Mechanical cardiac support in the young. Short-term support: ECMO

Trends in Mortality and Costs of Pediatric Extracorporeal Life Support

BACKGROUND

Extracorporeal life support (ECLS) has been used for >30 years as a life-sustaining therapy in critically ill patients for a variety of indications. In the current study, we aimed to examine trends in use, mortality, length of stay (LOS), and costs for pediatric ECLS hospitalizations.

METHODS

We performed a retrospective cohort study of pediatric patients (between the ages of 28 days and <21 years) on ECLS using the 2008-2015 National Inpatient Sample, the largest all-payer inpatient hospitalization database generated from hospital discharges. Nonparametric and Cochran-Armitage tests for trend were used to study in-hospital mortality, LOS, and hospitalization costs.

RESULTS

Of the estimated 5847 patients identified and included for analysis, ECLS was required for respiratory failure (36.4%), postcardiotomy syndrome (25.9%), mixed cardiopulmonary failure (21.7%), cardiogenic shock (13.1%), and transplanted graft dysfunction (2.9%). The rate of ECLS hospitalizations increased 329%, from 11 to 46 cases per 100 000 pediatric hospitalizations, from 2008 to 2015 (P < .001). Overall mortality decreased from 50.3% to 34.6% (P < .001). Adjusted hospital costs increased significantly ($214 046 ± 11 822 to 324 841 ± 25 621; P = .002) during the study period despite a stable overall hospital LOS (46 ± 6 to 44 ± 4 days; P = .94).

CONCLUSIONS

Use of ECLS in pediatric patients has increased with substantially improved ECLS survival rates. Hospital costs have increased significantly despite a stable LOS in this group. Dissemination of this costly yet life-saving technology warrants ongoing analysis of use trends to identify areas for quality improvement.

A transapical-to-aorta double lumen cannula-based neonate left ventricular assist device efficiently unloads the left ventricle in neonate lambs

OBJECTIVE

We are developing a transapical-to-aorta double lumen cannula (TAA DLC) for a less-invasive/more dependable neonatal left ventricular assist device.

METHODS

The 18-Fr TAA DLC prototypes were bench tested and evaluated for 6 hours in neonate lambs (n = 6, 7.7-10 kg). The cardiac apex was exposed through a left anterolateral thoracotomy through the sixth intercostal space. The TAA DLC was inserted through a mattress stitch on apex, passing LV-aortic valve, into the ascending aorta with insertion/deployment guided by pressure waveform. The DLC was connected to blood pump. Cardiac output and aortic root blood flow were measured with perivascular flow sensors. Activated clotting time was maintained at 180-250 seconds.

RESULTS

The DLC pumped up to 1.8 L/min flow against 63 mm Hg drainage pressure and 145 mm Hg infusion pressure in bench testing. In all lambs, the DLC was inserted/deployed properly within 1 minute on the first attempt. Pumping flow was maintained at 1.2-1.3 L/min. Systolic arterial pressure decreased and diastolic arterial pressure/mean arterial pressure increased, indicating decreased afterload and increased perfusion pressure. Left ventricular end-diastolic pressure decreased from 13 ± 1 mm Hg to 6 ± 2 mm Hg, indicating decreased preload. Aortic root backward flow was 2.4% ± 0.6% without DLC and 3.5% ± 0.8% of cardiac output with DLC, indicating no significant DLC-induced aortic valve regurgitation. After 6 hours, free hemoglobin was <5 mg/dL with hemoglobin/platelets unchanged. No significant thrombus was found in pumps/DLCs. No trauma was found in LV, aortic valve, and aorta.

CONCLUSIONS

Our TAA DLC-based neonate left ventricular assist device efficiently unloaded the LV in lambs.

Options for the failing ventricle in pediatric heart disease

The management of the pediatric patient with the failing ventricle poses its own therapeutic challenges, not least because patient size limits options available. Once medical management has hit its ceiling, attention is turned to surgical options for mechanical support. The approach to these options has to bear in mind that there may be many potential causes for pump failure, and that these occur often in the context of pulmonary hypertension and poor gas exchange. Although extracorporeal life support has been the mainstay of treatment for acute heart failure, in the last decade, attention has been focusing on longer-term options to bridge to recovery or eventual transplant. Added to this are more novel applications of ventricular assist devices, notable in the management of the failing Fontan circulation where there are no perfect solutions. There is growing interest in the use of such devices to power this delicate circulation and extend the functional capacity of patients without resorting to transplantation. In this review article, we explore the role each of these surgical modalities has to play in the management of the child with acute and chronic heart failure, and explore the recent developments in the rapidly growing field of pediatric ventricular assist.

