[Metabolic acidosis and ketone body in severely head-injured patients]

Increase of ketone body concentration in plasma is induced by various factors such as onset of diabetes. Secretion of excessive stress hormone including catecholamine is responsible for stimulation of lipolysis which increases plasma ketone body concentration. Catecholamine levels reflect the severity of the neurologic insult, so this is a basis for the use of catecholamine measurements as a physiological marker of patient outcome. Twenty-seven patients with severe head injury and twenty-five healthy volunteers were enrolled in this study, but patients with diabetes or liver dysfunction were excluded. The patients with severe head injury consisted of 19 with focal injury and 8 with diffuse injury. The outcome was as follows; 14 patients died and 13 patients survived. We collected arterial blood samples as promptly as possible after onset of severe head injury and measured the following: 1, base excess; 2, beta-hydroxybutyrate; 3, acetoacetate; 4, lactate; 5, epinephrine; 6, norepinephrine. The ketone body (beta-hydroxybutyrate + acetoacetate) concentration in plasma was significantly elevated in patients with severe head injury. The increment of beta-hydroxybutyrate levels was greater than that of acetoacetate levels, resulting decreased arterial ketone body ratio (AKBR; acetoacetate/beta-hydroxybutyrate). We demonstrated that plasma ketone body concentrations were elevated and the AKBR decreased in severe head-injured patients. Elevation of catecholamine has been reported as a stress reaction in severe head injury. Catecholamine is most potent in stimulating lipolysis, and ketogenesis. Therefore, the ketonemia observed in severe head injury is most likely to be induced by elevation of catecholamine levels. The degree of ketonemia may be an index of the severity of severe head injury.