Evaluation of stroke volume variations obtained with the pressure recording analytic method.

OBJECTIVE: To investigate whether stroke volume variations obtained with the pressure recording analytic method can predict fluid responsiveness in mechanically ventilated patients with circulatory failure. DESIGN: Prospective study. SETTING: Surgical intensive care unit of a university hospital. PATIENTS: Thirty-five mechanically ventilated patients with circulatory failure for whom the decision to give fluid was taken by the physician were included. Exclusion criteria were: Arrhythmia, tidal volume <8 mL/kg, left ventricular ejection fraction<50%, right ventricular dysfunction, and heart rate/respiratory rate ratio <3.6. INTERVENTIONS: Fluid challenge with 500 mL of saline over 15 mins. MEASUREMENTS AND MAIN RESULTS: Stroke volume variations and cardiac output obtained with a pressure recording analytic method, pulse pressure variations, and cardiac output estimated by echocardiography were recorded before and after volume expansion. Patients were defined as responders if stroke volume obtained using echocardiography increased by ≥15% after volume expansion. Nineteen patients responded to the fluid challenge. Median [interquartile range, 25% to 75%] stroke volume variation values at baseline were not different in responders and nonresponders (10% [8-16] vs. 14% [12-16]), whereas pulse pressure variations were significantly higher in responders (17% [13-19] vs. 7% [5-10]; p < .0001). A 12.6% stroke volume variations threshold discriminated between responders and nonresponders with a sensitivity of 63% (95% confidence interval 38% to 84%) and a specificity of 69% (95% confidence interval 41% to 89%). A 10% pulse pressure variation threshold discriminated between responders and nonresponders with a sensitivity of 89% (95% confidence interval 67% to 99%) and a specificity of 88% (95% confidence interval 62% to 98%). The area under the receiver operating characteristic curves was different between pulse pressure variations (0.95; 95% confidence interval 0.82-0.99) and stroke volume variations (0.60; 95% confidence interval 0.43-0.76); p < .0001). Volume expansion-induced changes in cardiac output measured using echocardiography or pressure recording analytic method were not correlated (r = 0.14; p > .05) and the concordance rate of the direction of change in cardiac output was 60%. CONCLUSION: Stroke volume variations obtained with a pressure recording analytic method cannot predict fluid responsiveness in intensive care unit patients under mechanical ventilation. Cardiac output measured by this device is not able to track changes in cardiac output induced by volume expansion.

The ability of pulse pressure variations obtained with CNAP™ device to predict fluid responsiveness in the operating room.

BACKGROUND: Respiratory-induced pulse pressure variations obtained with an arterial line (ΔPP(ART)) indicate fluid responsiveness in mechanically ventilated patients. The Infinity® CNAP™ SmartPod® (Dräger Medical AG & Co. KG, Lübeck, Germany) provides noninvasive continuous beat-to-beat arterial blood pressure measurements and a near real-time pressure waveform. We hypothesized that respiratory-induced pulse pressure variations obtained with the CNAP system (ΔPP(CNAP)) predict fluid responsiveness as well as ΔPP(ART) predicts fluid responsiveness in mechanically ventilated patients during general anesthesia. METHODS: Thirty-five patients undergoing vascular surgery were studied after induction of general anesthesia. Stroke volume (SV) measured with the Vigileo™/FloTrac™ (Edwards Lifesciences, Irvine, CA), ΔPP(ART), and ΔPP(CNAP) were recorded before and after intravascular volume expansion (VE) (500 mL of 6% hydroxyethyl starch 130/0.4). Subjects were defined as responders if SV increased by ≥15% after VE. RESULTS: Twenty patients responded to VE and 15 did not. The correlation coefficient between ΔPP(ART) and ΔPP(CNAP) before VE was r = 0.90 (95% confidence interval [CI] = 0.84-0.96; P < 0.0001). Before VE, ΔPP(ART) and ΔPP(CNAP) were significantly higher in responders than in nonresponders (P < 0.0001). The values of ΔPP(ART) and ΔPP(CNAP) before VE were significantly correlated with the percent increase in SV induced by VE (respectively, r(2) = 0.50; P < 0.0001 and r(2) = 0.57; P < 0.0001). Before VE, a ΔPP(ART) >10% discriminated between responders and nonresponders with a sensitivity of 90% (95% CI = 69%-99%) and a specificity of 87% (95% CI = 60%-98%). The area under the receiver operating characteristic (ROC) curve was 0.957 ± 0.035 for ΔPP(ART). Before VE, a ΔPP(CNAP) >11% discriminated between responders and nonresponders with a sensitivity of 85% (95% CI = 62%-97%) and a specificity of 100% (95% CI = 78%-100%). The area under the ROC curve was 0.942 ± 0.040 for ΔPP(CNAP). There was no significant difference between the area under the ROC curve for ΔPP(ART) and ΔPP(CNAP). CONCLUSIONS: A value of ΔPP(CNAP) >11% has a sensitivity of at least 62% in predicting preload-dependent responders to VE in mechanically ventilated patients during general anesthesia.