18 years supported with delayed extracorporeal membrane oxygenation after cardiac surgery between the period January, 2001 and March, 2012 at the Arkansas Children's Hospital, United States of America, and Royal Children's Hospital, Australia. The data collected in our study included patient demographic information, diagnoses, extracorporeal membrane oxygenation indication, extracorporeal membrane oxygenation support details, medical and surgical history, laboratory, microbiological, and radiographic data, information on organ dysfunction, complications, and patient outcomes. The outcome variables evaluated in this report included: survival to hospital discharge and current survival with emphasis on neurological, renal, pulmonary, and other end-organ function.

RESULTS

During the study period, 423 patients undergoing cardiac surgery were supported with extracorporeal membrane oxygenation at two institutions, with a survival of 232 patients (55%). Of these, 371 patients received extracorporeal membrane oxygenation <7 days after cardiac surgery, with a survival of 205 (55%) patients, and 52 patients received extracorporeal membrane oxygenation ≥7 days after cardiac surgery, with a survival of 27 (52%) patients. The median duration of extracorporeal membrane oxygenation run for the study cohort was 5 days (interquartile range: 3, 10). In all, 14 patients (25%) received extracorporeal membrane oxygenation during active cardiopulmonary resuscitation with chest compressions. There were 24 patients (44%) who received dialysis while being on extracorporeal membrane oxygenation. There were eight patients (15%) who had positive blood cultures and four patients (7%) who had positive urine cultures while being on extracorporeal membrane oxygenation. There were nine patients (16%) who had bleeding complications associated with extracorporeal membrane oxygenation runs. There were 10 patients (18%) who had cerebrovascular thromboembolic events associated with extracorporeal membrane oxygenation runs. Of these, 19 patients are still alive with significant comorbidities.

CONCLUSIONS

This study demonstrates that mortality outcomes are comparable among children receiving extracorporeal membrane oxygenation ≥7 days and <7 days after cardiac surgery. The proportion of patients receiving extracorporeal membrane oxygenation ≥7 days is small and the aetiology diverse.

Extracorporeal membrane oxygenation in children with heart disease and down syndrome: a multicenter analysis

The data on the outcomes of children with heart disease and Down syndrome receiving extracorporeal membrane oxygenation (ECMO) for cardiac or respiratory failure are limited. This study aimed to evaluate morbidity and mortality associated with ECMO in children with Down syndrome and heart disease. Children younger than 18 years undergoing heart surgery and ECMO reported in the Extracorporeal Life Support Organization (ELSO) registry (1998-2011) were included in the study. The registry was queried for the following five heart defects: common atrioventricular (AV) canal, tetralogy of Fallot, truncus arteriosus, transposition of great vessels, and interrupted aortic arch. Data collection included patient characteristics, ECMO characteristics, and outcomes. The outcomes evaluated included mortality, ECMO duration, and length of hospital stay for patients with Down syndrome and those with no Down syndrome. The study enrolled 2,815 patients qualified for inclusion. Of these patients, 121 had Down syndrome, whereas 2,694 had no genetic syndrome and were included in the control group. The median age of the patients was 45 days (interquartile range [IQR] 9-192 days), and the median weight was 3.8 kg (IQR 3.0-6.1 kg). The most common cardiac defects in Down syndrome group were common AV canal (63 %) and tetralogy of Fallot (40 %). The Down syndrome group included older patients with greater body weight than the control group. The mortality rate was lower in the Down syndrome group than in the control group (44 vs. 56 %; p = 0.01). The duration of ECMO and length of hospital stay were similar in the two groups. The findings showed that ECMO can be used for children with heart disease and Down syndrome with good results. The outcomes were comparable between the children with Down syndrome and the children without Down syndrome.

Contemporary management of pulmonary and systemic circulations after the Norwood procedure

Hypoplastic left heart syndrome remains one of the most challenging pathologies in pediatric cardiac surgery. The surgical techniques, and anesthetic and intensive care management, have evolved over the last decades, which has resulted in improved outcomes. A central component in the postoperative management of hypoplastic left heart syndrome patients is to achieve an optimal balance between the pulmonary and systemic circulations. This article discusses the contemporary postoperative management of pulmonary and systemic circulations in detail.

