Prediction of responsiveness to an intravenous fluid challenge in patients after cardiac surgery with cardiopulmonary bypass: a comparison between arterial pulse pressure variation and digital plethysmographic variability index.

OBJECTIVES: Arterial pulse pressure variation (PPV) and digital plethysmographic variability index (PVI) have been proposed to predict fluid responsiveness during anesthesia and in critically ill patients. The present study aimed to compare the clinical utility of PPV and PVI in predicting fluid responsiveness after elective cardiac surgery.

DESIGN: A prospective observational study.

SETTING: A university hospital.

PARTICIPANTS: Eighty-seven adult patients.

INTERVENTIONS: Admission to the intensive care unit after cardiac surgery. Investigation before and after fluid challenge.

MEASUREMENTS AND MAIN RESULTS: The discrimination of both PPV and PVI in predicting fluid responsiveness was compared by using areas under the receiver operating characteristics curves (ROCAUC). Sensibility analyses were conducted after exclusion of patients with a low perfusion index, patients receiving norepinephrine, and patients with right ventricular dysfunction. Fifty-seven (71%) patients were responders and twenty-three (29%) were nonresponders. ROCAUC were 0.73 [95% CI: 0.63-0.83] versus 0.60 [95% CI: 0.48-0.71] for PPV and PVI in the whole cohort of patients, respectively (p = 0.020). The inconclusive class of responses included 47 (59%) and 62 (77%) patients, respectively (p = 0.010); whereas the discrimination of PVI remained low whatever the subgroup of patients, the discrimination of PPV markedly increased in patients without perfusion index ≤ 1.3 (ROCAUC = 0.83 [95% CI: 0.68-0.93]) and in patients without right ventricular dysfunction (ROCAUC = 0.85 [95% CI: 0.67-0.95]).

CONCLUSIONS: PVI is not discriminant and probably inaccurate to predict fluid responsiveness after elective cardiac surgery. PPV could be of potential interest after exclusion of patients with a low perfusion index and right ventricular dysfunction.