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Pharm Test 4 > Malignant Hyperthermia > Flashcards

Malignant Hyperthermia Flashcards

1
Q

What is the incidence of MH?

A
  • 1:8000 to 1:30,000 depending on the source (higher in children)
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2
Q

What are some genetic mutations that have been linked to MH?

A
  • Genetic susceptibility: variety of inheritance patterns/commonly autosomal dominant
  • Linekd mutations in RYR1 (chormosome 19), CACNA 1S (chormosome 1) and STAC3 (chromosome 12)
  • Ryanodine (RYR1) gene mutations found in
    • 50% of MH families
    • 20% of all mH patients
    • major target, but there’s not a clear cut trigger to MH
    • Not all that carry trait have incidence, can also have multipled sx without incident, and then have MH
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3
Q

What is the pathophysiology behind MH?

A
  • A syndrom–> chain of clinical resposnes to muscle hypermetabolism
  • disregulation of Ca
  • ​General cascade of events–> increased myoplasmic Ca release upon membrane depolarizaiton and failure of negative feedback mechanisms to reduce subsequent Ca release
    • hypermetabolism: ATP needed for Ca release, reuptake into SR, and troponin decoupling
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4
Q

Succinylcholine causees MH ____

A

indirectly

  • Activates nACHR, resulting in continuous local depolarization. This overactivates local voltage gated Ca channels which stimulates further internal Ca release and further Ca entry from ECF
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5
Q

How do volatile agents (except N2O) trigger MH?

A

Directly

  • Work directly on ryanodine receptor which increases Ca release
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6
Q

What are some postulated theories for pathophys behind s/s of MH?

A
  • Aerobic metabolism increases to repalce ATP–> heat and CO2 produced as a byproduct
  • Ca accumulates in mitochondria–> failure of aerobic metabolism–> arterial hypoxemia
  • Anaerobic metabolism increases–> lactic acidosis
  • Rhabdomyolysis–> hyperkalemia and renal failure
  • Muscle ATP eventually depleted–> CV collapse

Main 2 features:

1) skeletal muscle involvement
2) sympathetic hyperactivity

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7
Q

S/S of MH?

A
  • Hypercarbia *** earliest sign- increased ETCO2/sns stimulation
  • Tachycardia ***
  • Tachypnea***
  • Hyperthermia **???** ( see increase 1-2 degrees q 5 min)
  • Hypertension
  • Dysrhythmia
  • Metabolic acidosis
  • hyperkalemia
  • masseter spasm ***
    • masseter muscle rigidiity after succ in children0 CPK > 20,000 confirms
  • myoglobinuria
  • hypoxemia

***= early sign

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8
Q

What other diagnosis may resemble MH?

A
  • Light anesthesia
  • pain
  • thyroid storm
  • pheochromocytoma
  • sepsis
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9
Q

Triggers for MH?

A
  • Diverse genetic causation and presentation
  • Full episodes
    • general anesthesia inhalational agents: halothane, enflurane, isoflurane, des, sevo,
    • MR: Succinylcholine (depolarizing agents)
      • it used to be thought that succ could not trigger MH by itself, but it most certainly can
      • unsafe to work at centers that have succinycholine but no dantrolene
  • Milder MH: (may need to take PO dantrolene routinely)
    • Excercise in hot conditions
    • neuroleptic drugs
    • alcohol
    • infections
  • However, some individuals can experience suddent death under stressful circumstances
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10
Q

What are some types of muscle rigidity that can be seen in MH?

A
  • Isolated trismus
    • early sign
    • can be benign after succ. will notice jaw is very stiff. can still open it, but stiffer
  • Masseter muscle rigidity- sustained contracture of jaw muscles following succ, disallowing mouth opening
    • may be forewarning of MH
    • Mild increase in masseter muscle tone following succ with limb flaccidity. may be normal response
      • not possible to determine, clinically, whether increase in tone represents MH reaction or not
    • If you see this, immediately check K and ABG
    • Clinical signs of MH occur in 20% of cases of MMR (signs can be immediate or delayed)
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11
Q

What are the current recommendations when you see masseter muscle rigidity (MMR)?

