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Anesthesia Pharm I > NMB Patho Implication > Flashcards

NMB Patho Implication Flashcards

1
Q

what is Dilantin’s effect on NMB?

A

*resistance, shorter duration
due to decreasing the activity of AChE, or induced cytochrome P-450 in the liver causing increased metabolism, or increased number of ACh receptor sites requiring more NMB
*seizure patients and even craniotomy patients who receive one time dose

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2
Q

How does Dilantin affect the common NMB?

A
  • Rocuronium decreased to 20% of control
  • Vecuronium decreased to 37% of control
  • Pancuronium decreased to 40% of control

for ex, Rocuronium’s duration is usually 20-30, Dilantin will cut it down to 4-6 minutes

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3
Q

what are the effects of corticosteroids on NMB?

A
  • resistance, shorter duration
  • chronic use causes resistance to steroidal NMB like vecuronium
  • in treated myasthenia gravis patients, steroids are given to improve neuromuscular function making them resistant, opposed to undiagnosed myasthenia gravis patients who are sensitive to NMB
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4
Q

what are the effects of aminophylline and theophylline on NMB?

A
  • resistance, shorter duration
  • inhibit phosphodiesterase, increasing the cAMP needed to synthesize and release ACh
  • leads to a greater amount of ACh for NMB to compete with, so more NMB is needed to compete for receptor sites
  • important for trach cases, sometimes on these meds
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5
Q

what are the effects of burn injuries on NMB?

A
  • resistance, shorter duration
  • resistance begins 10 days after injury, peaks at 40 days, and declines after 60 days
  • requires 30% or more BSA burned
  • Marathe: resistance not due to extrajunctional receptors, but a decreased sensitivity of the postjunctional receptors to ACh or nondepolarizing NMB
  • can use SCh within the first 48 hrs., then must use nondepolarizing and larger doses required for effect
  • important to keep NMB effective due to huge fluid shifts and lots of turning during burn cases
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6
Q

what are the effects of a hemiplegic limb of patients on NMB?

A
  • resistance, shorter duration
  • the paralyzed limb of a CVA patient is resistant due to more extrajunctional receptors due to denervation
  • be sure to monitor twitches on the non affected limb
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7
Q

what are the effects of multiple sclerosis on NMB?

A
  • unpredictable
  • may be resistant if in remission (no baseline muscle weakness) due to more extrajunctional receptors OR may have a prolonged response due to co-existing skeletal muscle weakness
  • avoid giving NMB, but if surgeon requires, use shortest acting drug (intermediate) to see if sensitive or resistant
  • can always redose
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8
Q

what other factors lead to an increase in extrajunctional receptors?

A
  • massive trauma
  • prolonged immobilization
  • expect resistance to NMB
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9
Q

what are effects of furosemide on NMB?

A
  • dose dependent
  • large does (1-4 mg/kg), inhibits phosphodiesterase, increasing cAMP, leading to more ACh at receptor sites. this causes RESISTANCE
  • in small doses (< 1mg/kg), decreases cAMP production, leading to less ACh to compete for receptor sites; causes SENSITIVITY
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10
Q

what are the effects of hyperkalemia on NMB?

A
  • resistance with nondepolarizing agents and sensitivity to SCh
  • increased resistance to nondepolarizers due to decreasing the resting potential of the membrane (moves it closer to depolarization), even may partially depolarize it
  • SCh is a depolarizing NMB, so this effect “helps” SCh, making more sensitive
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11
Q

what are the effects of volatile anesthetics on NMB?

A
  • sensitivity
  • decreases the skeletal muscle tone and decreases the sensitivity of muscle membranes to depolarization to lower the ED95
  • greatest impact on long acting NMB, also effect rocuronium
  • if you need to increase your twitches, try blowing off volatile agent
  • if case is almost over but need relaxant for a big stimulation at the end (pulling stones out during lap-chole; stitches) can increase volatile agent rather than re dose
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12
Q

what are the effects of local anesthetics on NMB?

A
  • sensitivity
  • interfere with the release of ACh from the prejunctional receptors (decreasing the competitor)
  • block ion channels
  • decrease skeletal muscle tone
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13
Q

what are the effects of antibiotics on NMB?

