Local and Regional Anesthesia (Mod 3) Flashcards
General traits of local anesthesia?
Prevents transmission of information to and from the CNS
- They aren’t selective to pain fibres; they block sensory, motor, autonomic fibres as well as skeletal and cardiac muscles
What is Nociception?
Nociception is the activation of primary sensory nerve fibers (nociceptors) by noxious stimuli such as:
- High temps
- Mechanical perturbations (trauma)
- Harsh chemicals
Where are Nocicepters located?
Nociceptors are free (bare) nerve endings found in all levels of skin (Figure 6.2), muscle, joints, bone and viscera.
- Tissue damage is the primary stimulus for nociceptors
- They are absent in certain areas, such as the lung and brain
Nociceptor transmission?
Nociceptors transmit impulses from the periphery to the spinal cord, where information is transmitted to the various parts of the brain
How is pain transmitted?
Electrical signals jump between fibers
- Myelinated fibres transmit impulses much faster than nonmyelinated fibers
Myelinated fibers vs. nonmyelinated fibers
First pain is derived from?
Myelinated fibers
- quick, sharp, and stinging pains
- highly localized
- Require weaker stimulus for excitation
Second pain is derived from
Nonmyelinated fibers are responsible for second pain
- Slower developing, longer lasting
- dull, throbbing, burning pain
- Present post stimulus removal
- Require stronger stimulus for excitation
Why is there a delay in topical anesthetics?
Has to work through layers of skin, muscles and fats.
- Recall the muscle bundle image (slide 8)
Why is a high concentration of anesthetic used for local anesthetics?
Only a fraction of molecules reach the target site (has to work through the layers of skin, fat, and muscles)
add slide 9
What is the general order in which a functional blockade occurs?
- First pain
- Second pain
- Temperature,
- Touch
- Proprioception (pressure, position, or stretch)
- Skeletal muscle tone and voluntary tension
What is differential functional blockade?
The general order in which a functional blockade occurs:
- First pain
- Second pain
- Temperature,
- Touch
- Proprioception (pressure, position, or stretch)
- Skeletal muscle tone and voluntary tension
What is often administered together w/local anesthetics?
Vasoconstrictors like Epinephrine
Why are vasoconstrictor agents administered in conjunction with local anesthetics
These agents reduce blood flow causing smooth muscles of the vessel to contract, slowing the rate of removal of the anesthetic
- Extend duration of anesthetic affect in the area
- Vasoconstrictors increase the concentration around the nerve (enhances the affect)
- Decreases systemic toxicity via slower distribution of anesthetic into circulation
- Secondary effect = reduces bleeding at injection site
What is a secondary affect of using a vasoconstrictor in conjunction with local anesthetics?
To reduce bleeding at the site of injection
Risks of vasoconstrictors with local anesthetics?
Decreases systematic toxicity as the local anesthetic is more slowly distributed to the circulatory system
- Could stop flow when trying during procedures such as ABG pokes (poking itself could also vasoconstrict the vessel)
SLide 12
What do topical drugs have to overcome?
The epidermal layer, once across topical anesthetics are absorbed rapidly into circulation
WHen would you provide topical anesthetics vs percutanous?
Topical anesthetics provide short term pain relief when applied to mucous membranes or skin
When is infiltration anesthesia used?
To numb an area of skin via injection
- The anesthetic is injected intradermally or subcutaneously, often at several neighboring sites near the area to be anesthetized
- Onset of action is much faster than topical anesthesia
When would Regional Anesthesia be used?
To anesthetize a large area of the body, such as extremities or the abdomen
- Regional anesthesia allows a procedure to be completed w/o the use of general anesthesia
- i.e a whole shoulder, c section, or leg would be regional
What are the risks of regional anesthesia
- Infection (low)
- Hematoma
- Systemic toxicity
- nerve injury
- wrong sided block
Add slides 17 and 18
- What are the risks of regional anesthesia