An Overview of Quantitative Capillary Refill Time: Measurement and Application in Clinical Practice
Abstract
Capillary refill time (CRT) is a vital clinical parameter used for the evaluation of peripheral perfusion status in emergency departments and critical care settings. Commonly used manual measurements lack a true criterion standard and are based on visual inspection of fingertip color, leading to low inter-observer reliability. Recent advances in spectroscopic and imaging technologies have made CRT measurement quantitatively significant (Q-CRT), thus enhancing its reliability and accuracy. Light intensity transmitted through the fingertip correlates with blood volume and can be measured using a pulse oximetry sensor. The time required for the transmitted light intensity to return to 90% of the original value after pressure application is defined as Q-CRT. In addition, certain technologies can evaluate Q-CRT via analysis of reflected light in various areas of the peripheral surface. Like manual CRT, Q-CRT is influenced by several factors, including temperature, anatomical measurement sites, gender, and age. However, for Q-CRT, the influence of other confounding factors (light conditions, intensity of applied pressure, “naked eye” assessment) on the measurement outcome is reduced or eliminated. Q-CRT correlates with standardized manual CRT, but it systematically shows higher values. The initial investigations have indicated that Q-CRT could be used to predict sepsis and to assess postoperative outcomes following liver transplantation.