Oxygenator performance and artificial-native lung interaction

Carbon Dioxide Targets in Extracorporeal Membrane Oxygenation for Acute Respiratory Distress Syndrome

Target values for arterial carbon dioxide tension (PaCO 2 ) in extracorporeal membrane oxygenation (ECMO) for acute respiratory distress syndrome (ARDS) are unknown. We hypothesized that lower PaCO 2 values on ECMO would be associated with lighter sedation. We used data from two independent patient cohorts with ARDS spending 1,177 days (discovery cohort, 69 patients) and 516 days (validation cohort, 70 patients) on ECMO and evaluated the associations between daily PaCO 2 , pH, and bicarbonate (HCO 3 ) with sedation. Median PaCO 2 was 41 (interquartile range [IQR] = 37-46) mm Hg and 41 (IQR = 37-45) mm Hg in the discovery and the validation cohort, respectively. Lower PaCO 2 and higher pH but not bicarbonate (HCO 3 ) served as significant predictors for reaching a Richmond Agitation Sedation Scale (RASS) target range of -2 to +1 (lightly sedated to restless). After multivariable adjustment for mortality, tracheostomy, prone positioning, vasoactive inotropic score, Simplified Acute Physiology Score (SAPS) II or Sequential Organ Failure Assessment (SOFA) Score and day on ECMO, only PaCO 2 remained significantly associated with the RASS target range (adjusted odds ratio 1.1 [95% confidence interval (CI) = 1.01-1.21], p = 0.032 and 1.29 [95% CI = 1.1-1.51], p = 0.001 per mm Hg decrease in PaCO 2 for the discovery and the validation cohort, respectively). A PaCO 2 ≤40 mm Hg, as determined by the concordance probability method, was associated with a significantly increased probability of a sedation level within the RASS target range in both patient cohorts (adjusted odds ratio = 2.92 [95% CI = 1.17-7.24], p = 0.021 and 6.82 [95% CI = 1.50-31.0], p = 0.013 for the discovery and the validation cohort, respectively).

Dissolved Oxygen Relevantly Contributes to Systemic Oxygenation During Venovenous Extracorporeal Membrane Oxygenation Support

When determining extracorporeal oxygen transfer (V ML O 2 ) during venovenous extracorporeal membrane oxygenation (VV ECMO) dissolved oxygen is often considered to play a subordinate role due to its poor solubility in blood plasma. This study was designed to assess the impact of dissolved oxygen on systemic oxygenation in patients with acute respiratory distress syndrome (ARDS) on VV ECMO support by differentiating between dissolved and hemoglobin-bound extracorporeal oxygen transfer. We calculated both extracorporeal oxygen transfer based on blood gas analysis using the measuring energy expenditure in extracorporeal lung support patients (MEEP) protocol and measured oxygen uptake by the native lung with indirect calorimetry. Over 20% of V ML O 2 and over 10% of overall oxygen uptake (VO 2 total ) were realized as dissolved oxygen. The transfer of dissolved oxygen mainly depended on ECMO blood flow (BF ML ). In patients with severely impaired lung function dissolved oxygen accounted for up to 28% of VO 2 total . A clinically relevant amount of oxygen is transferred as physically dissolved fraction, which therefore needs to be considered when determining membrane lung function, manage ECMO settings or guiding the weaning procedure.

PCO 2 Gradient Between Inlet and Outlet Blood of Extracorporeal Respiratory Support Is a Reliable Marker of CO 2 Elimination

Our objective was to assess the relationship between the pre-/post-oxygenator gradient of the partial pressure of carbon dioxide (∆ EC PCO 2 ; dissolved form) and CO 2 elimination under extracorporeal respiratory support. All patients who were treated with veno-venous extracorporeal membrane oxygenation and high-flow extracorporeal CO 2 removal in our intensive care unit over 18 months were included. Pre-/post-oxygenator blood gases were collected every 12 h and CO 2 elimination was calculated for each pair of samples (pre-/post-oxygenator total carbon dioxide content in blood [ ct CO 2 ] × pump flow [extracorporeal pump flow {Q EC }]). The relationship between ∆ EC PCO 2 and CO 2 elimination, as well as the origin of CO 2 removed. Eighteen patients were analyzed (24 oxygenators and 293 datasets). Each additional unit of ∆ EC PCO 2 × Q EC was associated with an increase in CO 2 elimination of 5.2 ml (95% confidence interval [CI], 4.7-5.6 ml; p < 0.001). Each reduction of 1 ml STPD/dl of CO 2 across the oxygenator was associated with a reduction of 0.63 ml STPD/dl (95% CI, 0.60-0.66) of CO 2 combined with water, 0.08 ml STPD/dl (95% CI, 0.07-0.09) of dissolved CO 2 , and 0.29 ml STPD/dl (95% CI, 0.27-0.31) of CO 2 in erythrocytes. The pre-/post-oxygenator PCO 2 gradient under extracorporeal respiratory support is thus linearly associated with CO 2 elimination; however, most of the CO 2 removed comes from combined CO 2 in plasma, generating bicarbonate.

