Severe hypoxemia during veno-venous extracorporeal membrane oxygenation: exploring the limits of extracorporeal respiratory support

Parallel oxygenators in the same circuit for refractory hypoxemia on veno-venous extracorporeal membrane oxygenation. A 3-patient series

Extracorporeal membrane oxygenator (ECMO) is a well-established therapy for respiratory failure. Refractory hypoxemia, despite the use of ECMO, remains a challenging problem. The ECMO circuit may not provide enough oxygenation support in the presence of high cardiac output, increased physiologic demand, and impaired gas exchange. Adding a second ECMO oxygenator using the same pump (sometimes needing a second drainage cannula) can improve oxygenation and facilitate lung-protective ventilation in selected patients. We describe a 3-patient series with severe ARDS secondary to SARS-CoV-2 infection and refractory hypoxemia during ECMO support successfully treated with this approach.

Venopulmonary Artery Extracorporeal Life Support (VPa ECMO): A Novel Strategy for Refractory Hypoxemia Complicating VV ECMO

Refractory hypoxemia (RH) during venovenous extracorporeal membrane oxygenation (VV ECMO) support is a complex problem that limits the benefit of this therapy. The need for sustained deep sedation and delays in active rehabilitation are considered as a direct consequence of RH. Changing from VV ECMO to a configuration that returns the flow to pulmonary artery, such as venopulmonary extracorporeal membrane oxygenation (VPa ECMO) may decrease recirculation and improve systemic oxygen delivery. We present a retrospective report that describes the impact of VPa ECMO on oxygenation during sedation withdrawal in 41 patients who received VV ECMO for coronavirus disease 2019 (COVID-19). We evidenced that arterial oxygen pressure (PaO 2 ) increased from 68 to 112.3 mm Hg ( p = 0.001) with a reduction of ECMO flow (5.7-4.8 L/m; p = 0.001). Other findings included lower rates of depth sedation (Richmond Agitation Sedation Scale [RASS] ≤3, 37-63%; p = 0.007) and lower requirement inotropic support assessed by LVIS score (4.7-1.1; p = 0.005). Discharge survival was 54% with a sustained benefit until day 79. This cannulation strategy improved effectively PaO 2 in this cohort, it may be an alternative in patients with RH in VV ECMO.

A novel strategy to reduce the recirculation of venovenous extracorporeal membrane oxygenation: Inferior vena cava closure technology

The recirculation of venovenous extracorporeal membrane oxygenation (VV-ECMO) will decrease the efficiency of respiratory support. We report a patient with refractory severe acute respiratory distress syndrome (ARDS). Even with the support of ECMO and mechanical ventilation (MV), it is still difficult to correct hypoxemia. In this case, we placed a balloon catheter above the ECMO drainage cannula in inferior vena cava (IVC), and then occlusion the IVC with the water-filled balloon. After the occlusion, the patient's hypoxemia was quickly improved, and angiography proved that the recirculation has been significantly reduced. In this case, IVC occlusion technology greatly reduces recirculation. Its advantages lie in simple operation, low cost, short term safety, which probably act as an innovative method to reduce recirculation.

Treatment of Refractory Cardiac Arrest by Controlled Reperfusion of the Whole Body: A Multicenter, Prospective Observational Study

Background: Survival following cardiac arrest (CA) remains poor after conventional cardiopulmonary resuscitation (CCPR) (6-26%), and the outcomes after extracorporeal cardiopulmonary resuscitation (ECPR) are often inconsistent. Poor survival is a consequence of CA, low-flow states during CCPR, multi-organ injury, insufficient monitoring, and delayed treatment of the causative condition. We developed a new strategy to address these issues. Methods: This all-comers, multicenter, prospective observational study (69 patients with in- and out-of-hospital CA (IHCA and OHCA) after prolonged refractory CCPR) focused on extracorporeal cardiopulmonary support, comprehensive monitoring, multi-organ repair, and the potential for out-of-hospital cannulation and treatment. Result: The overall survival rate at hospital discharge was 42.0%, and a favorable neurological outcome (CPC 1+2) at 90 days was achieved for 79.3% of survivors (CPC 1+2 survival 33%). IHCA survival was very favorable (51.7%), as was CPC 1+2 survival at 90 days (41%). Survival of OHCA patients was 35% and CPC 1+2 survival at 90 days was 28%. The subgroup of OHCA patients with pre-hospital cannulation showed a superior survival rate of 57.1%. Conclusions: This new strategy focusing on repairing damage to multiple organs appears to improve outcomes after CA, and these findings should provide a sound basis for further research in this area.

Extracorporeal Membrane Oxygenation During Pregnancy

In the last 2 decades, the use of venovenous (VV) and venoarterial (VA) extracorporeal membrane oxygenation (ECMO) during pregnancy and the postpartum period has increased, mirroring the increased utilization in nonpregnant individuals worldwide. VV ECMO provides respiratory support for patients with acute respiratory distress syndrome (ARDS) who fail conventional mechanical ventilation. With the COVID-19 pandemic, the use of VV ECMO has increased dramatically and data during pregnancy and the postpartum period are overall reassuring. In contrast, VA ECMO provides both respiratory and cardiovascular support. Data on the use of VA ECMO during pregnancy are extremely limited.

