Noninvasive monitoring of peripheral perfusion with physical examination and the peripheral flow index correlates with dynamic near-infrared spectroscopy measurements in patients with septic shock

Introduction

Peripheral blood flow can be markedly impaired in septic shock. Bedside assessment of this derangement has not yet been incorporated into routine clinical practice. We hypothesize that noninvasive monitoring of peripheral perfusion with physical examination and the peripheral flow index (PFI) derived from the pulse oximetry signal can reflect sepsis-induced microcirculation alteration as measured by near-infrared spectroscopy (NIRS) in patients with septic shock.

Methods

NIRS (InSpectra) was used to quantify sepsis-induced circulatory alterations by calculating the increase rate of tissue oxygen saturation (slope-StO₂) in a standard hyperaemia test (3 min arterial occlusion followed by rapid reperfusion). The increase rate of the PFI signal (slope-PFI) following the occlusion was compared with slope-StO₂. We performed a physical examination of the extremities before arterial occlusion, and abnormal peripheral perfusion was defined as an increase in the capillary refill time (>4.5 s). The measurements were registered at admission after hemodynamic stability was obtained. We performed regression analysis to study the effect of abnormal peripheral perfusion on slope-StO₂ and to study the relationship between slope-PFI and slope-StO₂.

Results

We prospectively studied 20 consecutive septic shock patients (age 54 ± 15 years; 16 males and four females). The admission diagnoses were 10 pneumonia, seven abdominal sepsis, two meningitis and one urosepsis. The slope-StO₂ was significantly different between patients with normal peripheral perfusion (n = 8; mean = 218%/min; 95% CI = 141–339) and abnormal peripheral perfusion (n = 12; mean = 92%/min; 95% CI = 68–123). Regression analysis showed that the slope-StO₂ is 138%/min lower in patients with abnormal than in patients with normal peripheral perfusion, controlled for the possible effects of central temperature (r² = 0.42; P < 0.01). We found a strong association between slope-PFI and slope-StO₂ (Pearson correlation = 0.84; P < 0.001). The effect of slope-StO₂ on the slope-PFI was an increase in slope-StO₂ of 90%/min per 1 unit/min slope-PFI (r² = 0.65; P < 0.001).

Conclusion

Peripheral vascular reactivity in patients with septic shock, as measured by changes in StO₂ following an ischemia-reperfusion challenge, is related to the clinical assessment with the capillary refill time and PFI.