Skin-color-independent robust assessment of capillary refill time

Capillary Refill Time (CRT) assesses peripheral perfusion in resource-limited settings. However, the repeatability and reproducibility of CRT measurements are limited for individuals with darker skin. This paper presents quantitative CRT measurements demonstrating good performance and repeatability across all Fitzpatrick skin phototypes. The study involved 22 volunteers and utilized controlled compression at 7 kPa, an RGB video camera, and cocircular polarized white LED light. CRT was determined by calculating the time constant of an exponential regression applied to the mean pixel intensity of the green (G) channel. An adaptive algorithm identifies the optimal regression region for noise reduction, and flags inappropriate readings. The results indicate that 80% of the CRT readings fell within a 20% range of the expected CRT value. The repetition standard deviation was 17%. These findings suggest the potential for developing reliable and reproducible quantitative CRT methods for robust measurements in patient triage, monitoring, and telehealth applications.

Comparison of Bedside and Video-Based Capillary Refill Time Assessment in Children

OBJECTIVES

Capillary refill time (CRT) to assess peripheral perfusion in children with suspected shock may be subject to poor reproducibility. Our objectives were to compare video-based and bedside CRT assessment using a standardized protocol and evaluate interrater and intrarater consistency of video-based CRT (VB-CRT) assessment. We hypothesized that measurement errors associated with raters would be low for both standardized bedside CRT and VB-CRT as well as VB-CRT across raters.

METHODS

Ninety-nine children (aged 1-12 y) had 5 consecutive bedside CRT assessments by an experienced critical care clinician following a standardized protocol. Each CRT assessment was video recorded on a black background. Thirty video clips (10 with bedside CRT < 1 s, 10 with CRT 1-2 s, and 10 with CRT > 2 s) were randomly selected and presented to 10 clinicians twice in randomized order. They were instructed to push a button when they visualized release of compression and completion of a capillary refill. The correlation and absolute difference between bedside and VB-CRT were assessed. Consistency across raters and within each rater was analyzed using the intraclass correlation coefficient (ICC). A Generalizability study was performed to evaluate sources of variation.

RESULTS

We found moderate agreement between bedside and VB-CRT observations (r = 0.65; P < 0.001). The VB-CRT values were shorter by 0.17 s (95% confidence interval, 0.09-0.25; P < 0.001) on average compared with bedside CRT. There was moderate agreement in VB-CRT across raters (ICC = 0.61). Consistency of repeated VB-CRT within each rater was moderate (ICC = 0.71). Generalizability study revealed the source of largest variance was from individual patient video clips (57%), followed by interaction of the VB-CRT reviewer and patient video clip (10.7%).

CONCLUSIONS

Bedside and VB-CRT observations showed moderate consistency. Using video-based assessment, moderate consistency was also observed across raters and within each rater. Further investigation to standardize and automate CRT measurement is warranted.

Standardized capillary refill time and relation to clinical parameters in hospitalized dogs

OBJECTIVE

To assess the relationship between various physical and clinicopathologic parameters and the capillary refill time (CRT) using a standard method; to evaluate the influence of emergency room (ER) versus ICU hospital location on CRT; and to identify latent subgroups among the CRT distribution.

DESIGN

Prospective, observational study.

SETTING

University teaching hospital.

ANIMALS

Client-owned dogs in the ER (n = 40) and ICU (n = 71).

INTERVENTIONS

The CRT was defined as the duration required for the oral mucosa of the upper lip to return to its original color after blanching for 4 seconds. The CRT was recorded in seconds to the 10ths place by a single observer using an automated recording device.

MEASUREMENTS AND MAIN RESULTS

Median CRT for all dogs was 1.1 seconds (ER, 1.2 s; ICU, 1.1 s; P = 1.000). The CRT was significantly associated with rectal temperature (P = 0.004), systolic blood pressure (P = 0.028), body weight (P = 0.031), mucous membrane color (P = 0.007), skin turgor (P = 0.039), and acute patient physiologic and laboratory evaluation mentation score (P = 0.019) for all dogs. The CRT was related to a greater number of variables in the ER than in the ICU patient population. In general, the total population of dogs had CRTs belonging to 1 of 2 groups: either ≤1.2 or ≥1.7 seconds. A statistically significant association was found between body weight CRT ≥1.3 seconds (P = 0.02).