Management of two circulations in a COVID-19 patient with secondary superinfection

Optimal oxygenation in the intensive care unit requires adequate pulmonary gas exchange, oxygen-carrying capacity in the form of hemoglobin, sufficient delivery of oxygenated hemoglobin to the tissue, and an appropriate tissue oxygen demand. In this Case Study in Physiology, we describe a patient with COVID-19 whose pulmonary gas exchange and oxygen delivery were severely compromised by COVID-19 pneumonia requiring extracorporeal membrane oxygenation (ECMO) support. His clinical course was complicated by a secondary superinfection with staphylococcus aureus and sepsis. This case study is provided with two goals in mind (1) We outline how basic physiology was used to address life-threatening consequences of a novel infection-COVID-19. (2) We describe a strategy of whole-body cooling to lower the cardiac output and oxygen consumption, use of the shunt equation to optimize flow to the ECMO circuit, and transfusion to improve oxygen-carrying capacity when ECMO alone failed to provide sufficient oxygenation.

The Impact of Recirculation on Extracorporeal Gas Exchange and Patient Oxygenation during Veno-Venous Extracorporeal Membrane Oxygenation-Results of an Observational Clinical Trial

Background: Recirculation during veno-venous extracorporeal membrane oxygenation reduces extracorporeal oxygen exchange and patient oxygenation. To minimize recirculation and maximize oxygen delivery (DO2) the interaction of cannulation, ECMO flow and cardiac output requires careful consideration. We investigated this interaction in an observational trial. Methods: In 19 patients with acute respiratory distress syndrome and ECMO, we measured recirculation with the ultrasound dilution technique and calculated extracorporeal oxygen transfer (VO2), extracorporeal oxygen delivery (DO2) and patient oxygenation. To assess the impact of cardiac output (CO), we included CO measurement through pulse contour analysis. Results: In all patients, there was a median recirculation rate of approximately 14−16%, with a maximum rate of 58%. Recirculation rates >35% occurred in 13−14% of all cases. In contrast to decreasing extracorporeal gas exchange with increasing ECMO flow and recirculation, patient oxygenation increased with greater ECMO flows. High CO diminished recirculation by between 5−20%. Conclusions: Extracorporeal gas exchange masks the importance of DO2 and its effects on patients. We assume that increasing DO2 is more important than reduced VO2. A negative correlation of recirculation to CO adds to the complexity of this phenomenon. Patient oxygenation may be optimized with the direct measurement of recirculation.

Exploring the association of two oxygenators in parallel or in series during respiratory support using extracorporeal membrane oxygenation

OBJECTIVE

To characterize the pressures, resistances, oxygenation, and decarboxylation efficacy of two oxygenators associated in series or in parallel during venous-venous extracorporeal membrane oxygenation support.

METHODS

Using the results of a swine severe respiratory failure associated with multiple organ dysfunction venous-venous extracorporeal membrane oxygenation support model and mathematical modeling, we explored the effects on oxygenation, decarboxylation and circuit pressures of in-parallel and in-series associations of oxygenators.

RESULTS

Five animals with a median weight of 80kg were tested. Both configurations increased the oxygen partial pressure after the oxygenators. The return cannula oxygen content was also slightly higher, but the impact on systemic oxygenation was minimal using oxygenators with a high rated flow (~ 7L/minute). Both configurations significantly reduced the systemic carbon dioxide partial pressure. As the extracorporeal membrane oxygenation blood flow increased, the oxygenator resistance decreased initially with a further increase with higher blood flows but with a small clinical impact.

CONCLUSION

Association of oxygenators in parallel or in series during venous-venous extracorporeal membrane oxygenation support provides a modest increase in carbon dioxide partial pressure removal with a slight improvement in oxygenation. The effect of oxygenator associations on extracorporeal circuit pressures is minimal.

Exploring the association of two oxygenators in parallel or in series during respiratory support using extracorporeal membrane oxygenation

OBJECTIVE

To characterize the pressures, resistances, oxygenation, and decarboxylation efficacy of two oxygenators associated in series or in parallel during venous-venous extracorporeal membrane oxygenation support.

METHODS

Using the results of a swine severe respiratory failure associated with multiple organ dysfunction venous-venous extracorporeal membrane oxygenation support model and mathematical modeling, we explored the effects on oxygenation, decarboxylation and circuit pressures of in-parallel and in-series associations of oxygenators.

RESULTS

Five animals with a median weight of 80kg were tested. Both configurations increased the oxygen partial pressure after the oxygenators. The return cannula oxygen content was also slightly higher, but the impact on systemic oxygenation was minimal using oxygenators with a high rated flow (~ 7L/minute). Both configurations significantly reduced the systemic carbon dioxide partial pressure. As the extracorporeal membrane oxygenation blood flow increased, the oxygenator resistance decreased initially with a further increase with higher blood flows but with a small clinical impact.

CONCLUSION

Association of oxygenators in parallel or in series during venous-venous extracorporeal membrane oxygenation support provides a modest increase in carbon dioxide partial pressure removal with a slight improvement in oxygenation. The effect of oxygenator associations on extracorporeal circuit pressures is minimal.

Flexible broncoscopy in patients in supportive therapy with oxygenation by extracorporeal membrane

Objective:

To report the experience of performing bronchoscopy in patients who underwent supportive therapy with extracorporeal membrane oxygenation in whom the bronchoscopy was performed.

