Systemic hypothermia after spinal cord injury : An experimental study in the rat

Abstract: Spinal cord injury following trauma results in suffering for each individual independent of the severity of the neurological deficits. Care of the acute spinal cord injured patients has developed from the purely conservative treatment advocated 20-30 years ago to today's active strategies. The introduction of neurointensive care, including monitoring of vital functions, pharmacological treatment and surgery for decompression and stabilization, has reduced the general complication rate. The neurological outcome has, however, not improved, and the search for alternative treatment strategies has to continue.Recently, several experimental and clinical brain trauma studies have demonstrated beneficial effects of treatment with moderate systemic hypothermia. The effects of this treatment modality have, so far, not been investigated following traumatic spinal cord injuries. We have therefore performed a series of experiments to evaluate the effects of moderate systemic hypothermic treatment on some of the basic physiologicalparameters, morphological characteristics and neurological outcome following spinal cord injury in the rat.We have demonstrated that the temperature in a contused spinal cord is about 1°C lower than the core temperature during normothermia (38°C). This difference disappears during the induction of moderate systemic hypothermia (30°C). The spinal cord blood flow (SCBF), as recorded by Laser-Doppler flowmetry, wasdemonstrated to decrease linearly by 25-30% in the temperature range between 38° and 30°C, independent of a moderate spinal cord compression injury 5 mm cranial to the recording spot. Hypothermia, trauma, or a combination of both, did not significantly affect the autoregulatory capacity.Morphological analysis using immuno-histochemistry demonstrated, 24 h following severe spinal cord injury, reduced edema formation, glial activation, vimentin formation, and axonal swelling in the peri-injury zones of animals treated with moderate systemic hypothermia, as compared to normothermic animals. The evolution of the animals' hind limb motor function, studied for two weeks following severe spinal cord injury, was not improved by a 2-h moderate systemic hypothermic treatment.This thesis has shown that systemic hypothermia exerts neuroprotective effects on the spinal cord following severe compression trauma, as demonstrated by morphological analyses. The clinical significance of these findings requires further studies using different degrees of trauma as well as various hypothermic procedures.