Preservation of post-compression spinal cord function by infusion of hypertonic saline

We tested the hypothesis that the administration of hypertonic saline, following traumatic injury to the spinal cord, could enhance blood flow to the cord and preserve function. Rats were used as the experimental model. Direct compression of the spinal cord for a period of 10 min was done to produce the injury. Somatosensory evoked potentials (SSEPs) and spinal cord blood flow were measured using a laser Doppler flow meter throughout the experiment. Comparisons of the blood flow values and SSEPs were made among four different groups of animals. The control group received no fluid resuscitation after injury. A second group received a bolus injection of isotonic saline (0.5 ml/100 g) as an i.v. infusion over a period of 1 min. A third group received a bolus infusion of 7.5% NaCl (0.5 ml/100 g) over a period of 1 min. The final group received 4 ml/100 g of 0.9% NaCl over a period of 10 min. The administration of hypertonic saline significantly reduced spinal cord vascular resistance during the first 10 min after infusion. During the first 30 min after the removal of compression, spinal cord blood flow was greater in the hypertonic saline group than in the other three groups. The hypertonic saline group had a reactive hyperemia whereas the flow in the other groups remained at or below control values. Beginning 10 min after injury and for the remainder of the 1-h observation period, the latency of the cortical peak of the SSEP in the group receiving hypertonic saline was significantly shorter than in any of the other three groups. These results indicate that the administration of hypertonic saline enhances blood flow and preserves spinal cord conduction following traumatic injury to the spinal cord.