Effect of Changes in Intravascular Volume on Inferior Vena Cava and Aorta Diameters and the Caval/Aorta Index in Healthy Volunteers.

Abstract

Although inferior vena cava diameter (IVCD) measurement can be useful as a noninvasive method for monitoring the volume status, the benefit of abdominal aorta diameter (AAD) measurement is unclear. The purpose of this study was to determine the value of the combined use of the IVCD and AAD in blood loss monitoring. This prospective observational study was conducted at the blood donor center of a training and research hospital. Standard blood donation criteria were followed during volunteer enrollment. Vital signs and ultrasound IVCD and AAD measurements were obtained before and after blood donation and after fluid resuscitation with 500 mL of 0.9% sodium chloride. Measurements before and after blood donation and after fluid resuscitation were compared by the paired t and Wilcoxon matched-pair tests. Thirty-nine volunteers were included in the study. With 500 mL of blood loss, percent changes in the shock index (SI; mean ± SD, 7% ± 6%), IVCD (6% ± 2%), and caval/aorta index (IVCD/AAD; 6.1% ± 3%) were similar and were higher (P < .001 for all parameters) than the changes in the pulse rate (3% ± 4%), AAD (0.5% ± 1.5%), systolic blood pressure (3% ± 4%), and diastolic blood pressure (2% ± 7%). Although IVCD and SI values changed significantly (P < .001 for both) after 500 mL of 0.9% sodium chloride resuscitation, no significant change was observed in the IVCD/AAD (P = .059). The IVCD/AAD, SI, and IVCD may have similar success rates in diagnosing early blood loss. Additionally, the SI and IVCD may be superior to the IVCD/AAD in bleeding patients requiring simultaneous fluid resuscitation.