Improving ECMO therapy: Monitoring oxygenator functionality and identifying key indicators, factors, and considerations for changeout

INTRODUCTION

The optimal timing for extracorporeal membrane oxygenation (ECMO) circuit change-out is crucial for the successful management of patients with severe cardiopulmonary failure. This comprehensive review examines the various factors that influence the timing of oxygenator replacement in the ECMO circuit. By considering these factors, clinicians can make informed decisions to ensure timely and effective change-out, enhancing patient outcomes and optimizing the delivery of ECMO therapy.

METHODOLOGY

A thorough search of relevant studies on ECMO circuits and oxygenator change-out was conducted using multiple scholarly databases and relevant keywords. Studies published between 2017 and 2023 were included, resulting in 40 studies that met the inclusion criteria.

DISCUSSION

Thrombosis within the membrane oxygenator and its impact on dysfunction were identified as significant contributors, highlighting the importance of monitoring coagulation parameters and gas exchange. Several factors, including fibrinogen levels, pre and post-membrane blood gases, plasma-free hemoglobin, D-dimers, platelet function, flows and pressures, and anticoagulation strategy, were found to be important considerations when determining the need for an oxygenator or circuit change-out. The involvement of a multidisciplinary team and thorough preparation were also highlighted as crucial aspects of this process.

CONCLUSION

In conclusion, managing circuit change-outs in ECMO therapy requires considering factors such as fibrinogen levels, blood gases, plasma-free hemoglobin, D-dimers, platelet function, flows, pressures, and anticoagulation strategy. Monitoring these parameters allows for early detection of issues, timely interventions, and optimized ECMO therapy. Standardized protocols, personalized anticoagulation approaches, and non-invasive monitoring techniques can improve the safety and effectiveness of circuit change-outs. Further research and collaboration are needed to advance ECMO management and enhance patient outcomes.

Lung ultrasound score for monitoring the withdrawal of extracorporeal membrane oxygenation on neonatal acute respiratory distress syndrome

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is considered an efficient and life-saving treatment for neonatal severe acute respiratory distress syndrome (ARDS). Bedside lung ultrasound (LUS) is an attractive and feasible method for evaluating neonatal ARDS.

OBJECTIVE

To evaluate the value of LUS score at veno-arterial (V-A) ECMO withdrawal in neonatal patients with severe acute ARDS.

METHODS

A retrospective preliminary study was conducted in our cardiac intensive care unit from June 2021 to June 2022. Eight severe ARDS neonates who received V-A ECMO were enroled in this study. LUS was measured daily during ECMO and when weaning off ECMO. The relationships between the LUS score and ECMO parameters (blood flow and the sweep gas of FiO2) were assessed.

RESULTS

(1) There was a significant improvement in LUS score by ECMO treatment. And, various diagnostic signs of lung ultrasound were detected during ECMO, including pulmonary edema (7 neonates) and lung consolidation (4 neonates), followed by pleural effusion (1 neonate) and bilateral white lung (1 neonate). (2) A total of 12 trials for weaning off ECMO were carried out, of which four failed, but all eight neonates finally succeeded in passing the weaning trial. LUS score of 21 or less was defined as a cut-off value for predicting ECMO weaning success. During ECMO treatment, LUS score was positively correlated with ECMO blood flow (r = 0.866, P < 0.05).

CONCLUSIONS

LUS can be used to evaluate the various lung diagnostic signs in ARDS neonatal patients during ECMO treatment, and the LUS score under ECMO treatment decreases over time. The reduction in LUS score is associated with lower ECMO blood flow. LUS score is regarded as a predictor of ECMO weaning success.

