Update on safety equipment for extracorporeal life support (ECLS) circuits

State of the art: Monitoring of the respiratory system during veno-venous extracorporeal membrane oxygenation

Monitoring the patient receiving veno-venous extracorporeal membrane oxygenation (VV ECMO) is challenging due to the complex physiological interplay between native and membrane lung. Understanding these interactions is essential to understand the utility and limitations of different approaches to respiratory monitoring during ECMO. We present a summary of the underlying physiology of native and membrane lung gas exchange and describe different tools for titrating and monitoring gas exchange during ECMO. However, the most important role of VV ECMO in severe respiratory failure is as a means of avoiding further ergotrauma. Although optimal respiratory management during ECMO has not been defined, over the last decade there have been advances in multimodal respiratory assessment which have the potential to guide care. We describe a combination of imaging, ventilator-derived or invasive lung mechanic assessments as a means to individualise management during ECMO.

Computational fluid dynamics analysis and experimental hemolytic performance of three clinical centrifugal blood pumps: Revolution, Rotaflow and CentriMag

Centrifugal blood pumps have become popular for adult extracorporeal membrane oxygenation (ECMO) due to their superior blood handling and reduced thrombosis risk featured by their secondary flow paths that avoid stagnant areas. However, the high rotational speed within a centrifugal blood pump can introduce high shear stress, causing a significant shear-induced hemolysis rate. The Revolution pump, the Rotaflow pump, and the CentriMag pump are three of the leading centrifugal blood pumps on the market. Although many experimental and computational studies have focused on evaluating the hydraulic and hemolytic performances of the Rotaflow and CentriMag pumps, there are few on the Revolution pump. Furthermore, a thorough direct comparison of these three pumps' flow characteristics and hemolysis is not available. In this study, we conducted a computational and experimental analysis to compare the hemolytic performances of the Revolution, Rotaflow, and CentriMag pumps operating under a clinically relevant condition, i.e., the blood flow rate of 5 L/min and pump pressure head of 350 mmHg, for adult ECMO support. In silico simulations were used to characterize the shear stress distributions and predict the hemolysis index, while in vitro blood loop studies experimentally determined hemolysis performance. Comparative simulation results and experimental data demonstrated that the CentriMag pump caused the lowest hemolysis while the Revolution pump generated the highest hemolysis.

Spontaneous breathing in patients with severe acute respiratory distress syndrome receiving prolonged extracorporeal membrane oxygenation

Background

The use of extracorporeal membrane oxygenation (ECMO) in awake, spontaneously breathing and non-intubated patients (awake ECMO) may be a novel therapeutic strategy for severe acute respiratory distress syndrome (ARDS) patients. The purpose of this study is to assess the feasibility and safety of awake ECMO in severe ARDS patients receiving prolonged ECMO (> 14 days).

Methods

We describe our experience with 12 consecutive severe ARDS patients (age, 39.1 ± 16.4 years) supported with awake ECMO to wait for native lung recovery during prolonged ECMO treatment from July 2013 to January 2018. Outcomes are reported including the hospital mortality, ECMO-related complications and physiological data on weaning from invasive ventilation.

Results

The patients received median 26.0 (15.5, 64.8) days of total ECMO duration in the cohort. The longest ECMO support duration was 121 days. Awake ECMO and extubation was implemented after median 10.2(5.0, 42.9) days of ECMO. Awake ECMO was not associated with increased morbidity. The total invasive ventilation duration, lengths of stay in the ICU and hospital in the cohort were 14.0(12.0, 37.3) days, 33.0(22.3, 56.5) days and 46.5(27.3, 84.8) days, respectively. The hospital mortality rate was 33.3% (4/12) in the cohort. Survivors had more stable respiratory rate and heart rate after extubation when compared to the non-survivors.

Conclusions

With carefully selected patients, awake ECMO is a feasible and safe strategy for severe pulmonary ARDS patients receiving prolonged ECMO support to wait for native lung recovery.

