Assessing Fluid Responsiveness by the Systolic Pressure Variation in Mechanically Ventilated Patients

Background Heart-lung interactions are used to evaluate fluid responsiveness in mechanically ventilated patients, but these indices may be influenced by ventilatory conditions. The authors evaluated the impact of respiratory rate (RR) on indices of fluid responsiveness in mechanically ventilated patients, hypothesizing that pulse pressure variation and respiratory variation in aortic flow would decrease at high RRs. Methods In 17 hypovolemic patients, thermodilution cardiac output and indices of fluid responsiveness were measured at a low RR (14-16 breaths/min) and at the highest RR (30 or 40 breaths/min) achievable without altering tidal volume or inspiratory/expiratory ratio. Results An increase in RR was accompanied by a decrease in pulse pressure variation from 21% (18-31%) to 4% (0-6%) (P < 0.01) and in respiratory variation in aortic flow from 23% (18-28%) to 6% (5-8%) (P < 0.01), whereas respiratory variations in superior vena cava diameter (caval index) were unaltered, i.e., from 38% (27-43%) to 32% (22-39%), P = not significant. Cardiac index was not affected by the changes in RR but did increase after fluids. Pulse pressure variation became negligible when the ratio between heart rate and RR decreased below 3.6. Conclusions Respiratory variations in stroke volume and its derivates are affected by RR, but caval index was unaffected. This suggests that right and left indices of ventricular preload variation are dissociated. At high RRs, the ability to predict the response to fluids of stroke volume variations and its derivate may be limited, whereas caval index can still be used.

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Pulse pressure variation and systolic pressure variation in mechanically ventilated children

Paediatrica Indonesiana ◽

10.14238/pi51.1.2011.34-40 ◽

2011 ◽

Vol 51 (1) ◽

pp. 34

Author(s):

Johnny Nurman ◽

Antonius H. Pudjiadi ◽

Arwin A. P. Akib

Keyword(s):

Cardiac Index ◽

Pulse Pressure ◽

Pulse Pressure Variation ◽

Systolic Pressure ◽

Pressure Variation ◽

Arterial Line ◽

Mechanically Ventilated ◽

Systolic Pressure Variation ◽

Bivariate Correlation ◽

Ventilated Patients

Background In mechanically ventilated patients, changes in breathing patterns may affect the preload, causing stroke volume fluctuation. Pulse pressure variation (PPV) and systolic pressure variation (SPV) are dynamic means of the hemodynamic monitoring in ventilated patients. No study on PPV and SPY in children has been reported to date.Objective To study changes in PPV and SPY values in mechanically ventilated children.Method A descriptive cross􀁏sectional study was done at the Pediatric Critical Care Unit (PICU), Cipto Mangunkusumo Hospital, Jakarta. Subjects were mechanically ventilated children aged > 12 months. Echocardiography was performed in all patients to determine the cardiac index. Arterial pressure was measured by connecting an arterial line to a vital signs monitor. PPV and SPV were calculated using the standard formulas. Bivariate correlation tests were performed between cardiac index and PPV and between cardiac index and SPV. Receiver operator characteristic (ROC) curve analysis was done to determine the optimum PPV and SPV cut-off points to predict normal cardiac index (2:3.5 L/minute/m2).Results Eighteen patients were enrolled in the study, yielding 48 measurements. Mean cardiac index was 2.9 (SD 1-2.6) L/minute/m2. Median PPV was 18.9 (range 4.1-45.5)% and SPV was 12.1 (range 3.8- 18.9)%. We found strong negative correlations between PPY and cardiac index (r= ; p = ) and SPY and cardiac index (r= ; p = ). To predict nonnal cardiac index, the optimum cut-off point was 11.4% for PPV (100% sensitivity, 100% specificity) and 9.45% for SPV (91.7% sensitivity, 100% specificity).Conclusion In mechanically ventilated children, cardiac index is negatively correlated with PPV and SPV.

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