Local and Regional Anesthesia Lecture PDF Flashcards
General vs local anesthetics
General abolish response to pain by depressing CNS and producing loss of consciousness vs local produce a temporary loss of sensation or feeling in a confined area of the body without loss of consciousness, much less risk and much more rapid recovery
Local anesthetics mechanism of action and how does epinephrine impact it?
- block nerve fiber conduction by directly acting on nerve membranes, inhibit sodium ions from crossing membrane by blocking sodium channels
- Reversible with metabolism and with time
- Perception of pain is lost first, followed by cold, warmth, touch, and deep pressure (small fibers), large motor nerves tend to be last nerves to be inhibited (large motor nerves, we don’t want these to be inhibited)
- epi injected with it increases time of effectiveness as it causes vasoconstriction of tissue decreasing blood flow increasing time in which the dispersion occurs (very dilute ratio of epi to anesthetic)
Examples of ester local anesthetics (4)
- benzocaine
- cocaine
- procaine
- tetracaine
Examples of amide local anesthetics (4) - these work longer than the esters!
- lidocaine
- mepivacaine
- dyclonine
- ethyl chloride
Topical anesthetics OTC products and their uses (3)
- benzocaine (sun burn)
- dibucaine (hemorrhoids)
- lidocaine (small cuts)
Peripheral nerve block (field block)
Anesthetic injected close to nerve trunk to block transmission along peripheral nerrve interrupted, either minor impacting 1 distinct nerve or major affecting a plexus
Central neural blockade and subtypes (3)
- Anesthetic directed within membranes surrounding the spinal cord, used when analgesia needed in a large region, frequently used during surgical and obstetric procedures
- epidural, caudal block, spinal block (btwn arachnoid and pia)
Adverse effects of central neural blockade (4)
- hypotension
- autonomic blockade
- headache from CSF leak (relieved in supine position)
- meningitis type effect
Cocaine surgical uses (2)
- topically in procedures on eyes and nasal mucosa because of vasoconstrictor action
- local anesthetic with epi
The only local anesthetic that causes vasoconstriction is ___, the rest cause vasodilatory effects
cocaine
Toxic buildup of systemic local anesthetics signs and symptoms (3)
- hypotension
- tremors
- convulsions
Injectable local anesthetics with epinephrine drug interactions (4)
- tricyclic antidepressants
- MAOI
- succinycholine
- diazepam
Procaine (novocain) function
Ester type local anesthetic only effective via injection often combined with epi, metabolized very rapidly and rarely systemic toxicity, used less often
Lidocaine (xylocaine) funciton
Prototype amide type anesthetic, most widely used, more effective then procaine and often combined with epi, higher risk of systemic toxicity
Cocaine function
Ester type anesthetic that has vasoconstriction effects and that also has pronounced sympathetic effect on CNS, only used topically for anesthesia of ears nose and throat, lasts about an hour
2 types of general anesthetics
- Inhalation
- Intravenous
Analgesia vs anesthesia
Loss of pain sensation vs loss of pain and other sensations sometimes including consciousness
Minimum alveolar concentration (MAC)
Measures general anesthetic potency, defined as minimum conc at which alveolar air will produce immobility in 50% of patients exposed to painful stimulus, low MAC indicates high anesthetic potency
Blood flow to brain is high, anesthetic levels drop rapidly when drug administration stops, therefore tissues with lower blood flow have slower decline in drug levels resulting in…
….patients waking up from anesthesia before all has left the body
General anesthesia adverse effects (4)
- respiratory and cardiac depression
- increased risk of heart arrhythmias
- malignant hyperthermia (rare)
- aspiration of gastric contents
Preanesthetic agents and examples (5)
- benzodiazepines (midazolam - versed)
- opioids (relieve pre and post op pain)
- clonidine (reduces anxiety and cause sedation)
- atropine (decrease risk of bradycardia and suppress bronchial secretions)
- neuromuscular blocking agents (succinycholine)
Postanesthetic agents and examples (3)
- analgesics (opioids, nsaids)
- antiemetics (odensetron)
- muscarinic agonists (bethanechol)
Isoflurane (forane) and enflurane (ethrane), and desflurane (adults only!) function and ADRs (2)
Prototype of volatile inhalation anesthetics, low MAC at 1.15%,
-respiratory depression, hypotension,
Nitrous oxide function
Very low anesthetic potency impossible to produce anesthesia alone as MAC is very high, but high analgesic potency so combined with other agents, inhaling 20% can provide analgesic effects similar to morphine
-no serious ADRs