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.

A retrospective analysis of the hemolysis occurrence during extracorporeal membrane oxygenation in a single center

INTRODUCTION

Extracorporeal membrane oxygenation (ECMO)-associated hemolysis still represents a serious complication. The present study aimed to investigate those predictive factors, such as flow rates, the use of anticoagulants, and circuit connected dialysis, that might play a pivotal role in hemolysis in adult patients.

METHODS

This is a retrospective single-center case series of 35 consecutive adult patients undergoing veno-venous ECMO support at our center between April 2014 and February 2020. Daily plasma-free hemoglobin (pfHb) and haptoglobin (Hpt) levels were chosen as hemolysis markers and they were analyzed along with patients' characteristics, daily laboratory findings, and corresponding ECMO system variables, as well as continuous renal replacement therapy (CRRT) when administered, looking for factors influencing their trends over time.

RESULTS

Among the many settings related to the ECMO support, the presence of CRRT connected to the ECMO circuit has been found associated with both higher daily pfHb levels and lower Hpt levels. After correction for potential confounders, hemolysis was ascribable to circuit-related variables, in particular the membrane oxygenation dead space was associated with an Hpt reduction (B = -215.307, p = 0.004). Moreover, a reduction of ECMO blood flow by 1 L/min has been associated with a daily Hpt consumption of 93.371 mg/dL (p = 0.001).

CONCLUSIONS

Technical-induced hemolysis during ECMO should be monitored not only when suspected but also during quotidian management and check-ups. While considering the clinical complexity of patients on ECMO support, clinicians should not only be aware of and anticipate possible circuitry malfunctions or inadequate flow settings, but they should also take into account the effects of an ECMO circuit-connected CRRT, as an equally important key factor triggering hemolysis.

Long-term ECMO, efficiency and performance of EUROSETS adult A.L.ONE ECMO oxygenator

BACKGROUND

The management of the oxygenator can be prolonged in the long-term procedures especially during extracorporeal membrane oxygenation (ECMO) for bridge to transplant or bridge to recovery. Long-term use often involves an overrun of the time of use with respect to certification of the oxygenating module of 14 days, for the maintenance of performance and efficiency of the oxygenator. The evaluation of the long-term oxygenator efficiency is complex and depends on the: patient pathology, ECMO configuration, the management of coagulation and anticoagulation, materials selection and circuit components, the structure, design and performance of the oxygenator. In this context we investgated the long-term performance of the A.L.ONE Eurosets ECMO oxygenator in relation to the parameters prodromal to replacement.

METHODS

We retrospectively collected eight years data from Anthea Hospital GVM Care & Research, Bari, Italy on the long-term use exceeding 14 days of Eurosets A.L.ONE ECMO Adult oxygenator in Polymetylpentene fiber, for ECMO procedures, including the procedures: Veno Arterial (VA) ECMO post-cardiotomy or not, veno-venous (VV) ECMO. The primary end points were the evaluation of Gas Transfer: oxygen partial pressure (PO₂) post oxygenator, Carbon dioxide partial pressure (PCO₂) post oxygenator, the oxygen transfer across the oxygenator membrane V'O₂, differential CO₂ content across oxygenator; Pressure monitoring: oxygenator pressure Drop in relation to Blood flow rate (BFR) (ΔP); Hematologic values: Hemoglobin, Fibrinogen, Platelets, aPTT, D-Dimer, LDH.

RESULTS

Nine VA ECMO patients who used the oxygenator for 18.5 days and two VV ECMO patients who used the oxygenators for 17.2 days on the seventeenth days reported average values PaO₂ (267 ± 29 mmHg); PaCO₂ (34 ± 4 mmHg) with gas blender values set to 3.8 ± 0.6 L/min of air and a FiO₂ of 78 ± 5%; the transfer across the oxygenator membrane V'O₂ was 189 ± 43 (ml/min/m²). The mean peak of partial pressure of carbon dioxide from the gas exhaust of oxygenator (P_ECO₂) was 38 ± 4 mmHg; differential CO₂ across the oxygenator "pre-oxygenator PCO₂-post-oxygenator PCO₂" (18 ± 6 mmHg); the mean blood flow rate (BFR) 4.5 ± 0.6 (L/minute); the pump revolution per minutes mean maximum rate was 4254 ± 345 (RPM); the mean pressure drop (ΔP) was 76 ± 12 mmHg; the mean peak of d-dimers (DDs) was 23.6 ± 0.8 mg / dL; the mean peak of LDH was 230 ± 55 (mg/dl); fibrinogen mean peak 223 ± 40 (mg/dl).

