Pulse Pressure Variations and Plethysmographic Variability Index Measured at Ear Are Able to Predict Fluid Responsiveness in the Sitting Position for Neurosurgery

Background: Pulse pressure variation (PPV) and plethysmographic variability index (PVI), dynamic indicators of preload dependence based on heart-lung interactions, are used to predict fluid responsiveness in mechanically ventilated patients in the supine position. The sitting position for neurosurgery, by changing intrathoracic blood volume, could affect the capacity of PPV and PVI to predict fluid responsiveness. The aim of the study was to assess the ability of PPV and PVI to predict fluid responsiveness during general anesthesia in the sitting position. Methods: In total, 31 patients were included after settling in the sitting position but before surgery began. PPV, PVI with a finger sensor (PVI finger), and PVI with an ear sensor (PVI ear) were recorded before and after a fluid challenge of hydroxylethylstarch 250 mL over 10 minute. Esophageal Doppler was used to record stroke volume. Patients were defined as fluid responders if stroke volume increased by more than 10% after the fluid challenge. Results: In total, 13 (42%) patients were fluid responders. PPV and PVI ear were higher in responders than in nonresponders before the fluid challenge (12 +/- 5 vs. 7 +/- 3;P=0.0005 and 14 +/- 5 vs. 8 +/- 3;P=0.001, respectively). Areas under the receiver-operating curves to predict fluid responsiveness were 0.87 for PPV (P<0.0001), 0.87 for PVI ear (P<0.0001), and 0.64 for PVI finger (P=0.17). PPV >= 8% or PVI ear >= 11% predicted fluid responsiveness with sensitivities of 83% for both, and specificities of 83% and 91%, respectively. However PVI ear data were not available in 26% of patients. Conclusions: PPV can be used to predict fluid responsiveness in the sitting position for neurosurgery.