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CARDIOVASCULAR
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Volume 5, 2000, No 1 |
Conductivity:
An issue for the Application of the Conductance Catheter System in Mice
B. Yang, D. F. Larson, R. Kelley, J. Beischel, R. R. Watson
Background: A new conductance catheter system (CCS) has been developed to analyze in vivo left ventricular pressure-volume relationships in mice. As with other CCS designs, this murine system quantifies the left ventricular volume by measurement of the conductance (G) of the blood which is proportional to its conductivity (s). One critical issue specific for the mouse model is the dilution of the blood with intravenous infusion of saline solutions and the resulting effect on s. Therefore, the objective of this study was to define the saline volumes that could be infused in the mouse without significantly affecting the blood s or the accuracy of the ventricular volumetric measurements obtained with the CCS.
Methods: An in vitro system was developed to determine the effect of changes in s on G. Seven cylindrical volumes in a plastic block modeling raw conductance volume signals (2 to 5 mm) were filled with mouse whole fresh blood diluted with 6% Hetastarch in 0.9% saline to final concentrations of 0%, 15% (5:1), 25% (3:1), 50% (1:1) and 100% Hetastarch solution. The conductance of each solution was measured by the CCS and plotted against the corresponding volume. Mice were infused with 200, 400, or 800 ml of 6% Hetastarch solution, equivalent to in vitro hemodilutions of 8%, 15%, and 25%, respectively. Pressure-volume loop analysis was performed with the CCS subsequent to the infusions.
Results: The in vitro model demonstrated that the s of 6% Hetastarch solution and 0.9% saline were 2.0 and 2.4 times greater, respectively, than that of murine fresh whole blood (p < 0.001). In both the in vitro and in vivo models, dilution of whole blood with Hetastarch in 0.9% saline by 15% or less did not significantly alter s nor the pressure-volume loop parameters. We conclude that infusion of saline solutions in the mouse model should be restricted to 400 ml or less for the acquisition of accurate measurements of ventricular contractile properties.
Key words: conductance catheter, conductivity, pressure volume relationship, mice
Address for Correspondence:
Douglas F. Larson,
Ph.D.
Department of Surgery, Room 4402
University of Arizona
Tucson, AZ 85724
USA
Reference:
(CVE. 2000; 5 (1): 57-60)
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