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18 Cards in this Set
- Front
- Back
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Amides vs. esters: duration of action, allergenicity, metabolism
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Amides: longer acting, less allergenic potential, metabolized in the liver. Esters: shorter acting, greater allergenic potential, hydrolyzed by plasma cholinesterase.
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Which is more potent, the ionized or unionized form of the LA?
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The ionized (hydrophilic, charged) form
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Where is the LA site of action?
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Associated directly with the Na+ channel, rather than a non-specific interaction with the cell membrane.
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Basic molecular structure of LAs
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A hydrophobic aromatic group is joined to a hydrophilic amine group and bound by either an amide or an ester
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MLAC (minimal LA concentration)
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The minimum concentration of LA that will block nerve impulse conduction.
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Do ionized or unionized LAs have faster onsets of action? What does this have to do w/ bicarb?
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Unionized, because they can diffuse across the neural sheath. Since LAs are weak bases, they can accept a proton to become ionized. Adding Bicarb will lead to a greater proportion of the drug in its unionized form, and therefore a shorter onset of action.
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Tachyphylaxis
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Decreasing response to a drug following multiple doses.
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EMLA
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Eutectic mixture of LA- Lidocaine and Prilocane. Penetrates intact skin. Used in children before IV placement.
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Why is infiltration ineffective in areas of inflammation?
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Decreased pH decreases proportion of unionized LA
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Where is the proper place to do a spinal?
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Injection below L2-L3
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Non-numbing effects of spinal anesthesia
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Sympathetic block: Venodilatation, decreased venous return to the heart, decreased CO, hypotension, bradycardia
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Do areas with more fat or more vascularity have greater uptake of LA?
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Areas with greater vascularity have greater uptake, regardless of the LA
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Toxic CV effects of LA
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Initial phase: HTN and tachycardia; intermediate phase: prolongation of conduction time, negative inotrope, decreased CO; terminal phase: peripheral vasodilation, hypotension and bradycardia
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Bupivicaine cardiotoxicity
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Cardiotoxicity simultaneous with CNS toxicity (usually CNS toxicity occurs first); ventricular arrhythmias (torsades de pointes); resistant to resuscitation
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Which drug is directly neurotoxic at high concentrations?
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Tetracaine
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Effects of epinephrine as an additive
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Prolongation of block, increased intensity, decreased systemic absorption of LA
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Effects of opioids as an additive
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Synergistic analgesia with prolongation and intensification of analgesia. Lower total administration of each agent.
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Which LA is used for labor (less motor block for an equivalent sensory block)?
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Bupivacaine
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