ASAIO journal : a peer-reviewed journal of the American Society for Artificial Internal Organs
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The authors analyzed factors that may influence the outcome of adult patients with respiratory failure who were treated with ECMO. Between December 1990 and July 1995, the authors used ECMO to support 33 patients (age range, 17-56 years) with respiratory failure from adult respiratory distress syndrome (ARDS; n = 9), primary graft failure after lung transplantation (n = 16), late graft failure after lung transplantation (n = 5), and miscellaneous reasons (n = 3). Twenty (61%) patients were successfully weaned from ECMO, and 13 (39%) survived to hospital discharge. ⋯ Compared with the nonsurvivors, survivors had higher PF ratios (PaO2/FIO2; 104 +/- 33 vs 81 +/- 8, p = 0.43) before ECMO was initiated, although the differences were not significant. Among the patients who received ECMO for primary graft failure, 75% were weaned from ECMO, and 56% survived to discharge. ECMO is beneficial for adult patients with respiratory failure, especially those with primary graft failure after lung transplantation.
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Comparative Study
Validation of a new method to measure cardiac output during extracorporeal detoxification.
Cardiac output was measured in 11 patients during extra-corporeal detoxification after open heart surgery. All patients were mechanically ventilated and had pulmonary artery catheters for cardiac output (COT) measured by thermodilution. A sensor on the arterial side of the extracorporeal circulation measured flow and sound velocity transients. ⋯ The regression equation was COUD = 1.09 x COT-0.32 (r = 0.97, n = 31). These data suggest agreement between the ultrasound dilution technique and thermodilution. Ultrasound dilution is preferable in patients undergoing extracorporeal detoxification when pulmonary artery catheterization is not required or dangerous.
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Arteriovenous carbon dioxide removal (AVCO2R) has been shown to achieve total carbon dioxide (CO2) exchange. To determine optimal blood and gas flow parameters that can provide maximal gas exchange and evaluate the utility of AVCO2R at reduced blood flow, the authors used a low resistance membrane gas exchanger within an arteriovenous shunt in mechanically ventilated sheep. Adult female sheep (n = 5) were anesthetized and underwent placement of the gas exchange device in a simple arteriovenous shunt created between the carotid artery and common jugular vein. ⋯ Optimizing AVCO2R blood and gas flow maximizes CO2 removal and allows a significant reduction in minute ventilation. In cases of severely limited blood flow, lung rest can still be realized at moderate hypercapnia. At flow rates achievable by percutaneous access, extracorporeal AVCO2R can be used to achieve lung rest during mechanical ventilation.
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The authors developed a new membrane oxygenator (MO) for long-term respiratory support and evaluated its performance in animal experiments for as long as 336 hr. The MO, with a membrane area of 1.2 m2 and priming volume of 140 ml, is compact and designed to be interposed in a ventricular assist system (VAS) conduit. It is made with a novel hollow fiber membrane, in which micropores are blind-ended so that serum leakage can be prevented during prolonged use. ⋯ The levels of coagulation parameters including fibrinogen, fibrin degradation products (FDP), antithrombin III (AT III), antiplasmin, prothrombin time (PT) and activated partial thromboplastic time (APTT) remained within physiologic ranges and relatively constant. At the end of the evaluation, no thrombus formation was noted in three of five MOs. These results suggest that this MO is a promising device for long-term respiratory support.
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Comparative Study
Hemodialysis access flow measurement. Comparison of ultrasound dilution and duplex ultrasonography.
Decreased hemodialysis access flow is associated with an increased risk of access thrombosis. Duplex ultrasonography can measure access flow and select a subset of patients at increased risk for access failure. With in-line techniques (ultrasound dilution), access flow can be measured during hemodialysis. ⋯ Regression analysis revealed a linear relationship between the two techniques described by the equation QAT = 246.14 + 0.8104(QAS) (correlation coefficient of 0.83; p < 0.0001). Measurement of hemodialysis access flow by ultrasound dilution was essentially equivalent to that obtained by duplex ultrasound. Additional studies are needed to determine if regular in-line flow measurements can predict and prevent future access thrombosis and decreased the cost of access management.