Estimation of Cardiac Output Under Veno-Venous Extracorporeal Membrane Oxygenation: Comparing Thermodilution Methods to 3D Echocardiography.

Thermodilution methods to determine cardiac output (CO) may be affected by veno-venous extracorporeal membrane oxygenation (ECMO). We compared CO estimations by pulmonary arterial thermodilution using a pulmonary arterial catheter (COPAC), transpulmonary thermodilution (COTPTD), and three-dimensional echocardiography (3DEcho) (CO3DEcho) in 18 patients under veno-venous ECMO. Comparisons between CO3DEcho and COPAC, and COTPTD were performed using correlation statistics and Bland-Altman analysis. Blood flow on ECMO support ranged from 4.3 to 5.8 L/min (median 4.9 L/min). Cardiac output measured with three-dimensional echocardiography was 5.2 L/min (3.8/5.9), COPAC was 7.3 L/min (5.9/7.9), and COTPTD was 7.3 L/min (6/8.2) (median [25%/75% percentile]). Bland-Altman analysis of CO3DEcho and COPAC revealed a mean bias of -2.06 L/min, with limits of agreement from -4.16 to 0.04 L/min. Bland-Altman analysis of CO3DEcho and COTPTD revealed a mean bias of -2.22 L/min, with limits of agreement from -4.18 to -0.25 L/min. We found a negative mean bias and negative limits of agreement between CO3DEcho and COPAC/COTPTD. We concluded an influence on the estimation of CO by thermodilution under ECMO most likely due to loss of indicator resulting in an overestimation of CO. Clinicians should consider this when monitoring thermodilution-based CO under ECMO.

Atrioventricular Coupling in Infants and Children Assessed by Three-Dimensional Echocardiography.

BACKGROUND: Parameters of the interaction of the left atrium and left ventricle, atrioventricular (AV) coupling, are used in the diagnosis and follow-up of diastolic dysfunction in adults. Pediatric parameters of AV coupling have not been evaluated so far. The aim of this multicenter study was to investigate parameters of AV coupling in a large cohort of healthy infants and children using noninvasive real-time three-dimensional echocardiography. The authors hypothesized that the contribution of the different left atrial (LA) volumes to left ventricular (LV) stroke volume differs over a range of different heart rates. METHODS: Three-dimensional echocardiographic data sets from 332 subjects (ages 0 days to 18.5 years) were analyzed prospectively. Volume-time curves of the left atrium and left ventricle were generated. Conduit volume was calculated and percentiles were established by the lambda-mu-sigma method of Cole and Green. Contributions of active, passive, and conduit volume to LV filling were measured and related to heart rate by linear regression. LV and LA peak filling rates (PFR) and peak emptying rates (PER) and time to PFR and PER normalized to the R-R interval (PFRt[%] and PERt[%]) were measured and correlated to each other. RESULTS: Conduit volume increased with body surface area. The contribution of LA active emptying to LV filling tended to increase with decreasing heart rate, while the contribution of passive emptying decreased. Conduit volume contributed most to LV filling (median, 57.58 %; interquartile range, 12.85%) with a tendency to increase with decreasing heart rate. Close diastolic AV coupling was demonstrated by virtually identical LV PFRt(%) and LA PERt(%) during diastole. LV PERt(%) occurred earlier than LA PFRt(%), showing less coupling during systole. LV PFRt(%) and LA PERt(%) were strongly correlated to heart rate (r = 0.76 and r = 0.73, respectively). Lower heart rate resulted in a prolongation of diastole after LV PFR. CONCLUSIONS: Assessment of conduit volume and AV coupling by three-dimensional echocardiography is feasible in infants and children. The references of this study can serve as a basis to further investigate the role of parameters of AV coupling in pediatric patients with heart diseases concerning diastolic and LA function.

Intraventricular Flow Simulations in Singular Right Ventricles Reveal Deteriorated Washout and Low Vortex Formation.

