Plasma Free Hemoglobin Generation Using the EOS PMP™ Oxygenator and the CentriMag® Blood Pump.

Hemolysis is a known consequence of extracorporeal membrane oxygenation (ECMO) resulting from shear force within the different components of the extracorporeal circuit. The primary aim of this study was to evaluate the EOS PMP™ oxygenator for generation of plasma free hemoglobin (PfHg) over 24 hours at nominal operating range flow rates. The EOS ECMO™ (LivaNova, Inc.; formerly Sorin, Arvada, CO) is equipped with a plasma tight polymethylpentene (PMP) hollow fiber oxygenator. We hypothesized that PfHg generation would be elevated in circuits with higher flow rates, because of the significant pressure drop across the oxygenator according to manufacturer provided flow charts. Generated PfHg concentrations were compared with PfHg concentrations from blood not exposed to an ECMO circuit. The secondary aim was to evaluate circuit flow-rate-induced changes in platelet count and platelet function over 24 hours. Circuits contained a CentriMag® (St. Jude Medical, St. Paul, MN) blood pump and an EOS ECMO PMP™ oxygenator. Circuits in triplicate were run continuously for 24 hours at three flow rates [1, 3, and 5 liters per minute {LPM}]. PfHg was analyzed at baseline, 6, 12, 18, and 24 hours. Platelet count and function were measured at baseline and 24 hours. Concentrations of PfHg at baseline for circuits operating at 1, 3, and 5 LPM were 24.4 ± 4.0, 38.4 ± 28.6, and 26.7 ± 6.9 mg/dL, respectively. PfHg concentrations after 24 hours were statistically compared for the three flow rates using analysis of variance; PfHg concentrations at 1 LPM (181.4 ± 29.1 mg/dL), 3 LPM (145.9 ± 8.7 mg/dL), and 5 LPM (100.1 ± 111.3 mg/dL) circuits. The F-test was not statistically significant (p = .632), indicating that PfHg generation at 24 hours was similar among the three flow rates. Excessive hemolysis using PfHg levels in the EOS PMP™ membrane oxygenator was not observed.

Comparison of routine laboratory measures of heparin anticoagulation for neonates on extracorporeal membrane oxygenation.

Our objective was to determine the best measure of heparin anticoagulation in neonatal patients on extracorporeal membrane oxygenation. Activated clotting time (ACT), activated partial thromboplastin time (aPTT), and antifactor Xa levels, along with corresponding heparin infusion rates and heparin bolus volumes, were collected from neonates receiving ECMO at our institution from 2008 to 2013. After natural log transformation of antifactor Xa, ACT, and aPTT, overall correlations between antifactor Xa levels and either ACT or aPTT and correlations between these tests and heparin infusion rates were evaluated using linear mixed models that accounted for both within- and between-patient correlations. Twenty-six neonates with an average weight of 3.4 kg (standard deviation .7) had a total of 27 separate ECMO runs during the study period. Within each patient, ACT (r = .40, p < .0001) and aPTT (r = .48, p < .0001) were both directly correlated with antifactor Xa levels. In contrast, between patients, only aPTT maintained a direct correlation with antifactor Xa (r = .61, p = .07), whereas ACT showed a statistically significant inverse correlation with antifactor Xa (r = -.48, p = .04). Compared with ACT, aPTT is more consistently reflective of the anticoagulation status both within each patient on ECMO and between patients treated with ECMO. Future efforts to develop standardized heparin infusion algorithms for patients on ECMO should consider using aPTT levels to monitor anticoagulation.

Contrast transthoracic echocardiography and the placement of a bicaval dual-lumen catheter in a Swine model of venovenous extracorporeal membrane oxygenation.

Placement of a bicaval dual-lumen (BCDL) catheter demands sophisticated visualization in patients to assure proper positioning in order to administer single-site venovenous extracorporeal membrane oxygenation (VV ECMO). Large animal models are needed and thus appropriate procedures to assure anatomic and functional cannula placement would assist in experimental design and procedures. This report describes the use of agitated blood and saline transthoracic contrast echocardiography to confirm appropriate placement and function of the BCDL catheter in a swine model of VV ECMO. Five consecutive common crossbred piglets had confirmation using this technique with assurances of cannulation while not significantly altering experimental time and procedures. Researchers studying VV ECMO in large animal models may want to consider this method of confirmation of BCDL catheter placement.

Rapid placement of bicaval dual-lumen catheter in a swine model of venovenous ECMO.

BACKGROUND: Venovenous (VV) extracorporeal membrane oxygenation (ECMO) applied through a single site with a bicaval dual-lumen (BCDL) catheter is a growing method of treatment of acute respiratory failure, thus animal models for research purposes are needed. We describe a rapid technique for the placement of the BCDL catheter for single-site VV ECMO in swine. DESIGN: Prior to the application of single-site VV ECMO model with common crossbred piglets, BCDL catheters were placed using anatomical landmarks. Transthoracic echocardiography (TTE) with color Doppler was used to determine catheter placement. Final determination of catheter placement was confirmed by necropsy. Arterial blood gas and hemodynamic parameters were recorded at baseline and then hourly. The values are mean ± SD. RESULTS: Using anatomical landmarks by positioning the BCDL catheter tip approximately 6.5 cm distal to the tip of the manubrium, cannulation was easily accomplished in five piglets with no positional adjustments of the catheter required. Cannula placement was confirmed with both TTE color Doppler and necropsy. Respiratory support was achieved with baseline and hourly measurements of pH 7.45 ± 0.03, 7.44 ± 0.07, 7.46 ± 0.05, 7.47 ± 0.06 (p = NS); PO2 86 ± 30 mmHg, 98 ± 30 mmHg, 94 ± 40 mmHg, and 79 ± 30 mmHg (p = NS); and PCO2 43 ± 3 mmHg, 44 ± 8 mmHg, 38 ± 5 mmHg, and 40 ± 4 mmHg (p = NS). CONCLUSIONS: Using anatomical landmarks for the placement of the BCDL catheter was rapid and effective in a swine model of VV ECMO, resulting in improved time efficiency for research.

Cardiac tamponade: new technology masking an old nemesis.

A 16-year-old male patient underwent bilateral pulmonary embolectomy complicated by reperfusion injury and acute respiratory distress syndrome requiring venovenous extracorporeal membrane oxygenation support using a bicaval double-lumen catheter. A unique hemodynamic profile developed consistent with tamponade but without an associated decrease in venovenous extracorporeal membrane oxygenation pump flow, improved venovenous extracorporeal membrane oxygenation circuit preload, and decreased recirculation. The use of newer bicaval double-lumen catheters can result in old problems presenting in new ways and require clinicians to be ever vigilant.