Gingival capillary refill time: a new approach to assess tissue perfusion

Acute circulatory is a life-threatening condition, marked by inadequate tissue perfusion and oxygen delivery, leading to cellular dysfunction. Capillary refill time (CRT) is a widely used bedside marker of tissue perfusion but has limitations due to its sensitivity to temperature, pigmentation, and peripheral vascular disease [1, 2]. In veterinary medicine, gingival capillary refill time (GRT) is used to assess circulatory status via mucosal microcirculation, but its relevance in humans is unexplored [3]. GRT may provide a more robust alternative by directly assessing mucosal microcirculation and mitigating CRT limitations.

We conducted an ancillary analysis of the PeachCART cohort (NCT02248025) [4] to evaluate the feasibility, reproducibility, and clinical relevance of GRT in critically ill patients receiving fluid resuscitation for acute circulatory failure. We hypothesized that GRT would be feasible, correlate with CRT, and be a reliable predictor of perfusion-based fluid responsiveness.

The protocol was approved by the institutional review board; Oral and written information was given to all patients or relatives. Signed consent was waived by the ethics committee. GRT and CRT were recorded using an iPhone 6™ (8 MP camera). GRT involved applying calibrated pressure to the gingival mucosa with a 2 mL air-filled syringe compressed to 1 mL for 7 s. Four videos were taken per step by a single investigator and analyzed by two blinded readers. CRT was measured on chest skin using a 10 mL syringe compressed to 7 mL, as previously described. Volume expansion consisted of 500 mL lactated Ringer over 20 min, without changes in sedation or vasoactive drugs. Patients were monitored with PiCCO™ and thermodilution was performed before and after volume expansion. Metabolic and hemodynamic parameters, general patient characteristics, and Fitzpatrick skin phototype were also recorded. Primary outcomes were GRT feasibility and reproducibility; secondary outcomes included its correlation with CRT, predictive value for perfusion based fluid responsiveness (≥ 25% CRT reduction) [4], and association with hemodynamic and metabolic parameters.

Thirty-two patients were analyzed (median age: 62 [54–69] years, median SOFA score: 9 (6–11), SAPS II: 43 (33–51), and 84% on mechanical ventilation). Median GRT was 2.3 (1.6–3.2) s, and median CRT was 2.9 [2.4–3.8] s. Based on our linear regression model, the classical threshold of 3 s to define abnormal CRT corresponds to an estimated GRT of approximately 2.12 s. GRT was feasible in all patients, with a slightly lower interobserver coefficient of variation (5.2% [95% CI 0.9–9.6]) compared to CRT (7.3% [95% CI 3.9–10.2]). The median Fitzpatrick skin phototype was 3, GRT was easier to read in patients with phototype 1 and 4 as illustrated in Fig. 1. GRT was successfully measured in 97% of patients. No major adverse events were reported, except mild discomfort in one patient.

Fig. 1

Visual representation of GRT and CRT dynamics in a phototype I and IV patients

Full size image

GRT strongly correlated with CRT at baseline (R²=0.621, p < 0.001) and after VE (R²=0.609, p < 0.001). GRT and CRT increased when body temperature decreased, GRT was less influenced by body temperature (R²=0.159, p = 0.054) compared to CRT (R²=0.322, p = 0.004).

Patients with a high GRT (> 2.3s) had significantly lower systolic arterial pressure (93 mmHg vs. 108 mmHg, p = 0.014) and higher central venous pressure (9 mmHg vs. 5 mmHg, p = 0.047) compared to those with a low GRT (≤ 2.3s). They also exhibited a lower cardiac index (2.3 vs. 2.9 L/min/m², p = 0.027). Patients with high CRT(> 2.9 s) had significantly lower systolic arterial pressure (94 mmHg vs. 108 mmHg, p = 0.028) and similar central venous pressure (9 mmHg vs. 7 mmHg, p = 0.364) compared to those with a low CRT (≤ 2.9s). They also exhibited a lower cardiac index (2.3 vs. 2.9 L/min/m², p = 0.006).

The diagnostic accuracy of ΔGRT for predicting perfusion-based fluid responsiveness, with 13 patients (42%) identified as perfusion-based responders, was excellent (AUC-ROC 0.94 [95% CI 0.84–0.99]). However, neither GRT (AUC-ROC of 0.65 (95% CI [0.44–0.82])) nor CRT (AUC-ROC of 0.55 (95% CI [0.33–0.76]).) reliably predicted cardiac index-based fluid responsiveness (≥ 15% increase in CI), with 12 patients (38%) classified as cardiac index-based responders.

