Alterations in Skin Blood Flow at the Fingertip Are Related to Mortality in Patients With Circulatory Shock

Objectives: Skin blood flow is rapidly altered during circulatory shock and may remain altered despite apparent systemic hemodynamic stabilization. We evaluated whether changes in skin blood flow during circulatory shock were related to survival. Design: Prospective study. Setting: Thirty-five-bed medical-surgical university hospital department of intensive care. Subjects: Twenty healthy volunteers and 70 patients with circulatory shock (< 12 hr duration), defined as the need for vasopressors to maintain mean arterial pressure greater than or equal to 65 mm Hg and signs of altered tissue perfusion. Interventions: We assessed skin blood flow using skin laser Doppler on the fingertip for 3 minutes at basal temperature (SBF BT ) and at 37°C (SBF 37 ) (thermal challenge test) once in volunteers and at the time of inclusion and after 6, 24, 48, 72, and 96 hours in patients with shock. Capillary refill time and peripheral perfusion index were measured at the same time points on the contralateral hand. Measurements and Main Results: The thermal challenge response (ΔSBF/ΔT) was calculated using the following formula: (SBF 37 –SBF BT )/(37–basal temperature). Area under the receiver operating characteristic curves were calculated to evaluate variables predictive of ICU mortality. At inclusion, skin blood flow and ΔSBF/ΔT were lower in patients than in volunteers. Baseline skin blood flow (31 [17–113] vs 16 [9–32] arbitrary perfusion units; p = 0.01) and ΔSBF/ΔT (4.3 [1.7–10.9] vs 0.9 [0.4–2.9] arbitrary perfusion unit/s) were greater in survivors than in nonsurvivors. Capillary refill time was shorter in survivors than in nonsurvivors; peripheral perfusion index was similar in the two groups. ΔSBF/ΔT (area under the receiver operating characteristic curve 0.94 [0.88–0.99]) and SBF BT (area under the receiver operating characteristic curve 0.83 [0.73–0.93]) had the best predictive value for ICU mortality with cutoff values less than or equal to 1.25 arbitrary perfusion unit/°C (sensitivity 88%, specificity 89%) and less than or equal to 21 arbitrary perfusion unit (sensitivity 84%, specificity 81%), respectively. Conclusions: Alterations in fingertip skin blood flow can be evaluated using a laser Doppler thermal challenge technique in patients with circulatory shock and are directly related to outcome. These novel monitoring techniques could potentially be used to guide resuscitation.