The capillary refill test, also called capillary refill time (CRT) or nail blanch test, is a technique that nurses use to assess for peripheral perfusion or dehydration in patients.
How is the Capillary Refill Test Performed?
Nurses typically perform the capillary refill test by pressing on the nail plate or the pad of a digit for around 5-10 seconds, causing the nail bed (or pad of digit) to lighten in color as the blood is expelled.
The nurse then releases the digit and observes the number of seconds it takes for the tissue to regain its natural color as blood flow resumes.
Note: The capillary refill test may sometimes be performed on the sternum or forehead in some patient populations, such as newborns .
Normal vs Abnormal Capillary Refill Time
If the blood flow returns to the tissue within 2 seconds (depending on your facility’s protocols), it is considered a normal finding, but longer than 2 seconds could be considered abnormal and should be reported immediately.
Note: Some guidelines or studies suggest that a capillary refill of up to three seconds could be normal in some patient populations , so always refer to your facility’s protocols for details.
What Causes an Abnormal Capillary Refill Time?
A capillary refill test of longer than 2 or 3 seconds could indicate that the patient is experiencing poor peripheral perfusion (blood flow to the extremities) or even dehydration.
Some examples of factors that can cause poor peripheral perfusion include the following:
- Decreased cardiac output: This may be due to shock, heart failure, anemia, and other similar conditions
- Bone fractures: compartment syndrome may develop during a fracture, which can restrict blood flow in the affected limb
- Cast care and placement: If a cast is placed on a broken limb, capillary refill time is often assessed to ensure that proper blood flow is reaching the extremity and that the cast is not too tight
- Peripheral vascular disease: In peripheral vascular disease, the narrowing of vessels can reduce tissue perfusion
- Raynaud’s disease: this can cause vessels to spasm and/or narrow in extremities that are exposed to cold, which reduces blood flow
In addition, some of the factors below may affect the reliability of the capillary refill test or lead to longer than normal capillary refill time:
- Colder temperatures (either the patient’s body or room temperature)
- Edema (swelling)
- Old age
How to Perform a Capillary Refill Test on a Fingernail
Here are some tips to perform the capillary refill test on a patient’s fingernail or pad of finger.
Note: This information is for educational purposes only. Before performing any nursing skills or assessments, it is important to verify the latest protocols for your facility, as nursing skills and assessment criteria may change over time.
1. Perform hand hygiene
2. Greet the patient, explain the procedure, and obtain consent.
3. Choose a digit without nail polish and anything that could restrict blood flow to the area, such as jewelry or a watch. If those items are present, you can either remove them or use an alternate site such as the pad (pulp) of the digit or another digit instead.
4. Position the patient’s hand at or above heart level, and observe the patient’s natural skin color at the nail bed (or finger pad) for reference.
5. Press on the nail plate (or pad of the finger) firmly for 5-10 seconds to expel blood from the tissue.
6. Release the fingernail (or pad of finger), and observe the number of seconds it takes for the tissue to return to its normal color, which indicates perfusion of the tissue. For accurate results, use a digital watch with a start/stop function to count the seconds as you observe the digit. Next, compare the results to a digit from another limb, if necessary.
7. If the skin’s natural color returns within 2-3 seconds (depending on your facility’s protocol), the capillary refill test is considered normal. If the capillary refill time is longer than 2-3 seconds, it could suggest poor tissue perfusion or dehydration, and these findings should be reported immediately. Note: Again, refer to your facility’s protocols to determine the appropriate guidelines for normal vs. abnormal refill time, as guidelines may vary for different facilities or different patient populations.
8. Perform hand hygiene, and document the capillary refill time (in seconds), including the location of the assessment (example: capillary refill was 2 seconds on fingernail of right index finger) and other necessary information, per your facility’s protocol.
- Strozik, K. S., Pieper, C. H., & Roller, J. (1997). Capillary refilling time in newborn babies: normal values. Archives of disease in childhood. Fetal and neonatal edition, 76(3), F193–F196. https://doi.org/10.1136/fn.76.3.f193