# Device-measured capillary refill time identifies critically ill cases in the emergency department

## TL;DR

A device that measures capillary refill time can help identify critically ill patients in emergency departments.

## Contribution

This study shows device-measured capillary refill time is a useful indicator of critical illness in the ED.

## Key findings

- Device-measured CRT was significantly prolonged in patients with high APACHE II scores.
- CRT had a higher predictive accuracy than lactate for critical illness.
- CRT correlated weakly with lactate and showed a trend with SOFA scores.

## Abstract

Capillary refill time (CRT) is a rapid, non-invasive indicator of tissue hypoperfusion and is associated with severity in critically ill patients. However, its clinical utility in the emergency department (ED) remains unclear, particularly when assessed using a quantitative device. We conducted a prospective, single-center observational study to evaluate whether device-measured CRT upon ED arrival is associated with clinical severity. One hundred nineteen adult patients transported to the ED by ambulance between August 2023 and October 2024 were enrolled. CRT was measured using the quantitative CRT device, and the average of three readings was analyzed. Critical illness was defined as an acute physiology and chronic health evaluation (APACHE) II score of ≥ 25. Among the participants, 27 (23%) had high APACHE II scores. CRT was significantly prolonged in this group (2.56 [1.84–3.36] vs. 1.67 [1.18–2.48] seconds, p = 0.0012) and showed a higher area under the receiver operating characteristic curve than lactate (AUC: CRT, 0.702; lactate, 0.669). CRT also demonstrated a weak but significant positive correlation with lactate levels (rs = 0.24, p = 0.0087) as well as a trend toward significant correlation with sequential organ failure assessment (SOFA) score (rs = 0.18, p = 0.051). These findings suggest that device-measured CRT is associated with clinical severity and may aid in the early identification of critically ill patients in emergency settings.

The online version contains supplementary material available at 10.1038/s41598-025-34672-2.