HTHSCI 2H03 Lecture Notes - Lecture 13: Local Anesthesia, Sodium Bicarbonate, Epidural Administration
17 Dec 2016
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Drugs for Local & General Anesthesia
Types of Anesthesia
• General:
o Loss of sensation throughout body, accompanied by a loss of consciousness
o Used for major surgeries, procedures where it would not be advantageous to the
client or healthcare provider for the client to be conscious
• Local:
o Loss of sensation to a limited body region, with no loss of consciousness
o Can be very specific where we are numbing a small area
o Regional anesthesia: loss of sensation to a larger body area, with no loss of
consciousness
▪ i.e. epidural, spinal, orthopedic procedures (knee replacement)
o Valuable strategies when we are looking at fairly minor procedures, or where the
liet eig osious o’t be.
▪ i.e. when a pediatric client is getting chemotherapy and we need to
access their Port-a-Cath, for dental procedures
• Monitored Anesthesia Care:
o Sedation is main goal; client remains responsive
o Used during diagnostic procedures or in combination with local anesthesia for
minor surgeries
o i.e. situations where the procedure is sufficiently anxiety-provoking; pediatric
clients having CT/MRI, adult clients with claustrophobia
o To ahiee a tilight state… patient is conscious, but are feeling pretty good
during a procedure
Routes of Administration
• For local; loss of sensation to a specific/limited area of the body, patient is conscious
• Route depends on the goal of anesthesia
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2
Local and Regional Anesthesia (Examples of Routes)
• Epidural: above the dura mater
• “pial/Itatheal: ito the C“F… loe doses eeded tha ith epidual
Local Anesthetics
• Most local anesthetics exert their effects through a common mechanism of action:
o Block voltage-gated sodium channels
o Ihiit a euo’s ailit to eate a atio potetial. Will affet a euo it
comes into contact with: sensory AND motor (will provide loss of sensation but
patient will have some loss of movement in the area that is anesthetized)
o Bid to ope sodiu haels lokig these… o atio potetial possile
o Active neurons are most susceptible
• Can improve functionality of local anesthetics with other co-administered medications
o Many are weak bases, co-administer with sodium bicarbonate to keep the
anesthetic in its fat-soluble form, making it easier for it to penetrate nerves
o Infections can make environment more acidic; when the environment is more
acidic, it is hard to get local anesthetics into the area… giig sodium bicarbonate
helps the drug penetrate the nerves easier
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3
o Epinephrine can also improve the duration of action
▪ Epinephrine is an alpha-1 agonist and it induces vasoconstriction
(restricts blood flow) and restricts distribution of local anesthetics (it
stays at the site of action for the whole procedure: remember, we give a
local anesthetic where it needs to work). When certain anesthetics cause
vasodilation, this would be a good idea.
• Local anesthetics are safer than general anesthesia
• Dosage will vary from client to client
Types of Local Anesthetics
• Estes ee the fist tpes of loal aesthetis used liiall…
o Highly problematic drugs:
o Rapidly metabolized in the blood stream
o Metabolized by enzyme esterizes and their half life is only 1-2 mins
o These drugs are the reason people HATED their dentists in the 30s-40s
▪ They never really worked well!
o Current usage: OTC medications (spray treatments for mild sunburn relief, spray
on the back of throat for sore throat), endoscopy, colonoscopy to temporarily
numb an area
• Amide Anesthetics:
o Metabolized in the liver
o Have a much longer half-life/length of coverage: 60-240 mins (varies from amide
to amide)
o Fast onset (comes in its non-ionized fat-soluble state and therefore gets
absorbed faster)
o You will see this more often clinically (in hospital)
• Different pKas: esters are more basic than amides. Amide is closer to physiological pH
(this distributes it into the axon faster, binds to sodium channels, gives anesthetic
coverage faster)
find more resources at oneclass.com
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Document Summary
Routes of administration: for local; loss of sensation to a specific/limited area of the body, patient is conscious, route depends on the goal of anesthesia. Local and regional anesthesia (examples of routes: epidural: above the dura mater, pi(cid:374)al/i(cid:374)t(cid:396)athe(cid:272)al: i(cid:374)to the c f lo(cid:449)e(cid:396) doses (cid:374)eeded tha(cid:374) (cid:449)ith epidu(cid:396)al. Local anesthetics: most local anesthetics exert their effects through a common mechanism of action, block voltage-gated sodium channels. I(cid:374)hi(cid:271)it a (cid:374)eu(cid:396)o(cid:374)"s a(cid:271)ilit(cid:455) to (cid:272)(cid:396)eate a(cid:374) a(cid:272)tio(cid:374) pote(cid:374)tial. Infections can make environment more acidic; when the environment is more acidic, it is hard to get local anesthetics into the area gi(cid:448)i(cid:374)g sodium bicarbonate helps the drug penetrate the nerves easier. When certain anesthetics cause vasodilation, this would be a good idea: local anesthetics are safer than general anesthesia, dosage will vary from client to client. Amide is closer to physiological ph (this distributes it into the axon faster, binds to sodium channels, gives anesthetic coverage faster)
