Effects of ropivacaine dosage on electrophysiologic changes of the sciatic nerve in diabetic rats

Abstract

Objective To observe the effects of clinical routine dasages 0.375% and 0.5% ropivacaine on electrophysiologic of changes of the sciatic nerve in diabetic rats. Methods Twelve healthy rsts and 12 rats with streptozotocin (STZ) induced diabetic peripheral,neuropathy were:used and further divided to 2 groups.Both sciatic nerves were exposed under general anesthesia.0.5 ml of either 0.375% or 0.5% ropivacaine wasiniected in close proximity to the right seiatic nerve which was the experimental side.0.5 ml of 0.9% sodium chloride was iniected in close proximity to the left sciatic nerve which served as control.Motor nerve conduction velocity(MNCV),amplitude (AMP) and latency (LAT) of compound muscle action potential were recorded before injection,at the moment of injection,at one minute intervals for to 15 minutes and 48 hours after the injection. Results MNCV,AMP and LAT didn't change at all the observed time points of the 0.9% sodium chloride iniected control side in either healthy rats or diabetic rats.MNCV and AMP in normal rats injected with 0.375% ropivaeaine began to decrease at average 4 minutes and became zero at 10 minutes,while they began to decrease at average 3 minutes and dropled to zero at average 9 minutes while injected with 0.5% ropivacaine.These parameters returned to baseline levels after 48 hours.MNCV and AMP in diabetic rats injected with 0.375% ropivacaine began to decrease at average one minute and became zero at 7 minutes,while they began to decrease at average one minute and dropped to zero at 6 minutes with 0.5% ropivacaine injection.The time course had statistically significant difference between diabetic and normal rats.LAT had the same change pattern as MNCV and AMP.After 48 hours.MNCV in 0.375% ropivacaine diabetic group was not different from baseline value(P＜0.05),but AMP and LAT Were still significantly different from baseline levels.MNCV, AMP and LAT in 0.5% ropivacaine diabetic group had significant difference comparing to baseline levels and levels of 0.375% ropivaeaine diabetic group(P＜0.05). Conclusion Either 0.375% or 0.5% ropivacaine may deteriorate the diabetic peripheral nerve injury,the latter more remarkable. Key words: Anesthetics; Diabetic neuropathies; Neural conduction