THE EFFECT OF ANESTHETICS ON NEUROLOGIC OUTCOME DURING THE RECOVERY PERIOD OF SPINAL-CORD INJURY IN RATS

We evaluated the effects of anesthetics on neurologic outcome in a mod el of recoverable experimental spinal cord injury (SCI). Adult rats we re implanted with various sizes of hygroscopic plastic material at the T12 spinal level to determine the dimensions that would produce a pro gressive neurologic deficit from which recovery could occur. Neurologi c evaluation was conducted on an inclined plane, noting the maximum an gle at which an animal was able to maintain orientation perpendicular to the longitudinal midline. Scores were statistically modeled for eac h group to develop profiles of neurologic deficits. Rats were subjecte d to a 4-h exposure to isoflurane, fentanyl/nitrous oxide, or ketamine 7 or 8 days postimplantation. Neurologic outcomes were compared to a SCI reference group which received no postimplant anesthesia. An anima l weight/desiccated implant volume (W-a/V-i) ratio of 53 to 73 g/mm(3) produced postimplant neurologic deficits which deteriorated to near m aximum within 3 days, followed by a gradual improvement beginning at D ay 8 and returning to near normal between 22 and 25 days. Final outcom e was based on modeled ramp scores for each group and reported in degr ees +/- SD: reference, 71.2 +/- 1.1; fentanyl/N2O, 70.4 +/- 0.3; isofl urane, 72.6 +/- 1.1; and ketamine, 64.9 +/- 0.6. The fentanyl group at tained maximum recovery first (P > 0.05) but did not recover to a leve l different on the average from the reference group. The ketamine grou p demonstrated a poorer (P > 0.05) recovery level relative to the othe r anesthetic protocols.