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Cerebrospinal fluid (CSF) lactate and pyruvate concentrations were determined in 20 patients with diabetes mellitus but without disturbance of consciousness and five who recovered from hypoglycaemic coma. CSF lactate was slightly but significantly higher in diabetes mellitus (1.78, SEM 0.04 m mol/l) than that in 15 control subjects (1.40, SEM 0.05 m mol/l). In those who recovered from hypoglycaemic coma, CSF lactate was markedly elevated to 2.45-4.43 m mol/l. CSF glucose concentrations, however, were substantially the same between treated hypoglycaemic and diabetes mellitus groups. These findings indicate that CSF lactate levels increase with glycaemic levels in diabetes mellitus owing to enhanced glucose influx into glycolytic pathway of the brain, and also increases in treated hypoglycaemic coma probably due to mitochondrial dysfunction or damage.

Some serum and CSF concentrations were measured in five patients with severe hyperosmolar coma (mean blood sugar = 58.9 mmol/l; osmolarity = 406 mosmol/l). A gradual decrease of serum osmolarity prevented the development of an osmotic gradient between CSF and extracellular space. Insulin treatment (1-20 IU/h) with a motor infusion pump and infusion of hypertonic solutions decreased serum osmolarity by 2-4 mosmol/l X h. The faster fall of glucose in the extracellular space was compensated by hypertonic saline infusions (up to 365 mosmol/l). All patients survived.