LAA Flashcards
Potency of an LAA is generally related to
Lipid solubility
Slower rate of absorption
Clinical efficacy of LAA may be increased by adding
Epinephrine
Opioids
A2 Agonist
Local anesthesia
Loss of sensation in a circumscribed area of the body
MoA of LA
Inhibition of conduction in peripheral nerve
Depression of excitation in nerve ending
Regional anesthesia
Loss of sensation over a portion of anatomy without loss of consciousness
Three layers of nerve tissue layer in PNS
Endoneurium
Perineurium
Epineurium
Purpose of nerve tissue layers in PNS
Protection and barrier for passive diffusion of LAA
Means of regeneration of ion gradient in neuron membrane
Protein pumps
Cotransporters
Channels
Permeability of cell membranes at rest and during depolarization
K+
Na+
Membrane expansion theory
LA molecule diffuse to hydrophobic regions of membrane and create disturbance and prevent permeability to Na+
Specific recptor theory
LAA acts by binding to specific receptors on channel
Metabolism of amino esters
Plasma cholinesterase
Metabolism of amino amides
Hepatic carboxylesterase
CP450
pH of; Commercially prepared LA LA after injection Solutions without epinephrine Solutions with epinephrine
- 5 - 7
- 4
- 5
- 5
Effect of increasing pH of LA solutions
Speeds its onset
Increase clinical effectiveness
Make injections more comfortable
Unstable
Precipitates
Effect of decreasing pH of LA solutions
Burning sensation
Slightly lower onset
Highest pKa and cationic/ionization at 7.4 pH
Procaine
Bupivacaine
Highest lipid solubility
Bupivacaine
Lidocaine
Sequence of Clinical anesthesia
Sympathetic block (VasoDial) Loss of sensation (Pain and Temp Proprioception Touch and Pressure Motor function)
Highest duration of action (PPB)
Bupivacaine (95%)
Lidocaine (64%)
Benzoic acid esters
Benzocaine
Cocaine
Amides
Lidocaine
Bupivacaine
Quinololes
Centbucridine
Effect of Epinephrine on LA activity
Prolonged action
Increased intensity of block
Decreased systemic absorption
Effect of Opioid on LA activity
Synergistic activity
Prolong and intensify analgesia and anesthesia
Exception to analgesic synergy of opioids
2-chloroprocaine (epidural)
Factor that influence rate of Absorption
Tissue vascularity
Areas with the greatest systemic absorption
Intercostal
Caudal and epidural
Brachial
Femoral and Sciatic
Potent agent at low concentration
Cause more vasoconstriction
Decrease rate of absorption
LAA at high concentration
Predominant vasodilatory effect
Effect of Renal disease on pharmacokinetics of LAA
Little effect
Effect of Severe Liver disease on pharmacokinetics of LAA
Slow their clearance
Accumulation of drug
Half life of Bupivacaine
3.5 hrs
Half life of Lidocaine
1.6 hrs
Use of Local anesthesia
Infiltration anesthesia
Regional anesthesia
Surface anesthesia
Cause of toxicity of LAA
Rapid injection
Rapid absorption from very vascular site (mucous membrane)
Overdose
Most cardiotoxic LAA
Bupivacaine
High toxic dose of LIdocaine
Hypotension
Bradycardia
Hypoxia
High toxic dose of Bupivacaine, Levobupivacaine, Ropivacaine
Ventricular dysrhythmias
Sudden CV collapse
