The value of pulse pressure variation to predict volume response in patients ventilated with low VT

Abstract

Introduction: The prediction value of pulse pressure variation (ΔPP) in patients ventilated with low VT is not well studied. A ΔPP of 12 to 13% is validated as a predictor of volume response in several studies, but in patients ventilated with VT >8 ml/kg. One study has shown that the ΔPP of 12 to 13% does not predict volume response in patients ventilated with a low VT. We hypothesized that a lower cut-off value for ΔPP can predict volume response in patients with low VT. Methods: Thirty-seven adult patients mechanically ventilated with a tidal volume <8 ml/kg (PBW), without cardiac arrhythmias, with a pulmonary artery catheter and a peripheral arterial catheter were included. An increase in cardiac index (thermodilution)) >15% output after a fluid challenge (Crystalloid 1,000 ml or Colloid 500 ml) was considered a positive response. Results: Seventeen patients were responders. The ROC curve showed that the best cut-off value for ΔPP was 10% (ROC area = 0.74, 95% CI: 0.51 to 0.9; sensitivity 53%, specificity 95%, positive likelihood ratio 9.4 and negative 0.34).Twelve patients consisted of a heterogeneous group of patients (liver transplant, acute pancreatitis, aortic surgery). Among 25 septic shock patients, a ΔPP >10% showed a ROC area of 0.84 (sensitivity 78%, specificity 93%). In any case, the greater ΔPP, the greater the fluid response. ΔPP >10% was a better predictor than CVP or PAOP. Conclusions: ΔPP has a limited value in patients ventilated with low VT. However, a ΔPP >10% may help identify septic shock patients that will respond to a fluid challenge.