A
  • sensitivity
  • have a magnesium-type effect to decrease release of ACh to make reversal unreliable (can give calcium)
  • usually giving ABT within an hour of incision
  • aminoglycosides: Gentamycin, Neomycin, Streptomycin, Kanamycin, Amikacin, Tobramycin, Vancomycin
  • Vancomycin must be given over an hour, so it will most likely run into the start of surgery; remember to lower NMB dose
  • **ABT with no NMB effect: penicillins and cephalosporins (will mostly use cephalosporins)
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14
Q

what are the effects of Lidocaine on NMB?

A
  • sensitivity
  • when given to a patient who is recovering from nondepolarizing NMB, the block is potentiated by the blockage of the prejunctional release of ACh
  • sometimes given to relax airway and before giving propofol IVP; may also be given at the end of a case if patient must be awake before extubation, so be cautious Lidocaine may weaken pt. due to increased sensitivity to NMB
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15
Q

what are the effects of Quinidine on NMB?

A
  • sensitivity

- potentiates both nondepolarizers and SCh

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16
Q

what are the effects of Lithium on NMB?

A
  • variable with nondepolarizers
  • prolonged onset and duration of SCh
  • similarity to Na+ ion; lithium intracellular influx hypopolarizes (brings closer to depolarization) the membrane and therefore potentiates depolarizing NMB
  • caution with ECTs, patient may be on lithium
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17
Q

what effect does cyclosporine have on NMB?

A
  • sensitivity
  • may cause leg cramps and contractions
  • study of renal transplant patients (usually take this med) showed more required post op ventilation with atracurium or vecuronium
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18
Q

what effect does SCh have on nondepolarizing NMB agents?

A
  • sensitivity
  • reduces the dose required possibly due to membrane desensitization causing enhance (not prolonged) blockade by the nondepolarizing NMB
  • if using SCh to intubate, will not give the intubating dose of the nondepolarizing agent
  • *always check twitches after SCh use before giving the nondepolarizer
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19
Q

what effect does combining nondepolarizing agents have?

A
  • synergistic effect seen with two drugs with different sites of action (pancuronium and metocurine)
  • allows smaller doses of each to minimize side effects
20
Q

what effect does calcium channel blockers have on NMB?

A
  • unpredictable
  • verapamil
  • usual site of action is on the slow channels, not fast channels like the postjunctional receptors
21
Q

what effect does hydrocortisone have on NMB?

A
  • sensitivity with acute administration
  • ICU patients on hydrocortisone may develop critical illness myopathy
  • at the beginning of some cases, may give a “stress dose” of hydrocortisone
22
Q

what effect do antihypertensives have on NMB?

A
  • sensitivity
  • can decrease sensitivity of the muscle membrane to cause relaxation of its own and potentiate nondepolarizers
  • also inhibit plasma cholinesterase activity, prolonging depolarizing block
  • ganglionic blockers: Trimethaphan, Hexamethonium
23
Q

what effect does hypothermia have on NMB?

A
  • extreme hypothermia like when induced during cardiac cases
  • sensitivity
  • prolongs duration by slowing clearance via hepatic enzymes and renal pathways
  • also slows clearance via Hofmann elimination and ester hydrolysis
24
Q

what effect does acute hypokalemia have on NMB?

A
  • increases the membrane potential (hyperpolarization), moving further from depolarization
  • increases sensitivity to nondepolarizers
  • increases resistance to SCh
25
Q

what effect does hypermagnesium have on NMB?

A
  • high mag acts like low Ca++
  • decreased release of ACh from prejunctional receptors (enhanced block)
  • pregnant women with toxemia being treated with magnesium should receive smaller dose of relaxant
26
Q

what effect does hypernatremia have on NMB?

A
  • sensitivity
  • dehydration causes decreased volume of distribution of NMB, thus, more drug reaches the receptors (increased concentration)
27
Q

what effect does gender have on NMB?

A
  • females usually have a decreased muscle mass than men

* have a greater block in women with similar mg/kg dose

28
Q

what is myasthenia gravis?

