Extracorporeal recording of mouse hemodynamic parameters by ultrasound velocity dilution

The use of mice as models for cardiovascular studies has traditionally been difficult because of their small size and the lack of appropriate instrumentation to perform fundamental measurements of cardiac output (CO) and total blood volume (TBV). The advent of transgenic techniques to develop mouse strains that mimic human disease makes the development of this instrumentation crucial. The current study outlines a novel technique for the determination of CO and TBV in the mouse using an extracorporeal arteriovenous (A-V) shunt, combined with the measurement of ultrasound dilution after the intravenous administration of small volumes of isotonic saline. The potential sources of error associated with Stewart-Hamilton dilution techniques were addressed by the research. The new techniques were applied in three anesthetized mice (27-36 gm). Isotonic saline (10-80 microl) was injected intravenously while measuring ultrasound dilution in the A-V shunt. The CO ranged from an average of 6.8+/-0.71 to 12.7+/-1.7 ml/min. Heart rates were not significantly altered by the intravenous administration of isotonic saline. The TBV ranged from 4.36+/-0.22 to 5.15+/-1.04 ml/100 gm. These results agree with the literature and suggest that these techniques will prove useful in cardiovascular studies of mice.