Dynamics of leucocytes correlate with increased pulmonary vascular permeability and decreased PaO2:FiO2 ratio early after major burns

• Introduction: The lung is affected soon after a major burn as indicated by a decreased PaO2:FiO2 ratio. The exact mechanism underlying this is not known. Polymorphonuclear leucocytes (PMN) are activated systemically and their numbers are largely increased soon after a burn followed by a rapid decline to low normal or subnormal numbers within 24 hours, possibly by increased extravasation. Experimental data have supported the hypothesis that an important target for this extravasation is the lungs. Other studies also show that when PMN adhere to endothelial cells they increase vascular permeability, and this effect is mediated, at least in part, by release of heparin binding protein (HBP, also known as CAP-37 and azurocidin). We hypothesised that there is a relation between early increased pulmonary vascular permeability or a decreased PaO2:FiO2 ratio and the dynamic change in blood leucocytes after a burn, possibly mediated by the local release of HBP.Material and methods: This is a prospective, descriptive, exploratory, singlecentre study at a national burn centre. We investigated the dynamic changes of leucocytes in blood, plasma concentrations of HBP, pulmonary vascular permeability index (PVPI) by thermodilution, and PaO2:FiO2 ratios in 20 patients during the first 21 days after a major burn (20% >total burn surface area %).Results: Median total burn surface area was 40% (IQR 25-52) and full thickness burn 28% (IQR 2-39). There was a correlation between the early (<24 hours) alteration in circulating white blood cell count and both early increased vascular permeability in the lung (r=0.63, p=0.004) and the decreased oxygenation index defined as PaO2:FiO2 < 27 kPa (p=0.004). There were no associations between plasma concentrations of HBP and measured pulmonary vascular permeability or PaO2:FiO2 ratios.Conclusions: The results indicate that trapping of leucocytes in the lung may be an important factor in early increased pulmonary vascular permeability and decrease of the PaO2:FiO2 ratio. Our data do not support the idea that HBP, assessed by systemic plasma concentrations, mediate this effect.

Nyckelord

ARDS

azurocidin

burn

CAP-37

HBP

leukocyte

mediator

permeability

PMN

trauma

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