Blocking Out the Pain:
by James Woessner, MD, PhD
 Nerve blocks are procedures during which an anesthetic agent is
introduced or injected to interrupt nerve impulses.1 Two of the most used medical
dictionaries (Taber’s2 and Gould’s3) include electricity as a means to produce
nerve block. The term ‘electric nerve block’ was coined by Dr. Jenkner4 several
years ago to describe the use of electrical impulses to create a nerve block instead of
injecting an anesthetizing agent into the site.
Electric nerve blocks (ENBs) represent a long tradition of the use of electricity in
medicine5 along with electrocardiography (EKG), electroencephalography (EEG),
electromyography (EMG), transcutaneous electrical nerve stimulation (TENS) for low back
pain, electroconversion therapy (ECT) for depression, dorsal column stimulators (DCS) for
chronic pain control, bone growth stimulators after orthopedic surgery, and neuromuscular
stimulation for disuse atrophy — all capitalizing on the electrical properties of the
human body.
The utilization of electrodes to produce high frequency electrical impulses to create
numbness in a localized area requires correct medical diagnoses and knowledge of the
physiologic mechanism of ENBs to optimize outcomes. Pain nerves typically repolarize
— i.e., get ready to fire again — at a frequency slower than 1/1000 sec. Thus,
the absolute minimum blocking frequency must be 1,000 Hz or greater; typically 4,000 to
20,000 Hz is used. Such frequencies prevent the pain nerves from repolarizing and firing
repeatedly and instead achieve a neural blockade (nerve block). The efficacy of nerve
blocks is illustrated by Hardy, et al6 in performing surgery while blocking sensory nerve
impulses with electricity.
Please refer to the Mar/Apr 2002 issue for the complete text. In the event
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— Mar/Apr 2002
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