CONCLUSIONS

The performance of the Eurosets A.L.ONE ECMO Adult polymethylpentene fiber oxygenator in our experience has proven efficiency in terms of O₂ uptake and CO₂ removal, blood fluid dynamics, metabolic compensation and heat exchange in the long-term treatment. The device was safe without iatrogenic problems over a period of 14 days in the patients undergoing ECMO VA and in all patients undergoing VV ECMO with continuous administration of anticoagulation therapy.

Quantitative Gas Exchange in Extracorporeal Membrane Oxygenation-A New Device: Accuracy, Approach-based Difficulties, and Caloric Targeting

Measurement of oxygen uptake (VO 2 ) and carbon dioxide removal (VCO 2 ) on membrane lungs (MLs) during extracorporeal membrane oxygenation (ECMO) provides potential for improved and safer therapy. Real-time monitoring of ML function and degradation, calculating caloric needs as well as cardiac output, and weaning algorithms are among the future possibilities. Our study compared the continuous measurement of the standalone Quantum Diagnostics System (QDS) with the published Measuring Energy Expenditure in ECMO patients (MEEP) approach, which calculates sequential VO 2 and VCO 2 values via blood gas analysis and a physiologic gas content model. Thirty-nine datasets were acquired during routine venovenous ECMO intensive care treatment and analyzed. VO 2 was clinically relevant underestimated via the blood-sided measurement of the QDS compared to the MEEP approach (mean difference -42.61 ml/min, limits of agreement [LoA] -2.49/-87.74 ml), which could be explained by the missing dissolved oxygen fraction of the QDS equation. Analysis of VCO 2 showed scattered values with wide limits of agreement (mean difference 54.95 ml/min, LoA 231.26/-121.40 ml/min) partly explainable by a calculation error of the QDS. We described potential confounders of gas-sided measurements in general which need further investigation and recommendations for enhanced devices.

Complications Associated With Venovenous Extracorporeal Membrane Oxygenation-What Can Go Wrong?

OBJECTIVES

Despite increasing use and promising outcomes, venovenous extracorporeal membrane oxygenation (V-V ECMO) introduces the risk of a number of complications across the spectrum of ECMO care. This narrative review describes the variety of short- and long-term complications that can occur during treatment with ECMO and how patient selection and management decisions may influence the risk of these complications.

DATA SOURCES

English language articles were identified in PubMed using phrases related to V-V ECMO, acute respiratory distress syndrome, severe respiratory failure, and complications.

STUDY SELECTION

Original research, review articles, commentaries, and published guidelines from the Extracorporeal Life support Organization were considered.

DATA EXTRACTION

Data from relevant literature were identified, reviewed, and integrated into a concise narrative review.

DATA SYNTHESIS

Selecting patients for V-V ECMO exposes the patient to a number of complications. Adequate knowledge of these risks is needed to weigh them against the anticipated benefit of treatment. Timing of ECMO initiation and transfer to centers capable of providing ECMO affect patient outcomes. Choosing a configuration that insufficiently addresses the patient's physiologic deficit leads to consequences of inadequate physiologic support. Suboptimal mechanical ventilator management during ECMO may lead to worsening lung injury, delayed lung recovery, or ventilator-associated pneumonia. Premature decannulation from ECMO as lungs recover can lead to clinical worsening, and delayed decannulation can prolong exposure to complications unnecessarily. Short-term complications include bleeding, thrombosis, and hemolysis, renal and neurologic injury, concomitant infections, and technical and mechanical problems. Long-term complications reflect the physical, functional, and neurologic sequelae of critical illness. ECMO can introduce ethical and emotional challenges, particularly when bridging strategies fail.

CONCLUSIONS

V-V ECMO is associated with a number of complications. ECMO selection, timing of initiation, and management decisions impact the presence and severity of these potential harms.

