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Malignant Hyperthermia Flashcards

1
Q

What is malignant hyperthermia?

A

Inherited disorder of skeletal muscle

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2
Q

What triggers Malignant Hyperthermia?

A

Triggered in susceptible humans or animals by volatile inhalation agents or succinylcholine

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3
Q

What anesthetics can cause Malignant Hyperthermia?

A
  • Sevoflurane
  • desflurane
  • isoflurane
  • halothane
  • enflurane
  • ether
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4
Q

What are other triggers for Malignant Hyperthermia?

A

Vigorous exercise and heat**

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5
Q

What is malignant hyperthermia characterized by?

A
  • Hyper metabolism
  • Skeletal muscle damage
  • Hyperthermia
  • Death
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6
Q

True incidence of Malignant Hyperthermia is ________

A

Unknown

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7
Q

What is the genetic component of Malignant Hyperthermia?

A

Autosomal dominant

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8
Q

What is the clinical incidence in adults with Malignant Hyperthermia?

A

1 in 3,000 – 1 in 50,000 anesthetics

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9
Q

What is the pediatric incidence of Malignant Hyperthermia?

A

Children under 15 years comprise approx. 52% of all reactions

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10
Q

Which gender is more like to cause Malignant Hyperthermia?

A

More common in males (2.5-4.5 times)

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11
Q

What is the autosomal dominant traits for Malignant Hyperthermia?

A

One abnormal gene needed to manifest symptoms

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12
Q

How many mutations are associated with Malignant Hyperthermia?

A

Associated with 34 genetic mutations

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13
Q

What are the most common genetic mutations for Malignant Hyperthermia?

A
  • RYRI (70%) (ryanodine receptor for Ca++ release at SR)
  • CACNA1S (1%) (subunit of dihydropyrdine Ca++ channel on T-tubes)
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14
Q

What is variable penetrance mean in association with Malignant Hyperthermia?

A

Susceptible patient does not necessarily trigger to every exposure

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15
Q

Review genetic components of Malignant Hyperthermia.

A
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16
Q

The gene for the RYR 1 receptor is located on _________

A

chromosome 19

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17
Q

Where are all of the genetic mutations associated with Malignant Hyperthermia located?

A

chromosome 19

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18
Q

Where is calicum stored?

A

Invaginations of plasma membrane known as t-tubules which are surrounded by sarcoplasmic reticulum which stores intracellular calcium.

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19
Q

What is the unique feater of the sarcolemma?

A
  • It has holes in it.
  • These “holes” lead into tubes called transverse tubules (or t-tubules for short).
  • These tubules pass down into the muscle cell and go around the myofibrils.
  • However, these tubules do not open into the interior of the muscle cell; they pass completely through and open somewhere else on the sarcolemma (i.e., these tubules are not used to get things into and out of the muscle cell).
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20
Q

What is the function of the T-tubules?

A

The function of t-tubules is to conduct impulses from the surface of the cell (sarcolemma) down into the cell and, specifically, to another structure in the cell called the sarcoplasmic reticulum.

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21
Q

How is the muscle fiber excited?

A
  • A muscle fiber is excited via a motor nerve that generates an action potential that spreads along the surface membrane (sarcolemma) and the transverse tubular system into the deeper parts of the muscle fiber.
  • A receptor protein (DHP) senses the membrane depolarization, alters its conformation, and activates the ryanodine receptor (RyR) that releases Ca2+ from the SR. Ca2+ then bind to troponin and activates the contraction process
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22
Q

Review the normal skeletal muscle.

A
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23
Q

Describe the normal skeletal muscle diagram.

A

Interior of skeletal muscle cell:

  1. Plasma membrane
  2. Invagination of plasma membrane into the cell (t-tubule)
  3. Protein embedded in the wall of the t-tubule – Dihydropyridine protein
  4. Large protein in sarcoplasmic reticulum - ryanodine
  5. Sarcoplasmic reticulum that stores calcium in the cell
  6. Contractile proteins in the cell
  7. Reuptake of intracellular calcium after contraction

Bottom left = mitochondria (energy producers)

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24
Q

What does the dihydropyridine receptor sense?

A
  • The dihydropyridine receptor senses the membrane depolarization, alters its conformation, and activates the ryanodine receptor (which releases Ca2 from the sarcoplasmic reticulum, a Ca2 storage area).
  • Ca2 binds to troponin and activates the contractile machinery.
  • In classic malignant hyperthermia, uncontrolled Ca2 release from the SR leads to an increased pump activity and heat production, mainly by the adenosine triphosphate-dependent Ca2 reuptake into the SR.
  • To cope with the increased energy consumption, glycogen stores will be depleted for maximal adenosine triphosphate production
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25
Q

What can the myoplasmic Ca2 overload may stimulate?

