Local Pharmacodynamic Flashcards
LA differential blocking of nerve type most sensitive to least
Degree of myelination
Autonomic (c fiber)>Sensory (alpha d) Motor Fibers (alpha b)
Unique Property of Chloroprocaine, favorable population
Most Rapid Hydrosis of ester classes
Neurotoxicity due to bisulfite preservative
OB can be used due to rapid onset, decreased risk of systemic tox/fetal exposure
Useful in Liver dz and SZ
Transient Neurologic Symptoms
which drug, when sx, tx
Lidocaine in Spinals
Pain in Lower back, buttock, thighs
No motor sx
within 2 to 24hr onset and clears within 10 days
supportive pain meds with NSAIDs and opioid prn
Bupicivaine Unique characteristics
High quality sensory vs motor blockade
Severe refractory cardiovascular collapse with toxic intravascular doses
Liposomal Bupivicaine indication, unique characterstic, Max dose, caution
Used for single dose infiltration block for postsurgical anesthesia
Suspension promotes extended release 72 hr
with dilution can be maxed to 266 mg.
Should not be given directly after given other LA or other vasodilators due to systemic toxicity
LAT CNS
CNS (first):
1) Lightheadedness-
2) CN involvementperioral Numbness, Metallic Taste, Facial TIngling, Tinnitus, Slurred Speech,
Major CNS SZ, Unconsciousness, Hypercarbia/Resp arrest; Cardiovasc arrest
Determination of Potency of LA
Lipid Solubility:
Large alkyl Group;
Adding NaHCO3/Inc pH (more unionized form)t
LA MOA
Membrane stabilizdiing drug; affects sodium specific ion channels binds directly to cytoplasmic side
-ergo cannot conduction action potential
LA Structure and function
Weak base and passes through lipid cell membrane which then binds to sodium channel
Nerve Characteristics to LA sensitivity
Decreases with Thickness of myelin Sheath and Axonal Diameter
Least sensitive to most sensitive nerve fiber type
A-Alpha; Beta; Gamma; Delta
C
B
Action form of LA vs crossing form of LA
Crossing: Nonionized
Active: Ionized.
What determine onset of action of LA
pkA of Drug (lower better)
pH of area of effect (higher better; e.g hco3)
Lipid solubility
Lower distance of diffusion
What determine duration of LA [6]
Protein Binding (more the better)
Vascularization of Site (less is better)
Degee of Vasodilation (note all but crack are dilators)
Lipid solubility (higher the better)
Pseudocholinesteras deficiency (esp in liver dz) Addition of EPI or decadron
Metabolism and Class of LA
Esters: Procaine; Benzocaine (no i before caine)
Via Pseudocholinesterase into Para aminobenzoic acid (PABA)
Amide: Lidocaine; mepivicaine; ropivicaine; bupivicaine (i before caine)
VIa direct Liver metabolism
Allergy Significance of LA
Cross allergy between classes (amide vs esters)
Esters: PABA allergen
Amide: Methylparaven (perservative)
pmhx that affects LA metabolism
Liver Dz; Liver Thrombosis, CHF, Bblockers, H2 blockers
Prilocaine Metabolism and Significance
Similar LA with similar effect
Metabolizs to o-toluidine
This can lead to methhemoglobinemia (such as in prilocaine creams)
Benzocaine can also cause methhemoglinemia (found in sprays)
Increases Susceptibility to CNS toxicity
Types of BLocks (rate of absoprtion)
Renal/Hepatic Compromise Acidosis Heart Block/Heart DZ Pregnancy Extreme In age Hypoxia
Highest to lowest Site of fast LA absoprtion
IV>Tracheal>Intercostal>
Caudaul>spinal>epidural
brachail Plexus>subQ
Ion Trapping for LA and SIgnificance
Ionization and Losing their lipid solubility leading ti ion staying in location
Happens with fetus if the are in distress (More acidic environment)
LAT onset Neuro Vs CVS?
Neuro First in awake pt only
LAT Sx in order of CVS
Cards: T wave Peaking
QRS widening
PR inc; QtC inc
Sinus Brady -> Arrest
Myocardial Contraction and conduction are weakened/elongated
Level of LA needed for CVS vs CNS in LAT
3x CNS for CVS usually
CC/CNS ratio?
Cardiotoxicity of LA: Ratio of dose needed for cardiovascular collaspe vs SZ
Lower Number = More cardiotoxic Drug
CC/CNS for Lidocaine, Bupivicaine and Etidocaine
Bupivicaine: 3
Lidocaine: 7
Etiodcaine: 4.4
Pregnancy Effect on Bupicivaine
Lower Dose needed to reach CC toxicity
Ropivicaine vs BUpivicaine
Ropicivaine has a better safety profile more vasoconstriction
EMLA? Risk for what? Susceptibility
Eutectic Mixture of LA (numbing cream)
Lidocaine-Prilocaine
Methhemoglobineia
especially in Anemia, , Cardio/pulm dz, Liver Dz, G6pD
Premmies (reduced p450 reductase)
Similar pharmacological properties of LA without the chemical strucutre of LA
Benzyl ETOH
Long term AE of LA
Mild Myotoxic especially with steroid creams
Chondromalacia