Methods:

This was a review of medical records of patients diagnosed with extracorporeal membrane oxygenation and who required diagnostic or therapeutic bronchoscopy. Records included were related to patients admitted to the intensive care unit of Hospital das Clínicas of Faculdade de Medicina of Universidade de São Paulo, between 2014 and 2020.

Results:

During the study, 16 bronchoscopies were performed in 8 patients admitted to the intensive care unit and who underwent supportive therapy with extracorporeal membrane oxygenation. The mean age of patients was 28.37 years. Four patients were women (50%). A total of 5 (31.25%) therapeutic bronchoscopies and 11 (68.75%) diagnostics were performed. In 5 of patients, material was collected: 4 samples of bronchoalveolar lavage, three collections of transbronchial biopsies, and 1 of endobronchial biopsies. No patient had radiological worsening or hemodynamic complications. One patient (6.25%) had transient desaturation. There was moderate bleeding after transbronchial biopsy in 1 (6.25%) procedure, which was resolved endoscopically.

Conclusion:

Patients undergoing extracorporeal membrane oxygenation can safely perform diagnostic or therapeutic bronchoscopy provided that they have a detailed indication. Procedures were performed by a specialized bronchoscopy team in intensive care environment and with the assistance of a qualified multidisciplinary team in membrane oxygenation therapy extracorporeal.

Extracorporeal Membrane Oxygenation Circuits in Parallel for Refractory Hypoxemia in COVID-19: A Case Series

Refractory hypoxemia despite the use of extracorporeal membrane oxygenation (ECMO) for coronavirus disease 2019 (COVID-19)-related acute respiratory distress syndrome remains a challenging problem. A single ECMO circuit may not provide adequate physiologic support in the setting of an elevated cardiac output, physiologic demand, and impaired gas exchange. In select patients with refractory hypoxemia, addition of a second ECMO circuit in parallel can improve oxygenation, facilitate lung protective ventilation, awakening, and physical rehabilitation. We report the largest case series to date of patients receiving ECMO circuits in parallel and the first to report this approach in COVID-19.

Lung perfusion during veno-venous extracorporeal membrane oxygenation in a model of hypoxemic respiratory failure

Background

Veno-venous extracorporeal membrane oxygenation (ECMO) provides blood oxygenation and carbon dioxide removal in acute respiratory distress syndrome. However, during ECMO support, the native lungs still play an important role in gas exchange, functioning as a second oxygenator in series with ECMO. The hypoxic vasoconstriction mechanism diverts regional blood flow within the lungs away from regions with low oxygen levels, optimizing ventilation/perfusion matching. ECMO support has the potential to reduce this adaptive pulmonary response and worsen the ventilation/perfusion mismatch by raising venous oxygen partial pressure. Thus, the objective of this study was to evaluate the effect of ECMO on regional pulmonary perfusion and pulmonary hemodynamics during unilateral ventilation and posterior lung collapse.

Methods

Five Agroceres pigs were instrumented, monitored and submitted to ECMO. We used the Electrical Impedance Tomography (EIT) to evaluate lung ventilation and perfusion in all protocol steps. Effects of ECMO support on pulmonary hemodynamics and perfusion involving two different scenarios of ventilation/perfusion mismatch: (1) right-lung selective intubation inducing collapse of the normal left lung and (2) dorsal lung collapse after repeated lung lavage. Data including hemodynamics, respiratory, lung perfusion/ventilation, and laboratory data over time were analyzed with a mixed generalized model using the subjects as a random factor.

Results

The initiation of ECMO support provided a significant reduction in Mean Pulmonary Artery Pressure (PAPm) in both situations of ventilation/perfusion mismatch. However, distribution of lung perfusion did not change with the use of ECMO support.

Conclusions

We found that the use of ECMO support with consequent increase in venous oxygen pressure induced a significant drop in PAPm with no detectable effect on regional lung perfusion in different scenarios of ventilation/perfusion mismatch.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40635-022-00442-x.

CARL – kontrollierte Reperfusion des ganzen Körpers

Hintergrund

Inzidenz und Letalität des akuten Herz-Kreislauf-Stillstands sind seit Jahrzehnten gleichbleibend hoch.

Fragestellung

Wie lassen sich die derzeit unbefriedigenden Ergebnisse nach einer Reanimation mit Blick auf das Überleben und die neurologischen, v. a. mit Blick auf die zerebralen Folgeschäden verbessern?

Material und Methoden

Entwicklung eines therapeutischen Verfahrens zur Eindämmung des Ischämie‑/Reperfusionsschadens im Tiermodell. Entwicklung eines für die Reanimation optimierten Gerätesystems, mit dem sich eine kontrollierte Ganzkörperreperfusion auch außerklinisch umsetzen lässt.

Ergebnisse

Etablierung der CARL-Therapie in der Klinik und in der Behandlung von OHCA-Patienten. Übernahme der Therapie und des CARL-Systems in eine klinische Beobachtungsstudie. Erste Fallberichte, in denen Patienten einen OHCA auch nach Ischämiezeiten bis zu 2 h ohne Schädigung des Gehirns überlebten.

Schlussfolgerungen

Die CARL-Therapie eignet sich potenziell zur Behandlung reanimationspflichtiger Patienten mit einem auch über längere Zeit therapierefraktären Herz-Kreislauf-Stillstand.

