Preliminary report. Noninvasive detection of blood volume redistribution in canine endotoxin shock

In 15 splenectomized dogs changes in blood volume distribution after injection of endotoxin or normal saline were followed during 2 hr with a noninvasive method. Autologous red cells were labeled with 6-8 mCi 99mTc in vitro. After injection of the tagged red cells radioactivity was collected by a gamma camera connected to a computer system. In six control animals the radioactivity over thorax, liver, abdomen, and hindlimb decreased in a similar way. This small decrease was found to be the result of elution of 99mTc from the red cells (3-5% per hour). After endotoxin an immediate decline in blood pressure was accompanied by a persisting decrease in radioactivity in the thoracic region and a considerable but temporary increase in hepatic activity. Changes in abdominal activity were variable. Over the hindlimb, a significant increase, 2 hr after endotoxin, was observed. These changes are generally in agreement with reported results obtained by invasive techniques. It is concluded that changes in blood volume distribution can be detected with the described noninvasive method, which in principle could be used in clinical investigation. Considering the elution of 99mTc the method is probably less suitable for longer observations.