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Capillary refill — is it a useful predictor of hypovolemic states?
ORIGINAL CONTRIBUTION capillary refill, hypovolemia
C a p i l l a r y Refill -- Is It a U s e f u l P r e d i c t o r of Hypovolemic States? Study objectives: To evaluate whether the capillary refill test can correctly differentiate between hypovolemic and euvolemic emergency department patients. Design: A prospective, nonrandomized, nonblinded time series. Setting: The orthostatic and hypotensive patients were seen in a university hospital ED with 44,000 visits per year. Blood donors were studied in the hospital's blood donor center. Type of participants: Thirty-two adult ED patients who presented with a history suggestive of hypovolemia and either abnormal orthostatic vital signs (19) or frank hypotension (I3), and 47 volunteer blood donors who ranged in age from 19 to 83 participated. Interventions: Capillary refill was measured before rehydration in the ED subjects and, in the donor group, before and after a 450-mL blood donation. Measurements: Sensitivity, specificity, accuracy, and positive and negative predictive values were calculated. Analyses were stratified by age, sex, and study group. Main results: For the blood donor group, mean capillary refill time before donation was 1.4 seconds and after donation was 1.1 seconds. Mean capillary refill time for the orthostatic group was 1.9 seconds and for the hypotensive group was 2.8 seconds. When scored with age-sex specific upper limits of normal, the sensitivity of capillary refill in identifying hypovolemic patients was 6% for the 450-mL blood loss group, 26% for the orthostatic group, and 46% for the hypotensive group. The accuracy of capillary refill in a patient with a 50% prior probability of hypovoIemia is 64%. Orthostatic vital signs were found to be more sensitive and specific than capillary refill in detecting the 450-mL blood loss. Conclusion: Capillary refill does not appear to be a useful test for detecting mild-to-moderate hypovolemia in adults. [Schriger DL, Baraff LJ: Capillary refill - Is it a useful predictor of hypovolemic states? Ann Emerg Med June 1991;20:601-605.]
David L Schriger, MD, MPH* Larry J Baraff, MD, FACEPt Los Angeles, California From the Departments of Medicine* and Pediatrics,t UCLA School of Medicine and the UCLA Emergency Medicine Center, Los Angeles, California. Received for publication November 20, 1989. Revisions received July 23, and November 26, 1990. Accepted for publication December 14, 1990. Presented at the 2nd International Conference on Emergency Medicine in Brisbane, Australia, October 1988. Address for reprints: David L Schriger, MD, MPH, UCLA Emergency Medicine Center, 924 Westwood Boulevard, Suite 300, Los Angeles, California 90024-2924.
INTRODUCTION In theory, capillary refill is an ideal clinical test. It is noninvasive, costs nothing, takes little time to perform, and might provide valuable information regarding the status of a patient's blood volume and circulatory function. It is, therefore, unfortunate that it was introduced into clinical practice as part of the Trauma Score, the basic trauma life support {BTLS) course, and the advanced trauma life support (ATLS) course without any attempts at experimental validationA -3 These scores and courses initially recommended a two-second upper limit of normal for capillary refill. We have previously reported that the capillary refill of typical citizens varies with age, sex, and temperature. 4 In a sample of 100 child, 104 adult, and 100 elderly volunteers, we have shown that application of the twosecond upper limit of normal results in a specificity of 96% for the children, 95% for adult males, 86% for adult females, and 71% for the elderly. To achieve a 95% specificity for the adult females the upper limit of normal would need to be raised to three seconds, and a 95% specificity for the elderly would require an upper limit of normal of 4.5 seconds. Capillary refill also varies with temperature. 4 A one-minute immersion
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of the hand of 20 normal adult subjects in a 14 C water bath results in the doubling of median capillary refill time. The low specificity of the test in adult females and the elderly when scored with the two-second upper limit of normal, its variation with temperature, and its dependence on the skills of the observer and the ambient lighting all suggest that capillary refill may not be efficacious in the prehospital care setting. Specificity is not, however, the sole standard for judging the performance of a clinical test. The sensitivity, accuracy, and positive and negative predictive values provide important information on the usefulness of a diagnostic test or procedure. We report our findings regarding these p a r a m e t e r s as m e a s u r e d in three different types of hypovolemic patients: blood donors who were phlebotomized 450 mL, emergency department patients with a history consistent with hypovolemia and abnormal orthostatic vital signs, and ED patients with a similar history and frank hypotension. Although the ideal design for an experiment evaluating the capacity of orthostatic vital signs to correctly identify hypovolemic states would involve the direct measurement Of cardiac output, systemic vascular resistance, and intravascular volume, we could not justify performing the required invasive procedures on volunteers. Furthermore, we could not use inpatients because those requiring right heart catheterization are virtually always on medication that alters their capillary refill. We therefore chose a group of subjects who were experiencing a small but acute blood loss (the blood donors) and two groups of patients who had histories, symptoms, and signs consistent with hypovolemia. We hypothesized that capillary refill times would be shortest in the blood donor group and longest in the patients with frank hypotension. We also hypothesized that capillary refill would be least sensitive in detecting the 450-mL blood loss and most sensitive in detecting hypovolemia with frank hypotension. MATERIALS A N D M E T H O D S Capillary refill was measured in two groups of patients. The first group comprised adult v o l u n t e e r 24/602
TABLE 1. Age and sex distribution of the experimental subjects Age Mean SD Range
Sex Female Male
Study Population
N
Blood donors Clinically hypovolemic patients Abnormal orthostatic vital signs Hypotension Total
47
33
13 19 - 83
23
24
19 13 32
40 50 44
21 18 80 22 17 - 90 22 17 90
10 7 17
9 6 15
TABLE 2. Capillary refill times for the study populations Mean Capillary Refill (sec)
SD
Range
Blood donors Before donation After donation
1.4" 1.1"t
0.7. 0,7
0,6 - 3.7 0.4 4.0
Clinically hypovolemic patients Abnormal orthostatic vital signs Hypotension Total
1.9t 2.8f 2.2
0.7 1.2 1.0
0.8 3.3 1.1 - 5.1 0.8 - 5.1
*Slalisticarly significant difference by paired t test (P < .001). tEach mean is diflerent from the others by analysis of variance with Scheffe comparisons (f- - 23.8; P < .01).
