Cardiovascular complications adversely affect survival during extracorporeal membrane oxygenation

Optimizing Outcomes in Extracorporeal Membrane Oxygenation Postcardiotomy in Pediatric Population

Extracorporeal membrane oxygenation (ECMO) is a rapidly emerging advanced life support technique used in cardiorespiratory failure refractory to other treatments. There has been an influx in the number of studies relating to ECMO in recent years, as the technique becomes more popular. However, there are still significant gaps in the literature including complications and their impacts and methods to predict their development. This review evaluates the available literature on the complications of ECMO postcardiotomy in the pediatric population. Areas explored include renal, cardiovascular, hematological, infection, neurological, and hepatic complications. Incidence, risk factors and potential predictors, and scoring systems for the development of these complications have been evaluated.

Neonatal Hypertension

Neonatal hypertension is uncommon but is becoming increasingly recognized. Normative blood pressure data are limited, as is research regarding the risks, treatment, and long-term outcomes. Therefore, there are no clinical practice guidelines and management is based on clinical judgment and expert opinion. Recognition of neonatal hypertension requires proper blood pressure measurement technique. When hypertension is present there should be a thorough clinical, laboratory, and imaging evaluation to promptly diagnose causes needing medical or surgical management. This review provides a practical overview for the practicing clinician regarding the identification, evaluation, and management of neonatal hypertension.

Systemic Hypertension in Pediatric Veno-Venous Extracorporeal Membrane Oxygenation

Systemic hypertension (HTN) is a recognized complication of veno-venous (VV) extracorporeal membrane oxygenation (ECMO) in children. We sought to determine the prevalence and associated features of HTN in a retrospective cohort of children (>1 year old) supported with VV ECMO from January 2015 to July 2019 at our institution. Patient and ECMO-related characteristics were reviewed, including intensive care unit (ICU) length of stay (LOS), ECMO duration, corticosteroids and nephrotoxic medication exposure, acute kidney injury (AKI), overall fluid balance, and transfusion data. We analyzed 23 children (43% female) with a median age of 8.5 years (interquartile range [IQR] = 4-14.5). Median ICU LOS was 26 days (IQR = 15-47) with a median ECMO duration of 288 hours (IQR = 106-378) and a mortality rate of 35%. HTN was diagnosed in 87% subjects at a median of 25 ECMO hours (IQR = 9-54) of whom 55% were hypertensive >50% of their ECMO duration. AKI and fluid overload were documented in >50% of cohort. All but two subjects received at least one nephrotoxic medication, and nearly all received corticosteroids. Our data demonstrate that HTN is present in a preponderance of children supported with VV ECMO and appears within the first 3 days of cannulation. Underlying etiology is likely multifactorial.

Time-Resolved Echo-Particle Image/Tracking Velocimetry Measurement of Interactions Between Native Cardiac Output and Veno-Arterial ECMO Flows

Determination of optimal hemodynamic and pressure-volume loading conditions for patients undergoing veno-arterial extracorporeal membrane oxygenation (VA-ECMO) would benefit from understanding the impact of ECMO flow rates (QE) on the native cardiac output in the admixing zone, i.e., aortic root. This study characterizes the flow in the aortic root of a pig with severe myocardial ischemia using contrast-enhanced ultrasound particle image/tracking velocimetry (echo-PIV/PTV). New methods for data preprocessing are introduced, including autocontouring to remove surrounding tissues, followed by blind deconvolution to identify the centers of elongated bubble traces in images with low signal to noise ratio. Calibrations based on synthetic images show that this procedure increases the number of detected bubbles and reduces the error in their locations by 50%. Then, an optimized echo-PIV/PTV procedure, which integrates image enhancement with velocity measurements, is used for characterizing the time-resolved two-dimensional (2D) velocity distributions. Phase-averaged and instantaneous flow fields show that the ECMO flow rate influences the velocity and acceleration of the cardiac output during systole, and secondary flows during diastole. When QE is 3.0 L/min or higher, the cardiac ejection velocity, phase interval with open aortic valve, velocity-time integral (VTI), and mean arterial pressure (MAP) increase with decreasing QE, all indicating sufficient support. For lower QE, the MAP and VTI decrease as QE is reduced, and the deceleration during transition to diastole becomes milder. Hence, for this specific case, the optimal ECMO flow rate is 3.0 L/min.

