Serum activities of hydroxybutyrate dehydrogenase (HBD) and the isoenzymes of lactate dehydrogenase (LD) as an index of traumatic brain injury.

The lactate dehydrogenase (LD), the hydroxybutyrate dehydrogenase (HBD), and the LD isoenzyme activities in serum were followed in the posttraumatic period in 113 patients with cranio-cerebral injury, 70 of whom had verified brain contusion--laceration. In patients with brain contusion the HBD activity, known to be exerted mainly by the anodal LD isoenzyme fractions dominating in brain tissue, was significantly raised in 91% of the blood samples taken within four hours, and in 92% of the samples taken between 12 and 24 hours after trauma, while it was within normal limits in all the samples taken within four hours in patients with brain concussion, and increased in only 17% of the concussion patients 12-24 hours after trauma. The LD1 and the LD1+2 activities were of less diagnostic importance in blood samples taken during the first 24 hours. However, after 24 hours the LD1 activity was as informative as the HBD activity. The LD1 activity was normal in all concussion patients from the third day after trauma, while 78% of the contusion patients still showed raised LD1 activity then. The determination of HBD activity in serum in the immediate post-traumatic period is recommended as an appropriate method for screening parenchymatous brain injury. A complete LD isoenzyme separation may later add some further information in doubtful cases.