Long-term Extracorporeal Life Support Research Articles

Comparison of complement consumption and platelet accumulation between membrane oxygenators coated with a polymer or heparin.

The membrane oxygenator in extracorporeal circulation circuits is coated with acrylate-copolymer (ACP) or immobilized heparin (IHP) to enhance hemocompatibility. To evaluate the relative features of both coatings, we compared blood components circulated in the circuits with ACP-and IHP-coated membranes in vitro using whole human blood. Whole human blood was heparinized and circulated in two experimental circuits with an ACP-coated reservoir, tubes, and an ACP- or IHP-coated membrane. Platelet (PLT) counts and the amount of total protein (TP), complement component 3 (C3), and complement component 4 (C4) were measured at 0, 8, 16, 24, and 32 h in each experiment (n = 5). The PLT count at 0-h circulation was lower in the IHP-coated than in the ACP-coated circuits (p = 0.034); however, no significant difference was observed at other time points. Reduction in TP at 8-h and 16-h circulation and in C3 at 32-h circulation was lesser in the ACP-coated than in the IHP-coated circuits (p = 0.004, 0.034, and 0.027, respectively); reduction in TP and C3 at other time points and C4 at each time point was not significantly different. There were significant interactions between coating type and circulation duration in the PLT, TP, and C3 transitions (p = 0.008, 0.020, and 0.043, respectively). Our findings suggest that ACP-coated membranes can prevent the initial drop in PLT count and C3 consumption over 32 h, whereas IHP-coated membranes could not prevent this drop in extracorporeal circulation. Therefore, ACP-coated membranes are suitable for short- and long-term extracorporeal life support.

Area Deprivation Index and Distress Community Index Scores Are Not Associated With Short-Term and Long-Term Extracorporeal Life Support Outcomes.

Distressed Communities Index (DCI) and Area Deprivation Index (ADI) are two composite ranking scores that report community level socioeconomic status (SES) by ZIP codes. The objective of this study was to evaluate the impact of SES as estimated by DCI and ADI scores on short-term and long-term outcomes after extracorporeal life support (ECLS) at a quaternary medical center. All patients on ECLS between January 1, 2015 and August 31, 2020 (N = 428) at Vanderbilt University Medical Center in Nashville, Tennessee, had their ADI and DCI scores calculated. Primary outcome was mortality during index hospitalization, and secondary outcome was survival to end of study follow-up. There was no significant difference in primary outcome between the top 25% ADI vs . bottom 75% ADI (53.8% vs . 50.6%; p = 0.56) or between top 25% DCI vs . bottom 75% DCI (56.1 vs . 49.2; p = 0.21). Adjusted odds ratio for the primary outcome with ADI and DCI was 1.13 (95% CI, 0.63-2.0; p = 0.67) and 1.28 (95% CI, 0.70-2.34; p = 0.41), respectively. Additionally, there was no significant difference in long-term survival curves based on their ADI or DCI scores. In conclusion, SES as estimated by baseline DCI and ADI scores does not appear to impact short- or long-term survival post-ECLS at a large volume center. http://links.lww.com/ASAIO/A951.

Outcomes of extracorporeal membrane oxygenation and cardiopulmonary bypass in children after drowning-related resuscitation.

Drowning is one of the leading causes of accidental deaths in children worldwide. However, the use of long-term extracorporeal life support (ECLS) in this setting is not widely established, and rewarming is often achieved by short-term cardiopulmonary bypass (CPB) treatment. Thus, we sought to add our experience with this means of support as a bridge-to-recovery or to-decision. This retrospective single-center study analyzes the outcome of 11 children (median 23 months, minimum-maximum 3 months-6.5 years) who experienced drowning and subsequent cardiopulmonary resuscitation (CPR) between 2005 and 2016 and who were supported by veno-arterial extracorporeal membrane oxygenation (ECMO), CPB, or first CPB then ECMO. All but one incident took place in sweet water. Submersion time ranged between 10 and 50 minutes (median 23 minutes), water temperature between 2°C and 28°C (median 14°C), and body core temperature upon arrival in the emergency department between 20°C and 34°C (median 25°C). Nine patients underwent ongoing CPR from the scene until ECMO or CPB initiation in the operating room. The duration of ECMO or CPB before successful weaning/therapy withdrawal ranged between 2 and 322 hours (median 19 hours). A total of four patients (36%) survived neurologically mildly or not affected after 4 years of follow-up. The data indicate that survival is likely related to a shorter submersion time and lower water temperature. Resuscitation of pediatric patients after drowning has a poor outcome. However, ECMO or CPB might promote recovery in selected cases or serve as a bridge-to-decision tool.

