Effects of dopamine on cerebral circulation and oxygen metabolism in endotoxic shock

Experimental endotoxic shock in normocapnic dogs decreases cerebral blood flow (CBF) and increases cerebral metabolic rate of oxygen (CMRO2). In 6 animals, an iv injection of 1.0-1.5 mg/kg of Escherichia coli endotoxin was followed by iv infusion of dopamine HCI at a rate of 3-24 Micrograms/kg . min. Doses of only 5 micrograms/kg . min maximally increased both CBF and CMRO2. There were no significant changes in cardiac output and whole body oxygen consumption. Mean aortic pressure and mean pulmonary artery pressure increased slightly after doses of 20 micrograms/kg . min. Results indicate that damage to the blood-brain barrier (BBB) after endotoxin administration allowed circulating monoamines to directly influence cerebral metabolisms.