The peripheral perfusion index (PI), as a real-time bedside indicator of peripheral tissue perfusion, may be useful for determining mean arterial pressure (MAP) after early resuscitation of septic shock patients. The aim of this study was to explore the response of PI to norepinephrine (NE)-induced changes in MAP.
Twenty septic shock patients with pulse-induced contour cardiac output catheter, who had usual MAP under NE infusion after early resuscitation, were enrolled in this prospective, open-label study. Three MAP levels (usual MAP -10 mmHg, usual MAP, and usual MAP +10 mmHg) were obtained by NE titration, and the corresponding global hemodynamic parameters and PI were recorded. The general linear model with repeated measures was used for analysis of variance of related parameters at three MAP levels.
With increasing NE infusion, significant changes were found in MAP (F = 502.46, P < 0.001) and central venous pressure (F = 27.45, P < 0.001) during NE titration. However, there was not a significant and consistent change in continuous cardiac output (CO) (F = 0.41, P = 0.720) and PI (F = 0.73, P = 0.482) at different MAP levels. Of the 20 patients enrolled, seven reached the maximum PI value at usual MAP -10 mmHg, three reached the maximum PI value at usual MAP, and ten reached the maximum PI value at usual MAP +10 mmHg. The change in PI was not significantly correlated with the change in CO (r = 0.260, P = 0.269) from usual MAP -10 mmHg to usual MAP. There was also no significant correlation between the change in PI and change in CO (r = 0.084, P = 0.726) from usual MAP to usual MAP +10 mmHg.
Differing MAP levels by NE infusion induced diverse PI responses in septic shock patients, and these PI responses may be independent of the change in CO. PI may have potential applications for MAP optimization based on changes in peripheral tissue perfusion.