Inferior vena cava ultrasonography before general anesthesia cannot predict arterial hypotension in patients undergoing vascular surgery

INTRODUCTION

Intraoperative hypotension (IH) is an independent predictor of mortality. Some experts have suggested that ultrasound measurement of the inferior vena cava (IVC) in spontaneous ventilation can predict IH.

OBJECTIVE

To evaluate the capacity of ultrasound measures of IVC in spontaneous ventilation to predict episodes of IH after anaesthesia induction.

PATIENTS AND METHODS

We studied 55 high-risk cardiac patients undergoing vascular surgery. The maximum (dIVCmax) and minimum (dIVCmin) diameter of the IVC were measured and the collapsibility index CI = (dIVCmax-dIVCmin)/dIVCmax was calculated prior to anaesthesia induction. Three definitions of IH were used: systolic blood pressure (SBP) less than 100 mmHg, mean arterial pressure (MAP) less than 60 mmHg, and a decrease in MAP greater than or equal to 30% compared to baseline.

RESULTS

There were no significant differences in dIVCmax or in CI between patients presenting IH after anaesthesia induction and those who did not. ROC curves for dIVCmax showed an area under the curve of 0.55 (0.39-0.70), 0.69 (0.48-0.90), and 0.57 (0.42-0.73) and ROC curves for the CI were 0.62 (0.47-0.78), 0.60 (0.41-0.78) and 0.62 (0.47-0.78) for the 3 definitions of IH (<100 mmHg, MAP < 60 mmHg, and MAP ≥30% baseline), respectively.

CONCLUSIONS

Ultrasound measurements of IVC in spontaneous ventilation are not good predictors of IH after anaesthesia induction in these patients. The optimal cut-off points show low specificity and moderate sensitivity for predicting IH.