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level: DEFINITIONS

Questions and Answers List

level questions: DEFINITIONS

Question	Answer
• are drugs that produce reversible conduction blockade of impulses along CENTRAL AND PERIPHERAL NERVE PATHWAYS after regional anesthesia; this produces transient loss of memory, motor and autonomic function.	LOCAL ANESTHETICS
• pain awareness • mediated by nerve ending receptors in peripheral tissues and transmitted to the CNS by primary afferent fibers and relayed by secondary afferent fibers to the brain	NOCICEPTION
Most local anesthetics consist of a __ group (eg, an aromatic ring) connected by an intermediate chain via an __ to an ionizable group.	lipophilic, ester or amide
are more prone to hydrolysis, thus have a shorter duration of action.	Ester links
• are weak bases and are usually made available clinically as salts to increase solubility and stability • exist inside the body as either uncharged base or as a cation • pKa range = 8.0-9.0 (the larger percentage in the body fluids at physiologic pH will be charged, cationic form)	Local Anesthetics
most active form at the receptor site because it cannot readily exit from closed channels	Cationic form
important for rapid penetration of biologic membranes and producing a clinical effect, since the local anesthetic receptor is not readily accessibe from the external side of the cell membrane	Uncharged form
Administration LOCAL ANESTHETICS	1 Topical 2 Injected into nerves 3 Epidural or Subarachnoid Space (spinal)
Local anesthetics are converted in the liver (amide type) or in the plasma (ester type) to more __, which are excreted in the urine.	water-soluble metabolites
reduce systemic absorption of local anesthetics from the injection site by decreasing blood flow in these areas	Vasoconstrictor substances (eg, epinephrine)
Functions of Sodium Channels can be disrupted by the following:	1 Biologic Toxins 2 Marine toxins
bind to receptors within the channel and prevent inactivation (prolonged influx of sodium)	Biologic Toxins (Batrachotoxin, Aconitine, Veratridine, Scorpion venoms) BAVS
block sodium channels by binding to channel receptors near the extracellular surface -- resembles local anesthetic action	Marine toxins (Tetrodotoxin & Saxitoxin) TS