PURPOSE: Patients with a functionally univentricular heart represent one of the most common severe cardiac lesions with a prevalence of 3 per 10,000 live births. Hemodynamics of the singular ventricle is a major research topic in cardiology and there exists a relationship between fluid dynamical features and cardiac behavior in health and disease. The aim of the present work was to compare intraventricular flow in single right ventricle (SRV) patients and subjects with healthy left hearts (LV) through patient-specific CFD simulations. METHODS: Three-dimensional real-time echocardiographic images were obtained for five SRV patients and two healthy subjects and CFD simulations with a moving mesh methodology were performed. Intraventricular vortex formation and vortex formation time (VFT) as well as the turbulent kinetic energy (TKE) and ventricular washout were evaluated. RESULTS: The results show significantly lower values for the VFT and the TKE in SRV patients compared with healthy LV subjects. Furthermore, vortex formation does not progress to the apex in SRV patients. These findings were confirmed by a significantly lower washout in SRV patients. CONCLUSIONS: The study pinpoints the intriguing role of intraventricular flows to characterize performance of SRVs that goes beyond standard clinical metrics such as ejection fraction.

Assessment of pressure-volume relations in univentricular hearts: Comparison of obtainment by real-time 3D echocardiography and mini pressure-wire with conductance technology.

OBJECTIVES: The gold standard to obtain pressure-volume relations (PVR) of the heart, the conductance technology (PVRCond), is rarely used in children. PVR can also be obtained by 3D-echocardiography volume data combined with simultaneously measured pressure data by a mini pressure-wire (PVR3DE). We sought to investigate the feasibility of both methods in patients with univentricular hearts and to compare them, including hemodynamic changes. METHODS: We studied 19 patients (age 2-29 years). PVR3DE and PVRCond were assessed under baseline conditions and stimulation with dobutamine. RESULTS: Obtaining PVR3DE was successful in all patients. Obtaining PVRCond was possible in 15 patients during baseline (79%) and in 12 patients under dobutamine (63%). Both methods showed that end-systolic elastance (Ees) and arterial elastance (Ea) increased under dobutamine and that Tau showed a statistically significant decrease. Intraclass correlation (95% confidence interval) showed moderate to good agreement between methods: Ees: 0.873 (0.711-0.945), Ea: 0.709 (0.336-0.873), Tau: 0.867 (0.697-0.942). Bland-Altman analyses showed an acceptable bias with wider limits of agreement: Ees: 1.63 mmHg/ml (-3.83-7.08 mmHg/ml), Ea: 0.53 mmHg/ml (-5.23-6.28 mmHg/ml), Tau: -0,76 ms (-10.73-9.21 ms). CONCLUSION: Changes of PVR-specific parameters under dobutamine stimulation were reflected in the same way by both methods. However, the absolute values for these parameters could vary between methods and, therefore, methods are not interchangeable. Obtaining PVR3DE in a single ventricle was easier, faster and more successful than PVRCond. PVR3DE provides a promising and needed alternative to the conductance technology for the assessment of cardiac function in univentricular hearts.

Assessment of spontaneous breathing during pressure controlled ventilation with superimposed spontaneous breathing using respiratory flow signal analysis.

Integrating spontaneous breathing into mechanical ventilation (MV) can speed up liberation from it and reduce its invasiveness. On the other hand, inadequate and asynchronous spontaneous breathing has the potential to aggravate lung injury. During use of airway-pressure-release-ventilation (APRV), the assisted breaths are difficult to measure. We developed an algorithm to differentiate the breaths in a setting of lung injury in spontaneously breathing ewes. We hypothesized that differentiation of breaths into spontaneous, mechanical and assisted is feasible using a specially developed for this purpose algorithm. Ventilation parameters were recorded by software that integrated ventilator output variables. The flow signal, measured by the EVITA® XL (Lübeck, Germany), was measured every 2 ms by a custom Java-based computerized algorithm (Breath-Sep). By integrating the flow signal, tidal volume (VT) of each breath was calculated. By using the flow curve the algorithm separated the different breaths and numbered them for each time point. Breaths were separated into mechanical, assisted and spontaneous. Bland Altman analysis was used to compare parameters. Comparing the values calculated by Breath-Sep with the data from the EVITA® using Bland-Altman analyses showed a mean bias of - 2.85% and 95% limits of agreement from - 25.76 to 20.06% for MVtotal. For respiratory rate (RR) RRset a bias of 0.84% with a SD of 1.21% and 95% limits of agreement from - 1.53 to 3.21% were found. In the cluster analysis of the 25th highest breaths of each group RRtotal was higher using the EVITA®. In the mechanical subgroup the values for RRspont and MVspont the EVITA® showed higher values compared to Breath-Sep. We developed a computerized method for respiratory flow-curve based differentiation of breathing cycle components during mechanical ventilation with superimposed spontaneous breathing. Further studies in humans and optimizing of this technique is necessary to allow for real-time use at the bedside.

