capillary filling time

Last edited 10/2019

Capillary filling time is used to assess dehydration, usually in infants.

Pressure is applied for five seconds to a pink area of skin at the extremities - for example the sole of the foot. This area should be held five centimetres above the heart. When the pressure is released the time taken for blood to return to the area of skin is measured.

Ordinarily the blood should return in two seconds or less. More time than this implies underperfusion of the limb, which, provided the limb is not cold, may be attributed to peripheral shutdown secondary to hypovolaemia.

Sometimes it is possible to use pressure to the skin on the sternum if the peripheries are cool from a cold environment.

A systematic review concerning the use of capillary refill time in children noted (1):

  • capillary refill time is a specific sign, indicating that it can be used as a 'red-flag': children with prolonged capillary refill time have a four-fold risk of dying compared to children with normal capillary refill time. The low sensitivity means that a normal capillary refill time should not reassure clinicians.

Some methods and interpretations of the use of capillary refill in children have been reviewed for example (2):

Method described Interpretation

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.

 Delay of only 2-3 s indicates moderate dehydration, and a measurement of more than 3 s occurs with severe fluid losses.
Check CRT at the kneecap or forearm. Normal CRT is less than 2-3 s.
It is most accurate in a fingernail depressed with gentle pressure for at least 3 s and under warm ambient conditions. Normal CRT for the paediatric patient is usually considered to be less than 2 s.
Skin perfusion may be assessed by the temperature of the skin or by CRT (the time required for color to return to the skin after pressure blanching that part of the skin is released). Normal CRT is 2 s or less; however, low environmental temperature may cause peripheral vasoconstriction and lengthening of capillary refill.
following cutaneous pressure on a digit held at the level of the heart or preferably on the center of the sternum for 5s, capillary refill should occur within 2s. A slower refill than this indicates poor skin perfusion

Capillary refill time in adults:

  • a study differentiated the cutoff values, based on age and gender, in healthy patients. The refill times identified as normal do not exceed 1.9 seconds for males and 2.9 for females aged 18 to 64 (3)
    • considering the practical difficulties related to decimal values, the authors have also suggested to consider as physiological a refill time of 2 and 3 seconds under 65 years of age, for males and females respectively,and 4 seconds in both genders for elderly persons (3)

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