Objective To compare the effects of 0.9% NaCl (normal saline, NS), 10% hydroxyethyl starch (HES, 200/0.5) and hypertonic-hyperoncotic solution (HHS, 7.5% NaCl-10% HES 1:1) on cerebral extracellular excitatory amino acids (EAA) and inhibitory amino acids (IAA) in a rat model of traumatic head injury (THI) combined with acute hemorrhagic shock (AHS). Methods Nineteen healthy adult male SD rats weighing 300-350 g were randomized into 3 groups: NS group (n = 7); HES group ( n = 6) and HHS group ( n = 6). THI was produced by modified Feeney method (a 20g weight drops from a height of 40 cm on the parietal region) and AHS was induced by modified Wiggers method (Blood was removed from femoral artery and MAP was maintained at 40 mm Hg for 1 hour). Fluid resuscitation was started at 1 hour of AHS with 0.9% NS (3 times the volume of the removed whole blood) or 10% HES (in a one to one ratio) or HHS 4 ml?kg-1 administered over 15 min. The extracellular fluid of injured brain tissue was collected using intracerebral microdialysis before head injury (baseline) during THI + AHS (1h) and resuscitatin (2h) for determination of the levels of EAA (glutamate, aspartate) and IAA (glycine, GABA, taurine) by HPLC.Results The 5 amino acids were significantly increased during THI + AHS as compared with their baseline values. Glutamate level was further increased during resuscitation with NS. GABA and taurine concentrations were maintained at high level during resuscitation with HES or HHS. The increase in glutamate was inhibited by resuscitation with HES and the increase in glutamate, aspartate and glycine were inhibited by HHS. Conclusions In a rat model of THI combined with AHS, resuscitation with NS can increase cerebral extracellular EAA. Both HES and HHS resuscitation can inhibit the increase in cerebral extracellulaar EAA and HHS is more effective.

0 05) HR in group A was faster than that in group B at T 3 (P