title: A pilot study of quantitative capillary refill time to identify high blood lactate levels in critically ill patients.
abstract: BACKGROUND
  We developed a new device to quantify capillary refill time (CRT) by applying the pulse oximeter principle, and evaluated the correlation between quantitative CRT (Q-CRT) and hypoperfusion status, as represented by blood lactate levels, in critically ill patients.
  
  
  METHODS
  A pilot study was undertaken in the intensive care unit (ICU) in a tertiary emergency medical centre. While the pulse oxygen saturation sensor was placed on the finger of the patients, transmitted light intensity (TLI) was measured with a pulse oximeter (OLV-3100; Nihon Kohden, Tokyo, Japan) before and during compression of the finger. Q-CRT was defined as the interval from the release of compression to the time when TLI reached 90% of baseline.
  
  
  RESULTS
  Q-CRT was analysed in a total of 57 waveforms among 23 patients and statistically correlated with lactate levels (Spearman's rank correlation coefficient, 0.681; p<0.001). The cut-off value of Q-CRT for predicting a lactate level of ≥2.0 mmol/L was 6.81 s (area under the curve (AUC) (95% CI 1.000 (1.000 to 1.000), p<0.001), and the value for predicting a lactate level of ≥4.0 mmol/L was 7.27 s (AUC=0.989 (95% CI 0.954 to 1.000), p<0.001).
  
  
  CONCLUSIONS
  Q-CRT correlated with blood lactate levels in this pilot study. The most useful threshold for Q-CRT was ∼6-8 s. Further study is needed to investigate the potential role of this modality as a non-invasive predictor of hypoperfusion in the emergency department, ICU and operating room settings.
authors.affiliation: Department of Emergency Medicine, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Morimura
authors.affiliation: Department of Emergency Medicine, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Takahashi
authors.affiliation: Department of Emergency Medicine, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Doi
authors.affiliation: Department of Emergency Medicine, Teikyo University School of Medicine, Tokyo, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ohnuki
authors.affiliation: Department of Emergency Medicine, Teikyo University School of Medicine, Tokyo, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Sakamoto
authors.affiliation: Department of Emergency Medicine, Teikyo University School of Medicine, Tokyo, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Uchida
authors.affiliation: Department of Emergency Medicine, Teikyo University School of Medicine, Tokyo, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Department of Emergency Medicine, Teikyo University School of Medicine, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujita
authors.affiliation: Department of Emergency Medicine, Teikyo University School of Medicine, Tokyo, Japan.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Ikeda
mesh_terms: D002196:Capillaries / Q000503:physiopathology*; D016638:Critical Illness; D005260:Female; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010092:Oximetry / Q000295:instrumentation*; D010173:Palpation; D010865:Pilot Projects; D011237:Predictive Value of Tests; D012372:ROC Curve; D012039:Regional Blood Flow / Q000502:physiology*
chemical_list: D019344:Lactic Acid
keywords: Assessment; Clinical Assessment; Equipment Evaluation; Intensive Care; Research, Clinical