In this episode, I’ll discuss an injection technique for lidocaine that reduces pain.
Lidocaine is an anesthetic with a time to onset of about a minute. For this reason, subcutaneous injections of lidocaine can be painful because it has not had a chance to work when the needle puncture is made.
However, researchers at the Department of Medicine, University of Chicago performed a randomized controlled trial examining a lidocaine administration technique that reduces injection pain.
The technique was simple – patients randomized to the intervention group had approximately 1 to 2 mL of lidocaine squirted onto the skin surface prior to subcutaneous lidocaine injection.
This is not enough time for lidocaine to exert an anesthetic effect, yet visual analog pain scores were decreased by 25% compared to the control group.
What the authors believe is responsible for the effect is the “gate control” theory of pain. Under this theory, the room temperature lidocaine solution generates sensory nerve traffic within the spinal cord dorsal horn that can “gate” or inhibit the noxious signal from the lidocaine injection. If this theory is correct then the injection of lidocaine should occur immediately after the lidocaine is dripped onto the patient’s skin to achieve maximum reduction of injection pain.
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