Abstract PR060

Abstract

Background & Objectives: Application of positive end expiratory pressure (PEEP) is known to induce hemodynamic instability particularly in patients with hypovolemia (1). Under constant elastic wall properties of large arteries, pulse pressure (PP) changes predominantly reflect stroke volume changes. Accordingly, we hypothesized that PEEP-induced percent changes of PP (PiPPP) predict circulatory volume (CV) conditions determined by the stroke volume variation (SVV). Materials & Methods: With approval of the IRB, we recruited 80 ASA PS I-II adult patients undergoing major surgeries requiring continuous arterial pressure monitoring with a Vigileo/FloTracTM (Edwards Lifesciences, Irvine, CA). Exclusion criteria included 1) BMI > 35, 2) ejection fraction < 40%, 3) SV index < 30 ml/m2 on zero end-expiratory pressure (ZEEP), 4) systolic blood pressure < 80 mmHg on ZEEP, 5) arrhythmia and 6) COPD. All patients were mechanically ventilated under general anesthesia and paralysis (tidal volume = 10 ml/kg, respiratory rate = 10 breaths/min, I/E ratio = 1:2). Hemodynamic parameters including SVV and PP were measured during ZEEP and 10 cm H2O PEEP application. PiPPP was calculated as (PPZEEP – PPPEEP) / (PPZEEP) %. Correlation analysis between SVV on ZEEP and PiPPP was performed by Spearman rank order test and P < 0.05 was considered significant. Results: We observed variable hemodynamic changes in response to PEEP application and significant dependence of the PiPPP on CV conditions (R = 0.66, P < 0.01). For different CV conditions determined by the SVV values at ZEEP (non-normovolemia: SVV > 10 %, severe hypovolemia: SVV > 13 %), we found a high positive predictive value (PPV) for non-normovolemic condition (83 %) and a high negative predictive value (NPV) for severe hypovolemic condition (93 %) when PiPPP > 15% is considered positive (2). This study demonstrated dependence of PiPPP on SVV on ZEEP while significant association between PEEP-induced SV changes and SVV on ZEEP was previously reported (3). Our results suggest potential usefulness of pulse pressure measurements before and during 10 cm H2O PEEP for determining CV conditions in anaesthetized and mechanically ventilated patients. Clinical usefulness of the PiPPP, a simple hemodynamic parameter, should be assessed by accuracy of fluid responsiveness prediction in a large sample size in the future.Conclusion: PEEP-induced pulse pressure changes predict stroke volume variation and possibly serve to optimal fluid management.