blood donors on w h o m orthostatic vital signs and capillary refill measurements were obtained before and immediately after a 450-mL blood donation. The second group comprised patients at a university hospital ED who presented with a history consistent with hypovolemia and either a systolic" blood pressure of less than 90 m m Hg or abnormal orthostatic vital signs. Patients on cardiovascular medication were excluded. Orthostatic vital signs were measured as follows. The subject was placed in the supine position for at least one minute. Pulse was counted for 30 seconds and blood pressure was measured with a mercury sphygmomanometer with the arm at the patient's side. Subjects then were asked to stand; after 30 seconds, their radial pulse was again counted for 30 seconds and their blood pressure was measured by the same observer in the same arm with the arm extended so that the blood pressure cuff was at the level of the heart. Postural vital signs were considered abnormal if the pulse increased by 20 beats per minute or more or the diastolic blood pressure decreased by more than 15 m m Hg when the patient changed from a supine to standing position. We previously established that these values result in a specificity of 99%, thereby ensuring that there would be no false-positive patients jn our Annals of Emergency Medicine
study group, s Capillary refill was measured by squeezing the distal phalanx of the middle finger for five seconds. The finger was released, and a digital stopwatch was started. The watch was stopped when the finger pulp returned to its baseline color. Times were measured in 100ths of a second and rounded and recorded to the nearest tenth. The test was repeated on the index finger, and the two measurements were averaged. Capillary refill m e a s u r e m e n t s were scored as normal or abnormal in two ways: first by using a two-second upper limit of normal for all subjects and second by using age- and sex-specific upper limits of normal for each subject. The age- and sexstratified cutoff points were two seconds for men less than 65 years old, three seconds for women less than 65 years old, and four seconds for subjects 65 years old or older. Sensitivity and specificity were calculated from the values resulting from each cutoff point strategy. For the blood donor group, sensitivity and specificity were calculated in standard fashion with the subjects considered "nondiseased" before donation and "diseased" after donation. The sensitivity of capillary refill for the hypovolemic ED patients was also calculated in standard fashion (true-positive/[true-positive + false20:6 June 1991
CAPILLARY REFILL Schriger & Baraff
TABLE 3. Sensitivity and specificity of capillary refill in detecting hypovolemia Scored With Two-Second Upper Limit of Normal Sensitivity (95% CI) Specificity(95% CI)
Study Population 450-mL blood loss
11% (3%
Clinically hypovolemic patients with Abnormal orthostatic vital signs Hypotension Total
23%)
47% (24% 71%) 77% (47% - 98%) 59% (40% - 76%)
Scored With Age- and Sex-Specific Upper Limits of Normal Sensitivity (95% CI) Specificity(95% CI)
89% (77% - 97%)
6% (0% - 16%)
86%* (81% - 91%) 86%* (81% 91%) 86%* (81% - 91%)
26% (7% - 50%) 46% (18% - 75%) 34% (18% - 53%)
93%
(82% -99%)
95%t (91% - 98%) 95%t (91% - 98%) 95%t (91% - 98%)
*Estimated as the weighted average of previously determined specilicities for adult males, adult females, and the elderly. tBased on measurements in 200 healthy adults (reference 4).