A
  • chronic autoimmune disorder where antibodies destroy and cause by a decrease in functioning ACh receptors at the NMJ
  • first symptoms: ocular, pharyngeal, laryngeal muscle fatigue and weakness
  • treatment includes anticholinesterases and immunosuppressive drugs (if treated, build resistance to NMB)
29
Q

what effect does undiagnosed or untreated myasthenia gravis have on NMB?

A

*sensitivity
*will be fully paralyzed with even a small pretreatment dose
-due to fewer receptors for which to compete
*do a baseline TOF to determine dose
-there are no correlation between base TOF and clinical
severity
-some correlation between base TOF and dose required
*titrate initial dose to response to peripheral nerve stimulator (reduce 1/2-1/3)
use short or intermediate
**avoid NMB if possible (best option)

30
Q

what is myasthenic syndrome (Eaton Lambert)

A
  • autoimmune disease where presynaptic calcium channels are destroyed by antibodies
  • seen with oat cell carcinoma of the lung
  • anticholinesterase drugs are ineffective
31
Q

what effect does myasthenic syndrome have on NMB?

A
  • sensitivity to both SCh and nondepolarizers

* caution with known cancer patients and those having diagnostic or biopsy procedures for lung cancer

32
Q

what effect does muscular dystrophy have on NMB?

A
  • no SCh due to extrajunctional receptors and risk for hyperkalemia
  • normal or prolonged effect of nondepolarizing NMB when muscle weakness or atrophy exists
33
Q

what effect does myotonia dystrophica have on NMB?

A
  • SCh causes prolonged contraction
  • normal response to nondepolarizing NMB
  • anticholinesterase could cause depolarization of the muscle membrane and contraction
  • *titrate carefully with shortest acting nondepolarizer to avoid need for reversal
34
Q

what is amyotrophic lateral sclerosis (ALS) and how does it effect NMB?

A
  • a degenerative disease of motor ganglia in the anterior horn of the spinal cord and spinal pyramidal tracts
  • upper and lower motor neuron dysfunction
  • skeletal muscle atrophy and weakness
  • *prolonged response to nondepolarizing NMB
  • *hyperkalemia with SCh
35
Q

what physiologic difference in pediatrics affect NMB?

A

-difference in volume of distribution
extracellular fluid is 44% of weight of neonate compared
to 23% of weight of an adult
-increased HR and CO

36
Q

what difference does vecuronium have on pediatrics?

A
  • onset is quicker in infants and children due to faster circulation times (higher CO)
  • infants and neonates have prolonged recovery
  • children have a faster recovery
37
Q

what difference does atracurium have on pediatrics?

A

-neonates require 25% lower dose by weight due to increased sensitivity

38
Q

what difference does fetal blockade in utero for intrauterine surgery have?

A

-pancuronium or pipecuronium
0.2 mg/kg IM
onset 4.5 minutes
duration 54 and 48 minutes respectively

39
Q

what physiologic differences in the elderly affect NMB?

A
  • decreased total body fluid, lean (decreased) muscle mass
  • relative increase in body fat
  • decreased plasma proteins: decreased proteins to bind to drug, leaving more free drug to act
  • decreased CO
  • decreased kidney function
  • decreased hepatic blood flow
40
Q

what difference does vecuronium have on the elderly?

A

*prolonged duration

41
Q

what effect does the priming technique have on elderly?

A

resulted in decrease in pulmonary parameters and oxygen saturation
*more likely to de-sat

42
Q

what effect does atracurium have on the elderly?

A

although age independent, histamine release was greater

43
Q

what effect does rocuronium have on the elderly?

A
  • no difference in onset time

* prolonged recovery times

44
Q

what effect does vecuronium have on the obese?

A

prolonged recovery times

45
Q

what is different when using SCh and rocuronium with obese patients?

A
  • SCh dosed based on total body weight

* rocuronium dosed based on ideal body weight but may use total body weight for longer cases

46
Q

what effects do CO and skeletal muscle blood flow have on NMB?

A

-ephedrine: beta1 agonist increasing HR & contractility
common vasoconstrictor used
when given prior to administration of rocuronium,
decreased onset time by 22% due to increased CO
-esmolol: beta1 antagonist decreasing HR, contractility
vasodilator
given prior to administration of rocuronium, increased
onset time by 26% (longer onset)

Anesthesia Pharm I (28 decks)

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