LAUSR

BACKGROUND Macro, and microcirculatory effects of crystalloids and colloids are difficult to compare, because interventions to achieve haemodynamic stability seldom follow similar criteria. OBJECTIVES Our aim was to compare the effects of crystalloids and colloids on the microcirculation during free flap surgery when management was guided by detailed haemodynamic assessment. DESIGN A prospective randomised, controlled clinical trial. SETTINGS The investigation was performed at the University of Szeged, Hungary. PATIENTS Patients undergoing maxillofacial tumour resection and free flap reconstruction were randomised into groups treated with either intra-operative crystalloid (Ringerfundin, n = 15) or colloid (6% hydroxyethyl starch, HES, n = 15) solutions. INTERVENTIONS Macrohaemodynamics were monitored by a noncalibrated device (PulsioFlex-PULSION). Central venous oxygen saturation, venous-to-arterial PCO2-gap, lactate levels and urine output were measured hourly. Maintenance fluid was Ringerfundin (1 ml kg h), and a multimodal, individualised, approach-based algorithm was applied to guide haemodynamic support. Hypovolaemia was treated with Ringerfundin or HES fluid boluses, respectively. The microcirculatory effects were assessed by laser-Doppler flowmetry (PeriFlux 5000 LDPM), with the probe placed on the flap and on a control area. Measurements were performed after the flap was prepared, then 1 and 12 h later. MAIN OUTCOME MEASURES The primary end-point was microcirculatory perfusion as determined by laser-Doppler flowmetry. RESULTS There was no difference between the groups regarding patient characteristics. Both groups remained haemodynamically stable throughout due to the use of approximately a 1.5 times higher total fluid volume in the Ringerfundin group than in the HES group: mean ± SD: 2581 ± 986 and 1803 ± 497) ml, respectively, (P = 0.011). There was no significant difference in the microcirculatory blood flow between the groups. CONCLUSION Our results showed that when fluid management was guided by detailed haemodynamic assessment, more crystalloid than colloid was needed to maintain haemodynamic stability, but there was no difference between the effects of crystalloids and colloids on the microcirculation. TRIAL REGISTRATION ClinicalTrials.gov (NCT03288051).