Clinical death and the measurement of stressed vascular volume

Abstract
To measure stressed vascular volume in humans and to review the concepts of stressed and unstressed vascular volume. Observational study during surgical procedure. Operating room at a university hospital. Five patients undergoing hypothermic circulatory arrest for surgery on major vessels. We measured the volume that drained from the patient to the reservoir of the pump when the pump was turned off. Stressed volume was 20.2 +/- 1.0 mL/kg, which is 30% of the predicted blood volume of these patients. The amount of blood volume that determines vascular filling pressure is only about a quarter of the total predicted volume, which means that there is a large reserve of unstressed volume that can be recruited to maintain vascular filling pressure. (Crit Care Med 1998; 26:1061-1064)