Kinetics of capillary refill time after fluid challenge

Background: Capillary refill time (CRT) is a valuable tool for triage and to guide resuscitation. However, little is known about CRT kinetics after fluid infusion.

Methods: We conducted a prospective observational study in a tertiary teaching hospital. First, we analyzed the intra-observer variability of CRT. Next, we monitored fingertip CRT in sepsis patients during volume expansion within the first 24 h of ICU admission. Fingertip CRT was measured every 2 min during 30 min following crystalloid infusion (500 mL over 15 min).

Results: First, the accuracy of repetitive fingertip CRT measurements was evaluated on 40 critically ill patients. Reproducibility was excellent, with an intra-class correlation coefficient of 99.5% (CI 95% [99.3, 99.8]). A CRT variation larger than 0.2 s was considered as significant. Next, variations of CRT during volume expansion were evaluated on 29 septic patients; median SOFA score was 7 [5-9], median SAPS II was 57 [45-72], and ICU mortality rate was 24%. Twenty-three patients were responders as defined by a CRT decrease > 0.2 s at 30 min after volume expansion, and 6 were non-responders. Among responders, we observed that fingertip CRT quickly improved with a significant decrease at 6-8 min after start of crystalloid infusion, the maximal improvement being observed after 10-12 min (-0.7 [-0.3;-0.9] s) and maintained at 30 min. CRT variations significantly correlated with baseline CRT measurements (R = 0.39, P = 0.05).

Conclusions: CRT quickly improved during volume expansion with a significant decrease 6-8 min after start of fluid infusion and a maximal drop at 10-12 min.