Myocardial oxidative metabolism and protein synthesis during mechanical circulatory support by extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) provides essential mechanical circulatory support necessary for survival in infants and children with acute cardiac decompensation. However, ECMO also causes metabolic disturbances, which contribute to total body wasting and protein loss. Cardiac stunning can also occur, which prevents ECMO weaning, and contributes to high mortality. The heart may specifically undergo metabolic impairments, which influence functional recovery. We tested the hypothesis that ECMO alters oxidative metabolism and protein synthesis. We focused on the amino acid leucine and integration with myocardial protein synthesis. We used a translational immature swine model in which we assessed in heart 1) the fractional contribution of leucine (FcLeucine) and pyruvate to mitochondrial acetyl-CoA formation by nuclear magnetic resonance and 2) global protein fractional synthesis (FSR) by gas chromatography-mass spectrometry. Immature mixed breed Yorkshire male piglets (n = 22) were divided into four groups based on loading status (8 h of normal circulation or ECMO) and intracoronary infusion [(13)C(6),(15)N]-L-leucine (3.7 mM) alone or with [2-(13)C]-pyruvate (7.4 mM). ECMO decreased pulse pressure and correspondingly lowered myocardial oxygen consumption (∼40%, n = 5), indicating decreased overall mitochondrial oxidative metabolism. However, FcLeucine was maintained and myocardial protein FSR was marginally increased. Pyruvate addition decreased tissue leucine enrichment, FcLeucine, and Fc for endogenous substrates as well as protein FSR. The heart under ECMO shows reduced oxidative metabolism of substrates, including amino acids, while maintaining 1) metabolic flexibility indicated by ability to respond to pyruvate and 2) a normal or increased capacity for global protein synthesis.

The impact of extracorporeal membrane oxygenation on survival in pediatric patients with respiratory and heart failure: review of our experience

Extracorporeal membrane oxygenation (ECMO) is widely used for circulatory support in pediatric cardiac patients with low cardiac output and hypoxemia. We retrospectively evaluated the efficacy of ECMO support for respiratory and heart failure in infants and children. From April 2002 to February 2011, 14 patients aged 19 days to 20 years old (average 44 months), with body weight 2.6 kg to 71 kg (median 14.1 kg), underwent ECMO support for failing cardiac function, hypoxemia, and low cardiac output syndrome. In 12 patients, ECMO was introduced after operation for congenital heart disease (four with complete repair including Fontan circulation, and eight with palliative repair). In one patient, ECMO was introduced after partial pulmonary resection for congenital cystic adenomatoid malformation because of respiratory failure. ECMO was introduced in a patient with severe heart failure caused by fulminant myocarditis. Patients' demographics, duration of extracorporeal membrane oxygenation, additional support, and outcomes were analyzed. Ten patients (71%) were successfully weaned from ECMO, and eight patients (57%) were discharged from the hospital. The mean duration of ECMO support was 332 h (range 11-2030 h). Although management of the ECMO circuit, including anticoagulation (activated clotting time: 150-250), was conducted following the institutional practice guidelines, it was difficult to control the bleeding. Seven patients required renal replacement therapy during ECMO support using peritoneal dialysis or continuous hemodiafiltration. Five patients had additional operative procedures: systemic-pulmonary shunt in two, bidirectional Glenn takedown with right modified Blalock-Taussig shunt, total cavopulmonary connection takedown, and redo ECMO in one patient each. The patient who had the longest ECMO support for respiratory failure due to acute respiratory distress syndrome after lung surgery was successfully weaned from ECMO because high-frequency oscillation (HFO) improved respiratory function. ECMO for heart and respiratory failure in infants and children is effective and allows time for recovery of cardiac dysfunction and acute hypoxic insult. The long-term ECMO support for over 2000 h was very rare, but it was possible to wean this patient from ECMO using HFO.

Perioperative mechanical circulatory support in children with critical heart disease

OPINION STATEMENT

The treatment of cardiovascular failure in the perioperative period with the use of mechanical circulatory support is a well-recognized, well-developed, and commonly utilized treatment modality. Regardless of the exact circumstances of initiation, the use of a support device is a "bridge." Where there has been an acute myocardial insult, short-term assist devices can serve as a "bridge to immediate survival," a "bridge to recovery," or even a "bridge to the next decision." Mechanical circulatory support can serve as a treatment of cardiovascular decompensation caused by myocarditis, acute myocardial insult, low cardiac output following surgery, and congenital heart disease. The utilization of such support carries significant risks such as bleeding, infection, and thrombosis. However, these can be minimized in order to allow for the safe and effective deployment of this therapeutic strategy. One specific therapeutic domain in which these devices provide immediate impact is during cardiac arrest. Although outcomes of cardiac arrest remain poor, use of a mechanical device as an intervention has allowed salvage of otherwise certain mortality. However, it is important to note that the utility of support was most pronounced in patients that were not on either extreme of the survival prediction curve. This can be best summarized by the concept of "not too early, not too late." Therefore, it is the responsibility of the entire care team to find the appropriate patient population in which to "pull the trigger" on mechanical support as a therapy. This decision point is supported by a monitoring strategy that can be utilized to predict deterioration and intervene adequately. Most importantly, an effective monitoring strategy allows the practitioner to judge the effectiveness of treatment and support strategies and make adjustments in a timely manner, potentially with mechanical support in the perioperative period.

Cleveland Clinic PediPump lamb cadaver fitting studies

We are developing the PediPump, a magnetically suspended, mixed-flow pump, as an implantable pediatric ventricular assist device (VAD). Lamb cadaver fitting studies were performed to determine the optimal pump location and optimal design of the inflow and outflow conduits for chronic in vivo studies. A prototype of the PediPump right and left ventricular assist devices (RVAD and LVAD, respectively) were implanted via a sternotomy or left thoracotomy in four lamb cadavers (3.7-34.2 kg). Via a sternotomy, the RVAD and LVAD required long inflow cannulas when placed into the right or left thoracic cavities, respectively. Via a left thoracotomy, with both pumps implanted in the left thoracic cavity, the RVAD required a 70 degrees inflow cannula and a bent outflow graft while the LVAD required a 130 degrees inflow cannula and a straight outflow graft. In conclusion, left thoracotomy provided optimal fitting for both LVAD and RVAD for the small lamb model.