A
  • Experts are divided on how to proceed
    • continue with anesthetic agent that will not trigger MH
    • discontinue anesthetics, and postpont elective sx
  • Unless clinical signs MH, not recommended to administer dantrolene for just occurrence of MMR ONLY
  • Patient experience MMR with associated s/s of MH, should be observed for at least 24 hours
  • discuss muscle bx with MH expert
  • dont’ be afraid to call MHAUS!
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12
Q

What are s/s rhabodmyolysis associated with MH?

A
  • S/S
    • muscle pain
    • myoglobinuria: may cause renal failure, ATN
    • cardiac arrhythmia: hyper kalemia
  • CPK increased >20,000
    • during episode. very high upt o 100,000
    • elevation correlates
      • best with rhabdoyolysis
      • less well with fever and acidosis
  • Urine color checked q 6 hours, untril retrun to normal
  • Rapidly developing rhabdomyolysis: includes rapdi increase in K
  • slowly developing rhabdo is safer
  • Myoglobinuria may occur within a few hours and should be anticipated to prevent ATN
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13
Q

What are findings on ABG during MH?

A
  • Hypermetabolism
    • increased o2 consumption
    • increased pco2
  • lactic acidosis
    • high lactate and acidosis: pH may be <7
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14
Q

What are some compensatory mechanisms associated with MH?

A
  • Heat loss
    • sweating
    • cutaneous vasodilation
  • sympathetic hyperactivity: increased circulating catecholamines
    • increased HR
    • cutaenous vasoconstriction
    • increased svr
  • increased CO
  • increased ventilation
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15
Q

How is testing done for MH?

A
  • Perform halothane- caffeine contracture test (gold standard)
    • skeletal muscle bx placed in solution of halothane. sustained contracture is diagnostic
      • muscle exposed 3% halothane and increasing caffeine concentrations 0.5mM–>32 mM
        • positive contracture response
        • requires 1 gm fresh muscle
  • Only 80% specificity (neg result does not rule it out)
  • Muscle biopsy centers in US, canada and europe have standardized the contracture test and determined its sensitivity and specificity
  • testing centers in north america listed on MHAUS website
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16
Q

What is genetic testing for MH like?

A
  • Multiple mutations identified as being casual for MH but mutations not always found in MH pt
  • May be used for determining susceptibility in some individuals
    • 5 labs currently perform this in US see MHAUS
    • Insurance coverage is inconsistent
    • MHAUSE has program to help pt cover cost
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17
Q

What is MH mortality with dantrolene? without?

A
  • With dantrolene- 5% mortality
  • without dantrolene- 70% mortality
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18
Q

What is dantrolene mechanism of action?

A
  • Reduces muscle tone and metabolism–> restores balance between release and uptake
    • prevents ongoing release of Ca from muscle (SR)
    • blocks external entry of Ca into sarcoplasm
    • hypothesized to inhibit Ca conductance through ryanodine channels
  • half life 10-15 hours
    • will need multiple doses
  • does not interfere with reversal of MR
    • However, make sure muscle strenght has returned prior to extubation
  • may cause sig muscle weakness in pt with pre-exiting muscle dx
19
Q

Concerns following admin of dantrolene?

A
  • Phlebitis following admin of dantrolene
  • When used with CCB, dantrolene may produce life-threatneing hyperkalemia and myocardial depression
  • after MH episodes resolve, may need oral dantrolene for several days
    • d/c CCB if any chance MH could be issue
20
Q

How much dantrolene needs to be stocked? Who needs to stock it?

A
  • Need 36 vials of standard forumalation (20mg/vial)
  • 3 vials of ryanodex (250mg/vial)
  • Any center that uses MH triggering anesthetics, needs dantrolene!
21
Q

Where should dantrolene be kept?

A

close of OR with supply of sterile water for injection (60mL/vial)

22
Q

What are some initial treatments when you notice s/s of MH?

