An increase in skin blood flow induced by fluid challenge is associated with an increase in oxygen consumption in patients with circulatory shock

To investigate whether an increase in skin blood flow (SBF) after fluid challenge was associated with an increase in oxygen consumption (VO2) in patients with circulatory shock.We studied 62 patients with shock who required fluid challenge. Using laser Doppler, we measured finger SBF at basal temperature (SBFBT) and after a thermal challenge test (SBFTCT), before and after a fluid challenge (500 ml of Plasmalyte®). In fluid responders (i.e., increase in cardiac index ≥15%), VO2 responders (VO2R) were those with a ≥15% increase in VO2.Of the 62 patients, 33 were fluid responders and 16 of these were VO2R. At baseline, VO2R had lower SBFBT (21[14-52] vs 83[24-116] PU, p = 0.03) and SBFTCT (2.1[1.2-3.3] vs 4.4[2.2-5.6] PU/°C, p = 0.02) than VO2 non-responders (VO2NR); hemodynamic variables were not significantly different. The increase in SBFBT (∆SBFBT) after fluid challenge was greater in VO2R than in VO2NR (141[83-174] vs 57[17-150]%, p = 0.03). Areas under the curves for baseline SBFTCT (0.83 ± 0.07 [0.68-0.98]) and ∆SBFBT (0.90 ± 0.05 [0.75-1.0]) to predict ∆VO2 ≥ 15% were higher than for other variables.A lower baseline SBFTCT and a greater ∆SBFBT can identify patients in whom VO2 will increase after fluid challenge, suggesting an improvement in cellular metabolism.