Intensivist use of hand-carried ultrasonography to measure IVC collapsibility in estimating intravascular volume status: correlations with CVP

BACKGROUND: Volume status assessment is an important aspect of patient management in the surgical intensive care unit (SICU). Echocardiologist-performed measurement of IVC collapsibility index (IVC-CI) provides useful information about filling pressures, but is limited by its portability, cost, and availability. Intensivist-performed bedside ultrasonography (INBU) examinations have the potential to overcome these impediments. We used INBU to evaluate hemodynamic status of SICU patients, focusing on correlations between IVC-CI and CVP.

STUDY DESIGN: Prospective evaluation of hemodynamic status was conducted on a convenience sample of SICU patients with a brief (3 to 10 minutes) INBU examination. INBU examinations were performed by noncardiologists after 3 hours of didactics in interpreting and acquiring two-dimensional and M-mode images, and > or =25 proctored examinations. IVC-CI measurements were compared with invasive CVP values.

RESULTS: Of 124 enrolled patients, 101 had CVP catheters (55 men, mean age 58.3 years, 44.6% intubated). Of these, 18 patients had uninterpretable INBU examinations, leaving 83 patients with both CVP monitoring devices and INBU IVC evaluations. Patients in three IVC-CI ranges (<0.20, 0.20 to 0.60, and >0.60) demonstrated significant decrease in mean CVP as IVC-CI increased (p = 0.023). Although <5% of patients with IVC-CI <0.20 had CVP <7 mmHg, >40% of this group had a CVP >12 mmHg. Conversely, >60% of patients with IVC-CI >0.6 had CVP <7 mmHg.

CONCLUSIONS: Measurements of IVC-CI by INBU can provide a useful guide to noninvasive volume status assessment in SICU patients. IVC-CI appears to correlate best with CVP in the setting of low (<0.20) and high (>0.60) collapsibility ranges. Additional studies are needed to confirm and expand on findings of this study.