BLUF: “Normal” values vary by age, gender, temperature (both environmental and casualty’s), and lighting conditions. Different providers will see different durations of refill time. With all these adjustments and limitations of how normal is defined, as well as no standard guidelines on how CFT is to be measured1 one must question the actual utility of this technique.
Capillary refill time (CRT) is the concept that if you press firmly on either the fingernail bed or fingertip pulp and hold it for 5 to 10 seconds, causing it to “blanch” the time it takes for “normal” color to return to the compressed finger reflects the individual’s tissue perfusion. Theoretically, poor tissue perfusion secondary to dehydration or shock should result in a longer time until normal color returns.
This technique was first advocated as an easy way to assess a casualty’s circulatory status in 1947. Beecher’s technique was to compress the finger or toenail bed for ten seconds and release. The capillary refill time was the duration in seconds it took until normal color returned. Beecher divided refill time into three categories: normal, “definite slowing”, or “very sluggish.” He felt this suggested either no, “slight to moderate,” or “severe” shock, respectively.2
CRT became common teaching in evaluating trauma patients during the 1980s, with normal defined as less than two seconds. This value was suggested based on the personal experience of those proposing it, not any medical or scientific literature.
Multiple factors are described as lengthening the normal capillary refill time, including skin pigmentation, age of the casualty, medications, gender, ambient environmental temperature, the casualty’s body temperature, nail polish, and ambient lighting conditions. Additionally, two observers might identify the refill time differently on the same casualty.
For this technique to be useful, we would have to settle on a standardized method and, additionally, what values constitute normal. Even formal medical studies frequently use different “blanch” durations and either the fingernail bed or fingertip pulp.3
The largest study I’m aware of was 1000 healthy Australian adult volunteers who had their CRT measured by a single observer. Their index finger was “blanched” for 5 seconds. CRT was time until the return of normal color on a stopwatch. There was no mention of whether they looked at the color return of the nailbed or fingertip pulp. The volunteers’ age ranged from 18 to 89 years old. CRT ranged from 0.8 to 6.1 seconds. 95% of the volunteers had CRT in less than 3.5 seconds.
The researchers found that on average, CRT was 7% lower in men than women, increased by 3.3% with each decade of life, increased 5% with each 1-degree Celsius decrease in body temperature, and decreased by 1.2% with each degree Celsius the environmental temperature increased. 21% of their volunteers were on cardiac medications (defined as beta-blockers and anti-hypertensives). Interestingly, despite the widely held assumption cardiac medications would affect CFT, they did not find that to be the case.4
Schriger, et all studied 304 healthy individuals from 2 weeks to 95 years old and determined normal CRT was under 2 seconds for children and adult males, 2.9 seconds for adult women, and 4.5 seconds for the elderly.3
A study of 32 well-hydrated children aged one month to 12 years old had their CRT measured in both a warm room (25.7C) and a cool room (19.4C). Observed CRT increased from less than 1 second in the warm room to nearly 2.5 seconds in the cool room. 100% of the children were felt to have a normal CRT in the warm room, but only 31% in the cool room. Some of the children had evaluations by three different observers who only agreed with each other 70% of the time.7
An emergency department study of “stable” adults in Australia used both a doctor and nurse to evaluate the CRT in 209 patients. They were blinded to each other’s values. To better simulate actual real-world conditions, they didn’t use a stopwatch but rather estimated the CRT. The CRT duration varied between the doctor and nurse plus or minus nearly 2 seconds (95% confidence interval). This means their values were within just about two seconds of each other, but individual values could range from nearly zero to 4 seconds. This is a huge range and big disparity between them, which in turn makes all the values suspect. This result led the authors to flatly title their article “Measuring capillary refill time is useless.”8
One of the most operationally useful studies of CRT was conducted at an EMS seminar where 309 EMS professionals were asked to evaluate CRT on a partner both in daylight and streetlight/moonlight. 94.2% were felt to have a normal CRT in daylight, but CRT was undetectable in 66.7% in a darker environment.9
1McGuire D, Gotlib A, King J. Capillary Refill Time. 2021 Apr 22. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan
2Beecher HK, Simeone FA, et al. The internal state of the severely wounded man on entry to the most forward hospital. Surgery. 1947 Oct;22(4):672-711.
3Schriger DL, Baraff L. Defining normal capillary refill: variation with age, sex, and temperature. Ann Emerg Med. 1988 Sep;17(9):932-5.
4Anderson B, Kelly AM, Kerr D, Clooney M, Jolley D. Impact of patient and environmental factors on capillary refill time in adults. Am J Emerg Med. 2008 Jan;26(1):62-5.
5Schriger DL, Baraff L. Defining normal capillary refill: variation with age, sex, and temperature. Ann Emerg Med. 1988 Sep;17(9):932-5.
6Anderson B, Kelly AM, Kerr D, Clooney M, Jolley D. Impact of patient and environmental factors on capillary refill time in adults. Am J Emerg Med. 2008 Jan;26(1):62-5.
7Gorelick MH, Shaw KN, Baker MD. Effect of ambient temperature on capillary refill in healthy children. Pediatrics. 1993 Nov;92(5):699-702.
8 Watson A, Kelly AM. Measuring the capillary refill time is useless. Emerg Med Hong Kong, 1993;5:90-93
9Brown LH, Prasad NH, Whitley TW. Adverse lighting condition effects on the assessment of capillary refill. Am J Emerg Med. 1994 Jan;12(1):46-7.