The hypertensive neonate

Hypertension in neonates is increasingly recognized because of improvements in neonatal intensive care that have led to improved survival of premature infants. Although normative data on neonatal blood pressure remain limited, several factors appear to be important in determining blood pressure levels in neonates, especially gestational age, birth weight and maternal factors. Incidence is around 1% in most studies and identification depends on careful blood pressure measurement. Common causes of neonatal hypertension include umbilical catheter associated thrombosis, renal parenchymal disease, and chronic lung disease, and can usually be identified with careful diagnostic evaluation. Given limited data on long-term outcomes and use of antihypertensive medications in these infants, clinical expertise may need to be relied upon to decide the best approach to treatment. This review will discuss these concepts and identify evidence gaps that should be addressed.

Nicardipine for the Treatment of Neonatal Hypertension During Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is one of the primary reasons systemic hypertension is experienced in hospitalized neonates. Commonly used antihypertensive agents have resulted in significant adverse effects in neonatal and pediatric populations. Nicardipine is a desirable option because of its rapid and titratable antihypertensive properties and low incidence of adverse effects. However, data for use in neonatal ECMO are limited. We conducted a retrospective review of patients less than 44 weeks post-menstrual age who received a nicardipine infusion for first-line treatment of systemic hypertension while on ECMO at our institution between 2010 and 2016. Systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressures were evaluated for 48-h after nicardipine initiation. Eight neonates received a nicardipine infusion while on ECMO during the study period. Nicardipine was initiated at a mean dose of 0.52 ( ± 0.22) mcg/kg/min and titrated to a maximum dose of 1.1 ( ± 0.85) mcg/kg/min. The median duration of nicardipine use was 51 (range 4-227) hours. Significant decreases in SBP, DBP, and MAP occurred within one hour of initiation of nicardipine and were sustained through the majority of the 48-h evaluation period. No patients experienced hypotension. Prospective studies are warranted to evaluate the optimal dose, safety, and efficacy of nicardipine in neonates who require ECMO.

Neonatal hypertension: cases, causes, and clinical approach

Neonatal hypertension is increasingly recognized as dramatic improvements in neonatal intensive care, advancements in our understanding of neonatal physiology, and implementation of new therapies have led to improved survival of premature infants. A variety of factors appear to be important in determining blood pressure in neonates, including gestational age, birth weight, and postmenstrual age. Normative data on neonatal blood pressure values remain limited. The cause of hypertension in an affected neonate is often identified with careful diagnostic evaluation, with the most common causes being umbilical catheter-associated thrombosis, renal parenchymal disease, and chronic lung disease. Clinical expertise may need to be relied upon to decide the best approach to treatment in such patients, as data on the use of antihypertensive medications in this age group are extremely limited. Available data suggest that long-term outcomes are usually good, with resolution of hypertension in most infants. In this review, we will take a case-based approach to illustrate these concepts and to point out important evidence gaps that need to be addressed so that management of neonatal hypertension may be improved.

An overview of medical ECMO for neonates

Extracorporeal membrane oxygenation (ECMO), a life-saving therapy for respiratory and cardiac failure, was first used in neonates in the 1970s. The indications and criteria for ECMO have changed over the years, but it continues to be an important option for those who have failed other medical therapies. Since the Extracorporeal Life Support Organization (ELSO) Registry was established in 1989, more than 29,900 neonates have been placed on ECMO for respiratory failure, with 84% surviving their ECMO course, and 73% surviving to discharge or transfer. In this chapter, we will review the basics of ECMO, patient characteristics and criteria, patient management, ECMO complications, special uses of neonatal ECMO, and patient outcomes.

