Cortical Extracellular Sodium Transients after Human Head Injury: An Indicator of Secondary Brain Damage?

Abstract

Animal studies indicate that elevated extracellular sodium can increase glutamate-induced excitotoxicity. Therefore, we investigated the relationship between sodium and glutamate and the effect of changes in sodium concentrations on the outcome of head-injured patients. Thirty-four (34) patients were selected for this study and divided into a group of patients having episodes (≥30-min) of high sodium in dialysates (≥200 mM; HIGH, n = 11) and a group of patients having no such episodes (NORMAL, n = 23). Levels for sodium (226 ± 5.7 mM), glutamate (12.53 ± 2.2 μM) and ICP (32.2 ± 4.0mm Hg,) were relatively high during the high sodium episodes. Overall, mean values for glutamate, ICP and outcome did not differ amono both groups. The mean dialysate sodium concentration, however, was significantly higher in the HIGH (178 ± 6 mM) compared to the NORMAL group (158 ± 3 mM; p < 0.01). Spearman rank correlation between sodium and glutamate or ICP were not significant. The HIGH sodium group did not have significantly more patients with poor outcome than the NORMAL group. The results indicated sodium concentrations did not affect the outcome of head-injured patients. However, other sodium monitoring techniques are desirable to elucidate these apparent potentially major sodium transients, which we have observed in the human cortex, after severe head injury.