A
  • D/C volatile anesthetics and succinylcholine
    • change anesthetic circuit and absorbant
      • use highest flow possible of oxygen through machine or ideally change to new, dedicated MH machine
      • avoid rebreathing in Bain circuit
  • Hyperventilation 100% O2 and switch technique to TIVA
  • Dantrolene
  • Treat acidosis with bicarb (monitor capnography q 15 min ABG)
    • remember bicarb produces a lot of CO2
  • Monitor core temp
  • maintain UOP 2mL/kg/hr
    • keep fluids to avoid ATN
  • Treat dysrhythmias
23
Q

Dantrolene dose?

A
  • Bolus: 2.5 mg/kg
  • Followed by Maintenance 2mg/kg IV q 5 min for total of 10mg/kg (give until you start to see things improve)
    • rarely exceeds 10mg/kg (if you’re giving more, the diagnosis might not be correct)
  • Then 1mg/kg q 6 hours x 72 hours
24
Q

What are recommendations for core temperature monitoring?

A
  • Cooling, lower temp to 38 degrees (don’t overcool)
    • monitor with esophageal probe
  • External ice packs
  • NG, bladder lavage
  • IV bolus with iced normal saline (15mL/kg q 10min)
  • Better survival with core temp monitoring
25
Q

What can we give to treat dysrhythmia in MH?

A
  • Avoid CCB
  • Persistent arrhythmias can be treated with any other standard antiarhythmia (lidocaine, procainamide 15 mg/kg ok)
  • Treat hyperkalemia
    • 1mL/kg D50 glucose
    • 0.15 units/kg regular insulin
    • 5-10 mg/kg IV calcium chloride
      • ok to give during MH since issue isn’t Ca in PLASMA but Ca in ICF
  • Most arrhythmias respond to correction of hyperkalemia and acidosis by herpventilation, dantrolene and bicarb
26
Q

How long do we continue dantrolene?

How long do they need to stay in ICU?

A
  • Continue dantrolene for at least 72 hours after control of episdoe
    • approx. 1 mg/kg q 6 horus
  • Minotr in ICU for 36 hours for recrudescence (reoccurrence)
    • recrudescence occurs in 25% of MH cases
27
Q

Things to avoid/monitor after initial control of MH?

A
  • Avoid parenteral potassium
    • NO LR. use only NS
  • Watch out for DIC
  • Measure CK q 6 hours
    • CK may be elevated for 2 weeks if elevation marked
    • measure CK on declining basis until normal after patient has improved and stabilized
28
Q

What drugs do you need in the MH cart?

A
  • Dantrolene for injection- 36 vials for standard formulation
    • standard formulation- 20 mg dantrolene with 3 g mannitol
      • diluted to 60 mL sterile water
    • New formulation- Ryanodex 5mL diluent in 250mg
      • only need 1-2 vials for total adult loading dose
  • Sterile water 1000mLx2 (DO NOT GIVE IV BOLUS!)
  • Sodium bicarb 50mL x5
  • Furosemid 40 mg/amp x 4 amp
  • D50 50 mL vials x 2
  • CaCl (10%) 20mL vial x 2
  • Regular insulin 100 units/mL x 1 (refirgerated)
  • Lidocaine HCl (2%)- 1 box= 2 grams or 10mL/100mg preloaded vial
29
Q

What general equipment do you need in MH cart?

A
  • Syringes (60mL x5) to dilute dantrolene
  • Mini spike IV additive pins x 2, multi ad fluid transfer sets x 2 to reconstitute dantroleneAngiocaths 20G, 2 in 22G, 1 in 24G, 3/4 in (4ea) for IC access and arterial line
  • D5W 250mL x 1
  • microdrip IV set
  • NG tubes
  • irrigation tray with piston syringe for NG irrigation
30
Q

What monitoring equipment do you need for MH?

A
  • Esophageal or other core temp probes
  • CVP kids: size appropriate for patient
  • Transducer kits for arterial and central venous cannulation
31
Q

Additional supplies needed for MH cart?

A
  • Large sterile steri drape
  • three way irrigating foley catheters
  • urine meter x 1
  • irrigation tray
  • rectal tubes
  • large clea plastic bags for ice X4
  • Small plstic bags for ice x 4
  • bucket for ice
  • ICE!
32
Q

What lab testing supplies do you need for MH?

