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PubMedDate not supplied

Regulation of coronary circulation during left ventricular assist.

Regulatory mechanisms of coronary circulation during left ventricular assist (LVA) were studied in chronic experiments using adult goats. In normal heart studies (n = 3), circumflex coronary artery flow (CxF) and endocardial blood flow (MBF) decreased in proportion to decrease of tension time index (TTI). Mean CxF/TTI was constant at 0.22, whether the LVA functioned or not. In the left anterior descending branch ligation model (AMI) study (n = 2), CxF decreased according to decrease of TTI throughout the experiment, if the bypass ratio was kept within a normal range of systemic pressure. Mean CxF/TTI was maintained at approximately 0.21 by LVA, fell to 0.16 when LVA was turned off during the early stages. Coronary circulation during LVA was regulated by oxygen demand if systemic circulation was maintained, and LVA improved oxygen demand-supply balance in failing hearts.

Animals↗
PubMed1992

[Clinical and experimental study of the production of renal hemodynamic effects of IABP-assisted pulsatile flow extracorporeal circulation].

Renal hemodynamics during IABP-assisted pulsatile flow extracorporeal circulation was assessed in terms of measurement values for intraoperative renal blood flow obtained by the local thermodilution method in human clinical patients. In addition, the effect of IABP on renal hemodynamics was investigated in an animal model of renal denervation in a study undertaken to elucidate the action mechanism of IABP. Eighteen patients with acquired heart disease were involved in the study and measured for the renal blood flow (RBF), cardiac output (CO), renal-systemic partition coefficient for blood flow (RBF/CO), renal vascular resistance (RVR) and perfusion pressure. In the pulsatile flow group, the RBF/CO increased as the number of pump runs increased, whole the RVR was conversely reduced with increasing pump runs. The experimental study without extracorporeal circulation was conducted on 19 mongrel dogs. During IABP runs RBF/CO increased, while the RVR decreased. After renal denervation, no noticeable influence of IABP upon renal hemodynamics was observed. Following a loading dose of noradrenaline (Norad), the RVR increased in a Norad concentration-dependent fashion, independently of IABP and renal denervation. These results indicate that IABP reduces the RVR and thereby exerts a favorable action on renal hemodynamics during pump times. The study thus warrants us to surmise that a mechanism involving the renal sympathetic nerves might play an important role in the production of favorable renal hemodynamic effects of IABP-assisted pulsatile flow extracorporeal circulation.

Animals↗
PubMedDate not supplied

[Treatment of left ventricular failure following extracorporeal circulation using ventricular assistance with centrifugal pump].

We report the use of left ventricular assistance with a centrifugal pump in a patient with refractory left ventricular failure after aortic valve replacement. Assistance was maintained during the first 24 hours until the hemodynamic status allowed its withdrawal. The used flows ranged from 1.5 to 5 l/min, and there were no complications except hemorrhage (95 ml in 3 hours) that could be stopped without reoperation.

Cardiac Output, Low↗
PubMed2006

Twenty-four hour cardiopulmonary stability in a model of assisted newborn Fontan circulation.

BACKGROUND: Morbidity and mortality after stage-1 palliation of hypoplastic left heart syndrome is high as a result of adverse physiologic conditions imposed by the systemic-to-pulmonary arterial shunt. Conversion to a systemic venous source of pulmonary blood flow (Glenn/Fontan) substantially decreases instability and mortality risk. Cavopulmonary assist has the potential to eliminate critical dependence on the problematic systemic arterial shunt. We studied this support modality during a 24-hour period in a neonatal animal model of univentricular Fontan circulation. METHODS: Lambs (8.1 +/- 0.9 kg, 8.3 +/- 2.1 days, n = 7) underwent total cavopulmonary diversion. A miniature centrifugal pump was used to assist cavopulmonary flow. Control animals (6.6 +/- 1.0 kg, 7.3 +/- 2.1 days, n = 11) underwent placement of monitoring lines only. Hemodynamic and gas exchange data were measured. Within-group and between-group comparisons were made using two-way repeated measures analysis of variance. RESULTS: After an initial phase of reactivity, pulmonary vascular resistance returned to low levels and was not significantly different from baseline values after hour 13 or significantly different from control values after hour 4. Systemic venous pressure remained low. Oxygenation and ventilation remained normal with no histologic evidence of parenchymal lung injury. CONCLUSIONS: Pump-assisted cavopulmonary diversion is well tolerated up to 24 hours in the neonatal period. Despite initial reactivity, pulmonary vascular resistance trended toward normal and approached control values. Cavopulmonary assist holds the potential to serve as a bridge to neonatal Fontan repair of single ventricle. Chronic studies are warranted to determine the duration and rate of weaning of support to transition to an unassisted univentricular Fontan circulation.

