Circulatory assist devices are used to treat patients awaiting cardiac transplantation to preserve life as well as to permit recovery of end-organ function. The efficacy of pulseless perfusion versus pulsatile perfusion in the recovery of end-organ function has not been fully determined. In this study, the efficacy of pulseless perfusion compared to pulsatile perfusion on the recovery of renal function after a 30 min period of normothermic ischemia was examined. Pigs were randomly assigned to four groups. In all groups, acute renal ischemia was induced by clamping both renal arteries for 30 min. Reperfusion for 120 min was performed using either pulsatile perfusion or pulseless perfusion at 65 +/- 1.6 mm Hg (Groups I [pulsatile] and II [pulseless]) and at 40 +/- 1.1 mm Hg (Groups III [pulsatile] and IV [pulseless]). After reperfusion, renal blood flow, hemodynamic power (pressure * flow: hemodynamic power), oxygen consumption (VO2), tissue ATP, and urine output (UO) in Groups I, II, and III were significantly higher than in Group IV (p < .01 by ANOVA). Histopathologic examinations were not significantly different between groups. Under hypotensive conditions, pulsatile perfusion improves hemodynamic power delivery to the organ compared to pulseless perfusion. These results suggest that a pulseless pump is acceptable as an assist device when normal flow or perfusion pressure is maintained.

Animals↗

PubMedDate not supplied

Development of a control algorithm for a rotary blood pump: prediction of recovery from cardiac failure.

Under extracorporeal membrane oxygenator (ECMO) support, it is difficult to predict recovery of cardiac function. The authors examined the rotary blood pump function curve and developed a new index of dynamic vascular impedance (DVI) for controlling the ECMO system. The cases of nine patients assisted by ECMO after cardiac surgery were analyzed. The index of DVI was calculated from the pump flow and the pressure difference (delta pressure) between the inlet and outlet of the pump. Seven patients were weaned from support. In the patients with recovery of cardiac function, the index of DVI was high and the delta pressure converged on the specific value. Analysis of the rotary blood pump function curve during ECMO support reflects the pump characteristics and provides data for the management of pump speed. The index of DVI can be used to predict the timing for weaning patients from ECMO support. The authors are developing an automatic control system that uses the index of DVI.

Algorithms↗

PubMedDate not supplied

Cytokine mediated endothelial activation during and after normothermic cardiopulmonary bypass: heparin-bonded versus non heparin-bonded circuits.

Studies evaluating cytokine production under normothermic cardiopulmonary bypass (CPB) are limited. We evaluated cytokine production, levels of thrombomodulin (TM), and soluble endothelium-derived adhesion molecules (ICAM-1) under normothermic CPB with and without heparin-bonded circuits. Nine patients treated with non heparin-bonded circuits (control group), and seven patients treated with heparin-bonded circuits (heparin group) were the subjects. Granulocyte elastase (G-E), and interleukin (IL) -6 and IL-8 were chosen as proinflammatory mediators, and TM and ICAM-1 served as indicators for endothelial damage. Blood samples were obtained before CPB, 30 minutes after initiation of CPB, at the termination of CPB, and 2 and 24 hours after CPB. G-E values in the heparin group were lower than those in the control group after 30 minutes of CPB. A G-E surge occurred at the end of CPB, and IL-6 and IL-8 surges were observed 2 hours after CPB in both groups. TM and ICAM-1 values, which were reduced at the initiation of CPB, returned to initial levels 2 hours after CPB, and exceeded them 24 hours after CPB compared with preCPB levels. Both groups showed similar changes. We conclude that there are no significant differences in serial G-E, IL-6, IL-8, TM, or ICAM-1 levels between the heparin and control groups during or after normothermic CPB for 2 to 3 hours.

Aged↗

PubMedDate not supplied

Pitfalls in the development of a rotary blood pump controller.

The controller presents a major obstacle in the development of the rotary blood pump as a left ventricular assist device (LVAD). Clinically, LVAD flow is a good indicator in the regulation of circulatory conditions and pump flow changes, depending on pump preload and afterload. Many investigators have tried estimating pump flow by referencing the motor current. There have been pitfalls in in vitro experimental settings, however. Using a test loop with a pneumatically driven LV chamber and a centrifugal pump as an LVAD, we monitored pump flow and pressure head to evaluate the pump performance curve (H-Q curve). Under pulsatile LV conditions, the H-Q curve was a loop that changed, depending on LV contractility. The pneumatically driven LV chamber cannot mimic the Starling phenomenon, so the developed LV pressure does not change according to the LV preload. Rotary pump flow estimation is the most effective control method. In pulsatile conditions, however, the H-Q curve is a loop that changes under various LV contractility conditions, complicating determination of linear equation for calculating flow. In addition, the LV chamber in the test loop cannot mimic native heart contractility as described by Starling's law. This finding can lead to a misanalysis of the H-Q curve under pulsatile conditions.