A
  • Syrings 3 mL or ABG kits x6
  • blood specimen tubes (2 ped, and 2 large tubes)
    • CK myoglobin, SMA 19
    • pT/PTT, fibrinogen, fibrin split
    • CBC, PLT
    • ABG syringe
  • Urine cup x 2
  • urine dipstick :Hgb
33
Q

How do we prepare anesthesia machine for MH patient?

A
  • Ensure anesthetic vaporizers disabled by removing them from machine
  • Change CO2 absorbent
  • flow 10L/m O2 through circuit for amt of time specified by machine
    • varies: 20-100 min
    • During this time, disposable unused bag should be attached to y-piece of circle system and ventialtor set to inflate bag periodically
    • use new or disposable breathing circuit
  • also coal filters to reduce concentration to <5ppm within minutes
34
Q

Is pretreatment with dantrolene necessary?

A

No

  • contact MH hotline for advice
  • dantrolene prophylaxis is usually not indicated- used with caution in pt with muscle disease/weakness
35
Q

Management/pretreatment of MH susceptible patients?

A
  • Do not use MH triggering agents with patient susceptible to MH or their relatives
    • no succ, VA
      • N2O, other NDNMB ok!
  • Treatment plan should be available to all OR team members
  • Pt susceptible to MH can be d/c’ed DOS if anesthetic has been uneventful
    • min of 4 hours obs is stongly recommended
36
Q

What muscle diseases predispose patients to MH or hyperkalemic reactions to MH?

A
  • Central core diseases such as:
    • King Denborough syndrome
    • Evan’s myopathy
  • CCD is auosomal dominant congenital myopathy (inborn muscle disorder)
    • leads to hypotonia
    • mild delay in child development
    • weakness of facial muscles
    • scoliosis
    • hip dislocation
37
Q

Is there an association with MH and muscular dystrophies?

A

NOT likely

  • However, msucular dystrophies can still have issue with hyperkalemia and rhabdomyolsis
    • BUT NO hypermetabolic state. DIFFERENT than MH
    • avoid triggering agents anyway
  • MD- has sarcolemma instability leading to increased Ca release with triggering agents
    • increased Ca result s in muscle breakdown and release of excessive Ca into blod
38
Q

What is a syndrome that mimics MH?

A
  • Neuroleptic Malignant Syndrome
    • many features in common
    • onset and recovery are diff
      • generally presents with muscle rigidity
      • fever
      • autonomic instability
      • cognitive changes such as delirium
      • elevated CPK
    • Susceptible pt
      • those on antipsychotics
        • haldol, prolixin, thorazine
39
Q

Why don’t we routinely use succinylcholine in children?

A
  • Children can have undiagnosed muscular dystrophy
  • stop using succ routinely across the board, decreases amount of unexpected deaths
40
Q

Are we able to use succinylcholine in children?

A
  • In emergency situations with use of atropine together
  • only in airway emergencies, risk of aspiration and special situations
  • Reason for changes:
    • masseter muscle rigiidty
    • rhabdomyolysis
    • sudden hyperkalemic cardiac arrest in pt with undiagnosed myopathies
41
Q

If sudden cardiac arrest, how do you know MH or occult myopathy?

A
  • Sudden cardiac arrest, especially after use of succinylcholine in young, male pt is usually related to hyperkalemia in pt with undiagnosed myopathy
  • over 40 cases since 1990
  • usually with IV/IM succ
  • 50% mortality rate
  • muscle rigiidty and/or hyperthermia may also be present
  • 50% mortality rate from hyperkalemia
  • Note if there was increase in ETCO2 before cardiac arrest–> most likely MH
42
Q

How do you treat sudden unexpected cardiac arrest from hyperkalemia?

A
  • Focus on treating hyperkalemia
  • CaCl
  • Bicarb
  • Insuline
  • Glucose
  • Hyperventialtion
  • Dialysis and CPB may be required
43
Q

Where is North American MH Registry housed?

A
  • Housed at Univ. of Florida
  • operating unit of MHAUS
  • Registers info about sepcific pt and their families
  • Report MH and MH like episodes to registry

Pharm Test 4 (4 decks)

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