CONCLUSIONS

A CRT following blanching for 4 seconds may provide insight into the hydration status and hemodynamic stability of canine patients. Further research into its clinical application is warranted.

Full Finger Reperfusion Time Measured by Pulse Oximeter Waveform Analysis in Children

OBJECTIVES

Capillary refill time is a noninvasive method to assess tissue perfusion to determine shock status. Capillary refill time is defined as the time required to regain skin color after blanching pressure is applied. Although common methods to measure capillary refill time depend on clinicians' visual assessment, a new approach using a pulse oximeter waveform analysis exists, referred to as full finger reperfusion time. We aim to evaluate reproducibility and validity of the novel full finger reperfusion time measurement using clinicians' visual capillary refill time assessment as a reference standard.

DESIGN

Prospective observational study.

SETTING

PICUs and operating suites at a large academic children's hospital.

PATIENTS

Ninety-nine children 1-12 years old with various skin color tones.

INTERVENTIONS

Each child had 10 measurements, including five full finger reperfusion time and five clinician capillary refill time, alternating second and third digits.

MEASUREMENTS AND MAIN RESULTS

Eighteen children had prolonged capillary refill time (> 2 s) and four children with capillary refill time greater than 3 seconds. Four-hundred eighty-five data pairs were analyzed. Intraclass correlation coefficient of full finger reperfusion time within each patient was 0.76 (95% CI, 0.68-0.83), demonstrating good reproducibility. Correlation coefficient between full finger reperfusion time and clinician capillary refill time was moderate: r = 0.37 (p < 0.0001; 95% CI, 0.29-0.44) for the pairs and r = 0.52 (p < 0.0001; 95% CI, 0.36-0.65) for patient average. Bland-Altman plot showed a consistent difference between full finger reperfusion time and clinician capillary refill time (full finger reperfusion time 1.14 s longer). Weak association was found between force and full finger reperfusion time (β = -0.033 ± 0.016; 95% CI, -0.065 to -0.0016; p = 0.04), finger thickness (β = -0.20 ± 0.089; 95% CI, -0.37 to -0.19; p = 0.03), except for color tone (p = 0.31). Finger temperature was associated with full finger reperfusion time (β = -0.18 ± 0.041; 95% CI, -0.26 to -0.0999; p < 0.0001).

CONCLUSIONS

Full finger reperfusion time demonstrated good reproducibility. Full finger reperfusion time showed moderate correlation with clinician capillary refill time. Full finger reperfusion time was 1.14 seconds longer than capillary refill time. Future studies should focus on the clinical value of full finger reperfusion time as a monitoring device for hemodynamics in critically ill children.

Prolonged Capillary Refilling as a Predictor of Mortality in Patients With Septic Shock

INTRODUCTION

Microcirculatory alterations characterize septic shock; increased blood lactate level has been described as markers of microcirculation alteration in patients with septic shock. Although useful, this serological analysis is not always feasible in all settings worldwide.

OBJECTIVE

To determine if a prolonged capillary refilling is a predictor of mortality in patients with septic shock.

METHODOLOGY

A 10-months prospective cohort study was carried out on 175 patients admitted to the Intensive Care Unit (ICU) with the diagnosis of septic shock. The capillary refilling time (CRT) was evaluated Immediately upon admission and after 6 hours post-resuscitation. Traditional tissue perfusion markers were also used to compare and analyze their predictive value on mortality at 28 days.