Mathematical modelling of oxygenation under veno-venous ECMO configuration using either a femoral or a bicaval drainage

BACKGROUND

The bicaval drainage under veno-venous extracorporeal membrane oxygenation (VV ECMO) was compared in present experimental study to the inferior caval drainage in terms of systemic oxygenation.

METHOD

Two mathematical models were built to simulate the inferior vena cava-to-right atrium (IVC → RA) route and the bicaval drainage-to-right atrium return (IVC + SVC → RA) route using the following parameters: cardiac output (Q_C), IVC flow/Q_C ratio, venous oxygen saturation, extracorporeal pump flow (Q_EC), and pulmonary shunt (PULM-Shunt) to obtain pulmonary artery oxygen saturation (S_PAO₂) and systemic blood oxygen saturation (SaO₂).

RESULTS

With the IVC → RA route, S_PAO₂ and SaO₂ increased linearly with Q_EC/Q_C until the threshold of the IVC flow/Q_C ratio, beyond which the increase in S_PAO₂ reached a plateau. With the IVC + SVC → RA route, S_PAO₂ and SaO₂ increased linearly with Q_EC/Q_C until 100% with Q_EC/Q_C = 1. The difference in required Q_EC/Q_C between the two routes was all the higher as SaO₂ target or PULM-Shunt were high, and occurred all the earlier as PULM-Shunt were high. The required Q_EC between the two routes could differ from 1.0 L/min (Q_C = 5 L/min) to 1.5 L/min (Q_C = 8 L/min) for SaO₂ target = 90%. Corresponding differences of Q_EC for SaO₂ target = 94% were 4.7 L/min and 7.9 L/min, respectively.

CONCLUSION

Bicaval drainage under ECMO via the IVC + SVC → RA route gave a superior systemic oxygenation performance when both Q_EC/Q_C and pulmonary shunt were high. The VV-V ECMO configuration (IVC + SVC → RA route) might be an attractive rescue strategy in case of refractory hypoxaemia under VV ECMO.

Extracorporeal Membrane Oxygenation for Pregnant and Postpartum Patients

Extracorporeal membrane oxygenation (ECMO) has seen increasing use for critically ill pregnant and postpartum patients over the past decade. Growing experience continues to demonstrate the feasibility of ECMO in obstetric patients and attest to its favorable outcomes. However, the interaction of pregnancy physiology with ECMO life support requires careful planning and adaptation for success. Additionally, the maintenance of fetal oxygenation and perfusion is essential for safely continuing pregnancy during ECMO support. This review summarizes the considerations for use of ECMO in obstetric patients and how to address these concerns.

A complication of ECMO cannula placement resulting in hemodynamic and oxygenation alterations: A case report

Veno-veno extracorporeal membrane oxygenation (VV ECMO) is used as a bridge to recovery in acute respiratory distress syndrome (ARDS) patients who have reversible lung failure. We present a complication of ECMO cannula placement/position resulting in hemodynamic and oxygenation alterations. These demonstrate principles related to the interaction of the VV ECMO circuit and patient cardio-pulmonary physiology. Consideration and comprehension of pulmonary shunt fraction, ECMO cannula recirculation ratio and ECMO blood flow to cardiac output (CO) ratio are central to continuous assessment and diagnosis of cardio-pulmonary changes encountered during management of VV ECMO.

New noninvasive methodology to measure cardiac output in veno-venous extracorporeal membrane oxygenation patients

INTRODUCTION

Cardiac output (CO) measurement is vital in veno-venous extracorporeal membrane oxygenation patient population to evaluate oxygen delivery and to early identify right heart failure. Standard clinical methods like pulmonary artery thermodilution and transpulmonary thermodilution are known to be inaccurate in the veno-venous extracorporeal membrane oxygenation setting, especially at high levels of recirculation.

OBJECTIVE

The aim of the study was to develop a simple noninvasive method to measure CO in patients during veno-venous extracorporeal membrane oxygenation.

METHODS

A mathematical model was developed where CO was analyzed as a combination of two flows: oxygenated blood from extracorporeal membrane oxygenation and less oxygenated mixed venous blood. The system of two mass balance equations for oxygen saturations was introduced to calculate CO. The procedure included measurement of recirculation (ELSA Monitor Transonic Systems Inc. Ithaca, USA) and arterial saturation at two extracorporeal membrane oxygenation flows after temporary pump flow decrease. Mathematic modeling that utilized a crude Monte Carlo method was used to analyze theoretical errors in CO calculations from unknown behavior of venous saturation. The developed concept was retrospectively applied to clinical data archive of 17 adult patients on veno-venous extracorporeal membrane oxygenation that included 52 measurement sessions.

RESULTS

Mathematical modeling suggests that proportion of results with error ⩽10% was between 86% and 100% if pre-oxygenated saturation was available and it was between 78% and 86% if pre-oxygenated saturation was not available. Application of two mass balance equation concept to clinical data suggests that as the decrease of the arterial saturation reaches 6% due to flow decrease, then CO calculations becomes highly reliable as 96% (2 standard deviations) of the results has a reproducibility within 6.4%.

CONCLUSION

The mathematical model and clinical retrospective analysis demonstrates that the new methodology has the potential to accurately measure CO in veno-venous extracorporeal membrane oxygenation patients. The next step is validation in animal and clinical settings.

