Clinical death and the measurement of stressed vascular volume

Abstract

Objectives: To measure stressed vascular volume in humans and to review the concepts of stressed and unstressed vascular volume.

Design: Observational study during surgical procedure.

Setting: Operating room at a university hospital.

Patients: Five patients undergoing hypothermic circulatory arrest for surgery on major vessels.

Intervention: We measured the volume that drained from the patient to the reservoir of the pump when the pump was turned off.

Measurements and main results: Stressed volume was 20.2+/-1.0 mL/kg, which is 30% of the predicted blood volume of these patients.

Conclusion: 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.