Relation between respiratory changes in arterial pulse pressure and fluid responsiveness in septic patients with acute circulatory failure

In mechanically ventilated patients with acute circulatory failure related to sepsis, we investigated whether the respiratory changes in arterial pressure could be related to the effects of volume expansion (VE) on cardiac index (CI). Forty patients instrumented with indwelling systemic and pulmonary artery catheters were studied before and after VE. Maximal and minimal values of pulse pressure (Pp(max) and Pp(min)) and systolic pressure (Ps(max) and Ps(min)) were determined over one respiratory cycle. The respiratory changes in pulse pressure (ΔPp) were calculated as the difference between Pp(max) and Pp(min) divided by the mean of the two values and were expressed as a percentage. The respiratory changes in systolic pressure (ΔPs) were calculated using a similar formula. The VE-induced increase in CI was ≥ 15% in 16 patients (responders) and < 15% in 24 patients (nonresponders). Before VE, ΔPp (24 ± 9 versus 7 ± 3%, p < 0.001) and ΔPs (15 ± 5 versus 6 ± 3%, p < 0.001) were higher in responders than in nonresponders. Receiver operating characteristic (ROC) curves analysis showed that ΔPp was a more accurate indicator of fluid responsiveness than ΔPs. Before VE, a ΔPp value of 13% allowed discrimination between responders and nonresponders with a sensitivity of 94% and a specificity of 96%. VE-induced changes in CI closely correlated with ΔPp before volume expansion (r2 = 0.85, p < 0.001). VE decreased ΔPp from 14 ± 10 to 7 ± 5% (p < 0.001) and VE-induced changes in ΔPp correlated with VE-induced changes in CI (r2 = 0.72, p < 0.001). It was concluded that in mechanically ventilated patients with acute circulatory failure related to sepsis, analysis of ΔPp is a simple method for predicting and assessing the hemodynamic effects of VE, and that ΔPp is a more reliable indicator of fluid responsiveness than ΔPs