Coadministration of methylprednisolone with hypertonic saline solution improves overall neurological function and survival rates in a chronic model of spinal cord injury

OBJECTIVE: We previously demonstrated that administration of 7.5% hypertoni c saline (HS) significantly improved spinal cord blood flow and neurologica l outcomes after spinal cord injury. The aim of this study was to determine whether hypertonicity would enhance the effects of methylprednisolone (MP) , further improving neurological function. METHODS: Rat spinal cords were compressed for 10 minutes with 50 g of weigh t, and neurological function was assessed for 28 days, using the Basso-Beat tie-Bresnahan locomotor rating scale. The control group received an intrave nous injection of isotonic saline (IS) (5 ml/kg). Group 1 received an intra venous injection of 7.5% HS (5 ml/kg). Group 2 received an intravenous inje ction of MP (30 mg/kg) and IS (5 ml/kg). Group 3 received an intravenous in jection of MP (30 mg/kg) administered with 7.5% HS (5 ml/kg). RESULTS: At 24 hours after spinal cord injury, the combination of MP plus H S provided significant (P < 0.01) neurological improvements, compared with all other treatment groups. At 10 days after injury, the animals that had r eceived MP plus HS exhibited significantly (P < 0.01) higher Basso-Beattie- Bresnahan scores, compared with the MP plus IS and control groups. The medi an survival time was significantly (P < 0.01) increased for the MP plus HS group (28 d), compared with the MP plus IS group (16 d). Because of the dra matic decrease in survival rates at 28 days after injury, there was a signi ficant (P < 0.01) difference in neurological function only between the MP p lus HS group and the control group. CONCLUSION: The results indicate that the administration of HS may enhance the delivery of MP and prevent immunosuppression, leading to improvements i n overall neurological function and survival rates after spinal cord injury .