MicroDAIMON study: Microcirculatory DAIly MONitoring in critically ill patients: a prospective observational study

Abstract

Background: Until now, the prognostic value of microcirculatory alterations in critically ill patients has been mainly evaluated in highly selected subgroups. Aim of this study is to monitor the microcirculation daily in mixed group of Intensive Care Unit (ICU)-patients and to establish the association between (the evolution of) microcirculatory alterations and outcome.

Methods: This is a prospective longitudinal observational single-centre study in adult patients admitted to a 12-bed ICU in an Italian teaching hospital. Sublingual microcirculation was evaluated daily, from admission to discharge/death, using Sidestream Dark Field imaging. Videos were analysed offline to assess flow and density variables. Laboratory and clinical data were recorded simultaneously. A priori, a Microvascular Flow Index (MFI) < 2.6 was defined as abnormal. A binary logistic regression analysis was performed to evaluate the association between microcirculatory variables and outcomes; a Kaplan-Meier survival curve was built. Outcomes were ICU and 90-day mortality.

Results: A total of 97 patients were included. An abnormal MFI was present on day 1 in 20.6%, and in 55.7% of cases during ICU admission. Patients with a baseline MFI < 2.6 had higher ICU, in-hospital and 90-day mortality (45 vs. 15.6%, p = 0.012; 55 vs. 28.6%, p = 0.035; 55 vs. 26%, p = 0.017, respectively). An independent association between baseline MFI < 2.6 and outcome was confirmed in a binary logistic analysis (odds ratio 4.594 [1.340-15.754], p = 0.015). A heart rate (HR) ≥ 90 bpm was an adjunctive predictor of mortality. However, a model with stepwise inclusion of mean arterial pressure < 65 mmHg, HR ≥ 90 bpm, lactate > 2 mmol/L and MFI < 2.6 did not detect significant differences in ICU mortality. In case an abnormal MFI was present on day 1, ICU mortality was significantly higher in comparison with patients with an abnormal MFI after day 1 (38 vs. 6%, p = 0.001), indicating a time-dependent significant difference in prognostic value.

Conclusions: In a general ICU population, an abnormal microcirculation at baseline is an independent predictor for mortality. In this setting, additional routine daily microcirculatory monitoring did not reveal extra prognostic information. Further research is needed to integrate microcirculatory monitoring in a set of commonly available hemodynamic variables. Trial registration NCT 02649088, www.clinicaltrials.gov . Date of registration: 23 December 2015, retrospectively registered.

Trial registration: ClinicalTrials.gov NCT02649088.

Keywords: Capillaries; Critical illness; Microcirculation; Physiologic monitoring; Tachycardia; Video microscopy.

Fig. 1

Kaplan–Meier survival analysis. a Represents two subgroups, separated by microvascular blood flow (MFI) < 2.6 versus MFI ≥ 2.6. b Represents four subgroups, separated by MFI with identical cut-off value and heart rate (HR) ≥ 90 versus < 90 bpm

Fig. 2

Prognostic model with stepwise inclusion of consecutive hemodynamic variables: mean arterial pressure (MAP) in mmHg, heart rate (HR) in bpm, (arterial) lactate in mmol/L and Microvascular Flow Index (MFI) in AU

Fig. 3

Evolvement over time of sequential organ failure assessment (SOFA) score and Microvascular Flow Index (MFI) in the first 7 days of ICU admission. Box and 10–90th percentile whisker plots with individual outliers