July 30, 2012

Q&A: Features of Peripheral Nerve Block

Peripheral nerve blocks (PNB) are widely-used for surgical anesthesia as well as for both postoperative and nonsurgical analgesia. PNBs offer distinct benefits over general or neuraxial anesthesia in certain clinical situations. In addition, PNBs provide analgesia that may be superior to other techniques for some patients.

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In this article:
Indications and types of peripheral nerve blocks
MCQ exam: clinical scenario
MCQ exam: answer
MCQ exam: explanation

Indications and types of peripheral nerve blocks

Indications for peripheral nerve blocks (PNBs) are diverse and vary widely. Blocks are often used to avoid the effects of alternative anesthetics or analgesics. The most common rationale for their use is to avoid side effects and complications of general anesthesia (GA), particularly respiratory-related effects, and to provide analgesia while minimizing opioid use.

There are 2 types of nerve blocks:
  • Single injection. Single-injection nerve block (sometimes called "single-shot" block) refers to a one-time injection of local anesthetic (LA) adjacent to the nerve or plexus for surgical anesthesia and/or analgesia. The duration and density of the block depends upon the dose, concentration, and pharmacology of the chosen LA; clinically effective duration may last from less than an hour to 24 hours or more.
  • Continuous nerve block. The continuous infusion of LA through a percutaneously-placed catheter adjacent to the peripheral nerve or plexus provides prolonged anesthesia/analgesia in the distribution of the nerve or plexus and may be managed as either an inpatient or an outpatient. Continuous blocks are useful in patients who are expected to have prolonged need for analgesia. This technique may increase patient satisfaction by decreasing pain, opioid use and side effects, and sleep disturbance.

MCQ exam: clinical scenario

A dental surgeon carries out a block of the inferior alveolar nerve by infiltrating local anaesthetic at the mandibular foramen.

Which clinical feature may result from this procedure?

a) Numbness of the lower lip on the injected side
b) Ineffective block for the incisor teeth
c) Numbness of the side of the tongue
d) Inability of the patient to clench his jaws
e) Transient weakness of the facial muscles on the injected side

MCQ questions & answers on medicalnotes.info

MCQ exam: answer

The correct answer is A.

MCQ exam: explanation

The inferior alveolar nerve, a branch of the mandibular division of the trigeminal nerve (V), traverses the inferior alveolar, or dental, canal of the mandible to supply all the teeth of that hemimandible; all the teeth on that side are therefore anaesthetised. The mental branch of the nerve emerges through the mental foramen to supply the lower lip, which becomes numb in a successfully performed block. The muscles of the tongue, of mastication and of facial expression are not affected.

1). UpToDate: Overview of peripheral nerve blocks. Available online: https://www.uptodate.com/contents/overview-of-peripheral-nerve-blocks

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