Ultrasound does not detect early blood loss in healthy volunteers donating blood.

Background: Ultrasound has been suggested as a useful non-invasive tool for the detection of early blood loss. Two possible sonographic markers for hypovolemia are the diameter of the inferior vena cava (IVC) and the thickness of the left ventricle (LV).

Study Objectives: The goal of the study was to evaluate the utility of ultrasound to detect signs of early hemorrhagic shock in healthy volunteers, compared with changes in vital signs.

Methods: In the current study, healthy volunteers from blood donation drives were used as models for early hemorrhage. Changes in vital signs, IVC diameter, and LV wall thickness were recorded after approximately 500 cc of blood loss.

Results: Thirty-eight subjects were enrolled and completed the study. After blood donation, there was a 7-mm Hg (8%) decrease in mean arterial pressure without a significant change in heart rate. There was a decrease in maximum IVC diameter (IVCmax) (12% decrease [95% confidence interval (CI) -6 to -19] in short axis and 20% decrease [95% CI -12 to -27] in long axis), but no change was seen in the respiratory caval index ((IVCmax - IVCmin)/IVCmax) × 100). There was no change in LV wall thickness.

Conclusion: In this study, serial changes in vital signs, IVC diameter, and LV wall thickness were clinically insignificant after approximately 500 cc of blood loss in healthy volunteers.