Capillary refill time (CRT) is a quick and simple clinical test used to assess the circulatory status and perfusion in patients. It involves measuring the time it takes for colour to return to a capillary bed after it has been compressed and then released. This test is commonly performed in emergency and critical care settings as part of a broader assessment of cardiovascular function.
How to Perform Capillary Refill Test
- Select the Site:
- The most common site is the nail bed of a finger or toe. Alternative sites include the forehead or sternum in cases where peripheral sites are not suitable (e.g., cold extremities).
2. Apply Pressure:
- Use your thumb or index finger to apply firm pressure to the selected site for about 5 seconds. This pressure should blanch (turn white) the skin, indicating that the blood has been pushed out of the capillaries.
3. Release Pressure:
- Quickly release the pressure and start timing the refill.
4. Observe and Time:
- Observe the time it takes for the colour to return to the blanched area. The normal capillary refill time is less than 2 seconds.
Interpreting Capillary Refill Time
- Normal CRT (< 2 seconds):
- Indicates adequate peripheral perfusion and circulatory status.
- Prolonged CRT (> 2 seconds):
- May indicate poor peripheral perfusion, which can be due to various causes, including:
- Hypovolaemia: Reduced blood volume due to bleeding, dehydration, or fluid loss.
- Shock: Conditions like septic shock, cardiogenic shock, or hypovolaemic shock.
- Peripheral Vascular Disease: Poor circulation due to narrowed or blocked blood vessels.
- Hypothermia: Reduced blood flow to extremities due to cold.
Factors Affecting Capillary Refill
Several factors can influence the accuracy and interpretation of capillary refill time:
- Environmental Temperature:
- Cold environments can prolong CRT even in healthy individuals due to vasoconstriction.
2. Age:
- In infants and young children, CRT may be slightly longer but still under 2 seconds.
- In elderly patients, CRT can be less reliable due to changes in skin elasticity and vascular function.
3. Skin Color and Thickness:
- Darker skin tones can make visual assessment more challenging.
- Thick or calloused skin can affect the observation.
4. Lighting Conditions:
- Poor lighting can affect the ability to accurately judge the return of color.
5. Pressure Application:
- Inconsistent pressure application can lead to variable results.
Clinical Significance
Capillary refill time is part of a comprehensive assessment and should not be used in isolation. It provides valuable information about the circulatory system but should be interpreted in conjunction with other signs and symptoms:
- Assessment of Shock:
- A prolonged CRT is a red flag in the assessment of shock. It suggests inadequate perfusion and the need for further evaluation and intervention.
2. Monitoring Response to Treatment:
- CRT can be used to monitor the effectiveness of interventions like fluid resuscitation in hypovolemic shock.
3. Pediatric Assessment:
- CRT is particularly useful in pediatric patients where other signs of shock (like blood pressure changes) may not be as apparent.
4. Emergency Situations:
- In emergency situations, CRT is a quick and non-invasive method to assess circulatory status and prioritize care.
Summary
Capillary refill time is a quick, simple, and non-invasive test to assess peripheral perfusion and circulatory status. While it provides valuable information, it should be interpreted in the context of the overall clinical picture and in conjunction with other assessment findings. Proper technique and consideration of influencing factors are crucial for accurate assessment.