Progressing cerebral infarction in relation to plasma glucose in gerbils

Acute mental status changes

Acute changes in mental status can occur in any hospital setting. Clinicians are often at a loss to define accurately the course of a change in mental status, because of poor differentiation in the terminology surrounding this difficult diagnosis. A clear understanding of the differences among several levels of altered mental status is needed to evaluate, accurately diagnose, and treat those patients with altered mental states. The differential diagnosis of altered mental status is diffuse and includes supratentorial mass lesions, infratentorial mass lesions, and metabolic disorders. Development of an individualized differential diagnosis and diagnostic approach for cases of altered mental status represents a challenge to all levels of clinicians.

The effect of hyperglycemia on cerebral metabolism during hypoxia-ischemia in the immature rat

Unlike adults, hyperglycemia with circulating glucose concentrations of 25-35 mM/L protects the immature brain from hypoxic-ischemic damage. To ascertain the effect of hyperglycemia on cerebral oxidative metabolism during the course of hypoxia-ischemia, 7-day postnatal rats underwent unilateral common carotid artery ligation followed by exposure to 8% O2 for 2 h at 37 degrees C. Experimental animals received 0.2 cc s.c. 50% glucose at the onset of hypoxia-ischemia, and 0.15 cc 25% glucose 1 h later to maintain blood glucose concentrations at 20-25 mM/L for 2 h. Control rat pups received equivalent concentrations or volumes of either mannitol or 1 N saline at the same intervals. The cerebral metabolic rate for glucose (CMRglc) increased from 7.1 (control) to 20.2 mumol 100 g-1 min-1 in hyperglycemic rats during the first hour of hypoxia-ischemia, 79 and 35% greater than the rates for saline-and mannitol-injected animals at the same interval, respectively (p < 0.01). Brain intracellular glucose concentrations were 5.2 and 3.0 mM/kg in the hyperglycemic rat pups at 1 and 2 h of hypoxia-ischemia, respectively; glucose levels were near negligible in mannitol- and saline-treated animals at the same intervals. Brain intracellular lactate concentrations averaged 13.4 and 23.3 mM/kg in hyperglycemic animals at 1 and 2 h of hypoxia-ischemia, respectively, more than twice the concentrations estimated for the saline- and mannitol-treated littermates. Phosphocreatine (PCr) and ATP decreased in all three experimental groups, but were preserved to the greatest extent in hyperglycemic animals. Results indicate that anaerobic glycolytic flux is increased to a greater extent in hyperglycemic immature rats than in normoglycemic littermates subjected to cerebral hypoxia-ischemia, and that the enhanced glycolysis leads to greater intracellular lactate accumulation. Despite cerebral lactosis, energy reserves were better preserved in hyperglycemic animals than in saline-treated controls, thus accounting for the greater resistance of hyperglycemic animals to hypoxic-ischemic brain damage.

Metabolic changes associated with altering blood glucose levels in short duration forebrain ischemia

31P nuclear magnetic resonance spectroscopy was used to follow changes in cerebral pH and high-energy phosphate metabolites during forebrain ischemia in hypo-, normo- and hyperglycemic rats, and during reperfusion in animals in which the blood glucose level was altered post-ischemia. Pre-ischemia, no differences in the levels of inorganic phosphate (Pi) and adenosine triphosphate (ATP) relative to phosphocreatine (PCr) or in tissue pH between blood glucose groups were observed. During ischemia, the decrease in tissue pH was found to be dependent on the pre-ischemic blood glucose concentration, being greatest in hyperglycemic and least in hypoglycemic animals. The increase of Pi, a consequence of the hydrolysis of high-energy phosphate metabolites, also depended on the blood glucose concentration, being greatest in hypoglycemic and least in hyperglycemic animals. ATP and PCr decreased more rapidly in hypoglycemic rats compared to normo- or hyperglycemic animals, which showed no differences in the rates of depletion. Post-ischemic hyperglycemia resulted in delayed recovery of tissue pH in all groups and of PCr and ATP in animals hyperglycemic throughout the experiment. Insulin administration immediately following ischemia increased the rate of recovery of pH, ATP and PCr in hyperglycemic animals. ATP remained significantly below pre-ischemia level in all subgroups at 1 h post-ischemic, while PCr was lower than it was pre-ischemia only in those subgroups hyperglycemic prior to and/or following ischemia. In animals maintained severely hypoglycemic throughout the experiment, erratic blood pressure and cerebral energy failure during the reperfusion interval were observed.