Water Condensation and Gas Exchange Correlation in Different Models and Fibers of Blood Oxygenators: “How Can We Improve Performance?”

Creation of water condensation in blood oxygenators is a phenomenon that is constantly present during cardiopulmonary bypass and in medium- to long-term extracorporeal life support. Clinical observation of condensation at the oxygenator exit is still a common event normally associated with sudden cooling of the gas flow proximal to the outlet cover (after exiting the fiber bundle), where the warming effect of blood is no longer present. Condensation could progressively obstruct a certain number of fibers, reducing the efficiency of gaseous exchange in the membrane of the oxygenator surface. The study included 48 patients divided into four oxygenator groups of 12 each: group 1 used an Inspire 6 F oxygenator from Livanova; group 2, an Affinity Fusion from Medtronic; group 3, an Alone from Eurosets, and group 4, an ECMO Alone from Eurosets; while the last group used an ECMO Alone oxygenator from Eurosets with polymethylpentene fiber. Each group of oxygenators comprising 12 patients were divided into two groups, namely, A and B, with six patients in each group. Group A used mild hypothermia during the procedure, and group B of six patients used normothermia; Groups A and B were further subdivided into four subgroups: A1, A2, B1, and B2, each consists of three patients; subgroups A1 and B1 used negative aspiration (−8 mmHg) measuring humidity (%) and temperature (°C) in the gas oxygenator output; consequently, a measurement system was necessary to be created; Subgroups A2 and B2 did not use negative aspiration in the oxygenator outlet. No statistically significant difference for PaO2 and humidity values was found in polypropylene and polymethylpentene oxygenators with mild hypothermia management with vacuum and without vacuum in the gas outlet in the first 60 minutes and 60 minutes later during cardiopulmonary bypass. In normothermia, a statistically significant difference in the PaO2–humidity relationship was observed with polypropylene and polymethylpentene fiber models. Results of this study show an inversely proportional correlation between gas exchange and condensation in statistically significant values during the use of normothermia and a reduction in oxygenation performance, in polypropylene and polymethylpentene fiber oxygenators.

Long term veno-venous extracorporeal life support without intravenous anticoagulation for diffuse alveolar hemorrhage

Diffuse alveolar damage is the histologic hallmark for the acute phase of acute respiratory distress syndrome and can occasionally present as diffuse alveolar hemorrhage. We report a patient with diffuse alveolar hemorrhage and acute respiratory distress syndrome requiring veno-venous extracorporeal life support for 210 days, who was successfully treated for a period of 130 consecutive days without intravenous anticoagulation. Although there are a few brief reports detailing long extracorporeal life support runs, the literature is largely devoid of data regarding long-term extracorporeal life support without full systemic anticoagulation. Regular inspection of the extracorporeal membrane oxygenation circuit is critical because externally visible thrombi may predict internal thrombus generation with the potential for systemic embolization or abrupt oxygenator failure. In our case, multiple circuit and oxygenators changes were required. We have demonstrated that a patient with a contraindication for systemic anticoagulation can safely have veno-venous extracorporeal life support for prolonged periods without catastrophic thrombotic complications.

Further options and survival results after failure following extracorporeal life support implantation.

A retrospective study was designed to analyze the outcome of patients with extracorporeal life support (ECLS) who needed a consecutive cardiac or pulmonary support system. From 2006 to 2016, 93 out of 587 patients with their age ranging from 2.4 to 77.3 years required an exchange of an ECLS by another mechanical support system. Sixty-one patients were inhospital cases, 39 patients were referred with ECLS from other institutions by ambulance car (N.=15) or helicopter (N.=24). Sixty-five patients came from internal medicine wards, of which 38 patients had CPR, whereas 24 patients suffered postcardiotomy failure with CPR in 11 cases. Ten patients were referred from other hospitals for failure to wean from ECLS. Leading symptoms were continuing cardiac failure in 43 patients (46%) and ongoing respiratory failure after cardiac recovery in 50 patients (54%). Patients with cardiac failure underwent implantation of a ventricular assist device (N.=36) or remained on long-term ECLS (N.=7) until a donor organ for heart transplantation was available (mean waiting time 43 days). Respiratory failure was treated by veno-venous ECMO (N.=34) or vav-ECMO (N.=16). Overall inhouse survival was 50.5% (N.=47). Only 22.6% of patients (N.=21) died during ongoing support. In contrast, 26.9% of patients (N.=25) deceased 35+/-51 days after weaning from vv- or vav-ECMO. Major reasons of death were multi-organ failure in 16 patients, cerebral hypoxia in 12 patients, sepsis in 10 patients, and intractable ow output in 5 patients. Despite a switch from ECLS to another mechanical support system, survival remains limited as irreversible multi-organ failure and sepsis still jeopardize the patients' life.

