Capillary refill time (CRT) is a quick test that assesses blood flow through capillaries in peripheral tissues, such as those in your fingers or toes. It measures how efficiently blood returns to these tissues after being briefly squeezed out. This assessment offers insights into a person’s overall circulatory status and peripheral perfusion (the delivery of blood to the extremities).
How to Perform the Capillary Refill Test
To perform a capillary refill test, ensure the patient’s hand or foot is warm, as cold extremities can affect blood flow and alter results. Remove any rings or nail polish from the finger or toe being tested, as these can interfere with accurate observation. The test should be conducted in a well-lit area to clearly see color changes.
Apply firm, even pressure to the nail bed or the soft pad of the finger or toe until the area turns white. Maintain this pressure for about five seconds. Immediately after releasing the pressure, observe and time how long it takes for the natural pink color to return to the blanched area.
The return of color signifies that oxygen-rich blood is refilling the capillaries. For reliable results, test the finger pulp rather than the fingernail. Comparing the refill time to an unaffected digit or limb, if applicable, can also provide valuable context.
Interpreting Capillary Refill Times
A normal capillary refill time indicates good blood flow and proper tissue perfusion. For healthy adults, a refill time of less than two seconds is considered normal. In children, a normal refill time is less than two seconds when measured on the hands.
A prolonged capillary refill time, greater than two or three seconds, suggests decreased peripheral perfusion. This can be an early sign of conditions like shock, where the body’s organs are not receiving enough oxygen, or dehydration, which reduces blood volume. For instance, a delay of two to three seconds might indicate moderate dehydration, while more than three seconds could point to severe fluid loss.
In critically ill individuals, a prolonged CRT can be a sign of compromised circulation and may prompt immediate medical attention. For example, in cases of significant blood loss, CRT may be notably prolonged in severe hemorrhagic shock. While a normal CRT is reassuring, it does not completely rule out serious underlying issues, and repeated measurements are often beneficial.
Factors Influencing Capillary Refill Readings
Several non-pathological factors can influence capillary refill times, causing readings to appear longer without a severe medical issue. Environmental temperature is a factor; cold hands or feet can slow blood flow and prolong the refill time due to peripheral vasoconstriction, where blood vessels narrow. Warming the extremity before testing can help mitigate this effect.
Age also plays a role, with capillary refill times longer in older adults compared to younger individuals. For example, studies have shown that the upper limit of normal for elderly individuals might extend to 4.5 seconds. The amount of pressure applied during the test and the specific site of measurement (e.g., finger pulp versus nail bed) can also affect the results. Poor lighting can make it difficult to accurately observe the return of color, potentially leading to inaccurate readings.