| Frequently Asked Questions |
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| Category #3 - Nerve Stimulation |
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What is the role of ultrasound in blocks?
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| Answer: |
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Ultrasound may offer the added advantage of knowledge of the anatomy in the
region of a block even before needle puncture occurs. Theoretically it offers
great advantage, but the deeper the nerve, the more you need it and the less it
helps you. Having said that, like ultrasound has not replaced X-rays but added
to the armamentarium of radiologists and orthopaedic surgeons, so will it add
value to our practice of regional anesthesia. It will not replace nerve
stimulation, but add to it.
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| Question: |
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What pulse width do you use on your nerve stimulator?
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We use 200-300 microseconds. It does not really matter which you use, as long as you use the same pulse width consistently, so that you get used to the quality of the motor response.
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Does blood interfere with the twitch response?
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Any substance that disperses current density (i.e. that conducts electricity) will decrease the twitch response to nerve stimulation.
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| Question: |
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Are twitches affected distal to your blocks? |
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No. The nerves can be viewed as "electrical wires". If it is cut proximally (blocked with a local anesthetic agent), when applying a stimulus (current) more distal, the motor response will not be influenced and will be as if not "cut" proximally. Obviously, if the nerve has been blocked distally, applying a stimulus proximal will evoke no motor response. |
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