ASAIO journal : a peer-reviewed journal of the American Society for Artificial Internal Organs
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Experimental and clinical use of the intravascular oxygenator (IVOX), an intravenacaval gas exchange device, in acute respiratory failure yielded a CO2 transfer of 40-70 ml/min (approximately 30% of adult CO2 production) at normocapnia. Although significant, this rate of CO2 removal is not clinically useful. To maximize CO2 transfer, given the same gas exchange properties and structure design of the IVOX, the authors analyzed the effects of permissive hypercapnia (stepwise increase in arterial blood pCO2 up to 100 mmHg) and active blood mixing (with an intraaortic balloon pump) on different sizes of IVOX (sizes 7, 8, and 9 mm, surface area 0.21, 0.32, and 0.41 m2, respectively) using a previously established ex vivo circuit to model the human vena cava. ⋯ A 0.42 m2 surface area is associated with an O2 transfer of 80 ml/min without and 107 ml/min with active blood mixing. It is concluded that CO2 removal by IVOX alone is limited by insufficient surface area and the resistance in the blood-surface boundary layer. The combination of permissive hypercapnia, adequate blood flow, and active blood mixing can substantially improve CO2 removal and can therefore achieve clinically significant CO2 removal by intravenacaval gas exchange devices during severe respiratory failure.
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Proinflammatory cytokines have been implicated in mediating tissue injury after cardiopulmonary bypass. Causative factors of inflammatory response after cardiopulmonary bypass include contact of the blood with the extracorporeal circuit and heart-lung reperfusion injury when discontinuing bypass. To evaluate proinflammatory cytokine release during cardiopulmonary bypass, plasma levels of interleukin-6, 8, and monocyte chemoattractant factor were measured in the radial artery (for systemic blood) and left atrium before and after cardiopulmonary bypass. ⋯ These changes may have been caused by removal of the aortic cross clamp and recommencement of artificial ventilation, which result in reperfusion of the pulmonary capillary beds. There were no differences in cytokine levels after cardiopulmonary bypass in the radial artery and left atrium. This result suggested that lung reperfusion injury after cardiopulmonary bypass may not be the major causative factor of the release of proinflammatory cytokines.
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To overcome problems derived from the shaft within conventional centrifugal pumps, we have developed a new centrifugal pump, the magnetically suspended centrifugal pump (MSCP), which has no shaft and operates as a bearingless centrifugal pump. The impeller is suspended freely and centrally by magnetic force within the pump. Hemolysis tests were performed in comparison with the Biopump. ⋯ In the other sheep, the MSCP ran for 15 days, and showed no thrombus on the impeller. During each experiment, plasma free hemoglobin levels were less than 15 mg/dl. The MSCP induced less hemolysis than did the Biopump, and the MSCP containing an impeller coated with silicone demonstrated the potential to run for 14 days without thrombus formation within the pump.
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Recent experimental studies have suggested that the initial nonstimulated stage of dynamic cardiomyoplasty acutely impairs ventricular function. Those investigations were performed on normal hearts and primarily examined diastolic alterations as a result of the passive muscle wrap. The purpose of this study was to assess the acute systolic and diastolic effects of a nonstimulated muscle wrap in chronic heart failure induced by rapid ventricular pacing in canines. ⋯ By the end of the pacing period and before wrap, left ventricular dysfunction developed in all dogs, manifested by significant deterioration of both systolic and diastolic indices of ventricular function, as well as progressive increases in left ventricular volumes. However, no further deterioration with load insensitive indices of systolic or diastolic indicators of ventricular function was found as a result of the passive muscle wrap. These results suggest that the cardiomyoplasty procedure can be safely performed on failing hearts without prohibitive acute impairment of ventricular function.
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Multicenter Study
Percutaneously inserted silastic jugular hemodialysis catheters seldom cause jugular vein thrombosis.
To find out whether internal jugular vein cannulation with a soft silastic hemodialysis access catheter causes jugular vein thrombosis, the authors carried out Doppler ultrasound examinations on 96 patients receiving hemodialysis who had undergone 144 separate catheter insertion episodes in 116 veins. Two internal jugular vein thromboses were found in 101 veins that had been the site of percutaneous insertions only. ⋯ The authors conclude that percutaneous internal jugular vein cannulation for hemodialysis access causes an acceptably low incidence of jugular vein damage. This strengthens the case for preferential use of the internal jugular vein for vascular access in patients with end-stage renal failure, and suggests that percutaneous cannulation is less damaging than surgical insertion.