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Module 6: Pharmacology of Local Anesthetic (reasons for anesthetic…
Module 6: Pharmacology of Local Anesthetic
profound anesthesia
onset and duration
agent
general factors
concentration
diffusion to site
lipid solubility
protein binding
technique
block:
longer duration
infiltration:
faster onset
PROS: faster onset, simple, safe, good hemostasis w vasoconstrictor
CONS: multiple injections for multiple teeth, shorter duration of anesthesia
vasoconstrictor presence
troubleshooting
block injection
PDL/intraosseous injection OR Buccal/Lingual infiltration w articaine/prilocaine
anesthetics
general characteristics
amides
types
lidocaine
2% plain : plural anesthesia 5-10min; soft tissue 1-2 hours
2% w/ 1:100k or 1:50k : pupal anesthesia 1-2 hours, soft tissue 3-5 hours
xylocaine, octocaine, lignospan
mepivacaine
3% plain : plural anesthesia 20-40 min, soft tissue 2-3 hours
2% w/ 20k levonordefrin : plural 1-1.5 hours, soft tissue 3-5 hours
good for short procedures <1 hour as infiltrate or block
prilocaine
4% plain = citanest; plural 40-60 min, soft tissue 2-3
4% 1:200k epi = citanest forte: pulpal 1-1.5 hours; soft tissue anesthesia 3-8 hours
short procedures <1 hour as a block
for difficult patients (w/ vasoconstrictor)
articaine
hybrid anesthetic; good for pt with liver problems
4% 1:100k -1:200k epi: pulpal anesthesia 1-1.5 hours, soft tissue 2-4 hours
bupivacaine
0.5% with 1:200k long-acting by block injection, plural anesthesia 1.5-4 hours, up to 7 hours; soft tissue anesthesia 5-12 hours
as a block, > 2 hour or post-op analgesia
physiology of anesthetics
size
:overall diameter of the nerve bundle
lipid
: amount of myelin sheath
Central Core Theory
: peripheral fibers anesthetized first;
proximal first = molars; central fibers to most distal = incisors
anesthetic volume, tissue space and density
critical length = 3 nodes minimum/ 5 mm
infiltrations : 1/2 to 3/4 cartridge
IA nerve block: 3/4-1 is ideal
delayed or failed onset
disassociation rate:
BH+ must disasociate to unionized base form to pass through nerve membrane
transport/perfusion rate :
rate of passage through membrane
reassociation rate :
needs to reassociate to bind
binding rate:
rate of actual binding to membrane/sodium gated ion channels
reasons for anesthetic failures
anatomical/physiological variations
technical errors of administration
patient anxiety
inflammation and infection
decreased tissue pH --> decreased disassociation of BH+ to B
defective/expired solutions
contraindications
relative
patients on tricyclic antidepressants
phenothiazine antipsychotics
nonselective beta blockers
recreational drugs or ADD/ADHD meds
absolute
unstable angina
myocardial infarction < 6 mo
coronary artery bypass surgery <3 mo
refractory arrhythmia
untreated/uncontrolled HTN
untreated or uncontrolled congestive heart disease
uncontrolled diabetes or other endocrine diseases