Estimation of left ventricular stroke work based on a large cohort of healthy children.

Left ventricular stroke work is an important prognostic marker to analyze cardiac function. Standard values for children are, however, missing. For clinicians, standards can help to improve the treatment decision of heart failures. For engineers, they can help to optimize medical devices. In this study, we estimated the left ventricular stroke work for children based on modeled pressure-volume loops. A lumped parameter model was fitted to clinical data of 340 healthy children. Reference curves for standard values were created over age, weight, and height. Left ventricular volume was measured with 3D echocardiography, while maximal ventricular pressure was approximated with a regression model from the literature. For validation of this method, we used 18 measurements acquired by a conductance catheter in 11 patients. The method demonstrated a low absolute mean difference of 0.033 J (SD: 0.031 J) for stroke work between measurement and estimation, while the percentage error was 21.66 %. According to the resulting reference curves, left ventricular stroke work of newborns has a median of 0.06 J and increases to 1.15 J at the age of 18 years. Stroke work increases over weight and height in a similar trend. The percentile curves depict the distribution. We demonstrate how reference curves can be used for quantification of differences and comparison in patients.

1H-NMR Metabolomics Identifies Significant Changes in Metabolism over Time in a Porcine Model of Severe Burn and Smoke Inhalation.

Burn injury initiates a hypermetabolic response leading to muscle catabolism and organ dysfunction but has not been well-characterized by high-throughput metabolomics. We examined changes in metabolism over the first 72 h post-burn using proton nuclear magnetic resonance (1H-NMR) spectroscopy and serum from a porcine model of severe burn injury. We sought to quantify the changes in metabolism that occur over time in response to severe burn and smoke inhalation in this preliminary study. Fifteen pigs received 40% total body surface area (TBSA) burns with additional pine bark smoke inhalation. Arterial blood was drawn at baseline (pre-burn) and every 24 h until 72 h post-injury or death. The aqueous portion of each serum sample was analyzed using 1H-NMR spectroscopy and metabolite concentrations were used for principal component analysis (PCA). Thirty-eight metabolites were quantified in 39 samples. Of these, 31 showed significant concentration changes over time (p < 0.05). PCA revealed clustering of samples by time point on a 2D scores plot. The first 48 h post-burn were characterized by high concentrations of histamine, alanine, phenylalanine, and tyrosine. Later timepoints were characterized by rising concentrations of 2-hydroxybutyrate, 3-hydroxybutyrate, acetoacetate, and isovalerate. No significant differences in metabolism related to mortality were observed. Our work highlights the accumulation of organic acids resulting from fatty acid catabolism and oxidative stress. Further studies will be required to relate accumulation of the four organic carboxylates identified in this analysis to outcomes from burn injury.

Left Atrial Volumes and Phasic Function in Healthy Children: Reference Values Using Real-Time Three-Dimensional Echocardiography.

BACKGROUND: Evaluation of left atrial (LA) size and function is important in congenital and acquired pediatric cardiac disease. Real-time three-dimensional echocardiography (3DE) offers noninvasive assessment of cardiac volumes and phasic function independent of geometric assumptions. The aim of this prospective multicenter study was to establish pediatric reference values for LA 3DE volumes and phasic function based on a large cohort of healthy children. METHODS: LA data sets of 432 subjects (0 days-222 months) were analyzed prospectively using a vendor-independent software. LA volumes (maximal [Vmax], minimal [Vmin], and before atrial contraction) as well as phasic function (active and passive emptying fraction [EF]) were assessed. For volumes, sex-specific reference values, percentiles, and z-scores were calculated by the LMS method of Cole and Green. RESULTS: Absolute volumes increased with age and body surface area. Active EF and relative duration of atrial emptying tended to increase with increasing R-R intervals, while passive EF decreased. Reproducibility of volumes was very good (intra- and interobserver variability for Vmax and Vmin (mean bias ± SD, 0.1 ± 0.9 mL and 0.7 ± 2.8 mL). Volumes were well correlated with cardiac magnetic resonance measurements showing known underestimation of volumes by 3DE (mean bias ± SD, Vmax -14.2 ± 14 mL; Vmin -11.5 ± 10 mL). CONCLUSIONS: Pediatric LA volumes and phasic function indices were reproducibly measured by 3DE. The provided pediatric reference values can be the basis for evaluation of the LA by 3DE and contribute to detection of LA dysfunction and follow-up of patients with congenital heart diseases.

