Defasciculating dose is what proportion of the paralytic dose?

Defasciculating dose is what proportion of the paralytic dose?

• A. 1/2
• B. 1/10
• C. 1/5
• D. 1/20

Answer: (B)

Defasciculating dose is a small pre-dose of a nondepolarizing neuromuscular blocker given before a depolarizing paralytic to blunt fasciculations without causing full paralysis. The amount used is about one-tenth of the dose you would give for intubation. This keeps enough receptor sites blocked to reduce the muscle twitching caused by the depolarizing agent, while still allowing rapid airway control when the main paralytic is given. So, if your intubating dose of the paralytic would be something like rocuronium or vecuronium in the tenths of a milligram per kilogram range, you’d use roughly one-tenth of that amount as the defasciculating dose (for example, about 0.01–0.06 mg/kg depending on the agent). The idea is to reduce fasciculations and potential adverse effects without producing noticeable weakness on its own. The other fractions are less appropriate: a half or one-fifth would cause substantial paralysis, defeating the purpose of a pre-dose meant to be subparalytic, while one-twentieth may be too small to reliably suppress fasciculations.

Defasciculating dose is a small pre-dose of a nondepolarizing neuromuscular blocker given before a depolarizing paralytic to blunt fasciculations without causing full paralysis. The amount used is about one-tenth of the dose you would give for intubation. This keeps enough receptor sites blocked to reduce the muscle twitching caused by the depolarizing agent, while still allowing rapid airway control when the main paralytic is given.

So, if your intubating dose of the paralytic would be something like rocuronium or vecuronium in the tenths of a milligram per kilogram range, you’d use roughly one-tenth of that amount as the defasciculating dose (for example, about 0.01–0.06 mg/kg depending on the agent). The idea is to reduce fasciculations and potential adverse effects without producing noticeable weakness on its own.

The other fractions are less appropriate: a half or one-fifth would cause substantial paralysis, defeating the purpose of a pre-dose meant to be subparalytic, while one-twentieth may be too small to reliably suppress fasciculations.