Bridging to Lung Transplantation

Lung transplantation is the gold standard for treating patients with end-stage lung disease. Such patients can present with severe illness on the waitlist and may deteriorate before a lung donor is available. Bridging strategies with extracorporeal membrane oxygenation (ECMO) are valuable for getting patients to transplant and provide a chance at survival. The current article describes the indications, contraindications, and techniques involved in bridging to lung transplantation with ECMO.

Decentralized safety concept for closed-loop controlled intensive care

This paper presents a decentralized safety concept for networked intensive care setups, for which a decentralized network of sensors and actuators is realized by embedded microcontroller nodes. It is evaluated for up to eleven medical devices in a setup for automated acute respiratory distress syndrome (ARDS) therapy. In this contribution we highlight a blood pump supervision as exemplary safety measure, which allows a reliable bubble detection in an extracorporeal blood circulation. The approach is validated with data of animal experiments including 35 bubbles with a size between 0.05 and 0.3 ml. All 18 bubbles with a size down to 0.15 ml are successfully detected. By using hidden Markov models (HMMs) as statistical method the number of necessary sensors can be reduced by two pressure sensors.

"Awake" Extracorporeal Membrane Oxygenation as a Bridge to Lung Transplant

Mortality of patients awaiting lung transplant remains a significant problem as the number of patients on the waiting list far surpasses the number of donor organs available. Interest in the use of "awake" extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplant has emerged because this strategy offers several benefits over mechanical ventilation. This article provides a review of relevant literature and discusses indications and complications of awake ECMO therapy, cannulation strategies, and nursing considerations for this patient population.

Extracorporeal life support as bridge to lung transplantation: a systematic review

INTRODUCTION

Patients with acute respiratory failure requiring respiratory support with invasive mechanical ventilation while awaiting lung transplantation are at a high risk of death. Extracorporeal membrane oxygenation (ECMO) has been proposed as an alternative bridging strategy to mechanical ventilation. The aim of this study was to assess the current evidence regarding how the ECMO bridge influences patients' survival and length of hospital stay.

METHODS

We performed a systematic review by searching PubMed, EMBASE and the bibliographies of retrieved articles. Three reviewers independently screened citation titles and abstracts and agreement was reached by consensus. We selected studies enrolling patients who received ECMO with the intention to bridge lung transplant. We included randomized controlled trials (RCTs), case-control studies and case series with ten or more patients. Outcomes of interest included survival and length of hospital stay. Quantitative data summaries were made when feasible.

RESULTS

We identified 82 studies, of which 14 were included in the final analysis. All 14 were retrospective studies which enrolled 441 patients in total. Because of the broad heterogeneity among the studies we did not perform a meta-analysis. The mortality rate of patients on ECMO before lung transplant and the one-year survival ranged from 10% to 50% and 50% to 90%, respectively. The intensive care and hospital length of stay ranged between a median of 15 to 47 days and 22 to 47 days, respectively. There was a general paucity of high-quality data and significant heterogeneity among studies in the enrolled patients and technology used, which confounded analysis.

CONCLUSIONS

In most of the studies, patients on ECMO while awaiting lung transplantation also received invasive mechanical ventilation. Therefore, whether ECMO as an alternative, rather than an adjunction, to invasive mechanical ventilation is a better bridging strategy to lung transplantation still remains an unresolved issue. ECMO support as a bridge for these patients could provide acceptable one-year survival. Future studies are needed to investigate ECMO as part of an algorithm of care for patients with end-stage lung disease.

Bridge to lung transplantation and rescue post-transplant: the expanding role of extracorporeal membrane oxygenation

Over the last several decades, the growth of lung transplantation has been hindered by a much higher demand for donor lungs than can be supplied, leading to considerable waiting time and mortality among patients waiting for transplant. This has led to the search for an alternative bridging strategy in patients with end-stage lung disease. The use of extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplantation as well as a rescue strategy post-transplant for primary graft dysfunction (PGD) has been studied previously, however due to initially poor outcomes, its use was not heavily instituted. In recent years, with significant improvement in technologies, several single and multi-center studies have shown promising outcomes related to the use of ECMO as a bridging strategy as well as a therapy for patients suffering from PGD post-transplant. These results have challenged our current notion on ECMO use and hence forced us to reexamine the utility, efficacy and safety of ECMO in conjunction with lung transplantation. Through this review, we will address the various aspects related to ECMO use as a bridge to lung transplantation as well as a rescue post-transplant in the treatment of PGD. We will emphasize newer technologies related to ECMO use, examine recent observational studies and randomized trials of ECMO use before and after lung transplantation, and reflect upon our own institutional experience with the use of ECMO in these difficult clinical situations.

