Primary and secondary pulmonary failure was supported by cervical ECMO via Avalon cannula (n = 5), apart from two patients (patients 7 and 16). The first was stabilized via cervical ECLS as she presented with cardio respiratory failure 6 months after cardiac surgery. The second suffered from streptococcal pneumonia with pneumothoraces despite multiple chest tubes and was supported by thoracic ECLS, to treat lung fistulae.
Patients with cardiac failure were usually approached by sternotomy and supported by ECLS (n = 19). Exceptions were made in two of those patients, who were cannulated via neck vessels because of ongoing CPR: patient 172 was resuscitated 4 months after Glenn-take down during cardiac catheterization; patient 15 was rewarmed after drowning and CPR over 75 minutes. In addition, VADs were implanted in four patients with isolated cardiac failure and sufficient pulmonary function (patients 4, 17,1 22, 24).
Four patients were changed to a different support device during the course of the treatment. Patient 22 received UNIVAD after he failed to wean off bypass. As his oxygen saturation dropped later on the same day, an oxygenator had to be implanted and he was switched to ECLS on ICU. Patients 5, 18, and 23 were first treated with ECLS, and then changed to UNIVAD as their lungs recovered after 5, 5, and 4 days, respectively.
Mean duration of support was 12 ± 15 days (median: 8 days [range: 2–69 days]). Flow ranges for neonates were considerably lower for ECMO therapy (range: 0.2–0.3 L/min) than for ECLS support (range: 0.4–0.75 L/min).
The average running time of a singular support system without exchange was 5 days (range: 0–20 days). In total, 37 exchanges of mechanical support systems were conducted in 13 patients. The median system exchange rate was 0 per patient (range: 0–8). There was no hemolysis related exchange of the pump head.
Weaning from extracorporeal support was successful in 89.3% (n = 25) of all DP3 runs. The 30 day survival was 85.7% (n = 24) and hospital survival accounted to 71.4% (n = 20; Figure 4).
All patients with pulmonary indication survived, except patient 20 with myelodysplastic syndrome, who received ECMO because of respiratory failure after bone marrow transplantation. Both patients with biventricular morphology and DP3-VAD survived. Moreover, all patients with UNIVAD, who did not need further extracorporeal respiratory assist (n = 4), were discharged. Patient 22 with coronary sinusoids was switched from UNIVAD to ECLS and died of cardiac failure despite successful weaning. Further six patients with primary ECLS died in hospital: In patient 1, aortic cannula dislocation led to urgent thoracotomy and system exchange but sufficiently stable circulation was not achieved. Patient 3 was successfully weaned from the device, extubated, and transferred to the ward but died later because of sudden circulatory arrest. In patient 10, upper caval rupture after balloon dilatation resulted in an air block after urgent rethoracotomy with a system standstill. The pump was damaged during CPR and deairing, and had to be exchanged. The patient could be weaned from the device, but expired later in hospital. In patient 13, increasing venous under pressure resulted in successive flow deregulation of the pump down to zero flow. Further mechanical support was abandoned after ineffective CPR. In two patients, ECLS was discontinued as the patients developed brain edema: Patient 172 had grave, congenital heart pathology, and ECLS in the context of post catheterization CPR; in patient 8, ECLS was implanted during CPR as bridge to EXCOR Pediatric (BerlinHeart GmbH, Germany) for decompensated dilated cardiomyopathy. Patient 15, who was rewarmed via cervical ECLS after drowning and CPR over 75 min, developed a left-sided hemiplegia with a right medial cerebral artery infarction confirmed on computed tomography (CT).
There is a lack of uniform nomenclature to distinguish between distinct extracorporeal therapies for cardiac, pulmonary, or cardiopulmonary failure.
Some authors in the field use ECLS17,21,22 or ECMO2–6,8–10,12,13,15,18–20,23 as all-inclusive terms, or use va-ECMO/vv-ECMO3,5 to differentiate by vessel cannulation. The German Society for Cardiovascular Engineering suggests the use of specific terminology (i.e., VAD, ECMO, and ECLS7,11,16,24) to differentiate between extracorporeal treatment scenarios, to enable precision in communication, maximize quality of treatment, and improve patient outcome. This will be reflected in the society’s newest guidelines, which are currently under review.
