Comparative evaluation of stroke volume variation and inferior vena cava distensibility index for prediction of fluid responsiveness in mechanically ventilated patients

Abstract

Objectives: To evaluate the correlation between stroke volume variation (SVV) and inferior vena cava distensibility index (dIVC) as a marker for fluid responsiveness in mechanically ventilated hypotensive intensive care unit (ICU) patients.

Methodology and design: This study is designed as prospective observational study conducted in patients admitted to an ICU who were mechanically ventilated and experienced a hypotensive episode.

Intervention: A fluid challenge of 10 mL/kg ringer's lactate was given over 20 min.

Measurements: Hemodynamic parameters as well as SVV, IVCmax, IVCmin, dIVC, and cardiac output (CO), were recorded at a different time interval. An increase in ≥15% of CO was taken as fluid responsiveness.

Results: Out of 67 patients, 67.2% responded to fluid challenge. Pearson's correlation graph at baseline showed a strong positive correlation between dIVC and SVV with r = 0.453, (P < 0.002). Non-responders also had a strong positive correlation (r = 0.474) at the baseline. Bland Altman's analysis of the correlation between dIVC and SVV post-fluid challenge showed a mean difference of - 4.444, with 1.49% of the values falling outside the limits of agreement (18.418 and -27.306). This difference was clinically significant. Pearson's correlation graph post-fluid challenge showed a moderately strong positive correlation between dIVC and SVV with r = 0.298 and P value = 0.047, which was statistically significant. Also, non-responders had a weak correlation as compared to the responder's group, r = 0.364 and P value = 0.095, which was not clinically significant. There was no significant difference in the trend of dIVC and SVV values between the non-surgical and surgical groups, nor was there any gender difference analyzed in the study.

Conclusion: This study ascertains the positive correlation between dIVC and SVV and justifies its use in a clinical setting of hypotension suspected to be due to hypovolemia.

Keywords: Cardiac output; distensibility index; inferior vena cava; intensive care unit; stroke volume variation.

Figure 1

Bland Altman Plot showing the correlation between baseline values of dIVC and SVV before and after fluid challenge

Figure 2

Pearson's Correlation coefficient between values of dIVC and SVV before, after post-initiation of fluid challenge and at 15- and 30-min initiation of fluid challenge

Figure 3

Left hand: Responder Operator Characteristic Curve For dIVC, Right-hand: Responder Operator Characteristic Curve for SVV