20-year experience of prolonged extracorporeal membrane oxygenation in critically ill children with cardiac or pulmonary failure

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a rescue therapy for life-threatening respiratory or circulatory failure. Although outcomes are favorable with short-term ECMO therapy, data on the outcomes of prolonged ECMO therapy in children are very limited. This study aimed to study morbidity and mortality associated with prolonged ECMO therapy (≥28 days) in children with refractory cardiac or pulmonary failure.

METHODS

We conducted a retrospective review of all children≤18 years supported with ECMO for ≥28 days between January 1991 and September 2011 at the Arkansas Children's Hospital. The data collected in our study included patient demographic information; diagnosis; indication for ECMO; ECMO support details; medical and surgical history; laboratory, microbiologic, and radiographic data; information on organ dysfunction; complications; and patient outcomes. The outcome variables evaluated in this report included survival to ECMO decannulation, survival to hospital discharge, and current survival with emphasis on neurologic, renal, pulmonary, and other end organ function.

RESULTS

During the study period, 984 events in 951 patients were supported with ECMO with a 30-day survival of 666 events (68%). Only 22 ECMO runs were ≥28 days and were eligible for inclusion in this report. The longest ECMO run in our series was 1,206 hours (50 days). The average length of ECMO run in this cohort was 855±133 hours, with a mean intensive care unit length of stay of 56±27 days. Ten patients (45%) were successfully decannulated from ECMO. Six patients (27%) were alive 30 days after decannulation, and only 4 patients (19%) survived to hospital discharge. Of the 4 survivors, only 3 patients (14%) are living to date. Of the 3 living children, 2 have significant neurologic issues with brain atrophy and developmental delay, and 1 is awaiting renal transplant; all 3 survivors have chronic lung disease.

CONCLUSIONS

This case series highlights that the prolonged use of ECMO in children with refractory cardiac failure, respiratory failure, or both is associated with low survival. Furthermore, it suggests that the survivors of prolonged ECMO runs have significant long-term sequelae.

Extracorporeal membrane oxygenation for the support of infants, children, and young adults with acute myocarditis: a review of the Extracorporeal Life Support Organization registry

OBJECTIVE

To describe survival outcomes for pediatric patients supported with extracorporeal membrane oxygenation for severe myocarditis and identify risk factors for in-hospital mortality.

DESIGN

Retrospective review of Extracorporeal Life Support Organization registry database.

SETTING

Data reported to Extracorporeal Life Support Organization from 116 extracorporeal membrane oxygenation centers.

PATIENTS

Patients < or = 18 yrs of age supported with extracorporeal membrane oxygenation for myocarditis during 1995 to 2006.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 19,348 reported pediatric extracorporeal membrane oxygenation uses from 1995 to 2006, 260 runs were for 255 patients with a diagnosis of myocarditis (1.3%). Survival to hospital discharge was 61%. Seven patients (3%) underwent heart transplantation and six patients survived to discharge. Of 100 patients not surviving to hospital discharge, extracorporeal membrane oxygenation support was withdrawn in 70 (70%) with multiple organ failure as the indication in 58 (83%) patients. In a multivariable model, female gender (adjusted odds ratio, 2.3, 95% confidence interval, 1.3-4.2), arrhythmia on extracorporeal membrane oxygenation (adjusted odds ratio, 2.7, 95% confidence interval, 1.5-5.1), and renal failure requiring dialysis (adjusted odds ratio, 5.1, 95% confidence interval, 2.3-11.4) were associated with increased odds of in-hospital mortality.

CONCLUSION

Extracorporeal membrane oxygenation is a valuable tool to rescue children with severe cardiorespiratory compromise related to myocarditis. Female gender, arrhythmia on extracorporeal membrane oxygenation, and need for dialysis during extracorporeal membrane oxygenation were associated with increased mortality.

