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ACRM > Malignant Hyperthermia > Flashcards

Malignant Hyperthermia Flashcards

1
Q

% of MH cases that have been previously exposed to anesthesia

A

> 50%

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2
Q

States with higher MH rates

A
  • Wisconsin
  • Nebraska
  • West Virginia
  • Michigan
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3
Q

Main culprit of excessive release of intracellular Ca2+ in MH

A

ryanodine receptor type 1

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4
Q

Pathophysiology of MH

A
  • genetic mutation of RYR receptor 1
  • triggered by succs & volatiles
  • ^ interact with RYR receptor causing excessive release and sequestration of Ca2+
  • tetanic contraction of muscle
  • hypermetabolic state (cellular hypoxia, acidosis, death)
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5
Q

RYR receptor 1 resides where? Why is this relevant?

A

resides on sarcoplasmic reticulum in skeletal muscle

important because interaction of this receptor + succs/volatiles = excessive Ca2+ release

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6
Q

MH triggering agent that works directly on the ryanodine receptor

A

volatiles

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7
Q

MH triggering agent that works INdirectly on the ryanodine receptor

A

succinylcholine

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8
Q

Volatile agents and their likelihood of triggering MH

A

Halothane > Iso > Sevo > Des

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9
Q

Severity of MH symptoms is dependent on…

A

amount of intracellular Ca2+ released

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10
Q

Manifestations of MH

A

*elevated EtCO2 out of proportion to minute ventilation
*masseter muscle rigidity
*tachycardia
*hyperthermia

later signs:
- decreased PaO2, increased PaCO2
- CV instability, arrhythmias
- hyperkalemia, elevated CK
- combined resp and metab acidosis

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11
Q

Incidence of hyperthermia in MH

A

first sign in 1/3 of patients, one of first 3 signs in 2/3 of patients

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12
Q

Consequences of increased intracellular Ca2+

A
  • sustained muscle contraction
  • hyper-metabolic rate
  • increased O2 consumption
  • increased heat production & CO2
  • rapid depletion of ATP
  • resp and metab acidosis
  • ## breakdown of sarcolemma
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13
Q

3 earliest symptoms of MH

A
  • elevated EtCO2
  • tachycardia
  • masseter spasm
    +/- hyperthermia
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14
Q

Most sensitive MH indicator

A

EtCO2 that rises out of proportion to minute ventilation

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15
Q

Initial treatment of MH

A
  • communicate
  • administer Dantrolene
  • stop volatiles
  • switch to non-triggering anesthetic
  • activated charcoal filters
  • hyperventilate 100%, high Ve
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16
Q

Main advantage of Ryanodex over Dantrium

A

faster constitution & administration

17
Q

Initial dose of Dantrolene

A

2.5mg/kg

18
Q

MOA of Dantrolene

A

RYR1 antagonist
- halts Ca2+ release from RYR1
- prevents Ca2+ entry into myocyte
- reduces Ca2+ (+) feedback system

19
Q

Describe the process of reconstituting Dantrium/Revonto

A
  • each vial has 20mg Dantrolene/3000mg Mannitol
  • reconstitute each vial in 60mL sterile H2O
  • takes 86 sec to dissolve
  • 12.5 vials needed
20
Q

How many vials of Dantrium/Revonto does MHAUS recommend be available?

A

36

21
Q

Dose range of Dantrolene

A

2.5 to max of 10 mg/kg

22
Q

Final concentration of Dantrium/Revonto after reconstitution:
Final concentration of Ryanodex after reconstitution:

A

Dantrium/Revonto: 1mg/3mL
Ryanodex: 50mg/1mL

23
Q

Describe the process of reconstituting Ryanodex

A
  • each vial contains 250mg Dantrolene/125mg Mannitol
  • reconstitute each vial in 5mL sterile H2O
  • takes 20 sec to dissolve
    -1 vial needed for patients up to 100kg
24
Q

How many vials of Ryanodex does MHAUS recommend be available?

A

3

25
Q

Which Dantrolene formulation is orange colored?

A

Ryanodex

26
Q

T/F Ryanodex is an extravasation risk? Why?

A

True; pH 10.3

27
Q

Labs included in the MH panel:

A
  • ABG
  • CBC
  • PT/PTT
  • lytes
  • CK
  • glucose
  • urine myoglobin
28
Q

SE of Dantrolene

A
  • muscle weakness
  • venous irritation
  • flu-like symptoms
29
Q

Additional treatments for MH

A
  • cooling measures
  • art line
  • treat arrhythmias
  • treat acidosis
  • treat K+
  • urinary catheter
  • trf to ICU
30
Q

Treatment of hyperkalemia should include…

A
  • CV protection (CaCl2)
  • promote intracellular shift of K+ (D50, insulin, bicarb, albuterol, hyperventilate)
  • promote excretion of K+ (lasix, kayexelate, dialysis)
  • monitor serial K
31
Q

Drugs to avoid when treating MH-associated arrhythmias

A
  • CCB
  • Lidocaine
  • Procainamide
32
Q

Likelihood of recurrent MH

A

25% in first 24h
- repeat Dantrolene

33
Q

When can Dantrolene be stopped post-MH crisis?

A
  • metabolic stability x24h
  • core temp <38
  • CK decreasing
  • no evidence of myoglobinuria
  • absence of muscle rigidity
34
Q

Evidence that a patient is stabilizing post-MH crisis:

A
  • EtCO2 declining/normal
  • HR stable, no dysrhythmias
  • hyperthermia resolving (<38)
  • muscle rigidity resolving
35
Q

3 disorders associated with MH

A

1) central core disease
2) multiminicore disease
3) King Denborough Syndrome

36
Q

How is MH diagnosed

A

gold standard = halothane contracture test w/ muscle biopsy

genetic testing (50% of MH susceptible people have a change in RYR1 gene

37
Q

Preparing the OR for MH susceptible patient:

A
  • new CO2 absorber
  • remove vaporizers from OR
  • (No charcoal filters) flush system with 100% O2 x35min @ 15L/min
  • (with charcoal filters) flush system with 10-15L/min x 90sec
  • goal is <5ppm trace volatiles
  • MH patients should be first case

ACRM (9 decks)

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