Effect On Neurostimulation Of Injectates Used For Perineural Space Expansion Sterile Water Versus Dextrose5%in Water

Background:When performing the peripheral nerve block with the guiding of nerve stimulator, now we usually inject a certain amount of Dextrose5%in water for expanding the perineural space and diminishing the minimal intensity of stimulation (MIS) of the nerve to increase successful rate and safety.Objectives:In this paper, we try to find if the sterile water can be used in the expanding the perineural space through comparing the MIS and human body resistance (HBR) before and after the injection. This study also attempt to determine if the sterile water is superior to Dextrose5%in water in locating and protecting the nerve, further more, to explore the reason of what cause the nerve impulse.Method:60patients who were about to undergo surgeries on upper limb were assigned randomly to one of two groups:Dextrose5%in water group (G group) and sterile water group (S group).We performed the nerve stimulator with the mode of1mA,0.1ms,2Hz in the first step, then gradually reduced the current intensity and started to insert the needle when a muscle vibration could be observed. When the current intensity was in the range of0.2mA-0.5mA and could cause the tremor on the upper arm, forearm and fingers with minimal amplitude, we considered the needle was close enough to the brachial plexus without intraneural injection, recorded the current intensity as the minimal intensity of stimulation(MIS) and the human body resistance (HBR).After the injection of Dextrose5%in water or sterile water, we adjusted the nerve stimulator as far as the muscle appeared the same amplitude of tremor as before the injection, also recorded the MIS and the HBR, compared the MIS and HBR either before and after the injectiong and between the G group and S group.Result:After injected5ml of the dextrose5%in water or sterile water, the MIS of two groups were both significant decreased compared with the MIS before the injection, and the HBR of two groups were both significant higher than the HBR before the injection. After injection, no significant difference was observed in both changes of MIS and HBR in two groups.Conclusion:The sterile water can be used in the peripheral nerve block like dextrose5%in water to expand the perineural space, reduce the MIS, help location and protect of the nerve.