TABLE 4. Accuracy and positive and negative predictive value of capillary refill in detecting hypovolemia capillary refill scored using age- and sexspecific upper limits of normal
Prior Probability of Hypovolemia
Accuracy
Positive Predictive Value
Negative Predictive Value
10%
89%
43%
93%
25%
80%
69%
81%
50%
64%
87%
59%
90%
40%
98%
14%
negative]). Specificity for this group was estimated using the weighted average of the previously determined specificities for adult males, adult females, and the elderly. The weighting was performed to create an overall specificity that was representative of the age and sex distribution of the sample used in the sensitivity determination. RESULTS Demographic characteristics of the study samples are presented (Table 1). The blood donor group comprised 47 adults (23 women and 24 men) ranging in age from 19 to 83 years (mean age, 33 years; SD, 13 years). The hypovolemic group included 32 adults who ranged in age from 17 to 90 years (mean age, 44 years; SD, 22 years). There were 17 women and 15 men; five of the men and two of the women were more than 65 years old. The suspected mechanism of hypovolemia was vomiting or diarrhea in 16 subjects, blood loss in six, and decreased intake in ten. Thirteen subjects 'met the inclusion criterion of hypotension (blood pressure of less than 90 m m Hg). The other 19 subjects had abnormal orthostatic vital signs. Capillary refill times are shown (Table 2). In the blood donor group, capillary refill times before donation ranged f r o m 0.6 to 3.7 s e c o n d s 20:6:June1991
(mean, 1.4 seconds; SD, 0.65 seconds). Donation capillary refill times after donation ranged from 0.4 to 4.0 seconds (mean, 1.1 seconds; SD, 0.7 seconds). Mean donation capillary refill time after donation was significantly shorter than the mean time before donation (P < .001, paired t test). Capillary refill times for the hypovolemic ED group ranged from 0.8 to 5.1 seconds (mean, 2.2 seconds; SD, 1.0 seconds). Mean capillary refill t i m e for hypotensive subjects was 2.8 seconds (SD~ 1.2 seconds; range, 1.1 to 5.1 seconds) and for orthostatic subjects was 1.9 seconds (SD, 0.7 seconds; range, 0.8 to 3.3 seconds). Mean capillary refill times for the 450-mL blood loss, orthostatic, and hypotensive groups were each statist i c a l l y d i f f e r e n t f r o m each o t h e r (analysis of variance, F = 23.8, P < .001, and Scheffe testing) and, as predicted, were longest in the hypotensive p a t i e n t s and s h o r t e s t in the blood donors. Sensitivity and specificity data are presented (Table 3). For the blood donor group, application of the two-second upper limit of normal results in a sensitivity of 11% and a specificity of 89%. The age- and sex-specific upper limits of normal yield a sensitivity of 6% and a specificity of 93%. Forty-five of the 47 donors (95%) had normal orthostatic vital signs before Annals of Emergency Medicine
donation, and 12 (26%) had abnormal orthostatic vital signs after donation. Application of the two-second upper limit of normal to the ED sample resulted in a sensitivity of 59% for the entire group, 77% for the hypotensive subjects, and 47% for the ort h o s t a t i c subjects. The e s t i m a t e d specificity of capillary refill for each of these groups was 86%. The ageand sex-specific upper limits of normal yielded sensitivities of 34% for the entire group, 46% for the hypotensive subjects, and 26% for the orthostatic subjects. Previous measurement of capillary refill in 204 healthy adults suggest that the specificity for each of these groups should be 95% .4 We hypothesized a linear trend in the sensitivity of capillary refill with sensitivity being greatest in the hypotensive group, intermediate in the orthostatic group, and poorest in the 450-mL blood loss group. A X2 test for linear trend supports this hypothesis (X¢2 = 24.5, P < .001). Three zmportant parameters that describe the performance of a test vary with the prevalence of the disease (prior probability) in the s t u d y population. We calculated the accuracy and positive and negative predictive values of capillary refill in populations where the prevalence of h y p o v o l e m i a was 10%, 25%, 50%, and 90% so that clinicians can estimate how the test will perform in their patient population (Table 4). Parameters were calculated in standard fashion using sensitivity and specificity data for the orthostatic subjects and age- and sex-specific upper limits of normal. When used on a patient who has a 50% prior probability of hypovolemia, capillary refill has a positive predictive value of 83%, a negative predictive value of 59%, and an accuracy of 63%. We also analyzed the performance of capillary refill w h e n the upper 603/2,5
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limit of normal was varied between 0.75 and 4.5 seconds to determine whether a different cutoff time would improve the performance of the test. There was no upper limit of normal that substantially improved test p a r a m e t e r s over t h o s e m e n tioned in this study. This was true whether we used a single upper limit of normal for the entire sample or specific upper limits of normal for adult male, adult female, and elderly cohorts. DISCUSSION
Capillary refill was introduced into clinical practice without any published evaluation of its performance as a test. Our experiments show that it performs poorly as an identifier of hypovolemie patients with hypotension, abnormal postural vital signs, or a 450-mL blood loss. Although the mean capillary refill time for each group appeared to reflect the degree of hypovolemia in that group and the sensitivity of the test improved when the test was applied to patients with more substantial volume loss, these differences cannot be exploited by the individual physician seeing an individual patient. In a population in which half of the patients have hypotension or postural vital signs, capi llary refill will classify subjects corr e c t l y o n l y 70% of the t i m e . It should also be noted that this 70% accuracy was achieved using trained observers with digital stopwatches in a t e m p e r a t u r e - c o n t r o l l e d environm e n t that had good lighting. One would expect accuracy to further deteriorate in the prehospita] setting where these variables are no longer maximized. Prehospital and ED evaluation of the hypotensive patient is straightforward. Capillary refill would be of greatest value if it successfully identified the hypovolemic patient who had not yet manifested hypotension. The orthostatic subjects represent such a population, and the sensitivity of capillary refill in this group was at best 47%. Thus, only half of the o r t h o s t a t i c p a t i e n t s would be identified; a coin toss would achieve the same result. Further evidence of the failure of capillary refill to identify mild-tomoderate hypovolemia is provided by the blood donor experiment. When 450 mL of blood was removed from these subjects, the mean capillary re26/604
