Non-invasive assessment of fluid responsiveness using CNAP™ technology is interchangeable with invasive arterial measurements during major open abdominal surgery.

Background: Dynamic variables of fluid responsiveness (FR), such as pulse pressure variation (PPV), have been shown to predict the response to a fluid challenge accurately. A recently introduced non-invasive technology based on the volume-clamp method (CNAP™) offers the ability to measure PPV continuously (PPV). However, the accuracy regarding the prediction of FR in the operating room has to be proved.

Methods: We compared PPV with an invasive approach measuring PPV using the PiCCO technology (PPV). We studied 47 patients undergoing major open abdominal surgery before and after a passive leg-raising manoeuvre and i.v. fluid resuscitation. A positive response to a volume challenge was defined as ≥15% increase in stroke volume index obtained with transpulmonary thermodilution. Bootstrap methodology was used with the grey zone approach to determine the area of inconsistency regarding the ability of PPV and PPV to predict FR.

Results: In response to the passive leg-raising manoeuvre, PPV predicted FR with a sensitivity of 81% and a specificity of 72% [area under the curve (AUC) 0.86] compared with a sensitivity of 76% and a specificity of 72% (AUC 0.78) for PPV Regarding the volume challenge in the operating room, PPV predicted FR with a sensitivity of 87% and a specificity of 100% (AUC 0.97) compared with a sensitivity of 91% and specificity of 93% (AUC 0.97) for PPV The grey zone approach identified a range of PPV values (11-13%) and PPV values (7-11%) for which FR could not be predicted reliably.

Conclusions: Non-invasive assessment of FR using PPV seems to be interchangeable with PPV in patients undergoing major open abdominal surgery.

Clinical Trial Registration: NCT02166580.