Hypovolemia in Extracorporeal Life Support Can Lead to Arterial Gaseous Microemboli

Next to severely decreased pump flow, hypovolemia in extracorporeal life support (ELS) can result in subatmospheric venous line pressure. Such pressure may lead to degassing and resultant gaseous microemboli (GME), with potential changes in neurological clinical outcome. CME activity resulting from degassing was investigated in relation to subatmospheric venous line pressure, partial oxygen pressure (pO2 ), and hematocrit in a model of a centrifugal pump-based circuit for long-term ELS. Additionally, a device that provides instantaneous volume buffer capacity during hypovolemia was evaluated in relation to GME appearance. An exponential relationship was found between decreasing venous line pressure and GME downstream of the centrifugal pump (P = 0.001). Arterial bubble activity appeared at subatmospheric venous line pressures of -200 mm Hg and less. A rising (pO2 ) increased formation of GME (P = 0.05). A rise in hematocrit, in contrast, did not affect embolic activity (P = 0.22). With simulated hypovolemia, volume buffer capacity added to the venous line dampened fluctuations of venous line pressure by approximately 40%, but a significant reduction in GME formation could not be found (P = 0.22). Moreover, the device enabled a 14% higher support flow. With ELS flow being related to patient volume status, hypovolemia can diminish support. A coherent decrease of venous line pressure triggers degassing of blood-dissolved gases and causes arterial GME, which can become massive during persistent conditions of limited venous return. Incorporation of a volume buffer capacity device into the extracorporeal support circuit enables a higher and more stable support flow in critically low patient filling.

Possibilities and limitations of a miniaturized long-term extracorporeal life support system as bridge to transplantation in a case with biventricular heart failure

In cardiac surgery extracorporeal life support systems (ECLS), also known as extracorporeal membrane oxygenation systems (ECMO), are often placed in case of postcardiotomy shock, until the patient's myocardial pump function recovers. Patients under ECLS are typically intubated and immobilized. We present a 57-year-old man suffering from severe ischemic cardiomyopathy in biventricular failure and intractable cardiogenic shock, who was supported with a miniaturized cardiopulmonary bypass system (MECC((R))) installed as venoarterial ECLS for 37 days. The patient was fully awake, spontaneously breathing, and practicing exercise in bed during life support for four weeks. He then required intubation for pneumonia, but later underwent successful transplantation. In conclusion, this case demonstrates that ECLS with miniaturized heart-lung machines offer the possibility of prolonged and safe support, ideal as a bridge to decision in patients with cardiogenic shock. On the other side, this report also indicates that ECLS is not recommended as a bridge to transplantation on a routine basis.

A Polymethylpentene Fiber Gas Exchanger for Long-Term Extracorporeal Life Support

A polymethylpentene (PMP) fiber gas exchange device was evaluated in healthy sheep (35-42 kg) to characterize its performance and potential use in clinical extracorporeal life support (ECLS). Five PMP devices (1.3 m2) were compared with five silicone rubber membrane lung (SRML) devices (1.5 m2) that were supported on venovenous ECLS for 72 hours. The two device groups were compared for differences in gas exchange, device pressure gradient, hematology, blood biochemistry, and pathology. The results showed superiority in the PMP devices in both oxygen and CO2 exchange when compared at similar blood flow rates. Platelet consumption and the device pressure gradient were significantly less when using the PMP device. The device pressure gradient across the PMP devices was < 20 mm Hg as compared with > 150 mm Hg for the SRML devices at all blood flow rates. Changes in plasma hemoglobin levels, leukocyte counts, blood chemistry results, and pathologic findings were not significantly different between the two device groups. Plasma leakage or device failure did not occur in any of the test devices. These data support the use of the PMP device for extended circulatory support. Patients may fare better because of improved preservation of platelets, and the low resistance may allow for wider use of centrifugal-style pumps or the use of the device in a pumpless arteriovenous mode.

Nitric oxide prevents human platelet adhesion to fiber membranes in whole blood.

