The effects of tramadol and morphine added to levobupivacaine on the action potential in rat sciatic nerve

Introduction: Local anesthetic and various drugs are administered by peripheral nerve blocks although there are only some clinical researchs about the comparison of the effects of these to the block time.Purpose: In our study, we compared the effects of morphine and tramadol added to levobupivacaine on the nerve conduction velocity and compound action potential (CAP) on an experimental rat model for examine effects of quality of blocks with morphine and tramadol added to local anesthetics in peripheral nerve blocks.Material and method: In this study, 28 Wistar albino rats, age of 4 months, weight of 200-300 g have been used.The rats were randomised into 4 groups: Group K: Control group, Group L: Levobupivacaine, Group LT: Levobupivacaine and tramadol, Group LM: Levobupivacaine and morphine. After the anesthesia was given with xylazine 3 mg/kg and ketamine 90 mg/kg i.m, the sciatic nerves of the rats were dissected with longitudinal incision. Two recording electrodes were placed to the nerve segment and then flow of 10 intervals of 5 minutes with current intensity of 10 milliampere (mA) were given to the segment. The compound action potential and the nerve conduction velocities were measured and recorded by Powerlab bioamphlifikator device. Control recordings were taken after the exploration of the nerve and then 0,2 ml of the drug impregnated to a cotton bud is administered around the nerve for 30 minutes. After that the nerve was washed with physiological saline for 5 minutes and then intervals of 5 minutes recorded for 30 minutes.Results: All groups showed a significiant decrease in nerve conduction velocity and amplitude of CAP in comparison of the control group. However, the significiantly reducing effect of levobupivacaine on nerve conduction velocity beginned about 20 minutes, although the onset of the effect of added morphine and tramadol groups were observed in the first minute.Conclusion: We concluded that morphine or tramadol added to levobupivacaine could have shorten the onset time of the block.Key words: Sciatic nerve, levobupivacaine, morphine, tramadol.