fill time actually decreased by a statistically significant 0.3 seconds. Although we m i g h t hypothesize that this decrease was a result of predonation times being unduly high as a result of peripheral vasoconstriction resulting from the patients' anxiety regarding the needlestick, the fact that the mean time actually decreased is further evidence of the unreliability of the test. Furthermore, if specificity is maintained at more than 90%, the sensitivity of capillary refill in this group was at best 6%, whereas the sensitivity of orthostatic vital signs in same subjects was 26%. This significant difference (McNemar's test, P < .05) suggests that orthostatic vital signs are a more sensitive test than capillary refill in detecting mild hypovolemia. The primary threat to the internal validity of this study was the method we used to identify hypovolemic patients. The validation of a test must always be performed in relation to an arbitrary gold standard, and although direct m e a s u r e m e n t of circulatory parameters with indwelling catheters would have been the best means of confirming that study subjects were hypovolemic, this was untenable because virtually all patients requiring right heart catheterization receive medications that affect their peripheral circulation and hence their capillary refill. An alternative means of ensuring that patients are hypovolemic is to render them so through phlebotomy. Although we were comfortable using this technique for the standard 450mL blood loss incurred during voluntary blood donation, we did not believe that it was feasible to subject volunteers to larger volume losses. Because a 450-mL blood loss seldom results in symptoms, testing the sens i t i v i t y of capillary refill in this group represents a very stringent test of its capacity to detect hypovolemia. To d e t e r m i n e the s e n s i t i v i t y of capillary refill in detecting greater degrees of hypovolemia, we used ED patients with a history suggestive of this condition who had either positive orthostatic vital signs or frank hypotension. We considered a subject to have abnormal orthostatic vital signs if the pulse increased by 20 beats per minute or more or the diastolic blood pressure decreased by more than 15 m m Hg on standing. We have previously shown that when Annals of Emergency Medicine
these cutoff points are used, orthostatic vital signs achieve a specificity of 99% (95% confidence intervals, 97% to 100%). s Although there is some controversy regarding how well orthostatic vital signs correlate with h y p o v o l e m i c states (particularly in children), the 99% specificity makes us confident that the orthostatic patients in our study were truly hypovolemic. 6-s This contention is supported by the observation that 18 of the 19 patients with abnormal orthostatic vital signs responded to hydration with normalization of their vital signs and resolution of their symptoms and were discharged from the ED. This study does not address the possibility that capillary refill maintains high sensitivity in patients who have incurred rapid intravascular depletion of large volumes of blood. The blood donor group comes closest to simulating these circumstances but involves a small amount of blood loss over a relatively long period of time (mean, 9.4 minutes). However, even if capillary refill performs well in patients with severe rapid blood loss, other parameters reliably identify class III shock, and it is unlikely that capillary refill will add much to the assessment of these severely ill patients. Capillary refill is not included in the Revised Trauma Score. 9 It continues to be taught, along with the two-second upper limit of normal, in BTLS and ATLS courses.lO, 11 We believe that the performance of capillary refill is insufficient to warrant its routine use in prehospital care or ED settings. It should be noted, however, that our previous research indicates that the specificity of capillary refill is quite good in children and that capillary refill is used routinely in neonatology. We did not study c h i l d r e n in this e x p e r i m e n t , and therefore cannot make any statement regarding the usefulness of this test in the pediatric population. CONCLUSION Capillary refill has m a n y characteristics that would make it a seemingly useful clinical test for the evaluation of hypovolemic states. Unfortunately, such a promising test performs quite poorly when subjected to critical examination. At this t i m e there is no evidence that capillary refill is of any value in assessing hypo20:6 June 1991
CAPILLARY REFILL Schriger & Baraff
volemic states in adults. The Revised Trauma Score does not use capillary refill, and we s u s p e c t that it w i l l soon be removed from other instruments used for prehospital trauma triage. The usefulness of capillary refill in children has yet to be evaluated. The authors thank Mina Tortes and Janet Reinsvold for their excellent technical assistance and Linda Heinz for help in manuscript preparation.
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REFERENCES 1. Champion HR, Sacco WJ, Carnazzo AJ, et al: Trauma score. Crit Care Med 1980~9:672-676. 2. Campbell JE (ed): Basic Trauma Life Support: Ad vanced Prehospital Care. Englewood Cliffs, New Jersey, Prentice-Hall, 1985, p 52. 3. Committee on Trauma: Advanced Trauma Life Sup port Course - Student Manual. Chicago, American Col lege of Surgeons, 1984, p 7. 4. Schriger DS, Baraff LJ: Defining normal capillary refill: Variation with age, sex, and temperature. Ann Emerg Med 1988;17:932 935. 5. Schriger DS~ Baraff LJ: The distribution of orthostatic vital sign changes in a normal adult population and the variation of these changes with age (abstract). Ann Emerg Med 1990;19:471.
Annals of Emergency Medicine
6. Knopp R, Claypool R, Leonardi D: Use of the tilt test in m e a s u r i n g a c u t e blood loss. A n n Emerg Med 1980;9:72-75. 7. Fuchs SM, Jaffe DM: Evaluation of the "tilt test" in children. Ann Emerg Med 1987;16:386-390. 8. Bergman GE, Reisner FF, Anwar RAH: Orthostatic changes in normovolemic children: An analysis of the "tilt test." ] Emerg Med 1983;hf37-141. 9. Champion HR, Sacco WJ, Copes WS: A revision of the Trauma Score. T Trauma 1989;29:623-629. 10. Campbell JE fed}: Basic Trauma Life Support: Ad vanced Prehospital Care, ed 2. Englewood Cliffs, New Jersey, Prentice-Hall, 1988, p 112-113. ii. Committee on Trauma: Advanced Trauma Life Support - Student Manual. Chicago, American College of Surgeons, 1989, p 60-61.
