ASAIO journal : a peer-reviewed journal of the American Society for Artificial Internal Organs
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Oxygenator thrombosis is a serious complication in extracorporeal membrane oxygenation (ECMO) and may necessitate a system exchange. Coagulation and fibrinolysis parameters, flow dynamics, and gas transfer performance are currently used to evaluate the degree of oxygenator thrombosis, but there is no technical approach for direct visualization and quantification of thrombotic deposits within the membrane oxygenator (MO). We used multidetector computed tomography (MDCT) with three-dimensional postprocessing to assess the incidence of oxygenator thrombosis, to quantify thrombus extent, and to localize clot distribution. ⋯ There was no correlation between clot volume and ECMO support time or aPTT. Clot formation within the MO is a common finding in ECMO despite adequate systemic anticoagulation. The clinical significance of thrombus formation and its influence on gas exchange capacity and hemostatic complications have to be addressed in further studies.
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Multicenter Study
Cerebral tissue oxygenation during the initiation of venovenous ECMO.
In an acute respiratory distress syndrome, venovenous extracorporeal membrane oxygenation (vvECMO) can rapidly normalize arterial hypoxemia and carbon dioxide tension (PaCO2). Considering the positive relationship between PaCO2 and cerebral blood flow, the aim of the current study was to evaluate cerebral regional tissue oxygen saturation (rSO2) during the implementation of vvECMO. Fifteen acute respiratory distress syndrome patients with recordings of cerebral rSO2 by near-infrared spectroscopy before vvECMO implementation until the optimization of the ECMO/ventilator settings were retrospectively studied. ⋯ median (interquartile range). The cerebral rSO2 increased significantly (p < 0.05) from 69(61-74) to 75(60-80)% after ECMO was started, concomitant to the arterial oxygenation. Until the end of the observation period after 83(44-132) minutes, cerebral rSO2 decreased significantly to 61(52-71)%. PaCO2 decreased from 70(61-87) to 43(38-54) mm Hg and the pH increased from 7.23(7.14-7.29) to 7.39(7.34-7.43). The baseline arterial oxygen saturation and tension as well as the actual bicarbonate concentration were negatively correlated with the absolute change in cerebral rSO2 (ΔrSO2). In the 11 nonhypoxemic patients (arterial oxygen saturation ≥90%) ΔPaCO2 was significantly correlated with ΔrSO2. Patients receiving vvECMO treatment are at risk for a decrease in cerebral rSO2. This decrease is more distinct in patients with normal baseline arterial oxygenation and high actual bicarbonate.
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Case Reports
Extracorporeal membrane oxygenation with subclavian artery cannulation in awake patients with pulmonary hypertension.
Pulmonary hypertension (PH) is a challenging disease process to manage. Respiratory and hemodynamic changes that accompany general anesthesia lead to a significant risk of cardiovascular collapse. ⋯ Performing ECMO cannulation without intubation or general anesthesia in these patients may be safer given the severity of their underlying disease process. We present three cases of upper body ECMO cannulation performed on patients with pulmonary hypertension while awake and without mechanical ventilation.
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Chronic hemodialysis is associated with significant thrombophilia. Of interest, hemodialysis patients have increased carboxyhemoglobin (COHb) and exhaled carbon monoxide (CO), signs of upregulated heme oxygenase (Hmox) activity. Given that CO enhances plasmatic coagulation, we determined whether patients requiring chronic hemodialysis had an increase in endogenous CO, plasmatic hypercoagulability and decreased fibrinolytic vulnerability. ⋯ Furthermore, over half of COHF positive patients had a hypofibrinolytic state, evidenced by an abnormally prolonged time to maximum rate of lysis (53.3%, [37.9%-68.6%]) and clot lysis time (64.4%, [48.8%-78.1%]). Carbon monoxide enhanced coagulation and diminished fibrinolytic vulnerability in hemodialysis patients. Future investigation of hemodialysis, CO-related thrombophilia is warranted.
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During veno-venous extracorporeal membrane oxygenation (VV-ECMO) support, optimization of oxygenation can be achieved by therapeutic interventions on both patient physiological variables and adjustment of ECMO settings. Based on the physiology of oxygen delivery during VV-ECMO support, we established the mathematical relationship between the variables which define the oxygenation state: hemoglobin (Hb), extracorporeal blood flow (ECBF), cardiac output (Q), and systemic oxygen consumption (VO2). ⋯ Despite the same value of SaO2, the DO2 resulting from the different combinations of Hb and ECBF progressively decreases with decreasing Hb. By demonstrating the quantitative relationship between Hb and ECBF as determinants of oxygenation during VV-ECMO support, this mathematical model could provide a theoretical basis for a rational approach to strategies to optimize oxygenation in patients on VV-ECMO.