07. Chap 5.1, 5.2 Local anesthetics and nerve blocks

What is the purpose of local anesthetics?

They block nerve conduction at the site of application to decrease local pain signals from reaching the CNS

What suffix is most commonly used for local anesthetics?

-caine

As in lidocaine, procaine, bupivacaine

How do local anesthetics affect cells?

Block sodium channels, don't allow action potential propagation, blocks local pain signals

What are the routes of administration for local anesthetics? (7)

Topical

Transdermal

Infiltration

Nerve blocks

Epidurals

Sympathetic blocks

IV regional blocks

What are topical anesthetics used for?

Minor abrasions and burns, used prior to IV insertions, may be useful for spasticity

How are transdermal local anesthetics used?

Applied to surface of skin and then enhanced via ionto, phono or other enhancers

Lidocaine patches fit here

Can we put a hot pack over a Lidocaine patch?

No, will cause the drug to move too quickly into the skin

What is infiltration for a local anesthetic?

Drug is applied subcutaneously near a wound, allows drug to penetrate the area, causes local wound to numb

How is a peripheral nerve block applied? What does it do?

Injected close to a nerve or plexus (NOT within nerve), anesthetizes a specific area of the body

Define an epidural local anesthetic

An injection near the spinal cord, before the meninges

Define a spinal block local anesthetic

An injection near the spinal cord, after the meninges

What is the benefit of using an epidural vs a spinal block?

Epidural: Safer, easier to do

Spinal block: Stronger

How are both an epidural and spinal block used?

Used to decrease sensation below the spinal level of application

Define a sympathetic block. What condition is it used for?

Sympathetic output is blocked to a local area

Used for CRPS to reduce sympathetic activity

Define a Bier block

A local anesthetic is injected into the venous system, and a tourniquet is applied to keep the anesthetic in place

Define a continuous nerve block

A catheter that's implanted near a nerve provides a constant drip of local anesthetic to the area

Define a differential nerve block

A nerve block that affects the smallest fibers first, which are the pain fibers

Pts cannot feel pain but can still feel touch

Define local anesthetic systemic toxicity (LAST). What are the major systems affected?

When there is too much local anesthetic applied

Affects brain and heart

What are the brain effects caused by LAST? (7)

Tinnitus

Agitation

Restlessness

Seizures

Decreased sensation in tongue and mouth

CNS depression

Respiratory depression

What are the heart effects caused by LAST? (4)

Bradycardia

ECG abnormalities

Fatigue and dizziness

Cardiac arrest