During cardiopulmonary bypass or long-term extracorporeal life support, foreign surface induced platelet deposition in the oxygenator causes deterioration of gas exchange. In this study, the authors evaluated the effectiveness of nitric oxide (NO) in reducing the adhesion of platelets in whole blood to the surface of hollow fiber membranes. For this purpose, a test chamber was designed consisting of a gas exchanger with ten mitsubishi multi-layered composite hollow fibers (MHF: 257 mm OD; 203 mm ID; 70 mm length) and a polypropylene tube (16 mm OD; 100 mm length). Pure N2 (control) or nitric oxide (NO) (100 ppm, 200 ppm in N2) were delivered into the test chamber previously filled with 13 ml human whole blood. Platelet counts and platelet factor 4 (PF4), as a measure of platelet activation, were measured before and after either 1 or 2 hr of testing, and fibers were observed under scanning electron microscopic study (SEM) after each experiment. In the control and 100 ppm NO groups, platelet counts decreased and the level of PF4 increased during the 1 hr period. In the 200 ppm NO group, almost no platelet deposition could be observed on the surface of fibers under SEM. In conclusion, NO flow through hollow fiber membranes can markedly reduce platelet adhesion. Additional quantitative studies should define the optimal concentration for this effect and determine if this finding could improve oxygenator function, especially under conditions of long-term support.

Emergency and long-term extracorporeal life support following acute myocardial infarction: Rescue from severe cardiogenic shock related to stunned myocardium: Clin. Cardiol. 1994; 17/10: 552–557

There has been no report regarding therapy of extracorporeal life support (ECLS) that showed stunned myocardium echocardiographically and electrocardiographically in patients with acute myocardial infarction. ECLS was performed in eight patients with cardiogenic shock or arrest unresponsive to catecholamines and intra-aortic balloon pumping following myocardial infarction; these patients required prolonged external cardiac massage. After the initiation of ECLS, both blood pressure and metabolic acidosis improved in all patients. Four of eight patients were weaned from ECLS after a mean of 69.3 h, which was far longer than previously reported in patients with ischemic heart disease. Three of these patients survived, and cardiac function recovered to NYHA class II in two of the survivors and class III in the other. The other five patients did not recover from coma during ECLS and died. A marked improvement of ventricular wall motion was seen in two survivors with the disappearance of pathologic Q waves after the initiation of ECLS. No occlusion of the coronary arteries or bypass grafts was observed in any of the survivors. These findings suggested the existence of stunned myocardium with myocardial reperfusion. The recovery of stunned myocardium may be delayed for days or even weeks, hence the extended period of ECLS therapy was theoretically justifiable. We conclude that long-term ECLS is a useful therapeutic method for patients with severe cardiogenic shock that is related to stunned myocardium.

Emergency and long‐term extracorporeal life support following acute myocardial infarction: Rescue from severe cardiogenic shock related to stunned myocardium

There has been no report regarding therapy of extracorporeal life support (ECLS) that showed stunned myocardium echocardiographically and electrocardiographically in patients with acute myocardial infarction. ECLS was performed in eight patients with cardiogenic shock or arrest unresponsive to catecholamines and intra-aortic balloon pumping following myocardial infarction; these patients required prolonged external cardiac massage. After the initiation of ECLS, both blood pressure and metabolic acidosis improved in all patients. Four of eight patients were weaned from ECLS after a mean of 69.3 h, which was far longer than previously reported in patients with ischemic heart disease. Three of these patients survived, and cardiac function recovered to NYHA class II in two of the survivors and class III in the other. The other five patients did not recover from coma during ECLS and died. A marked improvement of ventricular wall motion was seen in two survivors with the disappearance of pathologic Q waves after the initiation of ECLS. No occlusion of the coronary arteries or bypass grafts was observed in any of the survivors. These findings suggested the existence of stunned myocardium with myocardial reperfusion. The recovery of stunned myocardium may be delayed for days or even weeks, hence the extended period of ECLS therapy was theoretically justifiable. We conclude that long-term ECLS is a useful therapeutic method for patients with severe cardiogenic shock that is related to stunned myocardium.

Prolonged Extracorporeal Circulation without Heparin

Bleeding remains the most common complication of prolonged extracorporeal life support (ECLS). This study evaluated the Medtronic Minimax (Annaheim, CA) microporous oxygenator with the Carmeda Bio Active (heparin bonded) Surface (Stockholm, Sweden) for use in prolonged neonatal ECLS. Eight adult sheep were maintained on venovenous extracorporeal circulation (ECC) for a period of 4 days without systemic heparin. After 4 days of venovenous ECC without anticoagulation, there was no evidence of significant bleeding, circuit thrombosis, or systemic embolism. Gas exchange, hydrodynamic performance, coagulation, and biocompatibility studies suggest that the Minimax is safe and reliable for short-term or long-term ECLS in neonates.