Thyroid hormone regulation of perinatal cardiovascular function

Thyroid hormone plays an important role in regulating cardiovascular function during the transition to extrauterine physiology. Multiple mechanisms participate, ranging from transcriptional to more immediate nongenomic modes of regulation.

Factors influencing the outcome of paediatric cardiac surgical patients during extracorporeal circulatory support

BACKGROUND

Veno-arterial extracorporeal membrane oxygenation (ECMO) is a common modality of circulatory assist device used in children. We assessed the outcome of children who had ECMO following repair of congenital cardiac defects (CCD) and identified the risk factors associated with hospital mortality.

METHODS

From April 1990 to December 2003, 53 patients required ECMO following surgical correction of CCD. Retrospectively collected data was analyzed with univariate and multivariate logistic regression analysis.

RESULTS

Median age and weight of the patients were 150 days and 5.4 kgs respectively. The indications for ECMO were low cardiac output in 16, failure to wean cardiopulmonary bypass in 13, cardiac arrest in 10 and cardio-respiratory failure in 14 patients. The mean duration of ECMO was 143 hours. Weaning off from ECMO was successful in 66% and of these 83% were survival to hospital-discharge. 37.7% of patients were alive for the mean follow-up period of 75 months. On univariate analysis, arrhythmias, ECMO duration >168 hours, bleeding complications, renal replacement therapy on ECMO, arrhythmias and cardiac arrest after ECMO were associated with hospital mortality.On multivariate analysis, abnormal neurology, bleeding complications and arrhythmias after ECMO were associated with hospital mortality. Extra and intra-thoracic cannulations were used in 79% and 21% of patients respectively and extra-thoracic cannulation had significantly less bleeding complications (p = 0.031).

CONCLUSION

ECMO provides an effective circulatory support following surgical repair of CCD in children. Extra-thoracic cannulation is associated with less bleeding complications. Abnormal neurology, bleeding complications on ECMO and arrhythmias after ECMO are poor prognostic indicators for hospital survival.

Systemic hypertension associated with venovenous extracorporeal membrane oxygenation for pediatric respiratory failure

BACKGROUND/PURPOSE

Arterial hypertension (HTN) is common in neonates on venoarterial (VA) extracorporeal membrane oxygenation (ECMO), but HTN in pediatric venovenous (VV) ECMO has not been well described. The authors noted HTN in their VV ECMO experience and hypothesized that HTN was associated with fluid status, steroid use, and renal insufficiency.

METHODS

Records of 50 patients receiving VV ECMO for respiratory failure were reviewed. HTN was defined as systolic blood pressure greater than 95th percentile for age for > or =1 hour, unresponsive to sedation/analgesia. Hypertensive index (HI) is defined as total hypertensive hours per total ECMO hours. Fluid status was estimated by a fluid index (FI = total fluid balance during ECMO per ECMO hours per weight).

RESULTS

Forty-seven of 50 patients (94%) had HTN. Median HI was 0.21 (range, 0.01 to 1.0). Thirteen patients had renal insufficiency, 39 received steroids, and 23 received continuous venovenous hemofiltration (CVVH). There was no association between HI and FI, steroid use, or renal insufficiency. Thirty-three patients were treated for HTN, often requiring multiple agents. Bleeding complicated the course of 18 patients, and HI was significantly higher in those patients (P = .03). HI was not different between survivors (37 of 39 with HTN) and nonsurvivors (10 of 11 with HTN).

CONCLUSIONS

Hypertension is a common complication associated with VV ECMO with unclear etiology. HTN was frequently difficult to control. This study emphasizes the need for the development of treatment protocols to decrease the incidence, severity, and associated morbidity. Improved insight into the etiology of HTN associated with pediatric VV ECMO, including evaluation of the renin-angiotensin system, would help guide therapy.

