ABSTRACT
The decision to use a long-term preparation for cardiovascular studies should be considered carefully, because such studies demand a major commitment by both the investigator and the institution in which the work is to be done. Thus, the first step in any investigation is to select the most appropriate measurement technique and validate it in the preparation and under the conditions which will be used in the experiment. In long-term experiments, however, it is necessary to cut down on deeper vessels so that the catheter can be stabilized by ties around the blood vessel and the catheter, as well as be anchored into surrounding muscle. Direct measurements of blood pressure involve catheterization of the blood vessel. Various forms of the indicator-dilution principle, as previously mentioned, can be used to measure total blood volume as well as cardiac output. After the plasma volume is determined a hematocrit estimation is used to calculate total blood volume.
