The effects of moderate hypothermia and intrathecal tetracaine on glutamate concentrations of intrathecal dialysate and neurologic and histopathologic outcome in transient spinal cord ischemia in rabbits

The aim of the present study was to compare the effects of intrathecal tetr acaine (a sodium channel blocker) with those of moderate hypothermia on glu tamate concentrations of intrathecal dialysate, hindlimb motor functions, a nd histopathology in spinal cord ischemia. New Zealand White rabbits implan ted with an intrathecal dialysis probe were assigned to one of the three gr oups (seven in each): control (temperature 38 degrees C), tetracaine (tetra caine 0.5%, 0.6 mt, given intrathecally 30 min before ischemia, 38 degrees C), or moderate hypothermia (32 degrees C). Spinal cord ischemia (20 min) w as produced by occlusion of the abdominal aorta during isoflurane (1%) anes thesia. Glutamate concentrations significantly increased during ischemia in all groups, but the levels in the moderate hypothermia group were signific antly lower than those in the control and tetracaine groups. Neurologic sta tus (24 and 48 h after reperfusion) and histopathology (48 h) in the modera te hypothermia group were significantly better than in the other two groups . There were no significant differences between the tetracaine and control groups in either glutamate concentrations, neurologic status, or histopatho logy. We conclude that intrathecal tetracaine does not provide any protecti on against ischemic spinal cord injury, whereas moderate hypothermia does. Implications: Sodium channel blockers, including local anesthetics, have be en shown to reduce glutamate release in brain ischemia and have a neuroprot ective effect. However, in the present study, intrathecal tetracaine did no t attenuate either glutamate release or the neurologic or histopathologic o utcome in spinal cord ischemia, whereas moderate hypothermia did.