Distensibility index of inferior vena cava diameter in ventilated septic and trauma patients with shock

Introduction

We evaluated the distensibility index of the inferior vena cava (dIVC%) in ventilated septic and trauma patients with shock before and after fluid therapy. There are no data on this index in patients in shock post trauma.

Methods

This is a prospective study conducted in two ICUs between September 2008 and May 2009. Inclusion criteria were: shock (systolic arterial pressure below 90 mmHg and/or perfusion of vasopressor amines) related to severe sepsis or to trauma. The inferior vena cava diameter at end-expiration (IVCD_max) and at end-inspiration (IVCD_min) was measured by echocardiography using a subcostal approach. The distensibility index of the IVC was the ratio of IVCD_max - IVCD_min/IVCD_min expressed as a percentage (dIVC%). Cardiac index (CI) was calculated by analysis of the arterial pressure wave (FloTrac/Vigileo; Edwards). Measurements were performed at baseline and after a volume expansion using 7 ml/kg colloid and 20 ml/kg crystalloid for septic and trauma patients, respectively. Patients were separated into responders (increase in CI ≥15%) and nonresponders (NR) after fluid therapy. The Wilcoxon and Mann-Whitney tests were used to compare paired values. Statistical significance was tested at an α level of 0.05.

Results

Eleven patients in shock (five septic, six trauma; six responder, five NR) were included. The median age was 62 years (range 28 to 78 years) and mean SAPS II score was 52 ± 30 SD. There were no significant differences between responders (R) and NR regarding age, gender, and risk scores. Among all patients, at baseline, median CI and dIVC% were 2.6 l/minute/m² and 29%, respectively. Volume expansion significantly increased the median CI from 2.6 (2 to 3.3) to 3 (2.1 to 4) l/minute/m² (P = 0.005) and decreased dIVC% from 29.4% to 12.6% (P = 0.003). The median dIVC% in R was higher than NR: 31.3% vs 17% (P < 0.05). Fluid therapy decreased more dIVC% in R than in NR: R 31% to 12% (P = 0.03), NR 17% to 12% (P = 0.04). The dIVC% showed similar trend in both groups of septic shock (SS) and trauma shock (TS) patients before and after fluid therapy: dIVC% 27% in SS and 24% in TS before fluid therapy; 15% in SS and 11% in TS after therapy.

Conclusions

Our data suggest that dIVC% is a sensitive index of fluid responsive ness in septic and trauma patients in shock. Limitations: few patients.