Photoplethysmographic assessment of microcirculation and vascular reactivity in septic patientsy: Pilot study

INTRODUCTION. Clinical and experimental evidence indicates that microcirculatorydysfunction contributes to organ failure and mortality in sepsis but its non invasive assessmentat the bedside is difficult.OBJECTIVES. The purpose of this study was to evaluate utility of photoplethysmographic(PPG) assessment of microcirculatory perfusion in patients with sepsis, compare early microcirculatoryindices in sepsis survivors versus nonsurvivors, and describe patient variablesthat affect PPG measurements.METHODS. Prospective observational study. We studied 10 consecutive general ICUpatients (age 65 +/- 14 years) within 24 h of admission and 6 healthy volunteers (age47 +/- 27 years). Severity of sepsis was assessed with APACHE II score (15 +/- 7), SequentialOrganFailure Assessment (SOFA) score (6 +/- 4) and sepsis severity category (SIRS n = 3,severe sepsis n = 2 and septic shock n = 5). After 1 h observation to ensure that hemodynamicshave stabilized, mean arterial pressure (MAP), age and sepsis severity were recorded.3 min PPG signal recording was done with an originally designed photoplethysmograph at restand after 3 min of induced forearm ischemia. Outcomes were defined as development ofmultiple organ failure within 48 h and 28 day mortality.RESULTS. Of the 10 ICU patients 6 developed multiple organ failure and 3 died. The restingPPG pulsatile component mean amplitude decreased in groups from healthy to septic shock(healthy 18.7 +/- 5.2, SIRS 19.0 +/- 4.0, severe sepsis 16.3 +/- 2.7, septic shock 11.1 +/- 5.0arbitrary units) but the difference was only significant between septic shock and healthy group(p = 0.03), the median slope of recovery after ischemia was lower in septic non survivors (-0.53, IQ-1.97 to-0.30) versus survivors (-0.13, IQ-0.36 to 2.04), p = 0.04, with nodifference between other groups. Using linear regression PPG pulsatile component amplitudeof septic patients correlated well with survival, age and MAP (r = 0.88, p = 0.02). In healthypatients the slope of recovery after ischemia was proportional to resting amplitude, but in septicpatients direct relationship was lost and there was a weak correlation with outcome, but not ageorMAP(r = 0.68, p = 0.09). No correlation of amplitude or slope of recovery was found withmaximum SOFA score.CONCLUSIONS. Photplethysmographic microcirculatory indices vary between patients indifferent sepsis categories but are also influenced by age and MAP. Slope of postischemicrecovery depends on resting amplitude but in the subgroup of patients with severe sepsis couldpredict poor outcome regardless of resting amplitude, age or MAP. Larger study is needed toconfirm this finding.