Effects of burns and vasoactive drugs on human skin : Clinical and Experimental studies using microdialysis

Patients who require critical care, including those with burns, are affected by a systemic inflammatory reaction, which at times has consequences such as multiple organ dysfunction and failure. It has become increasingly evident that other factors important in the development of organ dysfunction are disturbances at the tissue level, in the microcirculation. Such disturbances activate cascade systems including stress hormones, all of which have local effects on organ function. Despite this knowledge, monitoring and treatment in critical illness today relies mainly on central haemodynamics and blood sampling. Microdialysis is a minimally invasive technique that enables us to study the chemical composition and changes in biochemistry in the extracellular, extravascular space in living tissues. Most of our current experience is from animal models, but the technique has also been used in humans and has become routine in many neurosurgical intensive care units to monitor brain biochemistry after severe injury. In skin, this experience is limited. During the first half of this thesis we studied the injured and uninjured skin of severely burned patients. The results show that there are severe local metabolic disturbances in both injured and uninjured skin. Most interesting is a sustained tissue acidosis, which is not detectable in systemic (blood) sampling. We also recorded considerable alterations in the glucose homeostasis locally in the skin, suggesting a cellular or mitochondrial dysfunction. In parallel, we noted increased tissue glycerol concentrations, which indicated appreciable traumainduced lipolysis. We also examined serotonin kinetics in the same group of patients, as serotonin has been claimed to be a key mediator of the vasoplegia and permeability disturbances found in patients with burns. We have shown, for the first time in humans to our knowledge, that concentrations of serotonin in skin are increased tenfold, whereas blood and urine concentrations are just above normal. The findings support the need ...