Animals↗
PubMed1992

[CO2 elimination via extracorporeal circulation in respiratory assistance: artificial lung or kidney? Experimental study].

In the context of a respiratory assistance protocol dissociating oxygenation of the blood from elimination of carbon dioxide, it is possible to rest the lungs which are used for oxygen exchange by diffusion via functional zones. CO2 is eliminated via extracorporeal circulation. In order to simplify this method, the authors investigated the optimal conditions for this elimination at flow rates similar to those used for haemodialysis (0.33 l/min). This study was designed to evaluate the in vitro elimination of CO2 obtained by a membrane artificial lung with and without "doping" by acidification (10 ml/min of 0.01 N HCl) of the blood inlet compared with that obtained with a haemodialysis machine with and without alkalinisation (0.5 ml/min of 0.5 N NaOH) of the dialysate inlet. The results obtained showed that haemodialysis with an alkaline bath ensured CO2 elimination 36% superior to that of the artificial lung associated with acidification.

Carbon Dioxide↗
PubMed1990

The role of mechanical devices.

Devices to support the circulation and directly assist the ventricle during surgery are now both reliable and essential. The intraaortic balloon counterpulsation device is used in patients who fail to wean easily from cardiopulmonary bypass, who develop ischemia in the immediate postoperative period, or who have low output in the maximal edema phase, 4 to 8 hours postoperatively. Complications relate to the insertion of the device, which may cause major arterial disruption, lower leg ischemia, or distal arterial thromboemboli. Ventricular assist device (VAD) support is indicated when, despite the use of the intraaortic balloon, the patient's hemodynamics remain severely depressed and the patient is unable to wean from bypass. There are several contraindications to the use of VADs, including pulmonary hemorrhage. Nevertheless, as experience with the many different types of VADs increases, their use may be extended to periods of days or even months. Various mechanical support devices have been used to bridge to cardiac transplantation, with ranging degrees of success. Decisions concerning the use of mechanical devices for this purpose must take into account both the standard contraindications to transplantation, and contraindications that develop or are acquired during intervention with the bridging device. Current and future experience will decide which devices will be accepted for common clinical use.

Assisted Circulation↗
PubMed1983

Artificial hearts and blood pumps in the treatment of profound heart failure.

The recent clinical use of a pneumatic artificial heart at the University of Utah has focused attention on the role of blood pumps in the support of the circulation. Pneumatically powered assist pumps are now in clinical trials in patients with profound but reversible heart failure after open-heart surgery; survival rates as high as 50% in a heretofore lethal condition have been encouraging. The results of animal studies with the pneumatic artificial heart suggest that these devices are ready for clinical trials; the major application is likely to be as a bridge to cardiac transplantation. Implantable electric motor-driven assist pumps and artificial hearts are being evaluated in animals as permanent cardiac support or replacement devices; clinical use is projected to begin late in this decade. Initially, these devices will be employed in patients with end-stage cardiac disease who are not suitable candidates for cardiac transplantation or for whom donor hearts are not available. The availability of compact blood pumps will offer new forms of therapy to patients with certain types of profound heart failure.

Animals↗
PubMed1977

[Computer assisted heart and circulation analysis in experimental septic shock (author's transl)].

Developping a model of shock applying to the clinical manifestation is necessary to investigate the pathogenesis of septic shock and to identify the letality causing organ. Perhaps the hyperkinetic syndrome may play an important role. The extensive experimental data is processed by a digital computer. Explanations are given for the experimental apparatus and the structure of the Fortran-program.

Animals↗