Definition of capillary refill according to the eleventh edition of the Orange Book (AAOS Emergency care and transport of the sick and injured): A test that evaluates distal circulatory system function by squeezing (blanching) blood from an area such as a nail bed and watching the speed of it return after releasing the pressure.
It goes on to say "When evaluated in an uninjured limb, capillary refill time (CTR) may provide an indication of the pediatric patient's level of perfusion. It should be kept in mind, however, that especially in an adult patient, capillary refill can be affected by the patient's position, age, history as a smoker, history of medical problems such as diabetes, medications the patient is currently taking, and exposure to a cold environment (hypothermia) including frozen tissue (frostbite) and vasoconstriction (narrowing of a blood vessel)."