Intraoperative extracorporeal membrane oxygenation and survival of pediatric patients undergoing repair of congenital heart disease

BACKGROUND

We studied the association between the introduction of extracorporeal membrane oxygenation (ECMO) into routine practice and the survival of children who failed weaning from cardiopulmonary bypass (CPB). We compare two periods, before formal introduction of ECMO in our institution (1993-1999, pre-ECMO era) and after ECMO became a formalized program (2000-2006, ECMO era).

METHODS

Retrospective review of Mayo Clinic Database between 1993 and 2006 for outcomes of patients <18 years old who required ECMO during repair of congenital heart malformations.

RESULTS

Thirty-five children during ECMO era received intraoperative ECMO, and 17 (54%) survived to hospital discharge. The frequency of ECMO use was the highest in neonates, therefore, this was the only subcohort of pediatric patients that allowed comparison of survival between the pre-ECMO and ECMO eras. When compared to pre-ECMO era, neonatal survival increased during ECMO era (P = 0.043). ECMO was mostly used in neonates with higher complexity of cardiac defects undergoing more complex repairs, and the overall improvement of survival was primarily due to better survival of these patients. During pre-ECMO era, survival was lower in patients with higher risk (P = 0.001). However, during ECMO era, no difference in survival was observed across assigned risk groups (P = 0.658).

CONCLUSIONS

The availability of ECMO for neonates failing to wean from CPB was associated with improved survival, especially in children undergoing repair of the most complex congenital heart malformations. After introduction of ECMO, survival improved and no longer depended upon the complexity of surgical repair.

B-type natriuretic peptide levels predict outcomes for children on extracorporeal life support after cardiac surgery

OBJECTIVE

Extracorporeal life support is used in 3% to 8% of infants and children after cardiac surgery. B-type natriuretic peptide may have utility as a biomarker in these patients. The objective of this study was to investigate potential associations between changes in B-type natriuretic peptide during trials off extracorporeal life support and clinical outcome.

METHODS

Ten infants and children requiring extracorporeal life support after cardiac surgery were studied prospectively. Before separation from extracorporeal life support, a shunt was placed in the circuit, allowing for temporary trials off life support. Serum lactate, arterial-venous oxyhemoglobin saturation difference, and B-type natriuretic peptide levels were determined before each trial off life support and at the end of each trial off life support, and the ability to predict postoperative outcome from these data was evaluated.

RESULTS

During trials off extracorporeal life support, lactate, the arterial-venous oxyhemoglobin saturation difference, and B-type natriuretic peptide levels increased above pre-trial values (P < .05). Only the arterial-venous oxyhemoglobin saturation difference predicted successful separation from extracorporeal life support after a trial (P < .05). There were no associations between long-term outcome and alterations in lactate and the arterial-venous oxyhemoglobin saturation difference during the final trials off life support. However, an increase in B-type natruiretic peptide levels during the final trial off life support (trial/pre-trial ratio of >1) had a sensitivity of 80% and a specificity of 100% for predicting the need for an unplanned operation or death within 3 months (P < .05).

CONCLUSION

B-type natriuretic peptide determinations may be a useful tool for clinicians caring for infants and children requiring extracorporeal life support after cardiac surgery.

Postoperative course in the cardiac intensive care unit following the first stage of Norwood reconstruction

The medical records of all patients born between 1 September, 2000, and 31 August, 2002, and undergoing the first stage of Norwood reconstruction, were retrospectively reviewed for details of the perioperative course. We found 99 consecutive patients who met the criterions for inclusion. Hospital mortality for the entire cohort was 15.2%, but was 7.3%, with 4 of 55 dying, in the setting of a "standard" risk profile, as opposed to 25.0% for those with a "high" risk profile, 11 of 44 patients dying in this group. Extracorporeal membrane oxygenation was utilized in 7 patients, with 6 deaths. Median postoperative length of stay in the hospital was 14 days, with a range from 2 to 85 days, and stay in the cardiac intensive care unit was 11 days, with a range from 2 to 85 days. Delayed sternal closure was performed in 18.2%, with a median of 1 day until closure, with a range from zero to 5 days. Excluding isolated delayed sternal closure, and cannulation and decannulation for extracorporeal support, 24 patients underwent 33 cardiothoracic reoperations, including exploration for bleeding in 12, diaphragmatic plication in 4; shunt revision in 4, and other procedures in 13. The median duration of total mechanical ventilation was 4.0 days, with a range from 0.7 to 80.5 days. Excluding those who died, the median total duration of mechanical ventilation was 3.8 days, with a range from 0.9 to 46.3 days. Reintubation for cardiorespiratory failure or upper airway obstruction was performed in 31 patients. Postoperative electroencephalographic and/or clinical seizures occurred in 13 patients, with 7 discharged on anti-convulsant medications. Postoperative renal failure, defined as a level of creatinine greater than 1.5 mg/dl, was present in 13 patients. Eleven had significant thrombocytopenia, with fewer than 20,000 platelets per microl, and injury to the vocal cords was identified in eight patients. Risk factors for longer length of stay included lower Apgar scores, preoperative intubation, early reoperations, reintubation and sepsis, but not weight at birth, genetic syndromes, the specific surgeon, or the duration of surgery. Although mortality rates after the first stage of reconstruction continue to fall, the course in the intensive care unit is remarkable for significant morbidity, especially involving the cardiac, pulmonary and central nervous systems. These patients utilize significant resources during the first hospitalization. Further studies are necessary to stratify the risks faced by patients with hypoplasia of the left heart in whom the first stage of Norwood reconstruction is planned, to determine methods to reduce perioperative morbidity, and to determine the long-term implications of short-term complications, such as diaphragmatic paresis, injury to the vocal cords, prolonged mechanical ventilation, and postoperative seizures.