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C a p i l l a r y Refill -- Is It a U s e f u l P r e d i c t o r of Hypovolemic States? Study objectives: To evaluate whether the capillary refill test can correctly differentiate between hypovolemic and euvolemic emergency department patients. Design: A prospective, nonrandomized, nonblinded time series. Setting: The orthostatic and hypotensive patients were seen in a university hospital ED with 44,000 visits per year. Blood donors were studied in the hospital's blood donor center. Type of participants: Thirty-two adult ED patients who presented with a history suggestive of hypovolemia and either abnormal orthostatic vital signs (19) or frank hypotension (I3), and 47 volunteer blood donors who ranged in age from 19 to 83 participated. Interventions: Capillary refill was measured before rehydration in the ED subjects and, in the donor group, before and after a 450-mL blood donation. Measurements: Sensitivity, specificity, accuracy, and positive and negative predictive values were calculated. Analyses were stratified by age, sex, and study group. Main results: For the blood donor group, mean capillary refill time before donation was 1.4 seconds and after donation was 1.1 seconds. Mean capillary refill time for the orthostatic group was 1.9 seconds and for the hypotensive group was 2.8 seconds. When scored with age-sex specific upper limits of normal, the sensitivity of capillary refill in identifying hypovolemic patients was 6% for the 450-mL blood loss group, 26% for the orthostatic group, and 46% for the hypotensive group. The accuracy of capillary refill in a patient with a 50% prior probability of hypovoIemia is 64%. Orthostatic vital signs were found to be more sensitive and specific than capillary refill in detecting the 450-mL blood loss. Conclusion: Capillary refill does not appear to be a useful test for detecting mild-to-moderate hypovolemia in adults. [Schriger DL, Baraff LJ: Capillary refill - Is it a useful predictor of hypovolemic states? Ann Emerg Med June 1991;20:601-605.]
David L Schriger, MD, MPH* Larry J Baraff, MD, FACEPt Los Angeles, California From the Departments of Medicine* and Pediatrics,t UCLA School of Medicine and the UCLA Emergency Medicine Center, Los Angeles, California. Received for publication November 20, 1989. Revisions received July 23, and November 26, 1990. Accepted for publication December 14, 1990. Presented at the 2nd International Conference on Emergency Medicine in Brisbane, Australia, October 1988. Address for reprints: David L Schriger, MD, MPH, UCLA Emergency Medicine Center, 924 Westwood Boulevard, Suite 300, Los Angeles, California 90024-2924.
INTRODUCTION In theory, capillary refill is an ideal clinical test. It is noninvasive, costs nothing, takes little time to perform, and might provide valuable information regarding the status of a patient's blood volume and circulatory function. It is, therefore, unfortunate that it was introduced into clinical practice as part of the Trauma Score, the basic trauma life support {BTLS) course, and the advanced trauma life support (ATLS) course without any attempts at experimental validationA -3 These scores and courses initially recommended a two-second upper limit of normal for capillary refill. We have previously reported that the capillary refill of typical citizens varies with age, sex, and temperature. 4 In a sample of 100 child, 104 adult, and 100 elderly volunteers, we have shown that application of the twosecond upper limit of normal results in a specificity of 96% for the children, 95% for adult males, 86% for adult females, and 71% for the elderly. To achieve a 95% specificity for the adult females the upper limit of normal would need to be raised to three seconds, and a 95% specificity for the elderly would require an upper limit of normal of 4.5 seconds. Capillary refill also varies with temperature. 4 A one-minute immersion
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of the hand of 20 normal adult subjects in a 14 C water bath results in the doubling of median capillary refill time. The low specificity of the test in adult females and the elderly when scored with the two-second upper limit of normal, its variation with temperature, and its dependence on the skills of the observer and the ambient lighting all suggest that capillary refill may not be efficacious in the prehospital care setting. Specificity is not, however, the sole standard for judging the performance of a clinical test. The sensitivity, accuracy, and positive and negative predictive values provide important information on the usefulness of a diagnostic test or procedure. We report our findings regarding these p a r a m e t e r s as m e a s u r e d in three different types of hypovolemic patients: blood donors who were phlebotomized 450 mL, emergency department patients with a history consistent with hypovolemia and abnormal orthostatic vital signs, and ED patients with a similar history and frank hypotension. Although the ideal design for an experiment evaluating the capacity of orthostatic vital signs to correctly identify hypovolemic states would involve the direct measurement Of cardiac output, systemic vascular resistance, and intravascular volume, we could not justify performing the required invasive procedures on volunteers. Furthermore, we could not use inpatients because those requiring right heart catheterization are virtually always on medication that alters their capillary refill. We therefore chose a group of subjects who were experiencing a small but acute blood loss (the blood donors) and two groups of patients who had histories, symptoms, and signs consistent with hypovolemia. We hypothesized that capillary refill times would be shortest in the blood donor group and longest in the patients with frank hypotension. We also hypothesized that capillary refill would be least sensitive in detecting the 450-mL blood loss and most sensitive in detecting hypovolemia with frank hypotension. MATERIALS A N D M E T H O D S Capillary refill was measured in two groups of patients. The first group comprised adult v o l u n t e e r 24/602
TABLE 1. Age and sex distribution of the experimental subjects Age Mean SD Range
Sex Female Male
Study Population
N
Blood donors Clinically hypovolemic patients Abnormal orthostatic vital signs Hypotension Total
47
33
13 19 - 83
23
24
19 13 32
40 50 44
21 18 80 22 17 - 90 22 17 90
10 7 17
9 6 15
TABLE 2. Capillary refill times for the study populations Mean Capillary Refill (sec)
SD
Range
Blood donors Before donation After donation
1.4" 1.1"t
0.7. 0,7
0,6 - 3.7 0.4 4.0
Clinically hypovolemic patients Abnormal orthostatic vital signs Hypotension Total
1.9t 2.8f 2.2
0.7 1.2 1.0
0.8 3.3 1.1 - 5.1 0.8 - 5.1
*Slalisticarly significant difference by paired t test (P < .001). tEach mean is diflerent from the others by analysis of variance with Scheffe comparisons (f- - 23.8; P < .01).
