INTRAFASCICULAR INJECTION OF AMMONIUM-SULFATE AND BUPIVACAINE IN PERIPHERAL-NERVES OF NEONATAL AND JUVENILE RATS

Background and Objectives. Regional nerve blocks are often used for th e treatment of postoperative pain in children. Ammonium sulfate is a n on-narcotic anesthetic agent, which has been reported to provide pain relief lasting days to weeks, with few reported side effects in adult studies. Prior to considering clinical use in children, the neurotoxic ity of ammonium sulfate in 4-day and 3-week old rats was assessed and compared with that of bupivacaine. Methods. Each rat received a poster ior tibial nerve intrafascicular injection (0.01 mL in 4-day-old and 0 .02 mt in 3-week-old rats) using either 10% ammonium sulfate (n = 24 p er age group), 0.5% bupivacaine (n = 18 per age group), 0.9% saline (n = 18 per age group), or 5% phenol (n = 18 per age group). A functiona l assessment by serial walking track analysis and a morphologic assess ment by neurohistology were made. Results. No abnormalities in serial walking track analysis and no structural nerve damage were detected af ter ammonium sulfate, bupivacaine, or saline injection. Bupivacaine ca used mild focal changes in both age groups, which recovered by 8 weeks . Conclusions. Intrafascicular injection of ammonium sulfate was as sa fe as bupivacaine in this animal model. Further animal studies must be made before human trials are initiated.