Structural recirculation and refractory hypoxemia under femoro-jugular veno-venous extracorporeal membrane oxygenation

The performance of each veno-venous extracorporeal membrane oxygenation (vv-ECMO) configuration is determined by the anatomic context and cannula position. A mathematical model was built considering bicaval specificities to simulate femoro-jugular configuration. The main parameters to define were cardiac output (Q_C ), blood flow in the superior vena cava (Q_SVC ), extracorporeal pump flow (Q_EC ), and pulmonary shunt (k_S-PULM ). The obtained variables were extracorporeal flow ratio in the superior vena cava (EFR_SVC  = Q_EC /[Q_EC  + Q_SVC ]), recirculation coefficient (R), effective extracorporeal pump flow (Q_eff-EC  = [1 - R] × Q_EC ), Q_eff-EC /Q_C ratio, and arterial blood oxygen saturation (SaO₂ ). EFR_SVC increased logarithmically when Q_EC increased. High Q_C or high Q_SVC /Q_C decreased EFR_SVC (range, 68%-85% for Q_EC of 5 L/min). R also increased following a logarithmic shape when Q_EC increased. The R rise was earlier and higher for low Q_C and high Q_SVC /Q_C (range, 12%-49% for Q_EC of 5 L/min). The Q_eff-EC /Q_C ratio (between 0 and 1) was equal to EFR_SVC for moderate and high Q_EC . The Q_eff-EC /Q_C ratio presented the same logarithmic profile when Q_EC increased, reaching a plateau (range, 0.67-0.91 for Q_EC /Q_C  = 1; range, 0.75-0.94 for Q_EC /Q_C  = 1.5). The Q_eff-EC /Q_C ratio was linearly associated with SaO₂ for a given pulmonary shunt. SaO₂  < 90% was observed when the pulmonary shunt was high (Q_eff-EC /Q_C  ≤ 0.7 with k_S-PULM  = 0.7 or Q_eff-EC /Q_C  ≤ 0.8 with k_S-PULM  = 0.8). Femoro-jugular vv-ECMO generates a systematic structural recirculation that gradually increases with Q_EC . EFR_SVC determines the Q_eff-EC /Q_C ratio, and thereby oxygen delivery and the superior cava shunt. EFR_SVC cannot exceed a limit value, explaining refractory hypoxemia in extreme situations.

Extracorporeal membrane oxygenation for acute respiratory distress syndrome in burn patients: a case series and literature update

Background

Acute respiratory distress syndrome (ARDS) has a reported incidence of 34–43% in ventilated burn patients and is associated with a mortality of 59% in the severe form. The use and experience with extracorporeal membrane oxygenation (ECMO) in burn patients developing ARDS are still limited. We present our results and discuss the significance of ECMO in treating burn patients.

Methods

A retrospective analysis of burn patients treated with ECMO for ARDS between January 2017 and January 2019 was performed. Demographic, clinical, and outcome data were collected and analyzed.

Results

Eight burn patients were treated at our institution with ECMO in the designated time period. Of these, all but one patient had inhalation injury, burn percentage of TBSA was 37 ± 23%, ABSI score was 8.4 ± 2, and R-Baux-score was 98 ± 21. Seven patients developed severe ARDS and one patient moderate ARDS according to the Berlin classification with a PaO₂/FiO₂ ratio upon initiation of ECMO therapy of 62 ± 22 mmHg. ECMO duration was 388 ± 283 h. Three patients died from severe sepsis while five patients survived to hospital discharge.

Conclusions

ECMO is a viable therapy option in burn patients developing severe ARDS and can contribute to survival rates similar to ECMO therapy in non-burn-associated severe ARDS. Consequently, patients with severe respiratory insufficiency with unsuccessful conventional treatment and suspected worsening should be transferred to burn units with the possibility of ECMO treatment to improve outcome.

Hemodynamics of neonatal double lumen cannula malposition

Objective:

Malposition of dual lumen cannula is a frequent and challenging complication in neonates and plays a significant role in shaping the in vitro device hemodynamics. This study aims to analyze the effect of the dual lumen cannula malposition on right-atrial hemodynamics in neonatal patients using an experimentally validated computational fluid dynamics model.

Methods:

A computer model was developed for clinically approved dual lumen cannula (13Fr Origen Biomedical, Austin, Texas, USA) oriented inside the atrium of a 3-kg neonate with normal venous return. Atrial hemodynamics and dual lumen cannula malposition were systematically simulated for two rotations (antero-atrial and atrio-septal) and four translations (two intravascular movements along inferior vena cava and two dislodged configurations in the atrium). A multi-domain compartmentalized mesh was prepared to allow the site-specific evaluation of important hemodynamic parameters. Transport of each blood stream, blood damage levels, and recirculation times are quantified and compared to dual lumen cannula in proper position.

Results:

High recirculation levels (39 ± 4%) in malpositioned cases resulted in poor oxygen saturation where maximum recirculation of up to 42% was observed. Apparently, Origen dual lumen cannula showed poor inferior vena cava blood–capturing efficiency (48 ± 8%) but high superior vena cava blood–capturing efficiency (86 ± 10%). Dual lumen cannula malposition resulted in corresponding changes in residence time (1.7 ± 0.5 seconds through the tricuspid). No significant differences in blood damage were observed among the simulated cases compared to normal orientation. Compared to the correct dual lumen cannula position, both rotational and translational displacements of the dual lumen cannula resulted in significant hemodynamic differences.

