Short axis inferior vena cava measures are more sensitive than long‐axis measures in defining acute volume loading in normal human volunteers.

Introduction Change in inferior cava diameter (IVC) during respiration is a potentially non invasive measure of blood volume in haemodialysis (HD) and heart failure (HF) patients. We tested its sensitivity to acute volume loading in normal volunteers (NV). Methods 30 NV (16 male; 48.7 ± 8.6 years, range 48–63) received intravenous 0.9% saline (IVS; 1.5 L over 20 minutes). IVC was measured by M‐mode echocardiography in long‐(LAX) and short‐axis (SAX) views during expiration (IVCe), inspiration (IVCi) and maximal inspiration (IVCmi) at 0, 1, 2 and 4 h. IVC was corrected for body surface area (IVCD) and IVC collapsibility index (IVCCI) was defined as IVCCIi=[(IVCe‐IVCi)/IVCe] × 100. Results There was good linear correlation between LAX and SAX IVC [IVCe: r=0.809; p<0.0001 , IVCi: r=0.660; p<0.0001 and IVCmi: r=0.498; p=0.005 ]. Parameters increased following IVS, with greater change from baseline in SAX. Only IVCe and IVCDe in SAX increased significantly following IVS (Table 1). Conclusions Despite good correlation between LAX and SAX, SAX inferior vena cava indices are more responsive to IVS in NV. Further studies to assess the utility of these indices in the routine care of HF and HD patients are indicated. Funding Haemostasis Thrombosis and Vascular Biology Unit charitable funds.