Automated pulse pressure and stroke volume variations from radial artery: evaluation during major abdominal surgery

Background. Off-line calculation of the pulse pressure variation (PPVref) has repeatedly been shown to be a reliable predictor of fluid responsiveness in mechanically ventilated patients. This study was designed to assess the ability of two algorithms for automated calculation of PPV (PPVauto) (Intellivue MP 70) and stroke volume variation (SVVauto) (FloTrac/Vigileo) to predict fluid responsiveness during abdominal surgery. Methods. We conducted a prospective study of 56 fluid challenges given for haemodynamic instability in 11 patients undergoing major abdominal surgery. Fluid responsiveness was defined as an increase in stroke volume index (SVI) >10%. PPVref, PPVauto, SVVauto, and SVI (oesophageal Doppler) were recorded simultaneously before and after each fluid challenge. Results. PPVauto and SVVauto both correlated with PPVref [r(corr)=0.87 (P<0.0001) and 0.84 (P<0.0001), respectively; n=77]. All three indices measured before fluid challenges were higher in responder (n=32) than in non-responder (n=24) fluid challenges (P <= 0.02). The mean areas under the receiver operating characteristic curves were 0.96 (PPVref), 0.96 (PPVauto), and 0.95 (SVVauto), and the optimal threshold value for each variable was 13%, 13%, and 12%, respectively. All indices correlated with the fluid challenge-induced changes in SVI (PPVref: r(corr)=0.65; PPVauto: r(corr)=0.58; SVVauto: r(corr)=0.58, P<0.001 for all). Conclusions. PPVauto and SVVauto to predict fluid responsiveness as accurately as off-line PPVref in patients with haemodynamic instability during major abdominal surgery.