OBJECTIVE: To evaluate the early myocardial biochemical inflammatory response with the microdialysis technique during porcine endotoxemia and to simultaneously monitor systemic hemodynamics. DESIGN: Prospective, randomized, placebo-controlled trial with parallel groups. SETTING: Animal research laboratory at the University Hospital of Uppsala, Sweden. SUBJECTS: Thirteen piglets aged 12-14 wks receiving general anesthesia. INTERVENTIONS: After thoracotomy and the insertion of microdialysis probes in standardized locations in the left ventricle of the heart and in the quadriceps muscle, seven pigs received a continuous infusion of endotoxin, initiating a severe endotoxemic shock. Six pigs received saline instead of endotoxin. MEASUREMENTS AND MAIN RESULTS: Endotoxemia caused a rapid and pronounced elevation of a metabolite obtained from prostaglandin degradation, 15-keto-dihydro-PGF(2alpha), in myocardial microdialysate fluid being specific of cyclooxygenase (COX)-mediated inflammation (p