Application of a pressure-relieving air compliance chamber in a single-pulsatile extracorporeal life support system: an experimental study

Nonpulsatile blood pumps are mainly used in extracorporeal life support systems. Although pulsating blood flow is known to be physiological, a pulsatile pump is not commonly applied in a circuit with a membrane oxygenator because of damage to the blood cells. The hypothesis that the placement of a pressure-relieving compliance chamber in a circuit might reduce blood cell trauma was tested. An extracorporeal life support circuit was constructed in an acute lung injury model of dogs by oleic acid infusion. The animals were divided into three groups. In group I (n = 6) a nonpulsatile centrifugal pump was used as a control. In group II (n = 4) a single-pulsatile pump was used, and in group III (n = 6) a single-pulsatile pump equipped with a compliance chamber was used. Pump flow was maintained at 1.8-2.0 L/min for 2 h. Hemodynamics and blood gas analyses indicated that the pulsatile groups II and III had better results than the nonpulsatile group I. The plasma-free hemoglobin level, which indicates blood cell trauma, was the lowest in group I and the highest in group II but was significantly decreased in group III. A pressure-relieving compliance chamber could significantly reduce high circuit pressures and blood cell trauma.     

Thoughts and Progress

In recent years, extracorporeal membrane oxygenation (ECMO) has been used for treatment of neonates with respiratory failure. A prototype of a compact ECMO system for neonates was developed. A single-lumen catheter, inserted into the right atrium via a jugular vein, was used for withdrawal and infusion of blood through the catheter. An extracapillary flow hollow-fiber membrane lung made of microporous polypropylene has a total surface area of 0.6 m2. To prevent the increase of plasma free hemoglobin, the ratio of withdrawal/infusion is controlled by a microcomputer. The system is compact in size with a low priming volume (less than 90 ml), which allows for ECMO with no additional blood transfusions. Its potential application as a respiratory support system is evaluated in animal experiments. The total intermittent veno-veno bypass flow was 15-30 ml/min/kg. The O2 transfer rate was 20 ml/min and the CO2 transfer rate was 33 ml/min at a blood flow rate of 300 ml/min. The O2 and CO2 exchange with the ECMO system was efficient enough to eliminate the respiratory failure induced by mechanical ventilation. The increase in plasma free hemoglobin was only 4 mg/dl after 6 h of ECMO. The system was considered applicable to respiratory aid for neonates.     

Current Status of Extracorporeal Membrane Oxygenation for Severe Respiratory Failure

Abstract: Extracorporeal membrane oxygenation (ECMO) for respiratory failure was reviewed. ECMO progressed from laboratory research to initial clinical trials in 1972. Following a decade of clinical research, ECMO is now standard treatment for neonatal respiratory failure refractory to conventional pulmonary support techniques worldwide. The application of neonatal ECMO has been extended with improved outcome to premature and low birth weight infants as well as older children and adults. As of July 1994, 9,258 neonates, 754 pediatric, and 130 adult patients with respiratory failure treated with ECMO were entered in the registry of the Extracorporeal Life Support Organization (ELSO). Overall survival rates were 81% in neonates, 49% in pediatric, and 38% in adult patients. Recently the adult and pediatric populations treated with ECMO have increased rapidly, and the outcome has improved significantly.     

Pathophysiology of cardiac extracorporeal membrane oxygenation

The treatment of cardiogenic shock using inotropic agents and vascular volume expansion places an added burden on the heart. The resultant increase in cardiac work may cause myocardial ischemia and lead to cardiac arrest. Extracorporeal membrane oxygenation (ECMO) may be used to treat cardiogenic shock. It supports systemic circulation, assures diastolic perfusion of the myocardium, and reduces cardiac workload. The rise in blood pressure associated with restoring systemic circulation afterloads the heart and can cause left atrial hypertension and pulmonary edema. ECMO does not automatically reduce cardiac work, especially in the presence of residual shunts. Left atrial drainage or decompression may be essential in certain patients both to avert pulmonary edema and to reduce cardiac work.     