A

also stimulate Ca2 sensitive proteases, liposomal enzymes, and nuclear DNases, potentially resulting in rhabdomyolysis.

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26
Q

What is the MOA of Malignant Hyperthermia?

A

Dysregulation in intracellular calcium homeostasis

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27
Q

MH: Calcium released from the sarcoplasmic reticulum in quantities that _______ normal

A

far exceed

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28
Q

What does excess calcium release lead to?

A

Leads to actin and myosin continually contracting = contracture

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29
Q

What do accelerations in cellular processes lead to? (8)

A
  • Heat production
  • Excess lactate
  • Oxygen consumption → Anaerobic metabolism, lactic acid
  • Carbon dioxide production
  • Depleted ATP stores
  • Cell breakdown with contents entering circulation and causing downstream effects
  • Acidosis, hyperthermia and ATP depletion lead to destruction of the sarcolemma
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30
Q

What moves into the extracellular fluid with malignant hyperthermia?

A

K+, myoglobin and creatine kinase move into extracellular fluid

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31
Q

What are the clinical signs of Malignant Hyperthermia?

A
  • Tachycardia**
  • Unanticipated increase in ETCO2 levels (>55mmHg) that are out of proportion to MV**
  • Tachypnea
  • Skin mottling
  • Rigidity
  • Hyperthermia
  • Myoglobinuria
  • Mottled, cyanotic skin
  • Decreased SaO2
  • Arrhythmias and labile BP
  • Mixed metabolic and respiratory acidosis
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32
Q

What are the hallmark signs of malignant hyperthermia?

A
  • Tachycardia**
  • Unanticipated increase in ETCO2 levels (>55mmHg) that are out of proportion to MV**
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33
Q

What are the characteristics of Rigidity with malignant hyperthermia?

A

Rigidity (present in 75% of cases): masseter muscle or generalized

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34
Q

What are the characteristics of hyperthermia with malignant hyperthermia?

A
  • Hyperthermia (1-2 degrees Celsius increased every 5 min)
  • May be early or late sign
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35
Q

What are the characteristics of Myoglobinuria with malignant hyperthermia?

A
  • Myoglobinuria (cola colored urine)
  • Myoglobin released from inside muscle cell
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36
Q

What causes of arrhythmias and labile BP with malignant hyperthermia?

A

Caused by acidosis, hyperkalemia and hyperthermia

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37
Q

What are the laborarotry findings for Malignant Hyperthermia?

A
  • ABG: Respiratory and metabolic acidosis
  • Serum potassium >6 mEq/L
  • CK >20,000 units/L
  • Serum myoglobin >170 mcg/L
  • Urine myoglobin >60 mcg/L
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38
Q

What is the onset of Malignant Hyperthermia?

A

Intraoperatively or shortly afterwards

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39
Q

What is the different types of rate of onset?

A
  • Fulminant
  • Indolent
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40
Q

Define Fulminant.

A

Onset of full-blown syndrome within minutes of induction of general anesthesia

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41
Q

What effects does succinylcholine have on the timing of malignant hyperthermia?

A

Succinylcholine may accelerate onset and increase MH severity

42
Q

What is the compenents of differential diagnosis for malignant hyperthermia?

A

Tachycardia, hyperpyrexia, tachypnea, hypercapnia and masseter muscle rigidity can be found in other disease states

43
Q

Other than MH, what could lead to an elevated end tidal carbon dioxide? (3)

A
  • Malfunction in the one-way valves of the circle system
  • Problem with carbon dioxide absorbent
  • Retained CO2 with pneumoperitoneum and subcutaneous air
44
Q

What other (disease) states may mimic malignant hyperthermia?

A
  • Insufficient anesthetic depth
  • Hypoxia
  • Pheochromocytoma
  • Sepsis
  • Hyperthyroidism/Thyrotoxicosis
  • Neuroleptic malignant syndrome
45
Q

What would an end tidal waveform look like in a patient with malignant hyperthermia?

46
Q

What is the overall treatment of Malignant Hyperthermia Crisis?

A
  • Call for help / Alert operating room staff
  • Turn off triggering agents (inhalational anesthetics)
  • Hyperventilation with FIO2 1.0
  • Cool
  • Consider cognitive aid
47
Q

What is the medication treatment for malignant hyperthermia?

A

Dantrolene or Ryanodex

48
Q

What is the malignant hyperthermia phone number?

A

1-800-MH-HYPER (MHAUS)

49
Q

What is the hyperventilation components of malignant hyperthermia?

A
  • High gas flows
  • Adding charcoal filter to circuit to scrub residual agent
50
Q

What diseases have a strong clinical and/or genetic links to MH susceptibility found with?

