Capillary Refill Test & Time

The capillary refill test provides gross information on the quality and quantity of blood flow to the extremities.

The capillary refill time in the nail beds of the toes and fingers can provide some clinical evidence as to the status of the cardiovascular and respiratory systems. If blood and/ or oxygen supply to the extremities is diminished, the nail beds often become cyanotic. Capillary refill should be assessed in digits that have a unique blood supply.

See Also: 

• Allen’s Test
• Homan’s Sign

How do you perform the Capillary Refill Test?

The patient is sitting or lying supine, while the examiner is in front of or beside the patient. The extremity is placed in a gravity neutral position (horizontal).

Observe the color of the nail bed:

• Squeeze the fingernail so that the nail bed turns white or a lighter shade and hold for 5 seconds.
• Release the pressure and note the speed of the capillary refill time as indicated by the baseline color returning to the nail bed.

Repeat using the other fingers or toes and then perform on the opposite extremity.

What does capillary refill time indicate?

Normal capillary refill time is usually 3 seconds or less.

A positive test is when markedly slow or absent return of the nail’s natural color for more than 3 seconds.

A delayed capillary refill time is a sign of:

1. Unilateral positive test: Occlusion of an artery or arteriole supplying the finger.
2. Bilateral positive test: Possible systemic cardiovascular compromise or disease.

Test Reliability

No standardized execution or evidence demonstrates the area of the digit giving the most accurate capillary refill time (CRT).

But a study investigated the reliability and validity of capillary refill time, and the relative merits of areas where the test could be performed, found that the capillary Refill Test used at appropriate areas is reliable. The most dependable site is the finger pulp, and the proposed cutoff for capillary refill time is 3s.

Notes

Clinical examination of the vascular system provides a gross assessment of the blood flow to and from the extremities. Decreased arterial blood flow can produce pain by depriving the tissues of oxygen; inhibition or failure of the vascular return network can produce pain secondary to edema. Symptoms often worsen during and following activity. It is often useful to have the patient repeat the motions and/or positions that provoke the symptoms.

Adequate arterial supply to the extremity is grossly determined by establishing the presence of a pulse:

• Lower extremity pulses are assessed at the femoral, posterior tibial, and dorsal pedal arteries.
• In the upper extremity, the brachial, radial, and ulnar arteries are frequently used.
• The carotid artery (supplying the brain) is used to determine a systemic pulse.

Unexplained vascular symptoms such as discoloration (cyanosis or pallor), swelling, or lack of capillary refill can be indicative of other cardiovascular or metabolic conditions such as diabetes. The insidious onset of vascular symptoms warrants referral for further medical examination.

References

1. Perlowski AA, Jaff MR. Vascular disorders in athletes. Vasc Med. 2010 Dec;15(6):469-79. doi: 10.1177/1358863X10382944. Epub 2010 Sep 30. PMID: 20884798.
2. Monteerarat, Y., Limthongthang, R., Laohaprasitiporn, P. et al. Reliability of capillary refill time for evaluation of tissue perfusion in simulated vascular occluded limbs. Eur J Trauma Emerg Surg 48, 1231–1237 (2022). https://doi.org/10.1007/s00068-020-01594-9