Cardiovascular stability during arteriovenous extracorporeal therapy: a randomized controlled study in lambs with acute lung injury

INTRODUCTION

Clinical application of arteriovenous (AV) extracorporeal membrane oxygenation (ECMO) requires assessment of cardiovascular ability to respond adequately to the presence of an AV shunt in the face of acute lung injury (ALI). This ability may be age dependent and vary with the experimental model. We studied cardiovascular stability in a lamb model of severe ALI, comparing conventional mechanical ventilation (CMV) with AV-ECMO therapy.

METHODS

Seventeen lambs were anesthetized, tracheotomized, paralyzed, and ventilated to maintain normocapnia. Femoral and jugular veins, and femoral and carotid arteries were instrumented for the AV-ECMO circuit, systemic and pulmonary artery blood pressure monitoring, gas exchange, and cardiac output determination (thermodilution technique). A severe ALI (arterial oxygen tension/inspired fractional oxygen <200) was induced by lung lavage (repeated three times, each with 5 ml/kg saline) followed by tracheal instillation of 2.5 ml/kg of 0.1 N HCl. Lambs were consecutively assigned to CMV treatment (n = 8) or CMV plus AV-ECMO therapy using up to 15% of the cardiac output for the AV shunt flow during a 6-hour study period (n = 9). The outcome measures were the degree of inotropic and ventilator support needed to maintain hemodynamic stability and normocapnia, respectively.

RESULTS

Five of the nine lambs subjected to AV-ECMO therapy (56%) died before completion of the 6-hour study period, as compared with two out of eight lambs (25%) in the CMV group (P > 0.05; Fisher's exact test). Surviving and nonsurviving lambs in the AV-ECMO group, unlike the CMV group, required continuous volume expansion and inotropic support (P < 0.001; Fisher's exact test). Lambs in the AV-ECMO group were able to maintain normocapnia with a maximum of 30% reduction in the minute ventilation, as compared with the CMV group (P < 0.05).

CONCLUSION

AV-ECMO therapy in lambs subjected to severe ALI requires continuous hemodynamic support to maintain cardiovascular stability and normocapnia, as compared with lambs receiving CMV support.

Ductus arteriosus with left-to-right shunt during venoarterial extracorporeal membrane oxygenation: effects on cerebral oxygenation and hemodynamics

OBJECTIVE

To investigate the effect on cerebral oxygenation and hemodynamics of a patent ductus arteriosus with left-to-right shunt during venoarterial extracorporeal membrane oxygenation in a lamb model.

DESIGN

Prospective intervention study in animals.

SETTING

Animal research laboratory of a university medical center.

SUBJECTS

Six anesthetized newborn lambs with patent ductus arteriosus and left-to-right shunt, installed on venoarterial extracorporeal membrane oxygenation.

INTERVENTIONS

Six lambs of 140 days gestational age were prepared to keep the ductus arteriosus open by infiltration of the vessel wall with formaline 10%. The animals were installed on standard venoarterial extracorporeal membrane oxygenation. With a mechanical occluder, the ductus was closed.

MEASUREMENTS AND MAIN RESULTS

Changes of mean arterial blood pressure and carotid artery blood flow were measured simultaneously. Using near infrared spectrophotometry, we calculated changes in cerebral concentration of oxyhemoglobin and deoxyhemoglobin (reflecting changes in cerebral oxygen supply) and total hemoglobin (reflecting changes in cerebral blood volume). Also, cerebral oxygen delivery before and after ductus closure was calculated. Before ductus closure there was a left-to-right shunt with a mean +/- SEM of 41 +/- 20% of total body blood flow. Closure of the ductus resulted in an immediate increase in mean arterial blood pressure and carotid artery blood flow. The concentration of oxyhemoglobin increased and the concentration of deoxyhemoglobin decreased, representing increased cerebral oxygen supply. The concentration of total hemoglobin was unchanged, representing unchanged cerebral blood volume. There was an increase in cerebral oxygen delivery.

CONCLUSIONS

In this lamb model, a considerable left-to-right shunt over the ductus during venoarterial extracorporeal membrane oxygenation reduced cerebral circulation and oxygenation.