Extracorporeal Membrane Oxygenation Can Save Lives in Children With Heart or Lung Failure After Liver Transplantation

The risk of cardiac or lung failure after liver transplantation (LT) is significant. In rare cases, the usual intensive care techniques fail to maintain organ oxygenation with a risk of multiorgan dysfunction. Although extracorporeal membrane oxygenation (ECMO) is a difficult and risky procedure, it can be proposed as life‐saving. Four children with either acute pulmonary (three) or cardiac (one) failure after LT, and the criteria that decided the use of ECMO (level of ventilation and results, dosage of inotropic drugs, cardiac ultrasound, blood lactate) were retrospectively reported. These patients, 1–11 years old, were treated with either veno‐arterial (three) or veno‐venous (one) ECMO. Two experienced a full recovery, with 3 and 6 years of follow‐up. Two died of systemic inflammatory response syndrome (SIRS) due to ECMO, and relapse of heart failure due to the underlying disease. Although our patients' survival was only 50%, we showed that ECMO can be useful in children after LT. It should be considered before the development of irreversible multiorgan failure.     

Cardiac Awake Extracorporeal Life Support—Bridge to Decision?

Severe acute heart failure requires immediate intensive care unit (ICU) treatment, but prognosis and outcome of further treatment regimens largely depends on the preprocedural status of the patient. Especially, multiorgan failure including mechanical ventilation are unfavorable predictors of clinical outcome. Here, we report a strategy of immediate initiation of extracorporeal life support (ECLS) in awake and spontaneously breathing patients with acute heart failure to achieve early multiorgan recovery and gain sufficient time for further treatment planning. Twenty‐three patients with severe cardiac failure refractory to standard medical management underwent ECLS treatment, after first clinical signs of cardiac failure appeared to avoid mechanical ventilation. Hemodynamic parameters and renal and liver functions were monitored. Outcome at 1 and 6 months was determined. Patients 46.1 ± 15.5 years of age were placed on ECLS due to various underlying diagnosis: ischemic heart disease (n = 6), dilatative cardiomyopathy (n = 4), myocarditis (n = 2), graft failure following heart transplantation (n = 6), or other diseases (n = 5). ECLS lasted 11.9 ± 12.9 days. Hemodynamic stabilization was achieved immediately after ECLS initiation. Vasopressors were reduced subsequently and the cardiac situation improved indicated by central venous saturation, which increased from 38.5 ± 11.3% before to 74.26 ± 8.4% (P < 0.0001) 24 h after ECLS initiation. Similarly, serum lactate levels decreased from 4.7 ± 4.6 to 1.7 ± 1.51 mmol/L (P = 0.003). Cumulative 30‐day survival was 87.5%, and 6‐month survival was 70.8%. In acute cardiac failure, early ECLS treatment is a safe, feasible treatment in awake patients allowing a gain of time for final decision. Moreover, this strategy avoids complications associated with sedation and mechanical ventilation and leads to recovery of secondary organ function, enabling destination therapy.     

Development of an artificial placenta I: pumpless arterio-venous extracorporeal life support in a neonatal sheep model

Purpose

Effective treatment of respiratory failure in premature infants remains an unsolved problem. The development of an artificial placenta, in the form of a pumpless arteriovenous extracorporeal life support (AV-ECLS) circuit that maintains fetal circulation, is an appealing alternative.

Methods

A near-term (140 d/term = 145 days) neonatal lamb model was used (n = 7). Fetuses were exposed by hysterotomy, and flow probes were placed on the ductus arteriosus, aorta, and carotid artery. Catheters were placed into the umbilical vessels, and pumpless AV-ECLS was initiated. Fetuses were submerged in a warm saline bath, and support was maintained for up to 4 hours.

Results

Mean initial device flow was 383 mL/min but steadily declined to 177 mL/min at 4 hours. Mean initial pO₂ was 24 mm Hg and 18 mm Hg at 4 hours. Initial mean pCO₂ was 60 mm Hg and declined to 42 mm Hg at 4 hours. Mean arterial pressure was initially 43 mm Hg and decreased to 34 mm Hg at 4 hours. Flow in the ductus arteriosus was maintained for 4 hours. Of 7 fetuses, 5 survived 4 hours of support.

Conclusions

Pumpless AV-ECLS can support gas exchange and maintain fetal circulation in a neonatal lamb model for a 4-hour period. Prolonged support (>4 hours) is hampered by high cannula resistance and declining device flow.     

