ASAIO transactions / American Society for Artificial Internal Organs
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In order to better understand the relationship among certain device related complications and Novacor left ventricular assist system (LVAS) pumping parameters, a Mock Circulatory Loop was utilized to simulate the following clinically realistic conditions: 1) inflow valve regurgitation, 2) inflow cannula obstruction, 3) outflow valve regurgitation, and 4) outflow cannula obstruction. Various pumping parameters (e.g., pump rate, stroke volume, pump output) were recorded at baseline (control) and during each simulation. ⋯ The results indicate that perfusion pressures and rates of filling and ejection change significantly in the presence of device complications. The implications of these findings, as relates to assessment of pump operation in LVAS patients, are discussed.
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The time constant for heat transfer may affect exact determination of cardiac output with Swan-Ganz catheters. Commercially available Swan-Ganz catheters are provided with thermistors with varying time constants. ⋯ The authors propose a new method of determining cardiac output with Swan-Ganz catheters with varying time constants from thermal dilution curve data based on Newton's cooling law. Values for blood flow rate determined by the new method using a completely stirred tank of original design, mimicking the natural heart and using bovine blood, are almost the same as values observed at varying saline infusion volumes, saline temperatures, and saline infusion times.
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A heparin coated cardiopulmonary bypass system was evaluated for canine veno-venous extracorporeal membrane oxygenation (ECMO). The ECMO system consisted of a hollow fiber membrane oxygenator and pediatric centrifugal pump but no reservoir. In Group 1 (N = 6), the ECMO system was coated with a covalent, heparin-binding method, except for the centrifugal pump, and animals underwent ECMO without systemic heparinization. ⋯ There was no apparent macroscopic thrombus formation in either group. In addition, it was suggested that Group 1 had less activation of platelets on the blood-contacting surfaces compared with Group 2. This ECMO system, with simplified circuits using a centrifugal pump, showed efficient gas exchange and antithrombogenicity when coated with heparin using a covalent binding method comparable to the non heparin coated system requiring systemic heparinization.
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Neuro-selective current perception threshold (CPT) values quantify peripheral nerve (n) integrity and provide an index of adequate hemodialysis (HD). Evaluation of polyneuropathy (PN) by CPT correlates with nerve conduction testing (NCT). CPT is convenient, painless, and may be performed during HD. ⋯ CPTs consistent with CTS (sufficiently greater impairment of the median vs ulnar n) were observed in 31% of the hands with combined median and ulnar n CPT abnormalities, and 11% were identified with CTS by NCT. The unique ability of the CPT exam to quantify hyperesthesia may account for its superior CTS detection sensitivity. These findings demonstrate that repeated CPT determinations are consistent and are diagnostic for CTS.