The International journal of artificial organs
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Randomized Controlled Trial Clinical Trial
Progress in veno-venous long-term bypass techniques for the treatment of ARDS. Controlled clinical trial with the heparin-coated bypass circuit.
Extracorporeal CO2 removal combined with low-frequency positive pressure ventilation (ECCO2-R LFPPV) is a new therapeutic approach in treatment of ARDS. The main problem during long-term extracorporeal support is anticoagulation and related bleeding problems. ⋯ Bleeding complications were less and more patients survived in group 2. The disadvantage of the hollow fiber oxygenators in the heparin-coated system was plasma leakage, which was more frequent in patients with pancreatitis and hyperbilirubinemia.
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Extracorporeal lung assist (ELA) has been recommended for the treatment of ARDS if conventional therapy fails. However, the need for nearly complete anticoagulation is a major risk factor for hemorrhagic complications. We describe our experience with 13 ARDS patients treated with ELA using heparin-coated systems (Carmeda). ⋯ Eight of the 13 patients survived. The use of heparin-coated systems allows prolonged ELA with nearly physiological coagulation function, permitting major surgical intervention. It enhances the safety margin of extracorporeal gas exchange and may ultimately extend its indications.
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Extracorporeal membrane oxygenation (ECMO) was used to achieve temporary artificial support in cardiac and pulmonary function in 22 patients from 1987 to September 1990. Standard indications were postcardiotomy cardiogenic shock (n = 4), neonatal (n = 1) and adult respiratory distress syndrome (n = 4). ECMO was also used for extended indications, such as graft failure following heart (n = 11) or lung transplantation (n = 2). ⋯ This series illustrates the results with ECMO in emergency situations, in patients under immunosuppressive protocols, or in patients with advanced lung failure requiring almost complete artificial gas exchange. In such complex situations, ECMO does provide stabilization until additional therapeutic measures are in effect. ECMO cannot be recommended for postoperative cardiogenic shock but short-term ECMO support is an accepted method in most cases with graft failure or pulmonary failure or other origin.
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Hemodialysis is a powerful tool for extracorporeal CO2 removal, because CO2 can be eliminated both as gas and as bicarbonate with blood flow rates as low as 10-15 ml/kg/min. An unsolved problem remains, however: how to make up for the bicarbonate loss. ⋯ CO2 removal was quantitatively the same as during routine acetate hemodialysis and could not be increased using other organic acids. b) NaOH alone, through theoretically the best substitute for NaHCO3, had serious side effects and led to an increase in pulmonary artery pressure. c) with TRIS at a rate of 5 mmol/min, all metabolic CO2 could be removed for up to seven hours without clinical side effects, but not for longer periods. We conclude that a combination treatment for realkalinisation has to be worked out to compensate for the bicarbonate loss.
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During the extracorporeal support (LFPPV-ECCO2R) of 11 patients suffering from severe lung failure (ARDS), we consistently noticed a higher arterial than mixed-venous PCO2 in blood samples drawn at the same time. Two explanations are possible: a) the Haldane effect (HE), b) CO2 from lung tissue metabolism. In order to distinguish changes in PCO2 due to the HE from those due to tissue CO2 production, CO2 content (CCO2) was calculated. ⋯ Oxygen saturation increased by 8.1% in the human group and 17.8% in the animal group. A significant relationship was found between changes in PCO2 and changes in O2-saturation. This is a demonstration of the Haldane effect.