Correlation between tissue lactate levels and electroencephalogram in evaluating the severity of experimental head trauma.

OBJECTIVE

The objective of this study was to develop an electroencephalographic grading scale for evaluating the severity of head trauma and assessing the correlation of this scale with brain tissue lactate concentrations.

DESIGN

Animal experiment.

SETTING

Animal research laboratory in a university hospital.

SUBJECTS

Thirty New Zealand rabbits were divided into three groups.

INTERVENTIONS

Rabbits were anesthetized, and bilateral frontoparietal craniectomy was performed. An electroencephalogram was recorded over the dura from both sides. After electroencephalographic recording, unilateral trauma was produced by using the weight drop method with a calculated force of 400 g.cm and 800 g.cm in group 2 (n = 10) and group 3 (n = 10), whereas in group 1 (n = 10) only craniectomy was performed. Electroencephalographic recording was repeated 60 mins after trauma or craniectomy, and cortical tissue samples were resected from both sides to evaluate tissue lactate concentrations in all three groups.

MEASUREMENTS AND MAIN RESULTS

Electroencephalographic recordings from both sides of the brain were evaluated together by using a 6-point scale (1 = best to 6 = worst) that was based on the presence or absence of electroencephalographic activity and the decrease in amplitude or frequency band of the electroencephalogram. Lactate was measured in resected tissue by using spectrophotometric enzymatic methods. One-way analysis of variance for repeated measures, Bonferroni-adjusted paired Student's -test, Kruskal Wallis analysis of variance, Bonferroni-adjusted Mann-Whitney-U, and Spearman's correlation tests were used as appropriate for statistical analysis. We considered p<.05 to be significant. The difference in lactate concentrations was significant between the three groups ( p<.05). Electroencephalographic grades were significantly different between the pretraumatic and posttraumatic recordings ( p<.05) and between the three groups after craniectomy or trauma ( p<.001). There was a positive high correlation between lactate concentrations and electroencephalographic grades.

CONCLUSIONS

Tissue lactate concentrations and electroencephalograhic grades change with the severity of the trauma, and there is a strong positive correlation between tissue lactate concentrations and electroencephalographic grades.