Conclusion:

Rotational or translational movement of dual lumen cannula is the determining factor for atrial hemodynamics, venous capturing efficiency, blood residence time, and oxygenated blood delivery. Results obtained through computational fluid dynamics methodology can provide valuable foresight in assessing the performance of the dual lumen cannula in patient-specific configurations.

Controlled automated reperfusion of the whole body after cardiac arrest

Background

Sudden circulatory arrest (CA) requiring cardiopulmonary resuscitation (CPR) has for decades been associated with high mortality and frequent neurological sequelae in the rarer survivors. The high mortality and morbidity are potentially related to a severe and global ischemia/reperfusion injury (IRI) of the whole body, especially the brain. Consequently, strategies to counteract this severe IRI may improve survival and neurological recovery of affected patients.

Methods

Based on the target to limit IRI in single organs, suitable parameters and methods were composed to form a global treatment concept, the CARL method (controlled automated reperfusion of the whole body). The concept centers on extracorporeal circulation, enhanced with readily available online monitoring. It allows for targeted adaption of different parameters (i.e., blood pressure and flow, temperature, oxygen content, electrolytes) during the reperfusion process, in the sense of a controlled reperfusion. Parameters and elements of the CARL method were extensively tested in a chronic animal model. An appropriate medical device, the system configuration "CIRD 1.0" (Controlled Integrated Resuscitation Device) is approved to be applied to patients.

Results

A set of parameters that support a limitation of a global IRI have been identified in over 250 animal experiments. Their specific targets and surveillance using adequate monitoring features are described. Using the CIRD in a single center, 14 patients with witnessed, but extremely prolonged CPR (51-120 minutes) have been treated with CARL. The outcome of these patients was favorable, with 7 of 14 patients regaining full consciousness and 6 of 7 allocated to Cerebral Performance Class (CPC) "1".

Conclusions

CA followed by CPR is associated with a very high mortality and frequent neurological sequelae. Limiting the occurring severe and global IRI may be a key to an improved survival and neurological recovery. Therefore, the therapeutic approach of CARL, which stands for a personalized, comprehensive therapy based on a readily available set of monitoring data and diagnostic findings, has been developed. First experience in patients indicates beneficial effects that call for further studies in the field of CARL.

Oxygen delivery, carbon dioxide removal, energy transfer to lungs and pulmonary hypertension behavior during venous-venous extracorporeal membrane oxygenation support: a mathematical modeling approach

Objective

To describe (1) the energy transfer from the ventilator to the lungs, (2) the match between venous-venous extracorporeal membrane oxygenation (ECMO) oxygen transfer and patient oxygen consumption (VO₂), (3) carbon dioxide removal with ECMO, and (4) the potential effect of systemic venous oxygenation on pulmonary artery pressure.

Methods

Mathematical modeling approach with hypothetical scenarios using computer simulation.

Results

The transition from protective ventilation to ultraprotective ventilation in a patient with severe acute respiratory distress syndrome and a static respiratory compliance of 20mL/cm H₂O reduced the energy transfer from the ventilator to the lungs from 35.3 to 2.6 joules/minute. A hypothetical patient, hyperdynamic and slightly anemic with VO₂ = 200mL/minute, can reach an arterial oxygen saturation of 80%, while maintaining the match between the oxygen transfer by ECMO and the VO₂ of the patient. Carbon dioxide is easily removed, and normal PaCO₂ is easily reached. Venous blood oxygenation through the ECMO circuit may drive the PO₂ stimulus of pulmonary hypoxic vasoconstriction to normal values.

Conclusion

Ultraprotective ventilation largely reduces the energy transfer from the ventilator to the lungs. Severe hypoxemia on venous-venous-ECMO support may occur despite the matching between the oxygen transfer by ECMO and the VO₂ of the patient. The normal range of PaCO₂ is easy to reach. Venous-venous-ECMO support potentially relieves hypoxic pulmonary vasoconstriction.

Extended Indications for Extracorporeal Membrane Oxygenation in the Operating Room

Background:

The use of extracorporeal life support (ECLS) for cardiorespiratory support is increasing. Traditional absolute contraindications are currently deemed relative contraindications. Extracorporeal life support is now considered for a wider cohort of patients on a case-by-case basis.

Method:

We performed a review of the literature and examined current Extracorporeal Life Support Organization guidelines that support the use of ECLS in the operating room, based on the underlying pathology and surgical procedure proposed. We discuss specific surgical populations and different modes of ECLS and cannulation strategies.

Results:

Based on the available literature, veno-venous extracorporeal membrane oxygenation (ECMO) can be used for the management of complex tracheobronchial and lung surgery, both in the elective and in the emergent setting. Elective veno-arterial (V-A) ECMO for cardiocirculatory support should be considered in high-risk patients undergoing ventricular tachycardia ablation. Extracorporeal life support should be considered as a potential life-saving intervention in almost all parturients with severe respiratory failure or refractory cardiogenic shock. V-A ECMO should be considered in unanticipated intraoperative cardiac arrest in patients without preexisting end-organ failure.

Conclusion:

As the number of indications for ECLS in the operating room is growing, anesthesiology and surgical staff should become familiar with the perioperative management of patients on ECLS.

Characterization of patients transported with extracorporeal respiratory and/or cardiovascular support in the State of São Paulo, Brazil

Objective

To characterize the transport of severely ill patients with extracorporeal respiratory or cardiovascular support.