A
  • Central Core disease
  • King Denborough syndrome
  • Multi-minicore disease
51
Q

Define Multi-minicore disease.

A

A rare, inherited condition which causes degeneration of the muscle fibers

52
Q

Define central core disease.

A

Genetic disease of the ryanodine receptor

53
Q

Define king denborough syndrome.

A

Rare genetic non-dystrophic myopathy characterized by the triad of congenital myopathy, dysmorphic features and susceptibility to malignant hyperthermia

54
Q

What diseases have no risk or link to MH?

A

There is NO risk for MH beyond the normal general population in patients with Duchenne or Becker muscular dystrophy, neuroleptic malignant syndrome, myotonia congenita or myotonic dystrophy

55
Q

What should be done first if MH is suspected?

A

Notify surgeon to halt surgery ASAP

56
Q

What needs to be done for your anesthetic in a MH crisis?

A
  • D/C inhalational agents (succinylcholine)
  • If surgery must continue - switch to TIVA
57
Q

Who needs to be called in a MH Crisis?

A

Call for help! (call 911 if at an ASC); call MHAUS

58
Q

What needs to be brought into the room in a MH Crisis?

59
Q

Why is hyperventilation of MH Crisis needed?

A
  • Hyperventilate (to rid agent and drive down PaCO2) at high flows (at least 10L/min)

•Remove vaporizers

  • flush machine
  • add charcoal filter (saturate at about 1 hour)
60
Q

What is the dose of the medication for MH Crisis?

A

Dantrolene 2.5 mg/kg rapidly via large bore IV until patient responds (lower HR, lower CO2, decreased rigidity (may require up to 10 mg/kg)

61
Q

What labs need to be monitored for MH Crisis?

A
  • Obtain ABG and treat metabolic acidosis (BE > 8)
  • Monitor serum electrolytes, blood glucose, coagulation profile, CK, blood and urine myoglobin and liver enzymes
62
Q

What is the dose of bicarbonate for the treatment of metabolic acidosis with MH Crisis ?

A

1-2 mEq/kg of bicarbonate

63
Q

What is the process of cooling a patient for MH Crisis?

A

Cool patient if temp > 39 C, stop when < 38.5 C – cooling lavage (orogastric, bladder, open cavities), chilled IV saline, cooling blanket, ice (groin axilla and neck)

64
Q

What electrolytes need to be treated with MH crisis?

A
  • Hyperventilation, bicarbonate, glucose/insulin
65
Q

What can be used to treat refractory hyperkalemia?

A

B-agonist such as albuterol, kayexalate, dialysis, ECMO

66
Q

What should be avoided for the treatment of dysrhythmias?

A

avoid Ca++ channel blockers – When given with dantrolene may cause life threatening myocardial depression and hyperkalemia

67
Q

What kidney interventions need to happen when treating MH?

A

Diurese to >1ml/kg/hr urine output with hydration, furosemide (0.5-1mg/kg and mannitol prn

68
Q

What needs to be followed as a result of MH crisis?

A

HR, core temperature, ETCO2, minute ventilation, blood gases, K+, CK, urine myoglobin and coagulation studies as warranted by the clinical severity of the patient

69
Q

What is the MOA of Dantrolene?

A
  • Muscle relaxant that doesn’t work at neuromuscular junction
  • Binds to ryanodine calcium channel and reduces calcium efflux from sarcoplasmic reticulum
70
Q

What are the two preparations of Dantrolene?

A
  • Dantrium/Revonto
  • Ryanodex
71
Q

What is the dose for Dantrium/Revonto?

A
  • 20mg vial to be reconstituted with 60mL of sterile water
  • 3 grams of mannitol in each 20mg vial
  • Dose is 2.5mg/kg for initial dose
72
Q

What is the solubility of Dantrium/Revonto?

A

Very poor water solubility

73
Q

What is the dose of Ryanodex?

A
  • 250mg vial to be reconstituted with 5mL of sterile water
  • 0.125 gram of mannitol in each 250mg vial
74
Q

Review the effect of dantrolene.

A
  • Effect of dose of dantrolene on MH symptoms
  • Time on x-axis
  • Minute ventilation and end tidal carbon dioxide on y-axes
  • After 6 hours of anesthesia time minute ventilation (blue line) and end tidal carbon dioxide increase
  • At 12 hours recognized as MH
  • Dantrolene administered at white arrow and symptoms resolve quickly
75
Q

What happens After Immediate Crisis?

A

Transfer to hospital

76
Q

If admitted to the ICU how long is the admission for MH last.

A

ICU admission for 36 hours minimum

77
Q

What are the monitoring that should be completed after the immediate crisis?

