ECMO may be considered as a bridge to interventional catheterization, given a rapidly deteriorating patient, a high-risk intervention, and a reasonable expectation of recovery of cardiac function following intervention.
By Jenni L. Raake, RRT; Robert H. Beekman III, MD; David P. Nelson, MD, PhD; and Steven M. Schwartz, MD
Extracorporeal membrane oxygenation (ECMO) replaces lung and/or heart function by oxygenating and/or pumping blood for the patient. During heart failure, ECMO provides oxygen to vital organs while the heart and lungs recover. This article describes the use of ECMO to support an infant with shock due to aortic stenosis and coarctation. While he was on ECMO, interventional cardiac catheterization was performed. This case is instructive because it highlights the use of ECMO to support newer, less traditional, and less invasive therapy, and points out the rapid deterioration that can occur with left heart obstruction in infants.
Figure 1. Blood from the ECMO circuit is pumped into a systemic artery so it can be delivered to the tissues without any pumping action by the heart.
On February 19, 2001, a male infant 3 months old and weighing 5.8 kg was seen by his physician with a history of poor feeding and increased work of breathing. On admission, he was mottled, and grunting, and had severe retractions. The physician referred him to the emergency department (ED) of the local children’s hospital where his temperature was 40.8°C, heart rate was 200 beats per minute, respiratory rate was 80 breaths per minute, and oximetry saturation was between 60% and 70%; he had very poor peripheral perfusion. Blood-gas analysis results were a pH of 6.96, a Pco2 of 35 mm Hg, and a base deficit of –29 mmol/L.Resuscitation included fluid administration (40 mL/kg) for peripheral perfusion, and intubation with initial ventilator settings that were an Fio2 of 100%, intermittent mandatory ventilation (IMV) rate of 30 bpm, positive end-expiratory pressure (PEEP) of 5 cm H2O, and peak inspiratory pressure of 20 cm H2O.
Chest radiography showed cardiomegaly and pulmonary edema while an echocardiogram confirmed severe aortic coarctation combined with aortic-valve stenosis. Most likely, this caused failure of the left ventricle and impairment of myocardial contractility, obstructing blood flow from the left ventricle to the peripheral tissues and imposing work on the heart.
Management focused on improving tissue oxygen delivery while readying the infant for transfer to Cincinnati Children’s Hospital Medical Center for definitive surgical intervention. Sodium bicarbonate and dobutamine were started and prostaglandin E1 was used in an attempt to reopen the ductus arteriosus. While unlikely, if the prostaglandin were to work, deoxygenated blood from the right ventricle would bypass the lungs, left ventricle, and aortic valve, and flow into the systemic circulation. Follow-up blood gases showed persistent acidosis, and the patient failed to improve, experiencing three episodes of electromechanical dissociation requiring cardiopulmonary resuscitation, epinephrine boluses, and an epinephrine infusion.
Despite resuscitative measures and transfer to the Cincinnati Medical Center cardiac intensive care unit (CICU) 80 km away, the infant’s condition continued to deteriorate. On arrival at the CICU, the patient was on a high dose epinephrine infusion, dobutamine infusion, dopamine infusion, and mechanical ventilation with pressure-regulated volume control at an Fio2 of 100%, a tidal volume of 130 mL, an IMV rate of 28 breaths per minute, and a PEEP of 5 cm H2O. Vital signs indicated a temperature of 36.8°C, a heart rate of 181 beats per minute, a respiratory rate of 28 breaths per minute, a blood pressure of 77 over 58, and an oxygen saturation of 100%. The patient appeared dusky and pale, with poor capillary refilling and thready peripheral pulses. Repeat blood-gas analysis showed a pH of 7.42, a Pco2 of 28 mm Hg, a Po2 of 445 mm Hg, and a base deficit of –4 mmol/L. Hemoglobin and hematocrit were 70 g/L and 21% respectively, and whole blood lactate was 8.81 mmol/L, demonstrating metabolic acidosis, hepatic insufficiency, and coagulopathy; the patient remained anuric.
Failure of the patient to improve left the CICU team with a choice: emergency open-heart surgery, interventional cardiac catheterization, or institution of ECMO. Because of the infant’s condition, the decision was made to restore organ perfusion using ECMO and delay intervention until the patient was more hemodynamically stable.
After initiation of ECMO, the epinephrine and dopamine infusions were discontinued, the lactate level decreased to 4.3 mmol/L, and urine output was established. Over the next 36 hours, the patient continued to improve with resolution of coagulopathy, improved urine output, and hemodynamic stability, prompting definitive therapy.
Because aortic stenosis and coarctation can be treated using interventional catheterization, this alternative was selected and the patient was transported to the cardiac catheterization laboratory on ECMO where he underwent balloon dilation of his valvar aortic stenosis and aortic coarctation. Hemodynamic measurements taken before and after intervention showed an aortic valve pressure gradient of 17 mm Hg and an aortic arch gradient of 20 mm Hg before intervention. Following balloon dilation, the aortic valve gradient decreased to 12 mm Hg and the coarctation gradient was completely resolved. After return to the CICU and over the next 24 hours, ECMO was decreased, and the patient was decannulated from ECMO on the first postprocedural day. The infant had developed a subdural hemorrhage, which placed him at risk for cerebrovascular accident due to the need for continuous anticoagulation during ECMO. Following ECMO decannulation, the patient improved rapidly and was extubated 72 hours after interventional catheterization; on the fifth postprocedural day, he was transferred to the referring hospital, where his recovery continued uneventfully.