Extracorporeal membrane oxygenation and retransplantation in lung transplantation: an analysis of the UNOS registry

BACKGROUND

Despite limited organ availability, extracorporeal membrane oxygenation (ECMO) and retransplantation are becoming more commonplace.

METHODS

Using the United Network for Organ Sharing (UNOS) database, we evaluated survival of patients treated with ECMO before lung transplantation and undergoing retransplantation. A query identified cadaveric recipients from 2001 to 2012 over the age of 6 years.

RESULTS

Of 15,772 lung recipients, 15 583 never received ECMO, whereas 189 did. Mean age was 52.1 ± 14.4 versus 46.8 ± 16.5 years for non-ECMO and ECMO groups, respectively (p < 0.0001). Using Kaplan-Meier method, there were survival differences between ECMO and non-ECMO groups (p < 0.0001) and first-time transplants with and without ECMO to retransplants with and without ECMO (p < 0.0001). The proportional hazards model identified higher risk with ECMO use in idiopathic pulmonary fibrosis (hazard ratio [HR] 1.09; 95 % confidence interval (CI), 1.02-1.17; p = 0.014) and retransplants (HR 1.77; 95 % CI, 1.55-2.03; p < 0.0001).

CONCLUSIONS

Survival for retransplantation was similar to ECMO as a primary option with significant mortality associated with ECMO use in patients with idiopathic pulmonary fibrosis and retransplants.

Successful coronary artery bypass grafting with the aid of a portable minimized extracorporeal life support system

Extracorporeal life support system has been successfully used in patients with cardiac failure after open heart surgery, as a bridge to transplantation, and in patients with prolonged cardiogenic shock or cardiopulmonary arrest. This report presents our early experience with the new system Cardiohelp in coronary artery bypass grafting (CABG). Between August 2010 and June 2011, 50 patients underwent CABG with the aid of Cardiohelp. This subgroup was matched for sex and logistic EuroSCORE with 100 patients, who underwent CABG using two different extracorporeal circulation systems, a minimized (MECC) (n = 50) and a conventional (CECC) (n = 50) during the same period. Because of less hemodilution, the intraoperative blood transfusion was significantly lower in the Cardiohelp group (36%) and MECC group (40%) compared with the CECC group (64%). Postoperative release of creatinine kinase and lactate was lower in the Cardiohelp and MECC groups (p < 0.001). Furthermore, these patients had shorter duration of ventilation and lengths of stay at the intensive care unit (p < 0.05). Device-related complications were not observed. A conversion to CECC was not necessary. In conclusion, the Cardiohelp is a safe alternative for CABG surgery. Valid technical innovations and limited number of side effects support its employment as a highly effective device for coronary surgery.

Increased sedation requirements in patients receiving extracorporeal membrane oxygenation for respiratory and cardiorespiratory failure

Critically ill patients receiving extracorporeal membrane oxygenation (ECMO) are often noted to have increased sedation requirements. However, data related to sedation in this complex group of patients is limited. The aim of our study was to characterise the sedation requirements in adult patients receiving ECMO for cardiorespiratory failure. A retrospective chart review was performed to collect sedation data for 30 consecutive patients who received venovenous or venoarterial ECMO between April 2009 and March 2011. To test for a difference in doses over time we used a regression model. The dose of midazolam received on ECMO support increased by an average of 18 mg per day (95% confidence interval 8, 29 mg, P=0.001), while the dose of morphine increased by 29 mg per day (95% confidence interval 4, 53 mg, P=0.021) The venovenous group received a daily midazolam dose that was 157 mg higher than the venoarterial group (95% confidence interval 53, 261 mg, P=0.005). We did not observe any significant increase in fentanyl doses over time (95% confidence interval 1269, 4337 µg, P=0.94). There is a significant increase in dose requirement for morphine and midazolam during ECMO. Patients on venovenous ECMO received higher sedative doses as compared to patients on venoarterial ECMO. Future research should focus on mechanisms behind these changes and also identify drugs that are most suitable for sedation during ECMO.