RESULTS

The area under the ROC curve (AUC) to estimate mortality in patients with septic shock with CRT at admission was 0.666 (0.584-0.748), while at 6 hours was 0.819 (0.753-0.885), with a cut-off point of 4.5 seconds at admission (PPV 52.87% NPV 72.73%) and 3.5 sec at 6 hours (PPV 95.56% NPV 79.23%). In those with CRT > 3.5 seconds at 6 hours, they had a RR of 4.60, while a CRT > 4.5 seconds at admission had a RR of 1.94, with a non-survivor proportion of 95.56% for a CRT > 3.5 sec at 6 hours vs 20.77% for CRT ≤ 3.5 sec (P value < 0.001). The CRT at 6 hours showed significant differences in the survival curves with P-value < 0.001, where for values > 3.5 sec, survival at 28 days was 4.44% vs 79.20% for values ≤ 3.5 sec.

CONCLUSION

CRT is a strong predictor of mortality in patients with septic shock. Evaluating changes in CRT during resuscitation from septic shock might be used as an important clinical tool to predict mortality; especially in low-resources settings where using other biomarkers might be sometimes difficult.

Alterations in Skin Blood Flow at the Fingertip Are Related to Mortality in Patients With Circulatory Shock

OBJECTIVES

Skin blood flow is rapidly altered during circulatory shock and may remain altered despite apparent systemic hemodynamic stabilization. We evaluated whether changes in skin blood flow during circulatory shock were related to survival.

DESIGN

Prospective study.

SETTING

Thirty-five-bed medical-surgical university hospital department of intensive care.

SUBJECTS

Twenty healthy volunteers and 70 patients with circulatory shock (< 12 hr duration), defined as the need for vasopressors to maintain mean arterial pressure greater than or equal to 65 mm Hg and signs of altered tissue perfusion.

INTERVENTIONS

We assessed skin blood flow using skin laser Doppler on the fingertip for 3 minutes at basal temperature (SBFBT) and at 37°C (SBF37) (thermal challenge test) once in volunteers and at the time of inclusion and after 6, 24, 48, 72, and 96 hours in patients with shock. Capillary refill time and peripheral perfusion index were measured at the same time points on the contralateral hand.

MEASUREMENTS AND MAIN RESULTS

The thermal challenge response (ΔSBF/ΔT) was calculated using the following formula: (SBF37-SBFBT)/(37-basal temperature). Area under the receiver operating characteristic curves were calculated to evaluate variables predictive of ICU mortality. At inclusion, skin blood flow and ΔSBF/ΔT were lower in patients than in volunteers. Baseline skin blood flow (31 [17-113] vs 16 [9-32] arbitrary perfusion units; p = 0.01) and ΔSBF/ΔT (4.3 [1.7-10.9] vs 0.9 [0.4-2.9] arbitrary perfusion unit/s) were greater in survivors than in nonsurvivors. Capillary refill time was shorter in survivors than in nonsurvivors; peripheral perfusion index was similar in the two groups. ΔSBF/ΔT (area under the receiver operating characteristic curve 0.94 [0.88-0.99]) and SBFBT (area under the receiver operating characteristic curve 0.83 [0.73-0.93]) had the best predictive value for ICU mortality with cutoff values less than or equal to 1.25 arbitrary perfusion unit/°C (sensitivity 88%, specificity 89%) and less than or equal to 21 arbitrary perfusion unit (sensitivity 84%, specificity 81%), respectively.

CONCLUSIONS

Alterations in fingertip skin blood flow can be evaluated using a laser Doppler thermal challenge technique in patients with circulatory shock and are directly related to outcome. These novel monitoring techniques could potentially be used to guide resuscitation.

Man versus machine: comparison of naked-eye estimation and quantified capillary refill

Background

Capillary refill (CR) time is traditionally assessed by ‘naked-eye’ inspection of the return to original colour of a tissue after blanching pressure. Few studies have addressed intra-observer reliability or used objective quantification techniques to assess time to original colour. This study compares naked-eye assessment with quantified CR (qCR) time using polarisation spectroscopy and examines intra-observer and interobserver agreements in using the naked eye.