Methods

A series of 18 patients in the state of São Paulo, Brazil is described. All patients were consecutively evaluated by a multidisciplinary team at the hospital of origin. The patients were rescued, and extracorporeal membrane oxygenation support was provided on site. The patients were then transported to referral hospitals for extracorporeal membrane oxygenation support. Data were retrieved from a prospectively collected database.

Results

From 2011 to 2017, 18 patients aged 29 (25 - 31) years with a SAPS 3 of 84 (68 - 92) and main primary diagnosis of leptospirosis and influenza A (H1N1) virus were transported to three referral hospitals in São Paulo. A median distance of 39 (15 - 82) km was traveled on each rescue mission during a period of 360 (308 - 431) min. A median of one (0 - 2) nurse, three (2 - 3) physicians, and one (0 - 1) physical therapist was present per rescue. Seventeen rescues were made by ambulance, and one rescue was made by helicopter. The observed complications were interruption in the energy supply to the pump in two cases (11%) and oxygen saturation < 70% in two cases. Thirteen patients (72%) survived and were discharged from the hospital. Among the nonsurvivors, there were two cases of brain death, two cases of multiple organ dysfunction syndrome, and one case of irreversible pulmonary fibrosis.

Conclusions

Transportation with extracorporeal support occurred without serious complications, and the hospital survival rate was high.

Perioperative Management of the Adult Patient on Venovenous Extracorporeal Membrane Oxygenation Requiring Noncardiac Surgery

The use of venovenous extracorporeal membrane oxygenation is increasing worldwide. These patients often require noncardiac surgery. In the perioperative period, preoperative assessment, patient transport, choice of anesthetic type, drug dosing, patient monitoring, and intraoperative and postoperative management of common patient problems will be impacted. Furthermore, common monitoring techniques will have unique limitations. Importantly, patients on venovenous extracorporeal membrane oxygenation remain subject to hypoxemia, hypercarbia, and acidemia in the perioperative setting despite extracorporeal support. Treatments of these conditions often require both manipulation of extracorporeal membrane oxygenation settings and physiologic interventions. Perioperative management of anticoagulation, as well as thresholds to transfuse blood products, remain highly controversial and must take into account the specific procedure, extracorporeal membrane oxygenation circuit function, and patient comorbidities. We will review the physiologic management of the patient requiring surgery while on venovenous extracorporeal membrane oxygenation.

Cannula Design and Recirculation During Venovenous Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is used as a lifesaving rescue treatment in refractory respiratory or cardiac failure. During venovenous (VV) ECMO, the presence of recirculation is known, but quantification and actions to minimize recirculation after measurement are to date not routinely practiced. In the current study, we investigated the effect of draining cannula design on recirculation fraction (R_f) during VV ECMO; conventional mesh cannula was compared with a multistage cannula. The effect of adjusting cannula position was also studied. Recirculation was measured with ultrasound dilution technique at different ECMO flows and after cannula repositioning. All patients who were admitted to our unit between October 2014 and July 2015 catheterized by the atrio-femoral single lumen method were included. A total of 108 measurements were conducted in 14 patients. The multistage cannula showed significantly less recirculation (19.0 ± 12.2%) compared with the conventional design (38.0 ± 13.7). Pooled data in cases improved from adjustment showing reduced R_f by 7%. In conclusion, the choice of cannula matters, as does adjustment of the draining cannula position during atrio-femoral VV ECMO. By utilizing the ultrasound dilution technique to measure R_f before and after repositioning, effective ECMO flow can be improved for a more effective ECMO treatment.

Extracorporeal respiratory support in adult patients

In patients with severe respiratory failure, either hypoxemic or hypercapnic, life support with mechanical ventilation alone can be insufficient to meet their needs, especially if one tries to avoid ventilator settings that can cause injury to the lungs. In those patients, extracorporeal membrane oxygenation (ECMO), which is also very effective in removing carbon dioxide from the blood, can provide life support, allowing the application of protective lung ventilation. In this review article, we aim to explore some of the most relevant aspects of using ECMO for respiratory support. We discuss the history of respiratory support using ECMO in adults, as well as the clinical evidence; costs; indications; installation of the equipment; ventilator settings; daily care of the patient and the system; common troubleshooting; weaning; and discontinuation.

Influence of central hemodynamics on VV ECMO oxygen delivery in neonatal animal model

BACKGROUND

Recirculation of oxygenated blood in venovenous extracorporeal membrane oxygenation (VV ECMO) can decrease the oxygen delivery provided by the ECMO support. This study investigated the influence of central hemodynamics and catheter position on the amount of recirculation and oxygen delivery during VV ECMO.

METHODS

Recirculation was measured in seven newborn lambs (mean weight 4.7 kg) during VV ECMO using the ELSA Monitor (Transonic Systems, Inc., Ithaca, NY) and using the central venous line (CVL) method. The ECMO pump was set at the prescribed flow of 110-120 mL/kg/min for a targeted oxygen delivery rate of 6cc/kg/min without recirculation. Hemodynamic status before and during ECMO was also measured by the COstatus Monitor (Transonic Systems, Inc.,Ithaca, NY).

RESULTS

Lambs with a higher cardiac index (>160 ml/min/kg), had a tendency to have higher percent oxygen delivery (65-94%, at prescribed flow) while lambs with lower cardiac index (<150 ml/min/kg), tended to have lower percent oxygen delivery (39-62%, at prescribed flow). ELSA recirculation measurements had a squared correlation coefficient R2 = 0.8 with the CVL method.

