Capillary refill time (CRT) is defined as “time required for return of color after application of blanching pressure to a distal capillary bed”.
There is limited data on the actual method to do CRT and there is no consensus on the correct practice. It is highly subjective and observer dependent, and it may vary with ambient or skin temperature, age, site of measurement, duration and amount of pressure, none of which have been standardized.
The test should be performed on the fingertip or nail bed in a warm room. Light pressure is applied to blanch the fingernail bed, and the time is measured until color returns.
Capillary refill or the return of "pink" in the nail bed ooccurs within 2-3 seconds for normal skin perfusion.
Capillary refill or the return of "pink" in the nail bed is delayed greater than 3 seconds for poor skin perfusion.