Comparison of Coagulation Parameters,Anticoagulation, and Need for Transfusion in Patients on Interventional Lung Assist or Veno‐Venous Extracorporeal Membrane Oxygenation

Clinical data on anticoagulation needs of modern extracorporeal membrane oxygenation (ECMO) and its impact on coagulation are scarce. Therefore, we analyzed coagulation‐related parameters, need for transfusion, and management of anticoagulation in adult patients with severe acute respiratory failure during treatment with either pumpless interventional lung assist (iLA) or veno‐venous ECMO (vv‐ECMO). Sixty‐three patients treated with iLA and 192 patients treated with vv‐ECMO at Regensburg University Hospital between January 2005 and May 2011 were analyzed. Data related to anticoagulation, transfusion, and coagulation parameters were collected prospectively by the Regensburg ECMO registry. Except for a higher, sequential organ failure assessment (SOFA) score in the ECMO group (12 [9–15] vs. 11 [7–14], P = 0.007), a better oxygenation, and a lower dosage of vasopressors in the iLA patients, both groups had similar baseline characteristics. No difference was noted in terms of outcome and overall transfusion requirements. Factors of the plasmatic coagulation system were only marginally altered over time and did not differ between groups. Platelet counts in ECMO‐treated patients, but not in those treated with iLA, dropped significantly during extracorporeal support. A more intense systemic anticoagulation with a mean activated partial thromboplastin time (aPTT) > 53 s led to a higher need for transfusions compared with the group with a mean aPTT < 53 s, whereas the average durability of membrane oxygenators was not affected. Need for red blood cell (RBC) transfusion was highest in patients with extrapulmonary sepsis (257 mL/day), and was significantly lower in primary pulmonary adult respiratory distress syndrome (ARDS) (102 mL/day). Overall, 110 (0–274) mL RBC was transfused in the ECMO group versus 146 (41–227) mL in the iLA group per day on support. The impact of modern iLA and ECMO systems on coagulation allows comparatively safe long‐term treatment of adult patients with acute respiratory failure. A moderate systemic anticoagulation seems to be sufficient. Importantly, platelets are more affected by vv‐ECMO compared with pumpless iLA.     

30-Day perioperative mortality following venoarterial extracorporeal membrane oxygenation for postcardiotomy cardiogenic shock in patients with normal preoperative ejection fraction

 Open in a separate windowOBJECTIVESAssessment of early outcomes in patients with normal preoperative left ventricular ejection fraction (LVEF) in whom venoarterial extracorporeal membrane oxygenation (VA-ECMO) was implanted for postcardiotomy cardiogenic shock (PCCS) during the first postoperative 48 h. METHODSRetrospective single-centre analysis in adult patients with normal LVEF, who received VA-ECMO support for PCCS from May 1998 to May 2018. The primary outcome was 30-day perioperative mortality during the index hospitalization.RESULTSA total of 62 125 adult patients underwent cardiac surgery at our institution during the study period. Among them, 173 patients (0.3%) with normal preoperative LVEF required VA-ECMO for PCCS. Among them, 71 (41.1%) patients presented PCCS due to coronary malperfusion and in 102 (58.9%) patients, no evident cause was found for PCCS. Median duration of VA-ECMO support was 5 days (interquartile range 2–8 days). A total of 135 (78.0%) patients presented VA-ECMO-related complications and the overall 30-day perioperative mortality was 57.8%. Independent predictors of mortality were: lactate level just before VA-ECMO implantation [odds ratio (OR) 1.27; P < 0.001], major bleeding during VA-ECMO (OR 3.76; P = 0.001), prolonged cardiopulmonary bypass time (OR 1.01; P < 0.001) and female gender (OR 4.87; P < 0.001).CONCLUSIONSMortality rates of VA-ECMO in PCCS patients are high, even in those with preoperative normal LVEF. Coronary problems are an important cause of PCCS; however, the aetiology remains unknown in the vast majority of the cases. The implantation of VA-ECMO before development of tissue hypoperfusion and the control of VA-ECMO-associated complications are the most important prognostic factors in PCCS patients. Lactate levels may help guide timing of VA-ECMO implantation and define the extent of therapeutic effort.     

Miniaturization: The Clue to Clinical Application of the Artificial Placenta

The artificial placenta as a fascinating treatment alternative for neonatal lung failure has been the subject of clinical research for over 50 years. Pumpless systems have been in use since 1986. However, inappropriate dimensioning of commercially available oxygenators has wasted some of the theoretical advantages of this concept. Disproportional shunt fractions can cause congestive heart failure. Blood priming of large oxygenators and circuits dilutes fetal hemoglobin (as the superior oxygen carrier), is potentially infectious, and causes inflammatory reactions. Flow demands of large extracorporeal circuits require cannula sizes that are not appropriate for use in preterm infants. NeonatOx, a tailored low‐volume oxygenator for this purpose, has proven the feasibility of this principle before. We now report the advances in biological performance of a refined version of this specialized oxygenator.     

