The relevance of fluid and blood management using microcirculatory parameters in chidren undergoing craniofacial (CF) surgery
Introduction: Managing the bleeding pediatric patient perioperatively can be extremely challenging. Non-invasive techniques such as orthogonal polarization spectral (OPS) imaging has allowed clinicians and researchers to perform bed-side monitoring of the microvascular network. Therefore, this present study was performed to investigate the effects of blood management using simultaneous macro- and microhemodynamic parameters measurement in children undergoing craniofacial surgery. 
Method: 14 children who underwent surgery were included in this study. The indications for RBC transfusion were changes of hb/hct levels, the presence of signs of altered tissue perfusion (i.e elevated lactate) and impaired microcirculation images. A 8% change from baseline capillary perfusion density was accepted as a clinically significant change to guide management. Haemodynamic variables (HR, MAP, CVP), laboratory parameters (Hb, Htc, lactate, SvO2 and K+) and microcirculatory variables (Total vascular density-TVD (mm/mm2), microvascular flow index-MFI (AU), perfused vessel density-PVD (mm/ mm2), proportion of perfused vessels-PPV (%) of vessels were obtained baseline(T1), before(T2) and after RBC
transfusion(end of the operation)(T3). These images have been analysed by using AVA (Automated Vascular Analysis) software. Data was analysed by Friedman, Wilcoxon and Spearman correlation test.
Main Results:  4 patients did not need RBC transfusion because of sufficient Hb values in whom a decrease in microcirculation parameters was observed which did not return to baseline values. In the other 10 patients who received RBCs, capillary perfusion was higher at T3 when compared with the values of at T2 (from 11.47(9.16-12.93) to 13.83(10.04-16.87); 12%, >8%)(p<0.05). Six patients reached baseline microcirculatory values(T1). RBC transfusions increased hct% values from 16.4(12.3-20.9)(T2) to 18.2(14.8-23.5)(T3)(p<0.05). There was no significant correlation between microvascular changes and other hemodynamic and tissue perfusion parameters (p>0.05). 
Conclusion: The sublingual microcirculation could change by RBC transfusion but there was not any correlation between microcirculation changes, hemodynamic and tissue perfusion parameters even with hct values. The indication, guidance and timing of fluid and blood therapy may be assessed by bedside microvascular analysis in combination with standard haemodynamic monitoring.