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27 Cards in this Set
- Front
- Back
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Equal potency between muscle relaxants is measured by the dose required to produce 95% supression of a single twitch response _______
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ED95
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ED95 is reduced in presence of _________
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volatile anesthetics
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What is the sequence of muscle relaxant Onset?
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small, repidly moving muscles (eyes, digits) before trunk and abdomen. Then intercostals, and diaphragm
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What is the sequence of muscle relaxant Recovery? (reverse order)
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Diagram first to regain normal function; intercostals; abdomen and trunk; eyes.
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Which two nerves closely reflects onset of blockade at the diaphragm?
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Facial nerve stimulation and orbicularis oculi.
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Single twitch response reflects events at the ________ membrane
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post-junctional
Single twitch (not used much) about 50 Hz for 0.2 sec |
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Train-of-four or continuous (50 to 100Hz) reflects events at the ____________ membrane
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pre-synaptic
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_________ neuromuscular blockers (NDMB) are highly ionized and water soluble at physiologic pH and have limited lipid solubility and Vd and don't easily cross lipid membrane barriers (blood-brain; renal tubules; GI epithelium or placenta)
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non depolarizing
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High degree of ionization - maintains high plasma concentration and prevents renal reabsorption of excreted drug.
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Non-depolarizing NMBs
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_________ drugs are not highly protein bound. Little effect on renal excretion.
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Non-depolarizing
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Elimination half-time are poorly correlated with the duration of action when given as a _________
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rapid IV injection
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Lack of specificity (NMB) for NMJ may effect other receptors.
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Cardiovascular effects (change in BP & HR)
Manipulation of the carbon chain attempts to increase specificity and decrease side effects. |
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Only depolarizing NMB in clinical use today and has a "copy cat" structure to Ach. Produces intence paralysis, rapid onset due to low lipid solubility. Has short duration of action (3-5 min). Effects are likely to wear off before a pre-oxygenated pt becomes hypoxic.
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Succinylcholine
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Chemical structure of Sux is _____
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two Ach molecules linked together. Thus it mimics the action of Ach.
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Cholinergic - having to do with ________
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Acetylcholine
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Adrenergic - having to do with ________
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Adrenergic (think epi)
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_______receptors- found at synaptic junction at both SNS and ANS ganglia. Ach like substances will excite post-ganglionic fibers of both systems. Low doses produce hypotension and neuromuscular weakness and high doses produce blockade. They are _______
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Cholinergic nicotinic receptors
They are voltage ion channel gated. |
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________ receptors - found at neuromuscular post-ganglionic junction and on pre-synaptic nerve terminals in the myocardium, coronary vessels and peripheral vasculature. If drug acts on these pre-synaptic sites, inhibit norepi release. They are ______
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Cholinergic muscarinic receptors.
They are G protein channel - requires carrier protein |
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__________ is the prototype muscarinic blocker.
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Atropine
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MOA of Succinylcholine
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attaches to one or both of the alpha subunits of the Ach receptor.
Depolorizes post junctional membrane; cannot respond to subsequent release of Ach. Depolarizing blockade is referred to as Phase I Blockade. Decreased amplitude but sustained response to TOF, NO post tetanic facilitation. |
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Succinylcholine is metabolized by_____
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Sux is NOT metabolized by "true pseudocholinesterase", but enter circulation to be metabolized into plasma pseudocholinesterase
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What are side effects of Sux?
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CV - bradycardia
Hyperkalemia - muscle realeases K+ when depolarized Fasiculation Myalgias Increased intragastric & intraocullar pressure Masseter muscle rigidity MH trigger DON'T USE IN PTS WITH DUCHENNE MUSCULAR DYSTROPHY |
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What causes transition from Phase I to Phase II block after giving Sux?
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Complex phenomenon - ion channels of motor end plate close for unknown reason & motor endplate repolarizes
Large doses of Sux or prolong infusion Post junctional membranes do not respond normally to Ach Combination of desentization, ion channel blockade and entrance of Sux into cytoplasm of skeletal muscle Test dose of anticholinesterase drug Looks like a Nondepolarizing Block, fade on twitch and post-tetanic facilitation |
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Pseudocholinesterase Deficiency
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Inherited autosomal recessive trait
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Heterozygous - causes __________
Homozygous - causes _________ |
modestly prolonged recovery
profound prolonged recovery |
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What is Dibucaine number and what is normal number?
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it reflects quality of cholinesterase enzyme, not the quantity.
Normal number is near 80 |
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What is not reflected in Dibucaine number?
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Liver disease
Anticholinesterase drugs Organophosphate poisoning |