Clinical Results of Extracorporeal Membrane Oxygenation (ECMO) Support for Acute Respiratory Failure: A Comparison of a Centrifugal Pump ECMO with a Roller Pump ECMO

Purpose The purpose of this study was to compare the clinical results of extracorporeal membrane oxygenation (ECMO) using a centrifugal pump (CP group) and that using a roller pump (RP group) for the treatment of acute respiratory failure (ARF).Methods From November 1990 to July 2001, the ECMO system was introduced for the treatment of 15 patients with ARF; 10 cases of pneumonia or adult respiratory distress syndrome (ARDS), 4 cases of pulmonary hemorrhage, and 1 case of hypoxemia following cardiac surgery. Five patients were included in the RP group, and 10 were included in the CP group.Results The mean PaO₂/FIO₂ ratio, PaCO₂ prior to ECMO induction, and the mean duration of ECMO support were 59.8, 38.8mmHg, and 125h, respectively, in the RP group, and 65.6, 82.0mmHg, and 107h, respectively, in the CP group. The mean PaCO₂ value was significantly (P 0.05) higher in the CP group than in the RP group due to the ventilation with permissive hypercapnia. In the RP group, all patients died of either complications or recurrence due to ARF. In the CP group, 3 patients including 2 with pulmonary hemorrhaging were discharged.Conclusions Although the centrifugal pump ECMO improved the clinical results of ARF, the overall prognosis nevertheless depended on the original disease.This study was reported at the 102nd Annual Congress of the Japan Surgical Society, Kyoto, April 11–13, 2002     

Evolution of Gas Permeable Membranes for Extracorporeal Membrane Oxygenation

Gas permeable membranes are a vital component of extracorporeal membrane oxygenation systems. Over more than half a century, membrane fabrication and packaging technology have progressed to enable safer and longer duration use of respiratory life support. Current research efforts seek to improve membrane efficiency and hemocompatibility, with the aim of producing smaller and more robust systems for ambulatory use. This review explores past and present innovations in oxygenator technology, suggesting possible applications of state‐of‐the‐art membrane fabrication methods to address shortcomings of earlier concepts.     

pH 48 h after onset of extracorporeal membrane oxygenation is an independent predictor of survival in patients with respiratory failure

Extracorporeal membrane oxygenation (ECMO) is a life-saving procedure in patients with severe respiratory failure, unresponsive to conventional therapy. We reviewed our series of 70 ECMO runs (April 1997 to December 2005) in patients with respiratory distress, refractory to standard ventilation. Survival at 90 days was 42.7%. Besides age, we found no statistical significant difference in patient demographics or preoperative patient data between survivors and nonsurvivors. Univariate analyses indicated that pH values at 24 and 48 h after onset of ECMO were significantly higher in survivors. In multivariate analysis, age and pH at 48 h remained independent predictors of survival. ECMO in respiratory failure saves lives. No other demographic or preoperative, patient-related parameter than age was identified as predictor of survival. Although there was no difference in pH at onset of ECMO, blood gas analysis at 48 h revealed pH as an independent predictor of survival.     

Factors influencing survival in newborns with congenital diaphragmatic hernia: the relative role of timing of surgery

Purpose

Controversy persists regarding the factors influencing survival in patients with congenital diaphragmatic hernia (CDH), in particular, the role of timing of surgery. The authors therefore sought to determine such factors and to assess the relative role of timing of surgery on outcome.

Methods

All CDH newborns 1991 through 2002 (n = 111) were divided into those undergoing repair before (“early” n = 35), or after (“late” n = 76) 48 hours. A multivariate analysis was performed to determine the relative impact of various factors on survival rate.

Results

Overall survival rate was 64%. There was no effect on survival of heart rate, temperature, systolic blood pressure, age, extracorporeal membrane oxygenation use, mesh use, infections, or intracranial hemorrhage, and there was no difference between early (68%) or late (62%) repair (P = .2). Initial pco₂ greater than 50, po₂ less than 40, cardiac defects, or renal failure significantly decreased survival rate.

Conclusions

Significant factors influencing survival rate in patients with CDH include cardiac defects, renal failure, and the initial blood gases and not the timing of surgery. CDH repair should be based on the optimization of clinical parameters as opposed to a specific time period to improve outcome.     

Extracorporeal membrane oxygenation as a lifesaving modality in the treatment of pediatric patients with burns and respiratory failure

Purpose

Several case series have described successful utilization of extracorporeal membrane oxygenation (ECMO) for the treatment of pediatric burn patients with respiratory failure. This study examines the Extracorporeal Life Support Organization registry experience in the treatment of these patients.