blood donors on w h o m orthostatic vital signs and capillary refill measurements were obtained before and immediately after a 450-mL blood donation. The second group comprised patients at a university hospital ED who presented with a history consistent with hypovolemia and either a systolic" blood pressure of less than 90 m m Hg or abnormal orthostatic vital signs. Patients on cardiovascular medication were excluded. Orthostatic vital signs were measured as follows. The subject was placed in the supine position for at least one minute. Pulse was counted for 30 seconds and blood pressure was measured with a mercury sphygmomanometer with the arm at the patient's side. Subjects then were asked to stand; after 30 seconds, their radial pulse was again counted for 30 seconds and their blood pressure was measured by the same observer in the same arm with the arm extended so that the blood pressure cuff was at the level of the heart. Postural vital signs were considered abnormal if the pulse increased by 20 beats per minute or more or the diastolic blood pressure decreased by more than 15 m m Hg when the patient changed from a supine to standing position. We previously established that these values result in a specificity of 99%, thereby ensuring that there would be no false-positive patients jn our Annals of Emergency Medicine
study group, s Capillary refill was measured by squeezing the distal phalanx of the middle finger for five seconds. The finger was released, and a digital stopwatch was started. The watch was stopped when the finger pulp returned to its baseline color. Times were measured in 100ths of a second and rounded and recorded to the nearest tenth. The test was repeated on the index finger, and the two measurements were averaged. Capillary refill m e a s u r e m e n t s were scored as normal or abnormal in two ways: first by using a two-second upper limit of normal for all subjects and second by using age- and sex-specific upper limits of normal for each subject. The age- and sexstratified cutoff points were two seconds for men less than 65 years old, three seconds for women less than 65 years old, and four seconds for subjects 65 years old or older. Sensitivity and specificity were calculated from the values resulting from each cutoff point strategy. For the blood donor group, sensitivity and specificity were calculated in standard fashion with the subjects considered "nondiseased" before donation and "diseased" after donation. The sensitivity of capillary refill for the hypovolemic ED patients was also calculated in standard fashion (true-positive/[true-positive + false20:6 June 1991
CAPILLARY REFILL Schriger & Baraff
TABLE 3. Sensitivity and specificity of capillary refill in detecting hypovolemia Scored With Two-Second Upper Limit of Normal Sensitivity (95% CI) Specificity(95% CI)
Study Population 450-mL blood loss
11% (3%
Clinically hypovolemic patients with Abnormal orthostatic vital signs Hypotension Total
23%)
47% (24% 71%) 77% (47% - 98%) 59% (40% - 76%)
Scored With Age- and Sex-Specific Upper Limits of Normal Sensitivity (95% CI) Specificity(95% CI)
89% (77% - 97%)
6% (0% - 16%)
86%* (81% - 91%) 86%* (81% 91%) 86%* (81% - 91%)
26% (7% - 50%) 46% (18% - 75%) 34% (18% - 53%)
93%
(82% -99%)
95%t (91% - 98%) 95%t (91% - 98%) 95%t (91% - 98%)
*Estimated as the weighted average of previously determined specilicities for adult males, adult females, and the elderly. tBased on measurements in 200 healthy adults (reference 4).