CONCLUSIONS

The ELSA monitor provides an easy to use, non-invasive method to measure recirculation in VV ECMO. The data suggests that cardiac function may play an important prognostic role in achieving effective VV ECMO support.

Low Blood Arterial Oxygenation During Venovenous Extracorporeal Membrane Oxygenation: Proposal for a Rational Algorithm-Based Management

PURPOSE

Venovenous extracorporeal membrane oxygenation (VV-ECMO) is a therapeutic option in the management of the most severe forms of acute respiratory distress syndrome. Oxygenation during VV-ECMO depends on many parameters, and its management is complex. The management of ECMO is still not completely codified. The aim of this study was to rationalize the management of hypoxemia during VV-ECMO.

METHODS

To build a comprehensive flow diagram for management of hypoxemia during VV-ECMO, we considered (1) relationship between O2 arterial saturation and its determinants; (2) analysis of physiopathology of oxygenation under VV-ECMO; and (3) main guidelines and recommendations recapitulated in troubleshooting charts.

RESULTS

We propose a stepwise approach that could guide specific intervention to improve oxygenation during VV-ECMO. The first step is to obtain adequate pump flow, the main determinant of oxygenation, by eliminating a mechanical problem or inadequate venous drainage. Second, if hypoxemia persists, algorithm considers multiple reasons for inadequate oxygenation, namely: (1) excessive recirculation, (2) excessive cardiac output (decrease of ratio pump flow/cardiac output), (3) decrease in SvO2 (oxygen saturation in mixed venous blood), (4) malfunction of oxygenator, and (5) deterioration of residual lung function. Finally, for each modification of oxygenation parameters, specific measures are proposed to restore an adequate oxygenation by extracorporeal membrane oxygenation.

CONCLUSION

If hypoxemia occurs during VV-ECMO, collecting oxygenation parameters and a clear step-by-step algorithm could guide specific intervention to improve oxygenation. This flow diagram is in accordance with current recommendations recapitulated in guidelines or troubleshooting chart but more accurate and complete. Although rational and appealing, it remains to be tested together with a number of still unsolved issues.

Factors associated with blood oxygen partial pressure and carbon dioxide partial pressure regulation during respiratory extracorporeal membrane oxygenation support: data from a swine model

Objective

The aim of this study was to explore the factors associated with blood oxygen partial pressure and carbon dioxide partial pressure.

Methods

The factors associated with oxygen - and carbon dioxide regulation were investigated in an apneic pig model under veno-venous extracorporeal membrane oxygenation support. A predefined sequence of blood and sweep flows was tested.

Results

Oxygenation was mainly associated with extracorporeal membrane oxygenation blood flow (beta coefficient = 0.036mmHg/mL/min), cardiac output (beta coefficient = -11.970mmHg/L/min) and pulmonary shunting (beta coefficient = -0.232mmHg/%). Furthermore, the initial oxygen partial pressure and carbon dioxide partial pressure measurements were also associated with oxygenation, with beta coefficients of 0.160 and 0.442mmHg/mmHg, respectively. Carbon dioxide partial pressure was associated with cardiac output (beta coefficient = 3.578mmHg/L/min), sweep gas flow (beta coefficient = -2.635mmHg/L/min), temperature (beta coefficient = 4.514mmHg/ºC), initial pH (beta coefficient = -66.065mmHg/0.01 unit) and hemoglobin (beta coefficient = 6.635mmHg/g/dL).

Conclusion

In conclusion, elevations in blood and sweep gas flows in an apneic veno-venous extracorporeal membrane oxygenation model resulted in an increase in oxygen partial pressure and a reduction in carbon dioxide partial pressure 2, respectively. Furthermore, without the possibility of causal inference, oxygen partial pressure was negatively associated with pulmonary shunting and cardiac output, and carbon dioxide partial pressure was positively associated with cardiac output, core temperature and initial hemoglobin.

Extracorporeal membrane oxygenation for acute respiratory distress syndrome

Extracorporeal membrane oxygenation (ECMO) can be a lifesaving therapy in patients with refractory severe respiratory failure or cardiac failure. Severe acute respiratory distress syndrome (ARDS) still has a high-mortality rate, but ECMO may be able to improve the outcome. Use of ECMO for respiratory failure has been increasing since 2009. Initiation of ECMO for adult ARDS should be considered when conventional therapy cannot maintain adequate oxygenation. ECMO can stabilize gas exchange and haemodynamic compromise, consequently preventing further hypoxic organ damage. ECMO is not a treatment for the underlying cause of ARDS. Because ARDS has multiple causes, the diagnosis should be investigated and treatment should be commenced during ECMO. Since ECMO is a complicated and high-risk therapy, adequate training in its performance and creation of a referring hospital network are essential. ECMO transport may be an effective method of transferring patients with severe ARDS.

Varicella associated acute respiratory distress syndrome in an adult patient: an example for extracorporeal respiratory support in Brazilian endemic diseases

A case of a 30 year-old man presenting with severe systemic chickenpox with refractory hypoxemia, central nervous system vasculitis and anuric renal failure is described. Ambulance transportation and support using veno-venous extracorporeal membrane oxygenation were necessary until the patient recovered. Ultimately, the potential use of extracorporeal membrane oxygenation support in low-middle income countries to manage common diseases is discussed.