This case demonstrates the various options available to clinicians for treatment of congenital heart defects (CHD), as well as considerations in using ECMO as a bridge to these procedures. It also highlights issues in the identification and management of infants in cardiogenic shock.
In congenital heart disease, ECMO is primarily used for pump failure, but is also suited for patients with marginal cardiopulmonary status during interventions. This principle is used during cardiopulmonary bypass (CPB) to conduct open-heart surgery. CPB maintains perfusion even when the heart is stopped for hours during complex surgical repairs of CHD. Reasons for use of ECMO outside the operating room include acute, reversible cardiac deterioration, as a bridge to transplantation, and when prolonged cardiac support is required due to myocardial dysfunction after cardiac surgery.1 The idea of using ECMO before, during, and after interventional cardiac catheterization is more recent.2
The major benefit of ECMO is oxygen delivery despite cardiopulmonary insufficiency. ECMO is invasive, and its risks include clots within the circuit, air in circuit and/or oxygenator, circuit rupture, central nervous system complications, bleeding, infection, and death.3,4 Nevertheless, ECMO may also be lifesaving with good outcomes when the cause of cardiopulmonary insufficiency is reversible and ECMO begins before end-organ damage has occurred.
Pediatric patients with cardiopulmonary arrest from cardiac disease have improved outcomes when rapidly supported with ECMO.1 In some institutions, survival rates (30% to 50%) for pediatric patients with congenital heart defects receiving ECMO after a cardiopulmonary arrest are comparable to all other pediatric patient groups that have been treated with ECMO.5 These patients were receiving CPR prior to ECMO, suggesting that survival without ECMO would have been substantially lower. This implied that use of ECMO to support pediatric patients with heart disease may warrant more aggressive use.
Another aspect of using ECMO for patients with CHD is consideration of the cardiac anatomy. The patient had coarctation of the aorta, and the aortic ECMO cannula was in the carotid artery with its tip proximal to the coarctation. It was essential to monitor for resolution of lactic acidosis and renal dysfunction caused by inadequate perfusion below the coarctation, prompting the team to proceed with therapy as the hemodynamic situation permitted. Although urine output improved within hours of starting ECMO, serum creatinine level did not decrease until after relief of the coarctation.
The aortic stenosis and coarctation could have been treated with catheter-based or surgical therapy. Surgical valvotomy would have required a period of cardioplegia, or planned cardiac arrest with CPB, causing myocardial dysfunction postoperatively, which would have been undesirable. Also, ECMO might have been needed following surgery. Patients requiring ECMO for cardiac support immediately after cardiac surgery have a high incidence of bleeding problems because ECMO requires persistent anticoagulation. This was avoided by choosing interventional catheterization to treat the aortic stenosis.
Catheter-based treatment of CHD has grown substantially, with balloon valvotomies of the aortic and pulmonary valves being the most common interventions.6,7 Although aortic valvotomy has been successfully performed in pediatrics since the mid 1980s, the risk of complications is higher in neonates.8 The most common complication is aortic regurgitation,6,9 but other complications include vascular or myocardial perforation, arterial or venous thrombosis, bleeding, and arrhythmia.10 Following relief of aortic obstruction, a decrease in the valvar pressure gradient is commonly seen, but when left ventricular dysfunction is severe, as in this case, the gradient may indicate ventricular function and transvalvar flow rather than the degree of obstruction.11 This is best demonstrated by echocardiographic data. A decline in the pressure gradient between the echocardiogram obtained at the referring hospital and the initial study at Cincinnati Children’s Hospital Medical Center indicated a reduction in cardiac output. After valvotomy, the pressure gradient increased, representing recovery of left ventricular function.
Although interventional catheterization is not the treatment of choice for neonates with aortic coarctation, it is well established in older children.12,13 Because this patient was already going to the catheterization laboratory for aortic valvotomy, balloon angioplasty of the coarctation site included little additional risk and much potential benefit, eliminating the need to operate on a critically ill infant.
In addition to the novel use of ECMO as a bridge to complex interventional catheterization and an appreciation for the rapidity with which infants in cardiogenic shock can deteriorate, one other aspect of this case is the late presentation of ductal-dependent heart defects. The ductus arteriosus typically closes in the first few days of life, and many types of heart defects, including severe aortic coarctation, are not readily detected until after ductal closure. The Baltimore-Washington infant study,14 an 8-year survey of the incidence of congenital heart defects in that area, found that 10% of deaths in the first year of life were due to undetected disease. Particularly applicable to this case is that undetected coarctation of the aorta was most commonly fatal after the second day of life. When these data are compared with more recent work15 showing that over 50% of mothers are discharged from the hospital before their infants are 24 hours old, it raises the concern that reducing medical observation of newborns has led to an increase in undetected ductal-dependent defects.14 Proposed legislation to increase in-hospital newborn care (no less than 48 to 72 hours) and/or mandatory home medical visits during the first week of life is aimed at reducing the number of cases resembling this one.
Individually, both ECMO and interventional cardiac catheterization may be lifesaving. Although such management is highly complex, this case documents the success of the combined use of these modalities.
Jenni L. Raake, RRT, is cardiac ICU coordinator for respiratory care; David S. Cooper, MD, is a fellow in cardiology; Robert H. Beekman III, MD, is director of cardiology; and David P. Nelson, MD, PhD, and Steven M. Schwartz, MD, are co-directors of the cardiac ICU, all at the Children’s Hospital Medical Center, Cincinnati.
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