Extracorporeal membrane oxygenation in awake patients as bridge to lung transplantation

RATIONALE

The use of extracorporeal membrane oxygenation (ECMO) in patients who are awake and spontaneously breathing may represent a novel bridging strategy toward lung transplantation (LuTx).

OBJECTIVES

To evaluate the outcomes of patients treated with the "awake ECMO" concept as bridge to transplantation.

METHODS

We performed a retrospective, single-center, intention-to-treat analysis of consecutive LuTx candidates with terminal respiratory or cardiopulmonary failure receiving awake ECMO support. The outcomes were compared with a historical control group of patients treated with conventional mechanical ventilation (MV group) as bridge to transplant.

MEASUREMENTS AND MAIN RESULTS

Twenty-six patients (58% female; median age, 44 yr; range, 23-62) were included in the awake ECMO group and 34 patients (59% female; median age, 36 yr; range, 18-59) in the MV group. The duration of ECMO support or MV, respectively, was comparable in both groups (awake ECMO: median, 9 d; range, 1-45. MV: median, 15 d; range, 1-71; P = 0.25). Six (23%) of 26 patients in the awake ECMO group and 10 (29%) of 34 patients in the MV group died before a donor organ was available (P = 0.20). Survival at 6 months after LuTx was 80% in the awake ECMO group versus 50% in the MV group (P = 0.02). Patients in the awake ECMO group required shorter postoperative MV (P = 0.04) and showed a trend toward a shorter postoperative hospital stay (P = 0.06).

CONCLUSIONS

ECMO support in patients who are awake and nonintubated represents a promising bridging strategy, which should be further evaluated to determine its role in patients with end-stage lung disease awaiting LuTx.

Perioperative mechanical circulatory support in children with critical heart disease

OPINION STATEMENT

The treatment of cardiovascular failure in the perioperative period with the use of mechanical circulatory support is a well-recognized, well-developed, and commonly utilized treatment modality. Regardless of the exact circumstances of initiation, the use of a support device is a "bridge." Where there has been an acute myocardial insult, short-term assist devices can serve as a "bridge to immediate survival," a "bridge to recovery," or even a "bridge to the next decision." Mechanical circulatory support can serve as a treatment of cardiovascular decompensation caused by myocarditis, acute myocardial insult, low cardiac output following surgery, and congenital heart disease. The utilization of such support carries significant risks such as bleeding, infection, and thrombosis. However, these can be minimized in order to allow for the safe and effective deployment of this therapeutic strategy. One specific therapeutic domain in which these devices provide immediate impact is during cardiac arrest. Although outcomes of cardiac arrest remain poor, use of a mechanical device as an intervention has allowed salvage of otherwise certain mortality. However, it is important to note that the utility of support was most pronounced in patients that were not on either extreme of the survival prediction curve. This can be best summarized by the concept of "not too early, not too late." Therefore, it is the responsibility of the entire care team to find the appropriate patient population in which to "pull the trigger" on mechanical support as a therapy. This decision point is supported by a monitoring strategy that can be utilized to predict deterioration and intervene adequately. Most importantly, an effective monitoring strategy allows the practitioner to judge the effectiveness of treatment and support strategies and make adjustments in a timely manner, potentially with mechanical support in the perioperative period.