Outcome after recannulation and a second course of extracorporeal membrane oxygenation

BACKGROUND/PURPOSE

Controversy surrounds the justification of a second course of extracorporeal membrane oxygenation (ECMO) for patients that deteriorate after initial decannulation. The authors' experience with a small number of patients requiring recannulation led them to investigate the results of a second ECMO course from all institutions that report to the ELSO registry.

METHODS

The ELSO neonatal registry for patients that underwent multiple ECMO courses was reviewed and mortality and complication rates between first and second courses were compared. Complications were classified according to the following ELSO registry defined categories: hemorrhagic, mechanical, metabolic, infectious, renal, pulmonary, neurologic, and cardiac.

RESULTS

Of the 16,450 patients in the ELSO neonatal registry in January 2000, 205 patients (1.25%) have required multiple ECMO courses. There have been 201 patients (1.22%) who have needed 2 courses of ECMO and 4 patients (0.024%) have undergone 3 ECMO runs. A total of 557 complications occurred during the first ECMO course in these 205 patients, and 672 complications developed during the second course. This represents an increase in the complication rate by 20.6% during the second ECMO course. Although mechanical complications were the most common, there was no change in the incidence between first and second courses. However, the frequency of complications increased in all other classifications during the second course when compared with the first. The largest increases occurred with neurologic and infectious complications (134% and 79% increases, respectively). Renal and metabolic complications also were markedly elevated (35% and 24%, respectively). Seventy-six of 201 (38%) patients who required 2 courses of ECMO and 1 of 4 patients undergoing 3 runs survived. Survival was more likely for patients with meconium aspiration. Primary pulmonary hypertension and total anomalous pulmonary venous return had low survival rates.

CONCLUSIONS

A small subset of patients may require recannulation and a second ECMO course. Although survival may be achieved in more than one third of these patients, complication rates are increased during the second course. Specifically, neurologic, infectious, renal, and metabolic complication rates are increased. Long-term consequences of recannulation are unknown. Selection criteria identifying patients that may benefit from recannulation have not been established.

Survival and renal function in pediatric patients following extracorporeal life support with hemofiltration

OBJECTIVE: To determine variables associated with survival in pediatric patients treated with hemofiltration while receiving extracorporeal life support and to determine the probability for recovery of renal function among survivors. DESIGN: Retrospective database analysis. SETTING: University of Michigan pediatric nephrology database. PATIENTS: All pediatric patients treated with continuous hemofiltration while on extracorporeal life support at the University of Michigan between January 1990 and May 1999. A pediatric patient was defined as any child between birth and 18 yrs of age, including children treated in both the pediatric intensive care unit and neonatal intensive care unit. Indications for extracorporeal life support included both cardiac and pulmonary failure. INTERVENTIONS: Data analysis of patients who were treated with hemofiltration while on extracorporeal life support. Hemofiltration includes both ultrafiltration and hemofiltration with countercurrent dialysis. MEASUREMENTS AND MAIN RESULTS: Thirty-five patients with a mean age of 39 +/- 65 months (median, 3 months) underwent hemofiltration while on extracorporeal life support. Forty-three percent survived to hospital discharge (95% CI, 26%-60%). All deaths occurred in the intensive care unit. Recovery of renal function occurred in 93% of survivors (95% CI, 79%-108%). Mean duration of hemofiltration in survivors, including time during and after extracorporeal life support, was 9 +/- 6 days. All nonsurvivors were on renal replacement therapy at the time of death. In this analysis, decreased survival was significantly associated with the use of vasopressor infusions (p =.01) and the presence of complications (p =.006). Vasopressor infusions were required in 89% of patients, and 37% of patients experienced complications. CONCLUSIONS: In patients receiving hemofiltration while on extracorporeal life support, survival is comparable to that reported in other extracorporeal life support or hemofiltration populations. Decreased survival in these patients may be associated with the use of vasopressor infusions and the occurrence of complications. Recovery of renal function occurs in most survivors.