NMB Succinylcholine.txt

SCh

intense paralysis rapids, and effects are likely to wane before preoxygenated patient becomes hypoxic

20mg/ml

1-2 mg/kg

3-4 x's the ED95

30 seconds

• 5-10 minutes
• because of hydrolysis by plasma cholinesterase enzyme.
• -hydrolyzed at such a fast rate only a small fraction of original iv dose reaches NMJ

• histamine
• muscarinic -cardiac
• nicotinic- nmj

8 minutes

• attaches to 1 or both alpha subunits of nAChRs and mimics the action of ACh (partial agonist) thus depolarizing the post junctional membrane
• -compared with Ach the hydrolysis of Sch is slow resulting in sustained depolarization of receptor ion channels
• -NM blockade develops b/c a depolarized post junctional membrane can not respond to subsequent Ach release

phase I blockade

• decreased contraction in response to single twitch stimulation
• -decreased amplitude but sustained response to continuous stimulation

• -TOF ration >0.7
• absence of posttetanic faciculation
• - enhancement of NM blockade if anticholinesterase drug given

skeletal muscle fasiculations that reflect the generalized depolarization of post junctional membrane produced by SCh

• a single large dose of SCh (>2 mg/kg IV), repeated doses, or continuous infusion
• -this causes post junctional membrane to no respond to Ach even after they have become repolarized
• -similar to nondepolarizing blockade

enhancement of existing NM blockade

anticholinesterase drugs

• give small dose of drug such as edriphonium 0.1-0.2 mg/kg IV and see if small dose improves neuromuscular transmission by using PNS if it does an additional dose will antagonize the NM blockade rather than enhance it ( enhanced if still in phase I)
• -this is best way to distinguish between

• influnces the duration of action of SCH by controlling the amount of NMBD that is hydrolyzed before reaching the NMJ
• -decrease in this results in slowed or absent hydrolysis of SCh and prolongation of NM blockade.

diffusion away from NMJ into the ECF

• liver
• -liver disease must be severe before decreases in plasma cholinesterase are sufficient to prolong NM blockade

• neostigmine
• anticholinesterase drugs (used in glaucoma and MG)
• chemo drugs
• reglan (metoclopramide)

obesity

presence often only recognized after an healthy pt experiences prolonged NM blockade (1-3 hours) after a conventional dose of SCh is given.

a local anesthetic that inhibits the activity of normal plasma cholinesterase activity by 80% compared with 20% atypical enzyme

• confirms the presence of normal plasma cholinesterase activity
• -

indicates atypical plasma cholinesterase and that blockade could last for 3 hours or longer after normal dose.

• cardiac dysrhythmias
• hyperkalemia
• myalgia
• myoglobinuria
• increased gastric pressure
• increased intraocular pressure
• increased ICP
• sustained skeletal muscle contractions

• SB junctional rhythm and even cardiac arrest can follow administration of SCh because of acton it has on muscarinic repectors
• - most likely to occur when 2nd dose is given 5 minutes after first
• -atropine will not help this response to 2nd dose.
• -increased heart rate and BP also reported

• may occur after administration to patient with clinically unrecognized muscular dystrophy, unhealed 3rd degree burns, denervation, leading to skeletal muscle atrophy, severe skeletal muscle trauma and upper motor lesions.
• -usually develops within 96 hours and may persist for up to 6 months.
• -sustained opening of receptor ion channels causes leakage of potassium ion concentration enough to produce a 0.5 meq/L increase

some forms of muscular dystrophy do not appear until children are 6 years old.

• post skeletal muscle myalgia especially in skeletal muscles of neck, back, and abdomen can occur after administration.
• -especially in young adults undergoing minor procedures that permit ambulation

• cardiac dysrhythmias
• myalgia
• increased intragastric and intraocular pressure

• damage to skeletal muscle is suggested by occurrence of myoglobinuria after administration
• -mostly seen in peds
• -rarely seen in adults

• related to intensity of fasiculations
• -give non paralyzing dose of non depolarizer and this may decreased risk of aspiration

• increase in pressure 2-4 min after administration and lasts 5-10 min
• -do not use with open eye injury

• not uncommon in kids and considered normal response
• -the difficulty is separating the normal response from the masseter muscle rigidity that may be associated with MH

• hyperkalemia
• malignant hyperthermia- SCh is biggest trigger for this
• tx with dantrolene