Red blood cell and tissue water content in experimental thermal injury

Oedema formation and changes in local blood flow are known phenomena in burns. The relationship between these two is not clearly described. The aim of this study was firstly to examine both the contents of red blood cells and tissue water in skin and subcutaneous fat after experimental burns of different depths in pigs, and secondly, to confirm our recent findings of the increased dielectric constant of skin and subcutaneous fat reflecting considerable oedema formation, especially in fat after thermal injury. Methods Superficial, partial and full thickness contact burns were created to pigs and followed for 24 h. Radioactive Cr-51 labelling of red cells was used to estimate the number of red cells in tissue, and the absolute amount of water was determined by lyophilisation. Results A decreased number of labelled red cells in skin and an increase in tissue water in subcutaneous fat were found regardless of burn depth. The highest water amount in fat was found in the partial thickness burns. Conclusion All burn depths resulted in a diminished number of labelled red blood cells in skin and a significant increase in the absolute water amount in subcutaneous fat at 24 h post injury. The findings in fat support our recent findings of highly elevated dielectric constants measured by the new in vivo method of dielectric measurements.