Optimizing PO2 during peripheral veno-arterial ECMO: a narrative review

During refractory cardiogenic shock and cardiac arrest, veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is used to restore a circulatory output. However, it also impacts significantly arterial oxygenation. Recent guidelines of the Extracorporeal Life Support Organization (ELSO) recommend targeting postoxygenator partial pressure of oxygen (P_POSTO₂) around 150 mmHg. In this narrative review, we intend to summarize the rationale and evidence for this P_POSTO₂ target recommendation. Because this is the most used configuration, we focus on peripheral VA-ECMO. To date, clinicians do not know how to set the sweep gas oxygen fraction (F_SO₂). Because of the oxygenator's performance, arterial hyperoxemia is common during VA-ECMO support. Interpretation of oxygenation is complex in this setting because of the dual circulation phenomenon, depending on both the native cardiac output and the VA-ECMO blood flow. Such dual circulation results in dual oxygenation, with heterogeneous oxygen partial pressure (PO₂) along the aorta, and heterogeneous oxygenation between organs, depending on the mixing zone location. Data regarding oxygenation during VA-ECMO are scarce, but several observational studies have reported an association between hyperoxemia and mortality, especially after refractory cardiac arrest. While hyperoxemia should be avoided, there are also more and more studies in non-ECMO patients suggesting the harm of a too restrictive oxygenation strategy. Finally, setting F_SO₂ to target strict normoxemia is challenging because continuous monitoring of postoxygenator oxygen saturation is not widely available. The threshold of P_POSTO₂ around 150 mmHg is supported by limited evidence but aims at respecting a safe margin, avoiding both hypoxemia and severe hyperoxemia.

Heparin-free after 3000 IU heparin loaded in veno-venous ECMO supported acute respiratory failure patients with hemorrhage risk: a novel anti-coagulation strategy

Background

The anti-coagulation protocol of patients with hemorrhage risk primary disease who need extracorporeal membrane oxygenation (ECMO) supported is controversial. This study evaluated the feasibility of a new anti-coagulation strategy, that is heparin-free after 3000 IU heparin loaded in veno-venous ECMO (VV ECMO) supported acute respiratory failure patients with hemorrhage risk.

Methods

A retrospective study was performed in a series of hemorrhage risk patients supported with VV ECMO at the First Affiliated Hospital of Zhengzhou University, between June 2012 to Sept 2020. A total of 70 patients received a low heparin bolus of 3000 units for cannulation but without subsequent, ongoing heparin administration. Patients were divided into survival (n = 25) and non-survival group (n = 45). Data of coagulation, hemolysis and membrane lung function were calculated and analyzed. The complications of patients were recorded. Finally, the binary Logistic regression was conducted.

Results

The longest heparin-free time was 216 h, and the mean heparin-free time was 102 h. Compared with survivors, the non-survivors were showed higher baseline SOFA score and lower platelet counts in 0.5 h, 24 h, 48 h and 96 h after ECMO applied. However, there was no significant differences between survivors and non-survivors in ACT, APTT, INR, D-dimer, fibrinogen, LDH, blood flow rate, Δp and P_post-MLO₂ (all p < 0.05) of all different time point. Moreover, only the baseline SOFA score was significantly associated with mortality (p < 0.001, OR(95%CI): 2.754 (1.486–5.103)) while the baseline levels of ACT, APTT, INR, platelet, D-dimer, fibrinogen and LDH have no association with mortality. The percentage of thrombosis complications was 54.3% (38/70) including 3 oxygenator changed but there was no significant difference of complications in survival and non-survival groups (p > 0.05).

Conclusions

The anticoagulation protocol that no heparin after a 3000 units heparin bolus in VV ECMO supported acute respiratory failure patients with hemorrhage risk is feasible.

Alkaline Liquid Ventilation of the Membrane Lung for Extracorporeal Carbon Dioxide Removal (ECCO2R): In Vitro Study

