Plethysmographic dynamic indices predict fluid responsiveness in septic ventilated patients

Abstract

Objectives: In septic patients, reliable non-invasive predictors of fluid responsiveness are needed. We hypothesised that the respiratory changes in the amplitude of the plethysmographic pulse wave (DeltaP(PLET)) would allow the prediction of changes in cardiac index following volume administration in mechanically ventilated septic patients.

Design: Prospective clinical investigation.

Setting: An 11-bed hospital medical intensive care unit.

Patients: Twenty-three deeply sedated septic patients mechanically ventilated with tidal volume >or=8 ml/kg and equipped with an arterial catheter and a pulse oximetry plethysmographic sensor.

Interventions: Respiratory changes in pulse pressure (DeltaPP), DeltaP(PLET) and cardiac index (transthoracic Doppler echocardiography) were determined before and after volume infusion of colloids (8 ml/kg).

Measurements and main results: Twenty-eight volume challenges were performed in 23 patients. Before volume expansion, DeltaPP correlated with DeltaP(PLET) (r2 = 0.71, p<0.001). Changes in cardiac index after volume expansion significantly (p<0.001) correlated with baseline DeltaPP (r2 = 0.76) and DeltaP(PLET) (r2 = 0.50). The patients were defined as responders to fluid challenge when cardiac index increased by at least 15% after the fluid challenge. Such an event occurred 18 times. Before volume challenge, a DeltaPP value of 12% and a DeltaP(PLET) value of 14% allowed discrimination between responders and non-responders with sensitivity of 100% and 94% respectively and specificity of 70% and 80% respectively. Comparison of areas under the receiver operator characteristic curves showed that DeltaPP and DeltaP(PLET) predicted similarly fluid responsiveness.

Conclusion: The present study found DeltaP(PLET) to be as accurate as DeltaPP for predicting fluid responsiveness in mechanically ventilated septic patients.