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Anesthesia Pharm I > NMB Patho Implication > Flashcards

Flashcards in NMB Patho Implication Deck (46)
1

what is Dilantin's effect on NMB?

*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

2

How does Dilantin affect the common NMB?

-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

3

what are the effects of corticosteroids on NMB?

*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

4

what are the effects of aminophylline and theophylline on NMB?

*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

5

what are the effects of burn injuries on NMB?

*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

6

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

*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

7

what are the effects of multiple sclerosis on NMB?

*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

8

what other factors lead to an increase in extrajunctional receptors?

-massive trauma
-prolonged immobilization
*expect resistance to NMB

9

what are effects of furosemide on NMB?

*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

10

what are the effects of hyperkalemia on NMB?

*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

11

what are the effects of volatile anesthetics on NMB?

*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

12

what are the effects of local anesthetics on NMB?

*sensitivity
-interfere with the release of ACh from the prejunctional receptors (decreasing the competitor)
-block ion channels
-decrease skeletal muscle tone

13

what are the effects of antibiotics on NMB?

*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)

14

what are the effects of Lidocaine on NMB?

*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

15

what are the effects of Quinidine on NMB?

*sensitivity
-potentiates both nondepolarizers and SCh

16

what are the effects of Lithium on NMB?

*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

17

what effect does cyclosporine have on NMB?

*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

18

what effect does SCh have on nondepolarizing NMB agents?

*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

19

what effect does combining nondepolarizing agents have?

*synergistic effect seen with two drugs with different sites of action (pancuronium and metocurine)
-allows smaller doses of each to minimize side effects

20

what effect does calcium channel blockers have on NMB?

*unpredictable
*verapamil
-usual site of action is on the slow channels, not fast channels like the postjunctional receptors

21

what effect does hydrocortisone have on NMB?

*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

what effect do antihypertensives have on NMB?

*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

what effect does hypothermia have on NMB?

*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

what effect does acute hypokalemia have on NMB?

-increases the membrane potential (hyperpolarization), moving further from depolarization
*increases sensitivity to nondepolarizers
*increases resistance to SCh

25

what effect does hypermagnesium have on NMB?

*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

what effect does hypernatremia have on NMB?

*sensitivity
-dehydration causes decreased volume of distribution of NMB, thus, more drug reaches the receptors (increased concentration)

27

what effect does gender have on NMB?

-females usually have a decreased muscle mass than men
*have a greater block in women with similar mg/kg dose

28

what is myasthenia gravis?

-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

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

*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

what is myasthenic syndrome (Eaton Lambert)

-autoimmune disease where presynaptic calcium channels are destroyed by antibodies
*seen with oat cell carcinoma of the lung
-anticholinesterase drugs are ineffective

31

what effect does myasthenic syndrome have on NMB?

*sensitivity to both SCh and nondepolarizers
*caution with known cancer patients and those having diagnostic or biopsy procedures for lung cancer

32

what effect does muscular dystrophy have on NMB?

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

33

what effect does myotonia dystrophica have on NMB?

*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

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

-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

what physiologic difference in pediatrics affect NMB?

-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

what difference does vecuronium have on pediatrics?

-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

what difference does atracurium have on pediatrics?

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

38

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

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

39

what physiologic differences in the elderly affect NMB?

-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

what difference does vecuronium have on the elderly?

*prolonged duration

41

what effect does the priming technique have on elderly?

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

42

what effect does atracurium have on the elderly?

although age independent, histamine release was greater

43

what effect does rocuronium have on the elderly?

-no difference in onset time
*prolonged recovery times

44

what effect does vecuronium have on the obese?

prolonged recovery times

45

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

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

46

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

-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)