Extracorporeal carbon dioxide removal (ECCO₂R) is a promising strategy to manage acute respiratory failure. We hypothesized that ECCO₂R could be enhanced by ventilating the membrane lung with a sodium hydroxide (NaOH) solution with high CO₂ absorbing capacity. A computed mathematical model was implemented to assess NaOH–CO₂ interactions. Subsequently, we compared NaOH infusion, named “alkaline liquid ventilation”, to conventional oxygen sweeping flows. We built an extracorporeal circuit with two polypropylene membrane lungs, one to remove CO₂ and the other to maintain a constant PCO₂ (60 ± 2 mmHg). The circuit was primed with swine blood. Blood flow was 500 mL × min⁻¹. After testing the safety and feasibility of increasing concentrations of aqueous NaOH (up to 100 mmol × L⁻¹), the CO₂ removal capacity of sweeping oxygen was compared to that of 100 mmol × L⁻¹ NaOH. We performed six experiments to randomly test four sweep flows (100, 250, 500, 1000 mL × min⁻¹) for each fluid plus 10 L × min⁻¹ oxygen. Alkaline liquid ventilation proved to be feasible and safe. No damages or hemolysis were detected. NaOH showed higher CO₂ removal capacity compared to oxygen for flows up to 1 L × min⁻¹. However, the highest CO₂ extraction power exerted by NaOH was comparable to that of 10 L × min⁻¹ oxygen. Further studies with dedicated devices are required to exploit potential clinical applications of alkaline liquid ventilation.

Ex vivo models for research in extracorporeal membrane oxygenation: a systematic review of the literature

With ongoing progress of components of extracorporeal membrane oxygenation including improvements of oxygenators, pumps, and coating materials, extracorporeal membrane oxygenation became increasingly accepted in the clinical practice. A suitable testing in an adequate setup is essential for the development of new technical aspects. Relevant tests can be conducted in ex vivo models specifically designed to test certain aspects. Different setups have been used in the past for specific research questions. We conducted a systematic literature review of ex vivo models of extracorporeal membrane oxygenation components. MEDLINE and Embase were searched between January 1996 and October 2017. The inclusion criteria were ex vivo models including features of extracorporeal membrane oxygenation technology. The exclusion criteria were clinical studies, abstracts, studies in which the model of extracorporeal membrane oxygenation has been reported previously, and studies not reporting on extracorporeal membrane oxygenation components. A total of 50 studies reporting on different ex vivo extracorporeal membrane oxygenation models have been identified from the literature search. Models have been grouped according to the specific research question they were designed to test for. The groups are focused on oxygenator performance, pump performance, hemostasis, and pharmacokinetics. Pre-clinical testing including use of ex vivo models is an important step in the development and improvement of extracorporeal membrane oxygenation components and materials. Furthermore, ex vivo models offer valuable insights for clinicians to better understand the consequences of choice of components, setup, and management of an extracorporeal membrane oxygenation circuit in any given condition. There is a need to standardize the reporting of pre-clinical studies in this area and to develop best practice in their design.

Carbon Dioxide Elimination During Veno-Venous Extracorporeal Membrane Oxygenation Weaning: A Pilot Study

Veno-venous extracorporeal membrane oxygenation (V-V ECMO) represents a component of the treatment strategy for severe respiratory failure. Clinical evidence on the management of the lung during V-V ECMO are limited just as the consensus regarding timing of weaning. The monitoring of the carbon dioxide (CO2) removal (V'CO2TOT) is subdivided into two components: the membrane lung (ML) and the native lung (NL) are both taken into consideration to evaluate the improvement of the function of the lung and to predict the time to wean off ECMO. We enrolled patients with acute respiratory distress syndrome (ARDS). The V'CO2NL ratio (V'CO2NL/V'CO2TOT) value was calculated based on the distribution of CO2 between the NL and the ML. Of 18 patients, 15 were successfully weaned off of V-V ECMO. In this subgroup, we observed a significant increase in the V'CO2NL ratio comparing the median values of the first and last quartiles (0.32 vs. 0.53, p = 0.0045), without observing any modifications in the ventilation parameters. An increase in the V'CO2NL ratio, independently from any change in ventilation could, despite the limitations of the study, indicate an improvement in pulmonary function and may be used as a weaning index for ECMO.

Different mechanisms of oxygenator failure and high plasma von Willebrand factor antigen influence success and survival of venovenous extracorporeal membrane oxygenation

OBJECTIVE

Failure of membrane oxygenator (MO) function of venovenous extracorporeal membrane oxygenators (VV ECMO) remains problematic. The development of device-induced coagulation disorder (COD) or worsened gas transfer (WGT) necessitates a system exchange. The aim was to correlate von Willebrand factor antigen (vWF:Ag) with the predisposition to MO failure and mortality.

