Association of sublingual microcirculation parameters and capillary refill time in the early phase of ICU admission

Abstract Background: Recent studies demonstrate the advantage of peripheral perfusion-targeted resuscitation protocols based on capillary refill time (CRT) assessment in critically ill patients. Additionally, sidestream dark field (SDF) imaging could direct visualize sublingual microcirculation of critically ill patients. This study aimed to determine the association between the sublingual microcirculation and CRT in critically ill patients in the early phase of intensive care unit (ICU) admission. Methods: This prospective, observational, pilot study included 282 patients in the ICU of Zhongnan Hospital of Wuhan University between October 2021 and January 2022. All patients underwent simultaneous measurements by CRT and SDF imaging within 24 hours of ICU admission. Additionally, other clinical data such as demographic variables, hemodynamics, laboratory values, treatment, and physiological parameters were also included. The primary outcome was the association between CRT and simultaneous sublingual microcirculation parameters in critically ill patients.Results: Of the 282 included patients, 106 (37.6%) were female, the median (IQR) age was 63 (53-74) years, and the median (IQR) SOFA score was 5 (2-7). Microcirculatory measurements (CRT and SDF imaging) were performed at 10.2 ± 5.7 hours after ICU admission. Significant relationships were observed between the CRT and MFI (r = -0.4430, p < 0.001), PPV (r = -0.3708, p < 0.001), PVD (r = -0.1835, p = 0.0020), and HI (r = 0.4378, p < 0.001). Neither TVD (p = 0.9641) nor De Backer score (p = 0.5202) were related to the CRT. Compare to CRT< 3s group, MFI (2.60 vs. 2.88, p < 0.001), PPV (91.35% vs. 99.10%, p < 0.001), PVD (13.36 mm/mm2 vs. 14.55 mm/mm2, p = 0.002), and HI (0.46 vs. 0.15, p < 0.001) were significantly worse in the CRT ≥ 3s group. The similar results were also found in the sepsis subgroup and the hyperlactatemia subgroup. Prolonged CRT was an independent predictor of 28-days mortality (OR = 1.296; (95%CI, 1.078-1.558); p = 0.006).Conclusions: Our findings suggested that there was a significant and moderate association between CRT and some sublingual microcirculation parameters more related to perfusion (MFI, PPV, and HI) in heterogeneous ICU patients at the early phase of admission.Trial registration: The study was retrospectively registered on November 7, 2021, ChiCTR2100052999.