Platelet and coagulation function before and after burn and smoke inhalation injury in sheep.

BACKGROUND: Smoke inhalation and burn injury remain a major source of morbidity and mortality. There is known dysregulation of hemostasis in burn patients, but either hypercoagulation or hypocoagulation states are reported. Sheep are an established animal model for studying burn pathology and provide robust data on hemostatic function at baseline and after injury. METHODS: After an IACUC-approved protocol, 15 sheep were anesthetized and subjected to a 40% full thickness burn with smoke inhalation. Blood was sampled at baseline, 1 day postinjury (early effects) and days 2, 3, and 4 (late effects) after injury. Assays at each timepoint assessed: hemostatic function by thromboelastography (TEG), platelet counts and function by flow cytometry and aggregometry, coagulation protein levels, and free hemoglobin. Data were analyzed by the Wilcoxon paired test (nonparametric) with significance set at less than 0.05. RESULTS: By 24 hours postinjury, platelet counts had dropped, whereas the percent activated platelets increased. Absolute platelet functional response to the agonist adenosine diphosphate (ADP) decreased, whereas response to collagen showed no significant difference. On a per platelet basis, ADP response was unchanged, whereas the collagen response was elevated. Prothrombin time and activated partial thromboplastin time were prolonged. TEG parameters decreased significantly from baseline. Fibrinogen and factor V were trending up; coagulation proteins ATIII, factors IX and X were decreased.Late effects were followed in six animals. At day 4, platelet counts remained depressed compared with baseline with a nadir at day 2; responses to agonist on a per platelet basis remained the same for ADP and stayed elevated for collagen. Platelets continued to have elevated activation levels. Fibrinogen and factor V remained significantly elevated, whereas TEG parameters and prothrombin time, factors IX and X returned to near baseline levels. CONCLUSION: Coagulation parameters and hemostasis are dysregulated in sheep after smoke inhalation and burn. By 24 hours, sheep were hypocoagulable and subsequently became hypercoagulable by day 4. These results suggest a three-stage coagulopathy in burn injuries with a known early consumptive hypercoagulable state which is followed by a relatively hypocoagulable state with increased bleeding risk and then a return to a relatively unknown hypercoagulability with increased susceptibility to thrombotic disorders.

Comparison of stroke volumes assessed by three-dimensional echocardiography and transpulmonary thermodilution in a pediatric animal model.

To compare stroke volumes (SV) in small hearts assessed by real-time three-dimensional echocardiography (3DE) with SV measured by transpulmonary thermodilution (TPTD) and continuous pulse contour analysis (PC) under various hemodynamic conditions. In thirteen anesthetized piglets (range 3.6-7.1 kg) SV were measured by 3DE, TPTD and PC at baseline and during phenylephrine and esmolol administration. 3DE and TPTD measurements were done successively while SV calculated by PC was documented at the time of 3DE. 3DE and TPTD showed a good correlation (r2 = 0.74) and a bias of -1.3 ml (limits of agreement -4.1 to 1.5 ml). While TPTD measured higher SV than 3DE, both methods tracked SV changes with a concordance rate of 91 %. PC and 3DE showed a lower correlation coefficient of r2 = 0.57 and a bias of -2.1 ml (limits of agreement -5.9 to 1.8 ml). Inter- and intra-observer variability of SV measured by 3DE was good with a mean bias <5 %. SV3DE showed a small variance and tracked acute small changes in SV in acceptable concordance with TPTD. PC measured SV with a higher variance and mean difference compared to 3DE. In an experimental setting 3DE has the possibility to offer non-invasive assessments of ventricular volumes volume changes. To determine whether 3DE could be used for SV assessment in a clinical routine our results need confirmation in a clinical setting.

3D Real-Time Echocardiography Combined with Mini Pressure Wire Generate Reliable Pressure-Volume Loops in Small Hearts.

