MH - Exam 4 Flashcards
Common triggers for MH
-POTENT inhalation anesthetics (sevo, des, iso, halo, enflurane, ether)
-sux
-stressors like heat or vigorous exercise
-notice N2O is not in this list
Children under _ yo make up 52% of all MH cases and _ are 2.5-2.5 x the rate of _.
15yo
male
female
-young BOYS; ALL ethnic groups
MH has been associated with _ genetic mutations, most of which involve the _ gene.
34
RYR1
MH is an _ disorder of the _ muscle involving a defect in the _ regulation, causing a rise of it in exposure to potent IA and sux.
inherited
skeletal
calcium
Aside from RYR1, 2 other genes involving muscle excitation-contraction and calcium ion inflow with mutations linked to MH are _ and _
CACNA1S
STAC3
RYR1 gene encodes the _ receptor which is the major calcium channel of the _ _
ryanodine
sarcoplasmic reticulum
CACNA1S encodes a subunit of a _ calcium channel found in the skeletal muscle _ _
dihydropyridine
T tubules
STAC3 gene variants are manifested as Native American _ in the _ Native American tribe of NC
myopathy
Lumbee
Most cases of MH result from gene mutation of _
RYR1
Patho of MH:
1. Triggers will induce increased calcium release from myocyte _ _.
2. Excess calcium causes muscle _ and abnormal metabolism
3. Energy-dependent _ mechs try to remove calcium but increase muscle metabolism 2-3x
4. Accelerated process increases _ consumption, depletes _, and increases CO2, _, and lactic acid production
5.Acidosis, hyperthermia, and ATP depletion cause _ destruction.
6. When this is destroyed, potassium, myoglobin, and _ levels will rise in the serum
- sarcoplasmic reticulum
- contraction
- reuptake
- O2, ATP, heat
- sarcolemma
- CK
Skeletal muscle makes up -% of the body mass, so small changes make a large difference.
40-50%
Which labs will you expect with MH?
-MIXED resp and metabolic acidosis
-hyperkalemia >6mEq/L
-CK >20,000 units/L
-serum myoglobin>170mcg/L
-urine myoglobin >60mcg/L
T/F Triggers for MH include all inhalation agents as well as succinylcholine
false
-not N2O!
Which 2 agents can cause MH to have a delayed onset up to 6hrs after?
Des and Sevo
Using succinylcholine can increase MH risk up to _ x with the use of volatile anesthetics.
20
T/F Succinylcholine admin with volatile anesthetics can increase risk by 20x, speed the onset, and increase the severity of MH.
True
Clinical s/s of MH:
-unexplained, sudden tachycardia and rise in EtCO2 (>55mmHg)-most reliable early sign
- VS: SpO2 drops, high RR, arrhythmias, low BP, high temp
-masseter muscle or generalized muscle rigidity
-brown/cola urine (myoglobinuria)
-MOTTLED or CYANOTIC skin
The hyperthermia seen with MH can increase the temp by -C every 5 mins and averages _C (102.7*F)
1-2C/5 min
39.3C (102.7*F)
Hyperthermia in MH can occur early or late and is the _ sign of MH.
confirming
Myoglobin in the urine puts pt at risk for _ obstruction and renal failure
tubular
Even if treated promptly, MH can cause complications such as:
-cerebral edema
-consumptive coagulopathy
-myoglobinuric renal failure
-compartment syndrome
-hepatic dysfunction
-pulmonary edema
Many conditions and clinical pictures look like MH, making it hard to dx. These include:
-hypoxia
-poor depth of anesthesia
-Neuroleptic malignant syndrome
-Pheochromocytoma
-sepsis
-Serotonin syndrome
-thyroid storm
-pneumothorax
-low MV and excess dead space
-blood transfusion reaction/ drug reaction
-TMJ
-gender-affirming surgery story Dr.Shannon had (if they take very high doses of testosterone!)
There is a lot, just be able to rattle off a couple, know that MH is hard to definitively dx
T/F Everyone who is MH Susceptible (MHS) will experience MH upon exposure to triggering agents.
False
not every time, could have triggering agents several times before having MH
T/F Everyone who has the MH gene mutation will experience MH upon exposure to triggering agents.
False,
not every time, may have agents a few times before a reaction occurs
People who are MH susceptible are phenotypically _ and usually healthy
normal
-they may be unaware they’re at risk until they are exposed :(
In the collection of pt history regarding MH, ask these other questions:
-any fam hx of unexpected intraop complications/death
-fam or personal hx of MH, muscle rigidity/stiffness, and/or high fever under anesthesia
-personal hx of cola-colored urine after exercise or surgery before
-personal or fam hx of high temp or death during exercise
T/F If a pt is MH susceptible they have a family history of MH
False, not always the case
-if they have a fam hx of MH, EVERYONE in the fam is considered MHS, but there are other causes for someone to be MHS
DIC is seen in MH after temperature exceeds
41 degrees c
What are Dantrolene’s MOA?
It reduces Ca+ release from the RyR1 receptor in the skeletal myocyte
It prevents Ca+ entry into the myocyte, which reduces the stimulus for calcium-induced calcium release
T/F: Dantrolene can be reconstituted with both sterile water or normal saline
False - only sterile water. normal saline does not dissolve the powder
What kind of medication is Dantrolene?
