Capillary Refill Test (CRT)

The Capillary Refill Test (CRT) is a quick and simple method used to assess blood flow to peripheral tissues. It is most commonly performed on the nail bed to evaluate circulation and identify possible dehydration or circulatory failure【1】. CRT provides insight into the efficiency of the vascular system, particularly in the hands and feet, which are furthest from the heart and more vulnerable to changes in blood supply【2】.

Alternative Names

CRT is also known as:

• Digital blood flow test

• Capillary refill time

• Capillary nail bed test【1】

Advantages and Limitations

Advantages:

• Simple and rapid bedside test requiring no equipment

• Provides immediate indication of circulatory status, especially in acute care

Limitations:

• Subjective; influenced by external factors such as temperature, lighting, and pressure applied

• Less accurate in patients with peripheral vascular disease or nail disorders

Procedure【3】

1. Remove obstructions– Take off rings and remove nail polish to ensure visibility of the nail bed.

2. Apply pressure– Press firmly on the nail bed until it turns white (blanching due to blood being pushed out).

3. Measure refill time– Upon release, measure the time it takes for the normal pink color to return. Normal refill is ≤ 3 seconds. A longer time suggests arterial insufficiency.

4. Compare sides– Always compare with the opposite hand or finger to detect abnormal findings.

Interpretation of Results

Normal results:

• CRT ≤ 2 seconds → indicates effective blood flow to the fingers; routinely used in acute patient assessment【4】.

• Immediate pink return after blanching → efficient tissue perfusion.

Abnormal results:

• CRT > 2 seconds → may indicate circulatory failure or early shock【5】.

Factors affecting CRT accuracy:

• Peripheral vascular disease

• Hypothermia or low ambient temperature

• Poor lighting conditions

• Advanced age

• Variability in applied pressure

• Observer differences (intra- and interrater reliability)【4】【5】

Integration into ABCDE Assessment

The Capillary Refill Test is part of the ABCDE approach, a systematic method used in emergency and critical care:

• A: Airway

• B: Breathing

• C: Circulation

• D: Disability (neurological status)

• E: Exposure

Within “C” (circulation), CRT is a key marker, but it must always be combined with other clinical parameters such as:

• Pulse rate and strength

• Blood pressure

• Level of consciousness

• Skin color, temperature, and texture

• Urine output

The ABCDE framework ensures early recognition of life-threatening conditions and rapid initiation of life-saving interventions【6】.

References

1. Capillary nail refill test. Available from: https://medlineplus.gov/ency/article/003394.htm (Accessed 24 October 2020)

2. Capillary nail refill test. Available from: http://pennstatehershey.adam.com/content.aspx?productid=117&pid=1&gid=003394 (last Accessed 25 October 2020)

3. David J. Magee. Orthopedic Physical Assessment. 6th edition. Elsevier. 2014.

4. Pickard A, Karlen W, Ansermino JM. Capillary refill time: is it still a useful clinical sign?. Anesthesia & Analgesia. 2011 Jul 1;113(1):120-3. 

5. How to measure capillary refill time in patients who are acutely ill. Available from: https://www.nursingtimes.net/clinical-archive/assessment-skills/how-to-measure-capillary-refill-time-in-patients-who-are-acutely-ill-20-07-2020/ (Accessed 24 October 2020)

6. The ABCDE Approach for Medical students. Available from: https://iem-student.org/2019/08/18/the-abcde-approach-for-a-medical-students/ ( Accessed 28 October 2020)

7. Paramedics Course -Capillary Refill Time - Australian Paramedical College. Paramedical College. Available from: https://youtu.be/wqaOwFI0ikI

8. Capillary Refill Test. Dr. Borst's Occupational Therapy Classroom. Available from: https://youtu.be/n--wFoZFklg