BACKGROUND: Pressure-volume loops (PVL) provide vital information regarding ventricular performance and pathophysiology in cardiac disease. Unfortunately, acquisition of PVL by conductance technology is not feasible in neonates and small children due to the available human catheter size and resulting invasiveness. The aim of the study was to validate the accuracy of PVL in small hearts using volume data obtained by real-time three-dimensional echocardiography (3DE) and simultaneously acquired pressure data. METHODS: In 17 piglets (weight range: 3.6-8.0 kg) left ventricular PVL were generated by 3DE and simultaneous recordings of ventricular pressure using a mini pressure wire (PVL3D). PVL3D were compared to conductance catheter measurements (PVLCond) under various hemodynamic conditions (baseline, alpha-adrenergic stimulation with phenylephrine, beta-adrenoreceptor-blockage using esmolol). In order to validate the accuracy of 3D volumetric data, cardiac magnetic resonance imaging (CMR) was performed in another 8 piglets. RESULTS: Correlation between CMR- and 3DE-derived volumes was good (enddiastolic volume: mean bias -0.03ml ±1.34ml). Computation of PVL3D in small hearts was feasible and comparable to results obtained by conductance technology. Bland-Altman analysis showed a low bias between PVL3D and PVLCond. Systolic and diastolic parameters were closely associated (Intraclass-Correlation Coefficient for: systolic myocardial elastance 0.95, arterial elastance 0.93, diastolic relaxation constant tau 0.90, indexed end-diastolic volume 0.98). Hemodynamic changes under different conditions were well detected by both methods (ICC 0.82 to 0.98). Inter- and intra-observer coefficients of variation were below 5% for all parameters. CONCLUSIONS: PVL3D generated from 3DE combined with mini pressure wire represent a novel, feasible and reliable method to assess different hemodynamic conditions of cardiac function in hearts comparable to neonate and infant size. This methodology may be integrated into clinical practice and cardiac catheterization programs and has the capability to contribute to clinical decision making even in small hearts.

Extracorporeal Carbon Dioxide Removal Enhanced by Lactic Acid Infusion in Spontaneously Breathing Conscious Sheep.

BACKGROUND: The authors studied the effects on membrane lung carbon dioxide extraction (VCO2ML), spontaneous ventilation, and energy expenditure (EE) of an innovative extracorporeal carbon dioxide removal (ECCO2R) technique enhanced by acidification (acid load carbon dioxide removal [ALCO2R]) via lactic acid. METHODS: Six spontaneously breathing healthy ewes were connected to an extracorporeal circuit with blood flow 250 ml/min and gas flow 10 l/min. Sheep underwent two randomly ordered experimental sequences, each consisting of two 12-h alternating phases of ALCO2R and ECCO2R. During ALCO2R, lactic acid (1.5 mEq/min) was infused before the membrane lung. Caloric intake was not controlled, and animals were freely fed. VCO2ML, natural lung carbon dioxide extraction, total carbon dioxide production, and minute ventilation were recorded. Oxygen consumption and EE were calculated. RESULTS: ALCO2R enhanced VCO2ML by 48% relative to ECCO2R (55.3 ± 3.1 vs. 37.2 ± 3.2 ml/min; P less than 0.001). During ALCO2R, minute ventilation and natural lung carbon dioxide extraction were not affected (7.88 ± 2.00 vs. 7.51 ± 1.89 l/min, P = 0.146; 167.9 ± 41.6 vs. 159.6 ± 51.8 ml/min, P = 0.063), whereas total carbon dioxide production, oxygen consumption, and EE rose by 12% each (223.53 ± 42.68 vs. 196.64 ± 50.92 ml/min, 215.3 ± 96.9 vs. 189.1 ± 89.0 ml/min, 67.5 ± 24.0 vs. 60.3 ± 20.1 kcal/h; P less than 0.001). CONCLUSIONS: ALCO2R was effective in enhancing VCO2ML. However, lactic acid caused a rise in EE that made ALCO2R no different from standard ECCO2R with respect to ventilation. The authors suggest coupling lactic acid-enhanced ALCO2R with active measures to control metabolism.

Early Utilization of Extracorporeal CO2 Removal for Treatment of Acute Respiratory Distress Syndrome Due to Smoke Inhalation and Burns in Sheep.