TABLE 4. Accuracy and positive and negative predictive value of capillary refill in detecting hypovolemia capillary refill scored using age- and sexspecific upper limits of normal
Prior Probability of Hypovolemia
Accuracy
Positive Predictive Value
Negative Predictive Value
10%
89%
43%
93%
25%
80%
69%
81%
50%
64%
87%
59%
90%
40%
98%
14%
negative]). Specificity for this group was estimated using the weighted average of the previously determined specificities for adult males, adult females, and the elderly. The weighting was performed to create an overall specificity that was representative of the age and sex distribution of the sample used in the sensitivity determination. RESULTS Demographic characteristics of the study samples are presented (Table 1). The blood donor group comprised 47 adults (23 women and 24 men) ranging in age from 19 to 83 years (mean age, 33 years; SD, 13 years). The hypovolemic group included 32 adults who ranged in age from 17 to 90 years (mean age, 44 years; SD, 22 years). There were 17 women and 15 men; five of the men and two of the women were more than 65 years old. The suspected mechanism of hypovolemia was vomiting or diarrhea in 16 subjects, blood loss in six, and decreased intake in ten. Thirteen subjects 'met the inclusion criterion of hypotension (blood pressure of less than 90 m m Hg). The other 19 subjects had abnormal orthostatic vital signs. Capillary refill times are shown (Table 2). In the blood donor group, capillary refill times before donation ranged f r o m 0.6 to 3.7 s e c o n d s 20:6:June1991
(mean, 1.4 seconds; SD, 0.65 seconds). Donation capillary refill times after donation ranged from 0.4 to 4.0 seconds (mean, 1.1 seconds; SD, 0.7 seconds). Mean donation capillary refill time after donation was significantly shorter than the mean time before donation (P < .001, paired t test). Capillary refill times for the hypovolemic ED group ranged from 0.8 to 5.1 seconds (mean, 2.2 seconds; SD, 1.0 seconds). Mean capillary refill t i m e for hypotensive subjects was 2.8 seconds (SD~ 1.2 seconds; range, 1.1 to 5.1 seconds) and for orthostatic subjects was 1.9 seconds (SD, 0.7 seconds; range, 0.8 to 3.3 seconds). Mean capillary refill times for the 450-mL blood loss, orthostatic, and hypotensive groups were each statist i c a l l y d i f f e r e n t f r o m each o t h e r (analysis of variance, F = 23.8, P < .001, and Scheffe testing) and, as predicted, were longest in the hypotensive p a t i e n t s and s h o r t e s t in the blood donors. Sensitivity and specificity data are presented (Table 3). For the blood donor group, application of the two-second upper limit of normal results in a sensitivity of 11% and a specificity of 89%. The age- and sex-specific upper limits of normal yield a sensitivity of 6% and a specificity of 93%. Forty-five of the 47 donors (95%) had normal orthostatic vital signs before Annals of Emergency Medicine
donation, and 12 (26%) had abnormal orthostatic vital signs after donation. Application of the two-second upper limit of normal to the ED sample resulted in a sensitivity of 59% for the entire group, 77% for the hypotensive subjects, and 47% for the ort h o s t a t i c subjects. The e s t i m a t e d specificity of capillary refill for each of these groups was 86%. The ageand sex-specific upper limits of normal yielded sensitivities of 34% for the entire group, 46% for the hypotensive subjects, and 26% for the orthostatic subjects. Previous measurement of capillary refill in 204 healthy adults suggest that the specificity for each of these groups should be 95% .4 We hypothesized a linear trend in the sensitivity of capillary refill with sensitivity being greatest in the hypotensive group, intermediate in the orthostatic group, and poorest in the 450-mL blood loss group. A X2 test for linear trend supports this hypothesis (X¢2 = 24.5, P < .001). Three zmportant parameters that describe the performance of a test vary with the prevalence of the disease (prior probability) in the s t u d y population. We calculated the accuracy and positive and negative predictive values of capillary refill in populations where the prevalence of h y p o v o l e m i a was 10%, 25%, 50%, and 90% so that clinicians can estimate how the test will perform in their patient population (Table 4). Parameters were calculated in standard fashion using sensitivity and specificity data for the orthostatic subjects and age- and sex-specific upper limits of normal. When used on a patient who has a 50% prior probability of hypovolemia, capillary refill has a positive predictive value of 83%, a negative predictive value of 59%, and an accuracy of 63%. We also analyzed the performance of capillary refill w h e n the upper 603/2,5
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limit of normal was varied between 0.75 and 4.5 seconds to determine whether a different cutoff time would improve the performance of the test. There was no upper limit of normal that substantially improved test p a r a m e t e r s over t h o s e m e n tioned in this study. This was true whether we used a single upper limit of normal for the entire sample or specific upper limits of normal for adult male, adult female, and elderly cohorts. DISCUSSION
Capillary refill was introduced into clinical practice without any published evaluation of its performance as a test. Our experiments show that it performs poorly as an identifier of hypovolemie patients with hypotension, abnormal postural vital signs, or a 450-mL blood loss. Although the mean capillary refill time for each group appeared to reflect the degree of hypovolemia in that group and the sensitivity of the test improved when the test was applied to patients with more substantial volume loss, these differences cannot be exploited by the individual physician seeing an individual patient. In a population in which half of the patients have hypotension or postural vital signs, capi llary refill will classify subjects corr e c t l y o n l y 70% of the t i m e . It should also be noted that this 70% accuracy was achieved using trained observers with digital stopwatches in a t e m p e r a t u r e - c o n t r o l l e d environm e n t that had good lighting. One would expect accuracy to further deteriorate in the prehospita] setting where these variables are no longer maximized. Prehospital and ED evaluation of the hypotensive patient is straightforward. Capillary refill would be of greatest value if it successfully identified the hypovolemic patient who had not yet manifested hypotension. The orthostatic subjects represent such a population, and the sensitivity of capillary refill in this group was at best 47%. Thus, only half of the o r t h o s t a t i c p a t i e n t s would be identified; a coin toss would achieve the same result. Further evidence of the failure of capillary refill to identify mild-tomoderate hypovolemia is provided by the blood donor experiment. When 450 mL of blood was removed from these subjects, the mean capillary re26/604