Our study demonstrates that GRT is feasible, reproducible, and strongly correlated with CRT. Moreover, GRT shows a weaker association with hemodynamic variables such as MAP, CO, and CVP. These findings support the classification of GRT as a perfusion-related parameter that is closely linked to CRT yet partially independent of macrocirculatory influences—consistent with other indices of tissue perfusion or microcirculation. Additionally, the reduced association between GRT and body thermoregulation suggests its potential utility in prehospital settings, where environmental factors can compromise the reliability of CRT measurements. Importantly, GRT may offer advantages over CRT in patients with very dark or light skin, where CRT assessment is challenging. Examples provided herein suggest that GRT may be easier to assess in patients with light and dark skin. However, further evaluation is needed in phototypes 5 and 6, as this study included only phototypes 1 to 4. In acute circulatory failure, monitoring tissue perfusion in vital organs is crucial, with gut perfusion playing a key role in multiple organ dysfunction syndrome. Although oral mucosal and gut perfusion are not identical, mucosal perfusion is generally more closely aligned with organ perfusion than skin perfusion. This holds true even though an association between gut perfusion and CRT has been suggested [5]. Since CRT may underdiagnose circulatory failure in some populations, developing equitable diagnostic methods remains essential [6]. Additionally, GRT’s diagnostic accuracy for perfusion-based fluid responsiveness suggests that it could be an alternative to CRT in guiding resuscitation strategies. However, further studies are needed to validate its clinical application across diverse patient populations and investigate its prognostic value beyond fluid responsiveness assessment.

GRT is a promising alternative to CRT for assessing tissue perfusion in critically ill patients, offering potential advantages in reliability and applicability across diverse skin pigmentations. Given that minority and ethnic populations are often underserved by traditional bedside tools like CRT, GRT may provide a more equitable and accurate method of evaluation for all patient groups. These findings highlight the need for further research to validate GRT’s feasibility and clinical utility in diverse populations.

As shown herein, the first image illustrates the compression of the skin of the chest (using a 10 mL air-filled syringe compressed to 7 mL, functioning as a piston to compress the skin for 7 s) (A) or gingival mucosa (using a 2 mL air-filled syringe compressed to 1 mL, functioning as a piston to compress the mucosa for 7 s)(B). The subsequent images depict time-stamped frames capturing the progression of both the CRT and GRT sequences in the same patient. Images of two patients are displayed (1.A, B and 2.A, B). In both patients—Patient 1 with light skin and phototype I, and Patient 2 with dark skin and phototype IV—the recoloration is more clearly observed in the GRT sequence compared to the CRT sequence.

No datasets were generated or analysed during the current study.

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Authors and Affiliations

1. Département d’Anesthésie Réanimation, Centre Hospitalier Louis Pradel, Hospices Civils de Lyon, Lyon, France

   Matthias Jacquet-Lagrèze, Martin Ruste, Elodia Noumedem, Nourredine Bouhamri, Philippe Portran & Jean-Luc Fellahi

2. Université Claude-Bernard, Lyon 1, Campus Lyon Santé Est, Lyon, France

   Matthias Jacquet-Lagrèze, Martin Ruste, Philippe Portran & Jean-Luc Fellahi

3. CarMeN Laboratoire, Inserm UMR 1060, Université Claude Bernard Lyon 1, Lyon, France

   Matthias Jacquet-Lagrèze, Martin Ruste & Jean-Luc Fellahi

4. Département d’anesthésie réanimation de l’hôpital Cardiologique Louis Pradel, 59 Boulevard Pinel, Bron, 69500, France

   Matthias Jacquet-Lagrèze

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1. Matthias Jacquet-LagrèzeView author publications

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Contributions

Substantial Contributions to Study Concept and Design: Acquisition of data, MJL, NB, PPAnalysis of data, MJL, MR, JLFInterpretation of data: MJL, EN, JLF Drafting the Manuscript or Revising It: MJL, MR, EN, NB, PP, JLFFinal Approval of the Version to Be Published: MJL, MR, EN, NB, PP, JLFAccountability for All Aspects of the Work: MJL, MR, EN, NB, PP, JLF.

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Correspondence to Matthias Jacquet-Lagrèze.

Ethics approval and consent to participate 

The experimental protocol was approved by the Institutional Review Board (IRB) for human projects (CPP Lyon Sud-Est, ANSM: 2014-A01034-43). It was registered a priori in Clinicaltrial.gov: (NCT02248025). Oral and written information was given to all patients or relatives. The need to obtain signed informed consent was waived by the IRB.

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Oral and written information was provided to all patients or their representatives, including details about video recordings of gingival and skin assessments, with no identifying features captured. The institutional review board waived the requirement for signed informed consent.

Competing interests

The authors declare no competing interests.

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Jacquet-Lagrèze, M., Ruste, M., Noumedem, E. et al. Gingival capillary refill time: a new approach to assess tissue perfusion. Crit Care 29, 331 (2025). https://doi.org/10.1186/s13054-025-05555-9

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• Received: 23 May 2025

• Accepted: 09 July 2025

• Published: 28 July 2025

• DOI: https://doi.org/10.1186/s13054-025-05555-9

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