Methods

The Extracorporeal Life Support Organization registry was queried from 1999 to 2008 for all patients not older than 18 years who suffered a burn-related injury.

Results

Thirty-six patients met inclusion criteria. The mean age was 4.45 years, with an average weight of 20.9 kg. Survivors vs nonsurvivors had a shorter average time to ECMO (97 vs 126 hours, P = .890) and shorter average ECMO run times (193 vs 210 hours, P = .745). Seventeen patients underwent venovenous ECMO and 19 patients underwent venoarterial ECMO, with survival of 59% (n = 10) and 47% (n = 9), respectively (P = .493; odds ratio, 1.587; 95% confidence interval, 0.424-5.945). Overall survival was 53% (n = 19). Complications occurred in 28 patients (33 mechanical, 101 medical). The venoarterial group had 21 mechanical (n = 8) and 61 medical complications (n = 17), compared with the venovenous group with 12 mechanical (n = 8) and 40 medical complications (n = 11).

Conclusions

Extracorporeal membrane oxygenation can be a lifesaving modality for pediatric burn patients with respiratory failure. Survival is comparable to the reported survival of non-burn-related pulmonary failure pediatric patients requiring ECMO.     

体外膜肺氧合在围术期及危重症患者中的应用进展

体外膜肺氧合(ECMO)作为一种改良的体外生命支持技术,可部分或完全替代患者的心肺功能,为常规治疗策略无效的顽固性心力衰竭和呼吸衰竭患者提供长时间体外心肺支持,使心肺脏器得到休息恢复,为救治原发病争取时间.经过长期的临床实践与不断探索,ECMO技术已取得长足进步.全文就ECMO的工作原理、围术期应用与急症救治作一综述.     

Computational model-based design of a wearable artificial pump-lung for cardiopulmonary/respiratory support

Mechanical ventilation and extracorporeal membrane oxygenation are the only immediate options available for patients with respiratory failure. However, these options present significant shortcomings. To address this unmet need for respiratory support, innovative respiratory assist devices are being developed. In this study, we present the computational model-based design, and analysis of functional characteristics and hemocompatibility performance, of an innovative wearable artificial pump-lung (APL) for ambulatory respiratory support. Computer-aided design and computational fluid dynamics (CFD)-based modeling were utilized to generate the geometrical model and to acquire the fluid flow field, gas transfer, and blood damage potential. With the knowledge of flow field, gas transfer, and blood damage potential through the whole device, design parameters were adjusted to achieve the desired specifications based on the concept of virtual prototyping using the computational modeling in conjunction with consideration of the constraints on fabrication processes and materials. Based on the results of the CFD design and analysis, the physical model of the wearable APL was fabricated. Computationally predicted hydrodynamic pumping function, gas transfer, and blood damage potential were compared with experimental data from in vitro evaluation of the wearable APL. The hydrodynamic performance, oxygen transfer, and blood damage potential predicted with computational modeling, along with the in vitro experimental data, indicated that this APL meets the design specifications for respiratory support with excellent biocompatibility at the targeted operating condition.     

An Evaluation of the System to Control Blood Flow in Maintaining Goat Fetuses on Arterio-Venous Extracorporeal Membrane Oxygenation: A Novel Approach to the Development of an Artificial Placenta

Abstract: We compared various methods to control blood flow for extrauterine incubation of goat fetuses without lung respiration using arterio-venous extracorporeal membrane oxygenation via umbilical vessels to develop a suitable system for a long-term life support system for premature neonates. In twenty-seven consecutive preparations of goat fetuses, 4 designs (System 1, manual flow control without a reservoir; System 2, manual flow control with an arterial open-top reservoir; System 3, semiautomatic flow control with an arterial open top reservoir; and System 4, semiautomatic flow control with a tube occluder and an arterial open top reservoir) were tested in terms of the duration of incubation periods during which fetuses were kept under stable conditions. The incubation periods be-came prolonged with the advancement of the system (System 1, 5.4 h; System 2, 11.6 h; System 3, 64.8 h; and System 4, 159.8 h medians of the incubation periods). The incubation periods with System 4 were significantly longer compared to those with System 1 and System 2. These results suggest that, for extrauterine incubation of goat fetuses using arterio-venous extracorporeal membrane oxygenation via umbilical vessels, the method to control blood flow is of utmost importance for long-term maintenance, and thus a control system with the fixed vascular resistance of the extracorporeal circuit is applicable to long-term maintenance of premature goat fetuses.