Quantitative Determination of Pulmonary Microembolism in the Dog

Comparison of In vivo and In vitro Methods

Abstract

External monitoring and in vitro measurement of pulmonary microembolism using ⁵¹Cr-labelled platelets and ¹²⁵I-labelled fibrinogen were compared. The micro-enbolism was induced in dogs by intravenous infusion of thrombin and the radioactivities were recorded by an external detector as well as at intervals in biopsy material. External detection proved to give lower estimates of the amount of trapped radioactivity than in vitro measurements. This was particularly so for ⁵¹Cr. Thus only about 2/13 of the in vitro amount of trapped ⁵¹Cr and about 1/3 of the ¹²⁵I radioactivity were revealed by external detection. External detection, however, records the changes continuously and therefore offers advantages over the biopsy technique, which requires open chest surgery and artificial respiration with consequent alterations in intrathoracic pressure and circulatory conditions.