INTRODUCTION: In thermally injured patients, inhalation injury is often associated with acute respiratory distress syndrome (ARDS), and is an independent predictor of increased morbidity and mortality. Extracorporeal CO2 removal (ECCO2R) therapy offers new possibilities in protective mechanical ventilation in ARDS patients. We performed an early application of ECCO2R in mild-to-moderate ARDS in sheep ventilated in BiPAP mode. Our aim was to investigate its effect on severity of the lung injury. MATERIAL AND METHODS: Non-pregnant farm-bred ewes (n = 15) were anesthetized and injured by a combination of wood-bark smoke inhalation and a 40% total body surface area full-thickness burn, and were observed for 72 h or death. The animals were randomized to a Hemolung group (n = 7) or a Control group (n = 8) at time of ARDS onset. ECCO2R was performed in the Hemolung group after onset of ARDS.Histopathology, CT scans, systemic and pulmonary variables, and CO2 removal were examined. RESULTS: Early application of ECCO2R therapy with Hemolung in spontaneously breathing sheep decreased PaCO2 significantly, while the device removed about 70  mL of CO2 per minute. This did not result in lower minute ventilation in the Hemolung group. Lungpathology and CT scans did not show a difference between groups. CONCLUSION: In an ovine model of ARDS due to smoke inhalation and burn injury, early institution of ECCO2R in spontaneously breathing animals was effective in removing CO2 and in reducing PaCO2. However, it had no effect on reducing the severity of lung injury or mortality. Further studies are necessary to detail the interaction between extracorporeal CO2 removal and pulmonary physiology.

Evaluation of the Cytosorb™ Hemoadsorptive Column in a Pig Model of Severe Smoke and Burn Injury.

INTRODUCTION: Host inflammatory response to any form of tissue injury, including burn, trauma, or shock, has been well documented. After significant burns, cytokines can increase substantially within the first 24 h after injury and may contribute to subsequent organ failure. Hemoadsorption by cytokine-adsorbing columns may attenuate this maladaptive response, thereby improving outcomes. The aim of this study was to investigate the feasibility, technical safety, and efficacy of cytokine and myoglobin removal by early use of a cytokine absorbing column (CytoSorb) in a porcine model of smoke inhalation and burn injury. METHODS: Anesthetized female Yorkshire pigs (n = 15) were injured by wood bark smoke inhalation and a 40% total body surface area deep burn and observed for 72 h or death. The animals were randomized to hemoadsorption treatment (n = 9) or a sham group (n = 6) before injury. A 6-h hemoadsorption or sham session was performed on days one, two, and three. Serum cytokines (IL-1b, IL-6, IL-8, IL-10, TNF-alpha) and myoglobin were measured systemically, locally in bronchoalveolar lavage fluid and also in circulating blood before and after the adsorbing column to evaluate single pass clearance by the device. RESULTS: Hemoadsorption caused significant removal of IL-1b, IL-6, IL-10, and myoglobin across the device mainly during the first run, ranging from 22% for IL-6 to 29% for IL-1b and 41% removal rates for myoglobin after 15  min of treatment. Systemic cytokine or myoglobin serum concentrations did not change. CONCLUSIONS: In a porcine model of smoke and burn injury, hemoadsorption using the CytoSorb cartridge did not result in significant systemic or pulmonary reductions in the measured cytokines or myoglobin despite efficient transmembrane reductions. Further investigations are needed to optimize the efficiency of mediator clearance to affect both circulating levels and clinically relevant outcomes.

Enhanced Extracorporeal CO2 Removal by Regional Blood Acidification: Effect of Infusion of Three Metabolizable Acids.

Acidification of blood entering a membrane lung (ML) with lactic acid enhances CO2 removal (VCO2ML). We compared the effects of infusion of acetic, citric, and lactic acids on VCO2ML. Three sheep were connected to a custom-made circuit, consisting of a Hemolung device (Alung Technologies, Pittsburgh, PA), a hemofilter (NxStage, NxStage Medical, Lawrence, MA), and a peristaltic pump recirculating ultrafiltrate before the ML. Blood flow was set at 250 ml/min, gas flow (GF) at 10 L/min, and recirculating ultrafiltrate flow at 100 ml/min. Acetic (4.4 M), citric (0.4 M), or lactic (4.4 M) acids were infused in the ultrafiltrate at 1.5 mEq/min, for 2 hours each, in randomized fashion. VCO2ML was measured by the Hemolung built-in capnometer. Circuit and arterial blood gas samples were collected at baseline and during acid infusion. Hemodynamics and ventilation were monitored. Acetic, citric, or lactic acids similarly enhanced VCO2ML (+35%), from 37.4 ± 3.6 to 50.6 ± 7.4, 49.8 ± 5.6, and 52.0 ± 8.2 ml/min, respectively. Acids similarly decreased pH, increased pCO2, and reduced HCO3 of the post-acid extracorporeal blood sample. No significant effects on arterial gas values, ventilation, or hemodynamics were observed. In conclusion, it is possible to increase VCO2ML by more than one-third using any one of the three metabolizable acids.

