The ability of a novel algorithm for automatic estimation of the respiratory variations, in arterial pulse pressure to monitor fluid responsiveness in the operating room

BACKGROUND: Respiratory variations in arterial pulse pressure(Delta pp(man)) are accurate predictors of fluid responsiveness in mechanically ventilated patients. However, they cannot be continuously monitored: In our study, we assessed the clinical utility of a novel algorithm for automatic estimation of Delta PP (Delta PPauto). METHODS: We studied 25 patients referred for coronary artery bypass grafting. Delta PPauto was continuously displayed using a method based on automatic detection algorithms, kernel smoothing, and rank-order filters. All patients were under general anesthesia, mechanical ventilation, and were also monitored with a pulmonary artery catheter. Delta PPman and Delta PPauto were recorded simultaneously at eight steps during surgery including before and after intravascular volume expansion (500 mL hetastarch). Responders to volume expansion were defined as patients whose cardiac index increased by more than 15% after volume expansion. RESULTS: Agreement between Delta PPman and Delta PPauto over the 200 pairs of collected data was 0.7% +/- 3.4% (mean bias +/- SD). Seventeen patients were responders to volume expansion. A threshold Delta PPman value of 12% allowed discrimination of responders to volume expansion with a sensitivity of 88% and a specificity of 100%. A threshold Delta PPauto value of 10% allowed discrimination of responders to volume expansion with a sensitivity of 82% and a specificity of 88%. CONCLUSION: Delta PPauto is strongly correlated to Delta PPman is an accurate predictor of fluid responsiveness, and allows continuous monitoring of Delta PP. This novel algorithm has potential clinical applications.