To date, this is the largest single centre serial study with the DP3 for extracorporeal mechanical support in a pediatric patient cohort.18,25 Compared with other studies, our pediatric patient cohort was heterogeneous comprising patients with pulmonary, postcardiotomy and other support indications, with both single and biventricular morphology. Of all seven patients with isolated respiratory support, only one patient with myelodysplastic syndrome (patient 20) could not be weaned from the device. This confirms other observations, which show that respiratory mechanical support offers higher chances of survival than cardiac assist22 but is often limited in patients with hematologic disorder.21 All patients, who were treated with VAD and did not require further extracorporeal respiratory support, survived. A waiver of the oxygenator has many advantages as around 90% reduction in surface area makes the patient prone to less coagulopathy, inflammatory reaction, and thrombembolic events.12 Extracorporeal life support ECLS patients are a much sicker patient group, as they suffer from combined cardio respiratory failure. All ECLS patients apart from two could be weaned from the device, yet only 63% could be discharged from hospital.
In literature, successful weaning rates from transient extracorporeal support range between 69% and 79% and the survival to hospital discharge rate is even lower, between 34% and 63%.9,12,19,22–24 In our cohort, almost all patients who survived at least 24 hours after mechanical support discontinuation (89.3%) also survived the first 30 days post mechanical support implantation. The gap between successful weaning and hospital survival (71.4%) may anticipate the sometimes still palliative character of extracorporeal support therapy as aspects influencing the outcome are mainly based on the underlying disease.
In this study, only the thoracic and cervical approach were used and therefore compartment syndrome, fasciotomy, or amputation of lower extremity, sometimes coincidental after cannulation of femoral vessels, did not occur.18
Technical complications comprised aortic cannula dislocation which could not adequately be managed (patient 1), and an air block leading to pump exchange because of damage of the pump during deairing (patient 10). Hence, pump failure was in first line user and not hardware induced. We did not observe long-standing macrohematuria indicating pump-induced corpuscular trauma under support system therapy.
A system standstill occurred in patient 13, resulting from venous under pressure. Stepwise down regulation of the DP3 prevented suction or rupture of the atrial wall and eliminated backflow from the aorta into the system. Nevertheless, immediate sufficient correction of hypovolemia or adequate positioning of the venous cannula might have saved the patient.
Neurologic complications were eminent in three patients (patients 5, 15, and 172), who had undergone prolonged CPR. Patient 15 was cannulated via neck vessels and developed signs of hemiplegia. It is unclear whether hemodynamic arrest before support, cerebral embolism, or the cannulation of one common carotid artery can be associated with diminished cerebral perfusion and hence induce cerebral ischemia. Reports on this cannulation technique usually refer to newborn or infant circulatory support, without giving any indication until what age this approach is safe.2
Small sized blood clots in the venous line or pump compartment of the system usually pass through the pump and accumulate in the oxygenator without endangering the patient. Despite the lack of this filtering mechanism by the oxygenator in patients with VAD no thrombosis or embolisms were observed even in this patient group. Lifetime of a support system in our cohort was usually dependent on the oxygenator, and terminated by system exchange on basis of elevated fibrin degradation products or increased platelet transfusion requirements.
Performance of the DP3
It was shown that calculated low flow rates needed for support particularly in neonates can be maintained over a long period of time. Even though other pumps offer the possibility of pulsatile flow15,17 or zero flow, it is the prevention of backflow and features for pressure, bubble, and flow control offering fine adjustments down to zero, which make the DP3 safe. Compared with its predecessors heat generation was abandoned and the DP3 treats corpuscular blood more gentle. Critical elements of construction related to the whole system are the connecting tubes, which conically increase from the venous 1/4 inch to 3/8 inch at the pump entrance. This may predispose to turbulent flow and thrombus formation.
Limitations are inherent in the nature of a single centre, retrospective study with a relatively small cohort and short observation period. Comparison to other support systems was not made. In our unit, markers of hemolysis (haptoglobin or free hemoglobin) are not part of routine laboratory chemistry control.
In a heterogeneous pediatric cohort, the Deltastream DP3 pump has proofed to be a versatile and safe tool in mechanical support therapy, which can be adapted to the individual circumstances and necessities of the patient, even in low-flow ranges.
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Keywords:Copyright © 2016 by the American Society for Artificial Internal Organs
extracorporeal life support; extracorporeal membrane oxygenation; diagonal pump; DP3; congenital heart disease