High or low current threshold for nerve stimulation for regional anaesthesia

Area of Science:

• Veterinary Anesthesiology
• Neuroanatomy
• Regional Anesthesia Techniques

Background:

• Accurate nerve localization is crucial for effective regional anesthesia.
• Stimulation current thresholds (SCT) are used to guide needle placement.
• The impact of varying SCT on needle-to-nerve proximity (NNP) requires further investigation.

Purpose of the Study:

• To compare the effectiveness of high versus low stimulation current thresholds (SCT) in achieving close needle-to-nerve proximity (NNP) during nerve localization in pigs.
• To evaluate if higher SCT leads to more distant NNP compared to lower SCT.

Main Methods:

• 16 anesthetized pigs underwent femoral or brachial plexus nerve stimulation.
• Needle placement was guided by minimal motor response using either low (0.01-0.3 mA) or high (0.8-1.0 mA) SCT, in random order.
• Synthetic resin injection and postmortem dissection determined NNP, categorizing it as close or distant.

Main Results:

• A total of 235 punctures were analyzed: 91 with low SCT, 92 with high SCT, and 52 as controls (1.8-2.0 mA).
• All injectates from both high and low SCT groups were classified as 'close needle tip to nerve placement'.
• In contrast, 27 out of 52 control group injectates were found distant to the nerve epineurium.

Conclusions:

• Both high and low stimulation current thresholds (SCT) resulted in resin deposition adjacent to the nerve epineurium.
• The study concludes that high and low SCT yield equivalent needle tip localization accuracy in pigs.
• These findings support the use of either high or low SCT for reliable nerve localization in this animal model.