Reduction of the onset response in kilohertz frequency alternating current nerve block with amplitude ramps from non-zero amplitudes.
T L Vrabec, T E Eggers, E L Foldes and 3 others
PMID 31253152WHAT IT FOUND
Slowly increasing a nerve-blocking current from 50, 75, or 90 percent of the blocking level often avoided a second burst of firing in five anesthetized rats, but starting at 25 percent never did.
This is an animal engineering finding, not a patient treatment.
Key findings
01Ramp transitions from 50%, 75%, and 90% of block threshold could eliminate the secondary onset, while 25% could not within 30 seconds.
02Subthreshold values closer to block threshold required shorter ramp times; 50% needed more than 5 times as long as 90% in the example.
03Trials that produced 0% block during subthreshold and then returned to block without a second onset occurred in one 75% trial and twenty 50% trials in 4 of 5 rats.
STILL TO COME
How it was doneWhat they found
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What it does not show
Only five animals provided randomized data, and the work was acute experiments in anesthetized rats, not people. The method was tested only in motor fibers, so it did not show what would happen in sensory or autonomic nerves. The ramp did not eliminate onset at 25% of block threshold in any trial, and it succeeded only sometimes at 50%. The animals and trials showed considerable variation in minimum ramp times and percentage of block, and ramp times increased from the first set to the second set. The paper mentions stroke spasticity as a possible application, but no stroke patients or spasticity outcomes were studied.
Declared interests
The supplied text names the National Institute of Biomedical Imaging and Bioengineering as the funder. It does not include author competing-interest declarations.
The easy way to misread this
Do not read this as evidence that a nerve block can treat spasticity in patients. It was tested only in acute anesthetized rats, and the stroke spasticity application is only a stated possibility, not a clinical result.