OBJECTIVE: This study was performed to investigate the effect of vasopressor therapy on systolic pressure variation (SPV) and pulse pressure variation (PPV) compared to experimentally measured left ventricular stroke volume variation (SVV). DESIGN AND SETTING: Prospective study in a university laboratory. SUBJECTS: Twelve anesthetized and mechanically ventilated pigs. INTERVENTIONS: Increase in mean arterial pressure (by 100%) using phenylephrine and decrease (by 38%) using adenosine. MEASUREMENTS AND RESULTS: SPV and PPV were calculated and compared to SVV derived from aortic blood flow measurements. SPV was significantly affected by changes in arterial pressure [4.6% (1.5) vs. 6.3% (2.1), p <0.05, increased vs. decreased arterial pressure], whereas PPV did not change during modifications of arterial pressure. During baseline conditions and decreased afterload, correlation with SVV was good both for SPV (r =0.892 and r = 0.859, respectively) and for PPV (r = 0.870 and r = 0.871, respectively) (all p <0.001). Correlation with SVV was only moderate during increased arterial pressure (r = 0.683 for SPV and r = 0.732 for PPV, p <0.05). CONCLUSION: For guiding fluid therapy in patients under vasopressor support, PPV seems superior to SPV.
