Background and aims Microcirculation is usually evaluated by indirect means in critically ill children. The aim of this study is to evaluate if there is correlation between microcirculation parameters using sidestream dark field (SDF) microscopy and macrohaemodynamic parameters, perfusion parameters and the need for some treatments used in critically ill children.

Methods Microcirculation measurements were performed using sublingual SDF microscopy in 18 children between 0.3 and 211.8 months. Microvascular flow index (MFI), Perfused vessel density (PVD), proportion of perfused vessels (PPV%) and heterogeneity index (HI) were determined. Clinical (heart rate, blood pressure, core and skin temperature), laboratory (blood gases, haemoglobin and lactate concentration) and treatment (vasoactive drug dose) variables were recorded simultaneously.

Results 21 measurements were analysed. MFI showed negative correlation with central venous pressure (r=-0.506 p = 0.023), venous pH (r=-0.719 p = 0.001), haemoglobin (r=-0.439 p = 0.045), arterial lactate (r=-0.553 p = 0.011) and adrenaline dose (r=-0.659 p < 0.001), and positive correlation with central venous O2 saturation (r = 0.565 p = 0.012) and systolic arterial pressure (SAP) (r = 0.534 p = 0.022). PPV% showed positive correlation with SAP (r = 0.604 p = 0.006) and core temperature (r = 0.491 p = 0.024) and negative correlation with adrenaline dose (r=-0.585 p = 0.025). HI showed negative correlation with SAP (r=-0.526 p = 0.005) and positive correlation with haemoglobin (r = 0.594 p = 0.005), venous lactate (r = 0.535 p = 0.032) and core temperature (r = 0.491 p = 0.024). PVD showed positive correlation with arterial O2 saturation (r = 0.453 p = 0.045).

Conclusions Microcirculation parameters showed moderate correlation with other macrohaemodynamic and perfusion parameters as well as with the need for some treatments. SDF microscopy may enable evaluation of microcirculation in critically ill children.