Modular extracorporeal life support: effects of ultrafiltrate recirculation on the performance of an extracorporeal carbon dioxide removal device.

The combination of extracorporeal carbon dioxide removal (ECCO2R) and hemofiltration is a possible therapeutic strategy for patients needing both lung and renal support. We tested the effects of the recirculation of ultrafiltrate on membrane lung (ML) CO2 removal (VCO2ML). Three conscious, spontaneously breathing sheep were connected to a commercially produced ECCO2R device (Hemolung; Alung Technologies, Pittsburgh, PA) with a blood flow of 250 ml/min and a gas flow of 10 L/min. A hemofilter (NxStage, NxStage Medical, Lawrence, MA) was interposed in series after the ML. Ultrafiltrate flow was generated and recirculated before the ML. We tested four ultrafiltrate flows (0, 50, 100, and 150 ml/min) for 25 min each, eight times per animal, resulting in 24 randomized test repetitions. We recorded VCO2ML, hemodynamics and ventilatory variables, and natural lung CO2 transfer (VCO2NL) and collected arterial and circuitry blood samples. VCO2ML was unchanged by application of ultrafiltrate recirculation (40.5 ± 4.0, 39.7 ± 4.2, 39.8 ± 4.2, and 39.2 ± 4.1 ml/min, respectively, at ultrafiltrate flow of 0, 50, 100, and 150 ml/min). Minute ventilation, respiratory rate, VCO2NL, and arterial blood analyses were not affected by ultrafiltrate recirculation. In the tested configuration, ultrafiltrate recirculation did not affect VCO2ML. This modular technology may provide a suitable platform for coupling CO2 removal with various forms of blood purification.

Extracorporeal blood purification in burns: a review.

A prolonged and fulminant inflammatory state, with high levels of pro- and anti-inflammatory mediators, is seen after extensive thermal injury. Blood purification techniques including plasma exchange, continuous venovenous hemofiltration, and adsorbing membranes have the potential to modulate this response, thereby improving outcomes. This article describes the scientific rationale behind blood purification in burns and offers a review of literature regarding its potential application in this patient cohort.

The effect of pumpless extracorporeal CO2 removal on regional perfusion of the brain in experimental acute lung injury.

BACKGROUND: Lung-protective mechanical ventilation with low tidal volumes (V(T)) is often associated with hypercapnia (HC), which may be unacceptable in patients with brain injury. CO2 removal using a percutaneous extracorporeal lung assist (pECLA) enables normocapnia despite low V(T), but its effects on regional cerebral blood flow (rCBF) remain ambiguous. We hypothesized that reversal of HC by pECLA impairs rCBF in a porcine lung injury model. METHODS: Lung injury was induced in 9 anesthetized pigs by hydrochloric acid aspiration. rCBF and systemic hemodynamics were measured by colored microsphere technique and transpulmonary-thermodilution during a randomized sequence of 4 experimental situations: pECLA shunt-on (1) with HC and (2) without HC, pECLA shunt-off (3) with HC and (4) without HC. RESULTS: HC increased rCBF (P<0.05). CO2 removal with pECLA resulting in normocapnia, decreased rCBF to levels comparable to those without pECLA and normocapnia. HC resulted in increased cardiac output (+25.5%). Cardiac output was highest during HC with pECLA shunt (+44.9%). During pECLA with CO2 removal, cardiac output (+38.1%) decreased compared with pECLA without CO2 removal, but stayed higher than during normocapnia/no pECLA shunt (P<0.05). CONCLUSIONS: In this animal model, mechanical ventilation with low V(T) was associated with HC and increased rCBF. CO2 removal by pECLA restored normocapnia, reduced rCBF to levels of normocapnia, but required a higher systemic blood flow for the perfusion of the pECLA device. If these results could be transferred to patients, extracorporeal CO2 removal might be an option for treatment of combined lung and brain injury in condition of a sufficient cardiac flow reserve.