Method

A film of 18 CR tests (shown in a random fixed order) performed in healthy adults was assessed by a convenience sample of 14 doctors, 15 nurses and 19 secretaries (Department of Emergency Medicine, Linköping University, September to November 2017), who were asked to estimate the time to return to colour and characterise it as ‘fast’, ‘normal’ or ‘slow’. The qCR times and corresponding naked-eye time assessments were compared using the Kruskal-Wallis test. Three videos were shown twice without observers’ knowledge to measure intra-observer repeatability. Intra-observer categorical assessments were compared using Cohen’s Kappa analysis. Interobserver repeatability was measured and depicted with multiple-observer Bland-Altman plotting. Differences in naked-eye estimation between professions were analysed using ANOVA.

Results

Naked-eye assessed CR time and qCR time differ substantially, and agreement for the categorical assessments (naked-eye assessment vs qCR classification) was poor (Cohen’s kappa 0.27). Bland-Altman intra-observer repeatability ranged from 6% to 60%. Interobserver agreement was low as shown by the Bland-Altman plotting with a 95% limit of agreement with the mean of ±1.98 s for doctors, ±1.6 s for nurses and ±1.75 s for secretaries. The difference in CR time estimation (in seconds) between professions was not significant.

Conclusions

Our study suggests that naked-eye-assessed CR time shows poor reproducibility, even by the same observers, and differs from an objective measure of CR time.

Is perception of quality more important than technical quality in patient video cases?

BACKGROUND

The use of video cases to demonstrate key signs and symptoms in patients (patient video cases or PVCs) is a rapidly expanding field. The aims of this study were to evaluate whether the technical quality, or judgement of quality, of a video clip influences a paediatrician's judgment on acuity of the case and assess the relationship between perception of quality and the technical quality of a selection of video clips.

METHODS

Participants (12 senior consultant paediatricians attending an examination workshop) individually categorised 28 PVCs into one of 3 possible acuities and then described the quality of the image seen. The PVCs had been converted into four different technical qualities (differing bit rates ranging from excellent to low quality).

RESULTS

Participants' assessment of quality and the actual industry standard of the PVC were independent (333 distinct observations, spearmans rho = 0.0410, p = 0.4564). Agreement between actual acuity and participants' judgement was generally good at higher acuities but moderate at medium/low acuities of illness (overall correlation 0.664). Perception of the quality of the clip was related to correct assignment of acuity regardless of the technical quality of the clip (number of obs = 330, z = 2.07, p = 0.038).

CONCLUSIONS

It is important to benchmark PVCs prior to use in learning resources as experts may not agree on the information within, or quality of, the clip. It appears, although PVCs may be beneficial in a pedagogical context, the perception of quality of clip may be an important determinant of an expert's decision making.

Clinical assessment of hemodynamically unstable patients

PURPOSE OF REVIEW

Clinical examination of hemodynamically unstable patients provides timely, low-risk, and potentially useful diagnostic and prognostic information. This review will examine the evidence behind the use of clinical examination findings to drive treatment decisions and predict outcomes in patients with hemodynamic instability. An additional goal of the review is to place the use of clinical examination in context of more invasive techniques to diagnose and treat hemodynamically unstable patients.

RECENT FINDINGS

The development of novel diagnostic tests based on recently developed technology has focused attention on methods to determine when a test should enter routine clinical use. The widespread incorporation of pulmonary artery catheterization into clinical practice prior to formal evaluation of its ability to improve outcomes highlights the importance of properly evaluating diagnostic tests in critically ill patients. Formal evaluation of clinical examination as a diagnostic test will allow better understanding of its role in the hemodynamic evaluation of critically ill patients.

SUMMARY

Clinical examination remains an important initial step in the diagnosis and risk stratification of patients. Despite limitations of current techniques, the availability, low risk, and ability to perform repetitive tests ensure that clinical examination of the hemodynamically unstable patient will continue to be a useful tool for the intensivist until more useful tests are validated in this patient population.