fill time actually decreased by a statistically significant 0.3 seconds. Although we m i g h t hypothesize that this decrease was a result of predonation times being unduly high as a result of peripheral vasoconstriction resulting from the patients' anxiety regarding the needlestick, the fact that the mean time actually decreased is further evidence of the unreliability of the test. Furthermore, if specificity is maintained at more than 90%, the sensitivity of capillary refill in this group was at best 6%, whereas the sensitivity of orthostatic vital signs in same subjects was 26%. This significant difference (McNemar's test, P < .05) suggests that orthostatic vital signs are a more sensitive test than capillary refill in detecting mild hypovolemia. The primary threat to the internal validity of this study was the method we used to identify hypovolemic patients. The validation of a test must always be performed in relation to an arbitrary gold standard, and although direct m e a s u r e m e n t of circulatory parameters with indwelling catheters would have been the best means of confirming that study subjects were hypovolemic, this was untenable because virtually all patients requiring right heart catheterization receive medications that affect their peripheral circulation and hence their capillary refill. An alternative means of ensuring that patients are hypovolemic is to render them so through phlebotomy. Although we were comfortable using this technique for the standard 450mL blood loss incurred during voluntary blood donation, we did not believe that it was feasible to subject volunteers to larger volume losses. Because a 450-mL blood loss seldom results in symptoms, testing the sens i t i v i t y of capillary refill in this group represents a very stringent test of its capacity to detect hypovolemia. To d e t e r m i n e the s e n s i t i v i t y of capillary refill in detecting greater degrees of hypovolemia, we used ED patients with a history suggestive of this condition who had either positive orthostatic vital signs or frank hypotension. We considered a subject to have abnormal orthostatic vital signs if the pulse increased by 20 beats per minute or more or the diastolic blood pressure decreased by more than 15 m m Hg on standing. We have previously shown that when Annals of Emergency Medicine
these cutoff points are used, orthostatic vital signs achieve a specificity of 99% (95% confidence intervals, 97% to 100%). s Although there is some controversy regarding how well orthostatic vital signs correlate with h y p o v o l e m i c states (particularly in children), the 99% specificity makes us confident that the orthostatic patients in our study were truly hypovolemic. 6-s This contention is supported by the observation that 18 of the 19 patients with abnormal orthostatic vital signs responded to hydration with normalization of their vital signs and resolution of their symptoms and were discharged from the ED. This study does not address the possibility that capillary refill maintains high sensitivity in patients who have incurred rapid intravascular depletion of large volumes of blood. The blood donor group comes closest to simulating these circumstances but involves a small amount of blood loss over a relatively long period of time (mean, 9.4 minutes). However, even if capillary refill performs well in patients with severe rapid blood loss, other parameters reliably identify class III shock, and it is unlikely that capillary refill will add much to the assessment of these severely ill patients. Capillary refill is not included in the Revised Trauma Score. 9 It continues to be taught, along with the two-second upper limit of normal, in BTLS and ATLS courses.lO, 11 We believe that the performance of capillary refill is insufficient to warrant its routine use in prehospital care or ED settings. It should be noted, however, that our previous research indicates that the specificity of capillary refill is quite good in children and that capillary refill is used routinely in neonatology. We did not study c h i l d r e n in this e x p e r i m e n t , and therefore cannot make any statement regarding the usefulness of this test in the pediatric population. CONCLUSION Capillary refill has m a n y characteristics that would make it a seemingly useful clinical test for the evaluation of hypovolemic states. Unfortunately, such a promising test performs quite poorly when subjected to critical examination. At this t i m e there is no evidence that capillary refill is of any value in assessing hypo20:6 June 1991
CAPILLARY REFILL Schriger & Baraff
volemic states in adults. The Revised Trauma Score does not use capillary refill, and we s u s p e c t that it w i l l soon be removed from other instruments used for prehospital trauma triage. The usefulness of capillary refill in children has yet to be evaluated. The authors thank Mina Tortes and Janet Reinsvold for their excellent technical assistance and Linda Heinz for help in manuscript preparation.
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REFERENCES 1. Champion HR, Sacco WJ, Carnazzo AJ, et al: Trauma score. Crit Care Med 1980~9:672-676. 2. Campbell JE (ed): Basic Trauma Life Support: Ad vanced Prehospital Care. Englewood Cliffs, New Jersey, Prentice-Hall, 1985, p 52. 3. Committee on Trauma: Advanced Trauma Life Sup port Course - Student Manual. Chicago, American Col lege of Surgeons, 1984, p 7. 4. Schriger DS, Baraff LJ: Defining normal capillary refill: Variation with age, sex, and temperature. Ann Emerg Med 1988;17:932 935. 5. Schriger DS~ Baraff LJ: The distribution of orthostatic vital sign changes in a normal adult population and the variation of these changes with age (abstract). Ann Emerg Med 1990;19:471.
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6. Knopp R, Claypool R, Leonardi D: Use of the tilt test in m e a s u r i n g a c u t e blood loss. A n n Emerg Med 1980;9:72-75. 7. Fuchs SM, Jaffe DM: Evaluation of the "tilt test" in children. Ann Emerg Med 1987;16:386-390. 8. Bergman GE, Reisner FF, Anwar RAH: Orthostatic changes in normovolemic children: An analysis of the "tilt test." ] Emerg Med 1983;hf37-141. 9. Champion HR, Sacco WJ, Copes WS: A revision of the Trauma Score. T Trauma 1989;29:623-629. 10. Campbell JE fed}: Basic Trauma Life Support: Ad vanced Prehospital Care, ed 2. Englewood Cliffs, New Jersey, Prentice-Hall, 1988, p 112-113. ii. Committee on Trauma: Advanced Trauma Life Support - Student Manual. Chicago, American College of Surgeons, 1989, p 60-61.
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