METHODS

Laboratory parameters (inflammation, coagulation) and ECMO-related data from 31 VV ECMO patients were analyzed before and after the first MO exchange. Study groups were identified according to the exchange reasons (COD, WGT) and the extent of vWF:Ag (low, ≤425%; high, >425%).

RESULTS

vWF:Ag remained unchanged after system exchange. High vWF:Ag was associated with systemic endothelial activation of older and obese patients with elevated SOFA score, increased norepinephrine and higher requirement of continuous renal replacement therapy without an effect on MO runtime and mortality. Including the mechanism of MO failure (COD, WGT), various patient group emerged. COD/low vWF:Ag summarized younger and less critically ill patients that benefit mainly from ECMO by a significant improvement of their inflammatory and coagulation status (CRP, D-dimers, fibrinogen) and highest survival rate (91%). Instead, WGT/high vWF:Ag presented older and more obese patients with a two-digit SOFA score, highest norepinephrine, and aggravated gas transfer. They benefited temporarily from system exchange but with worst survival (33%).

CONCLUSIONS

vWF:Ag levels alone cannot predict early MO failure and outcome in VV ECMO patients. Probably, the mechanism of clotting disorder in combination with the vWF:Ag level seems to be essential for clot formation within the MO. In addition, vWF:Ag levels allows the identification different patient populations In particular, WGT/high vWF:Ag represented a critically ill population with higher ECMO-associated mortality.

Protocol-driven daily optimisation of venovenous extracorporeal membrane oxygenation blood flows: an alternate paradigm?

Venovenous extracorporeal membrane oxygenation (VV ECMO) is now an established modality of support for patients with the who are failing evidence-based conventional therapies. Minimising ventilator-induced lung injury is the guiding principle behind patient management with VV ECMO. Patients with acute respiratory distress syndrome (ARDS) supported with VV ECMO are liberated from ECMO at a stage when native lungs have recovered sufficiently to support physiologic demands and the risks of iatrogenic lung injuries after discontinuation of ECMO are perceived to be small. However, native lung recovery is a dynamic process and patients rely on varying degrees of contributions from both native lungs and ECMO for gas exchange support. Patients often demonstrate near total ECMO dependence for oxygenation and decarboxylation early in the course of the illness and this may necessitate higher ECMO blood flow rates (EBFRs). Although, reliance on high EBFR for oxygenation support may remain variable over the course of ECMO, blood flow requirements typically diminish over time as native lungs start to recover. Currently, protocol-driven modulation of the EBFR based on changing physiologic needs is not common practice and consequently patients may remain on higher than physiologically necessary EBFR. This exposes the patient to potential risks because maintaining higher blood flows often requires a less restrictive fluid balance and deeper sedation. Both may be harmful in the setting of recovery from ARDS. In this article, we propose a strategy that involves daily assessments of native lung function and a protocol-driven daily optimisation of EBFR. This is followed by optimisation of sweep gas flow rate (SGFR) and the fraction of delivered oxygen in the sweep gas (FdO₂). This staged approach to weaning VV ECMO allows us to fully utilise the “decoupling” of oxygenation and decarboxylation that is possible only during extracorporeal support. This approach may benefit patients by allowing for greater fluid restriction, more aggressive fluid removal, expedited weaning of sedation and neuromuscular blocking agents (NMBAs), and early physical rehabilitation. Ultimately, prospective studies are needed to evaluate optimal VV ECMO weaning practices

Development of a CO2 Sensor for Extracorporeal Life Support Applications

Measurement of carbon dioxide (CO₂) in medical applications is a well-established method for monitoring patient's pulmonary function in a noninvasive way widely used in emergency, intensive care, and during anesthesia. Even in extracorporeal-life support applications, such as Extracorporeal Carbon Dioxide Removal (ECCO₂R), Extracorporeal Membrane Oxygenation (ECMO), and cardiopulmonary by-pass (CPB), measurement of the CO₂ concentration in the membrane oxygenator exhaust gas is proven to be useful to evaluate the treatment progress as well as the performance of the membrane oxygenator. In this paper, we present a new optical sensor specifically designed for the measurement of CO₂ concentration in oxygenator exhaust gas. Further, the developed sensor allows measurement of the gas flow applied to the membrane oxygenator as well as the estimation of the CO₂ removal rate. A heating module is implemented within the sensor to avoid water vapor condensation. Effects of temperature on the sensor optical elements of the sensors are disclosed, as well as a method to avoid signal-temperature dependency. The newly developed sensor has been tested and compared against a reference device routinely used in clinical practice in both laboratory and in vivo conditions. Results show that sensor accuracy fulfills the requirements of the ISO standard, and that is suitable for clinical applications.

