Blood Fluid Volume Research Articles

P72: Fully Coupled Computational Simulation of the Syncardia Total Artificial Heart May Optimize Clinical Performance

Background: The Syncardia Total Artificial Heart (TAH) is used as a bridge to transplant for patients with biventricular heart failure and currently the only FDA approved TAH. There is a dearth in studies investigating its mechanics, hemodynamics, and optimal performance. Previous studies have provided limited characterization of Syncardia’s dynamics with respect to platelet activation but did not fully realize a complete dynamic coupled solution. Thus, there is a knowledge gap with regards to understanding the operational capacity and performance characteristics of the TAH. The objective of this study is to characterize the hemodynamic performance of the Syncardia TAH to optimize operational parameters and further understand why the device is an effective bridge to transplant. Methods: COMSOL Multiphysics (COMSOL Inc.) was used to conduct fully coupled fluid-structure interaction simulations of the device in standard operation. The computational model contained a blood fluid volume within Syncardia’s housing assembly (ventricle), segmented polyurethane solution (SPUS) diaphragm chamber filled with air, and SynHall valves in the mitral and aortic positions. These components’ coupled physics allow for the cohesive motion of the blood volume, diaphragm, and valves by solving the fluid Navier-Stokes and solid motion equations. Results: Figure 1C is flow patterning representative of the left ventricular diastolic filling with the development of the ventricular vortex present within diastole. Negative pressure collapses and deforms the diaphragm as shown in Figure 1D to drive filling during diastole. Figure 1E shows regional stress on the SynHall mitral valve during diastole. Conclusions: We utilized a fully coupled model of the Syncardia to study hemodynamic properties including vorticity and shear stress spatial and temporal distributions. Future work will be to perform failure mode analysis to identify parameters that are associated with thrombosis as well as optimize clinical operational parameters including device setting and associated clinical management.

Euthanasia methods, corticosterone and haematocrit levels in Xenopus laevis: evidence for differences in stress?

AbstractAmphibians, like other vertebrates, respond to acute stressors by releasing glucocorticoid steroid hormones that mediate physiological and behavioural responses to stress. Measurement of stress hormones provides a potential means to improve the welfare of laboratory animals. For example, manipulations of laboratory housing and procedures combined with measurement of glucocorticoids may identify which conditions are more stressful to animals. This is important because there is very little experimental evidence to guide best practice for welfare in amphibians and other lower vertebrates. We investigated the effect of different methods of euthanasia on the circulating plasma corticosterone levels in the African clawed frog (Xenopus laevis), a model amphibian organism that is frequently used in laboratories. In particular, we investigated the effect of different concentrations and pH of the anaesthetic tricaine methanesulphonate (MS-222). Low concentration and unbuffered (low pH) solutions of MS-222 caused elevated corticosterone levels, but only after the effect of MS-222 treatment on blood fluid volume had been taken into account. The level of disturbance that animals experienced also affected corticosterone levels. Thus, our data suggest that to minimise stress to X. laevis, animals should be euthanised after minimal disturbance and in a 3 g L−1 MS-222 solution, buffered to pH 7. The potential for the improvement of amphibian welfare using corticosterone measures as a tool is discussed.

Effect of manidipine chloride on various aspects of endocrine function, including plasma levels of endothelin-1 and human atrial natriuretic peptide, in patients with essential hypertension

We assessed various aspects of endocrine function in patients treated for essential hypertension with manidipine chloride, a calcium channel blocker, to study the effects of this drug on several endogenous humoral factors, including human atrial natriuretic peptide (hANP) and endothelin-1 which influence vasoconstriction and blood fluid volume. The study included 19 patients with essential hypertension. All patients received manidipine chloride 10 mg/d for 24 weeks. After treatment blood pressure was normalized in all patients, and there were no significant changes in plasma renin activity or blood concentrations, adrenaline, or noradrenaline. There was a statistically significant negative correlation between the change in ET levels and hANP levels before and after treatment. We also observed a statistically significant negative correlation between the change in systolic blood pressure caused by manidipine chloride and the change in hANP levels before and after treatment. These findings suggest that hANP and ET levels are systematically changed by manidipine chloride in patients with essential hypertension. We also speculate that changes in blood pressure may be closely related to levels of hANP in patients treated with manidipine chloride.

Effects of refeeding fasted chicks on serum thyroid hormones

Fasted chicks adapted to meal eating were bled prior to and at .5, 1.0, 1.5, 2 and 3 hr after presentation with feed. Serum triiodothyronine (T 3) and thyroxine (T 4) values were not influenced by amount of food consumed, body weight or blood fluid volume but significant quadratic effects of time after eating were found. Rapid changes occurred in blood thyroid hormones of chicks after ingesting a meal which demonstrated that time of food consumption relative to determination of these hormones should be known.