MH-Awareness-MAC

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Author:
ariadne9
ID:
238896
Filename:
MH-Awareness-MAC
Updated:
2013-10-06 13:56:24
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BC CRNA CP1
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BC CRNA
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  1. Is MH more common in adults or adolescents?
    adolescents
  2. Is it ok to use succ in adolescents?
    NO!  There's a BBW for use of succ in kids (ages 0-18)
  3. In what pts are you most likely to see MH?
    Young men, avg age=15 yo, caucasian N. european decent
  4. T or F, if you've had GA before and had no issues with MH you are not at risk
    F, 1/3 of pts will manifest MH with subsequent GA administration.  2/3 manifest with first exposure to GA.
  5. Mortality rate of MH
    <5% due to use of dantrolene
  6. Genetic component to MH
    • AD
    • -defect in ryanodine receptor (RYR1)
  7. Patho of MH
    • -defect in RYR1 causes uncontrolled release of free Ca++ from the sarcoplasmic reticulum in muscle cells
    • -increase in Ca++ causes sustained muscle contraction (hyper metabolic state)
    • -excessive breakdown of ATP leads to skeletal muscle rigidity
    • -skeletal muscle membrane is disrupted causing hyperK, hyperCa, acidosis (excess CO2), CK, and myoglobin in ECF
  8. What effects does myoglobin in the ECF have?
    renal failure, DIC, myoglobinuria
  9. MH triggers
    • succ
    • volatile anesthetics
  10. Most sensitive and specific sign of MH
    Large and sudden increase in ETCO2 in absence of equipment failure
  11. Most common cause of death with MH
    Arrhythmias including VF
  12. Late signs of MH
    Fever, skeletal muscle swelling, cerebral edema, hepatic failure, heart failure
  13. Presenting s/sx of MH
    • -Increased ETCO2
    • -Masseter muscle rigidity (trismus)
    • -tachycardia
    • -2 or more of these signs greatly increases likelihood of MH
  14. Pre-op managment of MH (ABCD)
    • A- ask about MH history, aware of clinical signs of MH
    • B- body temp monitoring for GA
    • C- capnograph for GA
    • D- dantrolene available whenever MH trigger anesthetics are used
  15. Intra-op managment of MH (ABCDE)
    • A- ask for help, MH cart, and dantrolene
    • B- breathing- hyperventilate with 100% O2
    • C- cooling with IVF (irrigate wound and stomach with cold IVF), ice packs; call MH hotline
    • D- dantrolene
    • E- electrolytes (K, CO2, Ca)
  16. Dantrolene dose
    • -2-2.5 mg /kg q5 min until MH symptoms resolve
    • -then continue 1 mg /kg q6h x 24-48 h
  17. Secondary steps of MH intra-op managment
    • A- acidosis?  get ABG
    • B- bicarb, give at 1-2 meq/kg guided by pH
    • C- circulation (CL or A line), CBC, CK, coags
    • D- dysrhythmias, treat per ACLS, Diurese
    • E- electrolytes, treat hyperkalemia
    • F- follow-up
  18. Are CCB ok to use when treating MH with dantrolene?
    NO!!  They can interact to produce hyperkalemia and myocardial depression
  19. How does dantrolene work?
    • -direct acting skeletal muscle relaxant
    • -dissociates intracellular excitation-contraction coupling by binding to RYR1 Ca++ channel receptor
    • -this interferes with the release of Ca++ from the SR
  20. Why is dantrolene supplied with mannitol?
    To provide osmotic diuresis as well as excretion of K, Ca, urea, Cl, Mg
  21. Once reconstituted how long is dantrolene good for?
    6 hours
  22. T1/2 dantrolene
    6 hours
  23. Most serious adverse effect of dantrolene
    hepatotoxicity
  24. Awareness
    -explicit memories (specific events, noises, and sensations during GA)

    • -does NOT include implicit memories (subconscious changes in behavior or performance without the ability to recall specific events during GA)
    • -dreaming
  25. Types of surgeries with increased risk for awareness
    • -c section
    • -trauma / emergency
    • -cardiac

    in these cases preservation of HD may inhibit ability to provide GA
  26. types of pts at risk for awareness
    • -h/o substance abuse  
    • -difficult intubation
    • -chronic pain pt on increased opioid doses
    • -ASA 4-5
    • -h/o awareness
  27. Anesthetic techniques that may cause awareness
    • -TIVA
    • -N20 / opioid
    • -muscle relaxants
  28. minimal sedation
    • -normal response to verbal stim
    • -airway, CV, and spontaneous vent unaffected
  29. moderate sedation
    • -purposeful response to verbal or tactile stimulation
    • -no airway intervention required
    • -CV usually maintained
    • -adequate spontaneous vent
  30. deep sedation
    • -purposeful response following repeated or painful stimulation
    • -airway may require intervention
    • -spontaneous ventilation may be inadequate
    • -CV usually maintained
  31. GA
    • -unarousable even to painful stimuli
    • -airway often requires intervention
    • -spontaneous vent frequently inadequate
    • -CV function may be impaired

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