Management of Peripheral Venoarterial Extracorporeal Membrane Oxygenation in Cardiogenic Shock

OBJECTIVES

Cardiogenic shock is a highly morbid condition in which inadequate end-organ perfusion leads to death if untreated. Peripheral venoarterial extracorporeal membrane oxygenation is increasingly used to restore systemic perfusion despite limited understanding of how to optimally titrate support. This review provides insights into the physiologic basis of extracorporeal membrane oxygenation support and presents an approach to extracorporeal membrane oxygenation management in the cardiogenic shock patient.

DATA SOURCES, STUDY SELECTION, AND DATA EXTRACTION

Data were obtained from a PubMed search of the most recent medical literature identified from MeSH terms: extracorporeal membrane oxygenation, cardiogenic shock, percutaneous mechanical circulatory support, and heart failure. Articles included original articles, case reports, and review articles.

DATA SYNTHESIS

Current evidence detailing the use of extracorporeal membrane oxygenation to support patients in cardiogenic shock is limited to isolated case reports and single institution case series focused on patient outcomes but lacking in detailed approaches to extracorporeal membrane oxygenation management. Unlike medical therapy, in which dosages are either prescribed or carefully titrated to specific variables, extracorporeal membrane oxygenation is a mechanical support therapy requiring ongoing titration but without widely accepted variables to guide treatment. Similar to mechanical ventilation, extracorporeal membrane oxygenation can provide substantial benefit or induce significant harm. The widespread use and present lack of data to guide extracorporeal membrane oxygenation support demands that intensivists adopt a physiologically-based approach to management of the cardiogenic shock patient on extracorporeal membrane oxygenation.

CONCLUSIONS

Extracorporeal membrane oxygenation is a powerful mechanical circulatory support modality capable of rapidly restoring systemic perfusion yet lacking in defined approaches to management. Adopting a management approach based physiologic principles provides a basis for care.

Continuous monitoring of membrane lung carbon dioxide removal during ECMO: experimental testing of a new volumetric capnometer

Background:

Extracorporeal membrane oxygenation constitutes a complex support modality, and accurate monitoring is required. An ideal monitoring system should promptly detect ECMO malfunctions and provide real-time information to optimize the patient–machine interactions. We tested a new volumetric capnometer which enables continuous monitoring of membrane lung carbon dioxide removal (V′CO2ML), to help in estimating the oxygenator performance, in terms of CO2 removal and oxygenator dead space (VDsML).

Methods:

This study was conducted on nine pigs undergoing veno-arterial ECMO due to cardiogenic shock after induced acute myocardial infarction. The accuracy and reliability of the prototype of the volumetric capnometer (CO2RESET™, by Eurosets srl, Medolla, Italy) device was evaluated for V′CO2ML and VDsML measurements by comparing the obtained measurements from the new device to a control capnometer with the sweep gas values. Measurements were taken at five different levels of gas flow/blood flow ratio (0.5-1.5). Agreement between the corresponding measurements was taken with the two methods. We expected that 95% of differences were between d − 1.96s and d + 1.96s.

Results:

In all, 120 coupled measurements from each device were obtained for the V′CO2ML calculation and 40 for the VDsML. The new capnometer mean percentage bias (95% confidence interval limits of agreement) was 3.86% (12.07-4.35%) for V′CO2ML and 2.62% (8.96-14.20%) for VDsML. A negative proportional bias for V′CO2ML estimation with the new device was observed with a mean of 3.86% (12.07-4.35%). No correlations were found between differences in the coupled V′CO2ML and VDsML measurements and the gas flow/blood flow ratio or temperature. Coupled measurements for V′CO2ML showed strong correlation (rs = 0.991; p = 0.0005), as did VDsML calculations (rs = 0.973; p = 0.0005).

Conclusion:

The volumetric capnometer is reliable for continuous monitoring of CO2 removal by membrane lung and VDsML calculations. Further studies are necessary to confirm these data.