Cardiac Output↗

PubMedDate not supplied

An unusual complication associated with the Carpentier-Edwards porcine bioprosthesis.

Primary tissue failure of bioprosthetic heart valves refers primarily to calcification of the leaflets of the bioprosthesis. A 75 year old patient underwent reoperation 15 years after mitral valve replacement with a Carpentier-Edwards porcine bioprosthesis. The extracted bioprosthetic valve was found to have one prolapsed leaflet and a small amount of calcification on all three leaflets without tear or perforation. The two commissures suspending the prolapsed leaflet were detached, causing mitral valve regurgitation.

Aged↗

PubMedDate not supplied

Polydextrose and activities of brush-border membrane enzymes of small intestine in rats and glucose absorption in humans.

We investigated the effect of polydextrose, one of the water-soluble non-digestible polysaccharides, on the activities of brush-border membrane enzymes of small intestine in rats and on glucose absorption with relation to the thickness of the unstirred water layer in humans. Rats were fed a 5% polydextrose-supplemented elemental diet for 2 or 4 wk. The mucosal alkaline phosphatase, maltase, and sucrase activities were measured in the upper, middle, and lower intestine. There was no significant difference between control and polydextrose groups. The potentiometric tube was inserted orally in the jejunum. Glucose absorption was measured by perfusion with the solutions with or without 5% polydextrose. There was no significant difference in the glucose absorption rate or the thickness of the unstirred water layer between control and polydextrose solutions. The increase in viscosity of the polydextrose solution was negligible. This study indicated that polydextrose had no effect on the thickness of the unstirred water layer and did not inhibit glucose absorption in humans.

Alkaline Phosphatase↗

PubMedDate not supplied

Clinical experience with an anatomic snuff box arteriovenous fistula in hemodialysis patients.

The present study was performed to evaluate the clinical usefulness of an anatomical snuff box arteriovenous fistula with special reference to its short-term and long-term patency in 139 hemodialysis patients. A snuff box fistula was established in 139 patients, including 39 with diabetic nephropathy (DN group) and 100 with non diabetic nephropathy (non DN Group). Fistula blood flow was measured by Doppler ultrasound in 18 patients. Early and late obstruction was observed in 24 (17%) of the 139 patients. The long-term patency rate of the snuff box fistula in the non DN group was 87% at 57 months, whereas the patency rate at 57 months in the DN group (72%) was significantly (p < 0.05) lower than that in the non DN group. The increase in arterialized vein blood flow in DN patients was less marked than that in the non DN patients. These results suggest that the high prevalence of late obstruction in DN patients may partly be reflected by an insufficient increase of arterialized vein blood flow at the snuff box site.

Adolescent↗

PubMedDate not supplied

Pulmonary microcirculation during pulsatile and non pulsatile perfusion.

During development of a rotary blood pump as an assist device, the efficacy of non pulsatile perfusion to the end organ has to be verified. However, there are few evaluations of two different perfusion mechanisms through the tissue microcirculation. In this study, the pulmonary microcirculation was analyzed by vital microscopic observation. Wistar rats weighing 400-500 g were anesthetized and ventilated by a respirator. After establishing right heart bypass from the right atrium to the pulmonary artery using a roller pump, the pulmonary microcirculation was observed during intravenous infusion of bovine albumin tagged with fluorescein isothiocyanate. The images were recorded on a videotape through an ultra-sensitive SIT TV camera. Initially, the pulmonary circulation was pulsatile, produced by the native heart, and the pulmonary capillary network was evenly perfused by the blood. After starting the pump, the flow became non pulsatile and the distribution of capillary perfusion was displaced to the short circuit connecting the pulmonary arterioles and venules. Flow distribution during non pulsatile perfusion was heterogeneous compared with pulsatile perfusion. This result suggests that non pulsatile flow may lead to the deterioration of function. Further investigation is necessary to evaluate the relationship between the microcirculation and organ function.

Animals↗