Neurologic monitoring on cardiopulmonary bypass: what are we obligated to do?

Improving survival from congenital cardiac repairs using cardiopulmonary bypass has appropriately shifted focus to neurologic outcomes. Hypoxic-ischemic mechanisms are the major cause of neurologic injury in neonatal cardiac surgery, and modifications of techniques of cardiopulmonary bypass can affect organ oxygen delivery and the propensity to injury both during and after surgery. Through successive refinements in the techniques of cardiopulmonary bypass, the risk factors for hypoxic-ischemic injury have been reduced, but not eliminated. The application of specific monitoring to enhance detection of hypoxic conditions associated with neurologic injury would both allow intervention on individual patients and drive refinements in strategies to further reduce risk. Specific neurologic monitoring techniques that can be used during cardiopulmonary bypass include near-infrared spectroscopy, transcranial Doppler ultrasonography, and electroencephalographic techniques. Of these, only near-infrared spectroscopy provides a continuous quantitative signal of the physiologic variable most related to injury and most amenable to intervention. This review will advocate wide adoption of near-infrared spectroscopy monitoring throughout the perioperative period, to enhance detection of hypoxic conditions and to drive patient-specific interventions.

New developments in pediatric cardiac anesthesia

As the practice of pediatric cardiac anesthesia continues to grow, anesthesiologists now routinely care for patients ranging in size from less than 2 kg to more than 100 kg. New clinical and laboratory research has enhanced our understanding of the effects of anesthetic drugs on the pediatric myocardium, and improvements in survival statistics for even the smallest and sickest infants have shifted the emphasis to evaluation of quality of life and neurological outcome in pediatric cardiac patients. The use of circulatory support in infants and children, both for rapid resuscitation and for more chronic indications such as bridge to transplantation, also continues to evolve, with the recent introduction of pulsatile and axial pumps for pediatric use. This article reviews anesthetic agents, bleeding and coagulation, neurological monitoring, and mechanical circulatory support in the treatment of infants and children.

Postoperative support with the centrifugal pump ventricular assist device (VAD)

Centrifugal pump left ventricular assist device is a useful adjunct in pediatric cardiac surgery, as a bridge to recovery, or in some cases, to transplantation. This form of circulatory support may not have the universal applicability of extracorporeal membrane oxygenation, but it is equally or more effective in properly selected patients. The technology for centrifugal pump support is now quite standardized, and the advantages well documented. In this chapter we discuss the problems of indications, case selection, technical aspects of the circuit, and general clinical management. Results since 1989 are also presented.

Decision making for mechanical cardiac assist in pediatric cardiac surgery

The practice of pediatric cardiac surgery has evolved to the point where the majority of patients operated on represent the most complex end of the spectrum of congenital heart disease. Given this, the potential role for mechanical cardiac assist will continue to expand. Although extracorporeal membrane oxygenation remains the mainstay of mechanical circulatory assist, the increased use of centrifugal ventricular assist devices is changing the approach to the treatment of acute cardiac failure. A range of newly developed implantable and paracorporeal devices is beginning to make its way into the clinical practice of pediatric cardiac surgery. This article addresses the different types of support available for mechanical cardiac assist and the clinical considerations in selecting the appropriate device.