Clinical evaluation of two different extracorporeal membrane oxygenation systems: a single center report

Refinements in extracorporeal membrane oxygenation (ECMO) equipment, including heparin-coated surfaces, centrifugal pump, membrane oxygenator, and more biocompatible pump-oxygenator circuits, have reduced procedure-related complications and have made ECMO a safe and effective therapy for critical patients. The aim of this study was to evaluate the performance of two different ECMO circuit systems in a clinical setting and compare their outcomes. From December 2004 to December 2009, 121 patients required ECMO for primary or postcardiotomy cardiogenic shock at our heart center. We used the Medtronic circuit system in our earlier series (Group M, n = 64), and from July 2007, ECMO was carried out mainly with the Quadrox D PLS circuit system (Group Q, n = 56). We retrospectively summarized and analyzed the data of these patients. The evaluation was based on the comparison between properties of the membrane oxygenators and pumps, anticoagulation therapy, circuit-related complications, and clinical outcomes. Support pump flow rates, platelet counts, and trans-membrane pressure drops (TMPDs) of preoxygenator and postoxygenator pressures were compared between two groups at the time of support established (T1) and support established for 24 h (T2). There were no significant differences between the two groups with regard to patient characteristics and pre-ECMO data. The support pump flow rates and platelet counts at different times were comparable in the two groups. The cannulation technique, ECMO duration, and mean heparin dosage were similar in both groups. There were also no significant differences between the groups in mortality or complications related to bleeding and organ dysfunction. Compared with the M group, the Q group experienced less mechanical failure of the ECMO circuit. The Quadrox PLS circuit system showed less circuit thrombus formation (P < 0.045), less plasma leakage (P < 0.001), and less need for replacement of oxygenators (P < 0.001). Furthermore, frequency of hemolysis during ECMO was significantly lower (P < 0.045). In addition, at T1 and T2, TMPDs were significantly lower in the Q group. Our results suggest that both ECMO circuit systems provide similar effects for safe clinical application, but the Quadrox PLS ECMO circuit system demonstrated partially improved biocompatibility in terms of improved cell preservation, lower TMPDs, less plasma leakage, and thrombus formation.

Impact of tubing length on hemodynamics in a simulated neonatal extracorporeal life support circuit

During extracorporeal life support (ECLS), a large portion of the hemodynamic energy is lost to various components of the circuit. Minimization of this loss in the circuit leads to better vital organ perfusion and decreases the risk of systemic inflammation. In this study, we evaluated the hemodynamic properties of differing lengths of tubing in a simulated neonatal ECLS circuit. The neonatal ECLS circuit used in this study included a Capiox Baby RX05 oxygenator (Terumo Corporation, Tokyo, Japan), a Rotaflow centrifugal pump (MAQUET Cardiopulmonary AG, Hirrlingen, Germany), and a heater and cooler unit. An 8Fr Biomedicus arterial and a 10Fr Biomedicus venous cannula were connected to the pseudopatient. One-fourth inch tubing was used for both the arterial and the venous line. A Hoffman clamp was located upstream from the pseudopatient to maintain a certain patient pressure. Three pressure transducers were placed at different sites: postoxygenator, prearterial cannula, and postarterial cannula. The system was primed with Lactated Ringer's solution; human blood was then added to maintain a hematocrit of 40%. The volume of the pseudopatient was 500mL. We hemodynamically evaluated three circuits with different lengths of tubing: 6, 4, and 2 feet (182.88, 121.92, and 60.96 cm, respectively) for both arterial and venous lines; the priming volumes including all of the components of the circuits were 195, 155, and 115mL, respectively. In each circuit, we measured the pressure drops of the arterial tubing and the arterial cannula, as well as the flow rates at different rpm (1750-3000, 250 intervals) under three patient pressures (40, 60, and 80mm Hg). All the experiments were conducted at 37°C. The pressure drop across the arterial cannula is much larger than that of arterial tubing in all set-ups, especially under high flow rates. Upon cutting the tubing from 6 to 2 feet, the pressure drop of the arterial tubing decreased by half, while the pressure drop of the arterial cannula increased due to the slightly higher flow rates. These results suggest that compared to the arterial tubing, the arterial cannula has a larger impact on the hemodynamics of the circuit. There is a little influence of tubing length on the circuit flow rate.