A
  • Continuous central temperature monitoring
  • Serial labs
78
Q

What needs to be monitored for peak levels?

A

CK peaks many after hours the event. Monitor for peak and declination

79
Q

How long should dantrolene be administered?

A
  1. Continue dantrolene for minimum 24 hours
  2. Dose: 1mg/kg every 4-6 hours as a bolus OR 0.25mg/kg/hr via continuous infusion
80
Q

What is the rate of reoccurrence of MH?

A

Recrudescent rate 25% in first 24 hours, mean 13 hours

81
Q

What can be administered for kidney protection?

A
  • Saline and NaHCO3
  • Myoglobin is toxic to kidneys
82
Q

What needs to be done after the MH crisis?

A
  • Patient and family counseling
  • ID bracelet/necklace
83
Q

What registry does patient needed to be added to after MH crisis?

A

North American Malignant Hyperthermia Registry

84
Q

What form needs to be completed following a MH crisis?

A

AMRA (Adverse Metabolic Reaction to Anesthesia) form

  • To be completed by anesthesia providers involved in case
  • Can be anonymous or with patient information with patient consent
85
Q

What do patients need to be referred to after a MH crisis?

A
  • Testing
  • Refer to MH testing center
86
Q

What is not the gold standard for MH testing?

A

Genetic testing is not the gold standard because we don’t yet understand all of the mutations that may make an individual susceptible to MH

87
Q

What is the gold standard for MH testing?

A

Caffeine Halothane Contracture Test

  • Skeletal muscle sample contractile response to caffeine, halothane or both
88
Q

What is the MOA of the Caffeine Halothane Contracture Test?

A

Invasive - Uses fresh vastus lateralis muscle biopsy and test must be completed within hours of muscle harvest

89
Q

What are properties of the Caffeine Halothane Contracture Test?

A
  • Requires travel to 1 of 4 designated centers in North America
  • Expensive
90
Q

Review components of the Caffeine Halothane Contracture Test.

91
Q

Identify the normal versus abnormal test.

A
  • X-axis = time
  • Y-axis = tension
  • Top graph – tension increases after exposure to caffeine or halothane
  • Bottom graph – muscle tension significantly increases with exposure.
  • Diagnosed with MH susceptibility
92
Q

Define sensitivity.

A
  • (measures how often a test correctly generates a positive result for people who have the condition that’s being tested for)
  • Very few false negatives
93
Q

Define specificity.

A
  • (measures a test’s ability to correctly generate a negative result for people who don’t have the condition that’s being tested for)
  • Significant number of false positives
94
Q

What is the sensitivity and specificity?

95
Q

What should be done for MH Susceptible Patients?

A
  • Standard monitors and consider a cooling blanket under the patient
  • Consider regional or local anesthetic if possible
  • Use of a non-triggering general anesthetic
96
Q

What should be done to the AGM for MH Susceptible Patients?

A

Remove trace anesthetic gases from AGM (review specific AGM instructions)

  • Change CO2 absorbant
  • Ensure vaporizers are disabled by removing or taping them off
  • Flush AGM and ventilator with oxygen at ≥10 L/min for 20-104 minutes
  • Use new breathing circuit and reservoir bag
  • Add charcoal filters to inspiratory and expiratory limbs
  • Have MH cart in OR
  • Monitor postoperatively for a minimum of 2 hours
97
Q

Where can you find information regarding the AGM for MH susceptible patients?

A

review specific AGM instructions

98
Q

How long should MH susceptible patients be monitored after uneventful anesthesia?

A
  • The patient susceptible to MH undergoing outpatient surgery may be discharged on the day of surgery if the anesthesia has been uneventful.
  • A minimum period of 1 hour in PACU monitoring vital signs at least every 15 minutes and an additional hour is phase II PACU/step down unit is recommended.
99
Q

Can calcium gluconate or calcium chloride be used when treating hyperkalemia cardiac toxicity during an MH crisis?

100
Q

Is MH linked to other serious medical problems? If so, which ones?

A
  • Central core disease
  • King Denborough syndrome
  • Multi-minicore disease
101
Q

If you were responsible for making the MH kit for your operating room, what supplies would you include?

A
  • Required Medications
    • Dantrolene 36 vials
      • Ryanodex?
    • Sterile water
    • Sodium bicarbonate
    • Dextrose
    • Mannitol
    • Furosemide
    • Antidysrhythmic drugs
  • Necessary Equipment
    • Temperature probes
    • Nasogastric tubes
    • Assorted catheters
    • Blood collection tubes
    • Syringes
    • Needles
    • Normal saline
102
Q

What is the hotline number to call during a MH crisis?

A

1-800-MH-HYPER

2-General Principles Exam 3 (11 decks)

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