Lactosuria - a new metabolic feature of severe cerebrocranial trauma.

Under controlled dietary conditions the urinary excretion of lactose was studied in 15 healthy persons, 15 patients with cerebrocranial trauma and 15 patients with extracranial trauma. Urinary lactose levels were found to be markedly increased in patients with head injury and ranged from 10.3 to 147.7 mg/24 h with a mean 63.4 mg/24 h in contrast to patients with other injuries (3.1 to 17.0 mg/24 h, mean 9.4 mg/24 h; P less than 0.001), and healthy individuals (3.3 to 17.93 mg/24 h, mean 7.6 mg/24h; P less than 0.001). In the head injury group the lowest values were found in drowsy or disoriented patients with cerebral concussion and the highest in comatose subjects. The level of lactosuria decreases after approximately 12 to 16 days to normal levels even when the patient remains unconscious. An earlier return to normal excretion parallels or preceeds the reappearance of consciousness. Unlike alimentary lactosuria, caused by ingestion of milk or other dairy products in large quantities, the elevated lactose levels in head injury patients were not usually accompanied by a comparable rise in galactose excretion, mean 11.45 mg/24 h versus 9.17 mg/24 h in controls; P less than 0.2. The mechanism of enhanced lactose excretion in severe cerebrocranial trauma remains unknown. It is suggested that it may be associated with either an increased catabolism of brain gangliosides or a stimulated lactose synthesis in peripheral tissues probably due to the participation of the lactogenic hormone prolactin.