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Flashcards in NMB Patho Implication Deck (46)

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


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


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


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


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


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


what are the effects of multiple sclerosis on NMB?

-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


what other factors lead to an increase in extrajunctional receptors?

-massive trauma
-prolonged immobilization
*expect resistance to NMB


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


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


what are the effects of volatile anesthetics on NMB?

-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


what are the effects of local anesthetics on NMB?

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


what are the effects of antibiotics on NMB?

-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)


what are the effects of Lidocaine on NMB?

-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


what are the effects of Quinidine on NMB?

-potentiates both nondepolarizers and SCh


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


what effect does cyclosporine have on NMB?

-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


what effect does SCh have on nondepolarizing NMB agents?

-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


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


what effect does calcium channel blockers have on NMB?

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


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


what effect do antihypertensives have on NMB?

-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


what effect does hypothermia have on NMB?

*extreme hypothermia like when induced during cardiac cases
-prolongs duration by slowing clearance via hepatic enzymes and renal pathways
-also slows clearance via Hofmann elimination and ester hydrolysis


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


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


what effect does hypernatremia have on NMB?

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


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


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)


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

*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
-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)


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


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


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


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


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


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


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


what difference does atracurium have on pediatrics?

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


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


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


what difference does vecuronium have on the elderly?

*prolonged duration


what effect does the priming technique have on elderly?

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


what effect does atracurium have on the elderly?

although age independent, histamine release was greater


what effect does rocuronium have on the elderly?

-no difference in onset time
*prolonged recovery times


what effect does vecuronium have on the obese?

prolonged recovery times


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


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
given prior to administration of rocuronium, increased
onset time by 26% (longer onset)