Muscle relaxant
How is Dantrolene dosed?
2.5mg/kg IV and repeat q5-10 minutes, up to 10mg/kg
What is the target cooling temp for MH?
38 degrees C
What is the gold standard for MH testing?
Caffeine Halothane Contracture Test.
Entails a muscle biopsy. Test must be run within 6 hours of specimen collection.
Rare diseases that have a clinical or genetic link to MH (pt is MHS)
-Evans Myopathy (most common myopathy)
-Central Core Disease
-King-Demborough Syndrome
-Multiminicore Disease
-Centronuclear Myopathy
-Congenital myopathy with cores and rods
-Periodic Paralysis
-Nemaline Rod Myopathy
-Idiopathic hyperCKemia
-Native American Myopathy
-Congenital Fiber Type Disproportion
-NOT DMD, Myotonic Dystrophy, or Becker muscular dystrophy
States where MH is more common:
MI (shit)
WV
NE
Is MH an allergy?
no
Why would a pt with DMD show signs mirroring MH if they do not have the same gene mutation?
they lack dystrophin (which stabilizes sarcolemma)
-causes excess calcium and similar reaction
-not TRUE MH
T/F If my DMD pt starts experiencing what looks like MH, even though I know it isn’t MH, Dantrolene will still help due to the similar patho mechanism
false
similar patho but without RYR1 mutation but dantrolene will not help bc it targets that receptor specifically
-DMD pts have a NORMAL RYR1 gene
Upon doing an insanely thorough chart review, you find out your otherwise healthy pt has a history of unexplained elevated CK levels and during preop when talking about the weather she mentions not tolerating heat well. What is your concern?
She has a myopathy/ is MH sus
You’re sitting in the preop area outside of your pt’s room waiting for them to finish up in the bathroom. You overhear their family talking about exercise, and when referring to the patient, they say: “That’s why she doesn’t go for runs; she overheats and says her pee is brown for days after. Even last summer she could only tolerate a few minutes working in the garden before she had heat stroke.”
What is your concern and how could you adjust your anesthesia plan last minute to optimize safety for this patient?
Concern for MHS
-give trigger-free anesthesia with regional or TIVA
-cooling water mattress under pt prior to surgery
-change CO2 absorbers
-remove or disable vaporizers
-flush AGM with high flow O2 for however long the machine’s MH information indicates to
-ensure sources of ice and an MH kit are stocked and nearby
-charcoal filters on both ends of circuit, then flush for 90s on >10L FGF
-see if you can quickly switch to a dedicated vapor free AGM or ICU vent
-inform those who you would call on for help if need be
The only drug known to treat MH is
Dantrolene
-may also work for neuroleptic malignant syndrome
T/F Dantrolene binds at the NMJ and stops the outflow of calcium from the sarcoplasmic reticulum.
FALSE
-does NOT work at the NMJ, but goes father and binds to the RYANODINE CALCIUM CHANNEL that then stops the outflow from the sarcoplasmic reticulum
T/F In addition to giving Dantrolene, starting a diltiazem gtt on a pt experiencing MH will help safely lower their BP and help alleviate tachycardia as well.
FALSE
-it will lower these things and possibly kill your pt from hyperkalemia and severe myocardial depression
-Diltiazem (Cardizem) is a CALCIUM CHANNEL BLOCKER :(
-don’t give CCBs to MH pts!
Gold standard core temp measurement methods include:
-PA
-distal esophageal
-nasopharyngeal
-bladder (I thought this was NOT considered core temp from Miller’s thermoreg chapter bc urine flow varies but whatev, Nagelhout)
-tympanic membrane
-risk of dying from MH was 13.8x more likely with only skin temp monitoring per some study
What should be hung in every OR capable of giving volatile anesthetics and sux?
an MHAUS “Emergency Therapy for MH” poster
Simplified steps for MH reaction:
-Call for help, tell surgeon to stop asap
-DC volatile anesthetics, if surgeon must continue, use TIVA
-Prep and give Dantrolene boluses and repeat until symptoms are gone
-hyperventilate with 100%O2 and high FGF
-put charcoal filters on from MH kit
-cooling lavage, cold IV fluids, or ice packs
-treat dysrhythmias
-start an A line, check ABG, lytes, and BG
-large amount of fluids
Dantrolene dose:
Bolus: 2.5mg/kg (ACTUAL BODY WT) repeat Q 5-10 until symptoms resolve (HR lower, EtCO2 lower, less rigidity)
-can give typically 10mg/kg or more, but if more is used, think about possible other diagnoses
Dantrolene is an _ solution and irritates vessels easily so it should be given thru a large IV!
alkaline
-get several IVs TBH, you’ll need them
When should you replace activated charcoal filters on the circuit limb with MH?
Q 1 hr
-even if volatile anesthetics were stopped
T/F Stop cooling measures for MH once skin temp reaches <38*C
false!
-CORE TEMP
During MH give Bicarb for a pH<_ and a serum bicarb of <- mEq/L.
pH< 7.2
Serum Bicarb <10-12mEq/L
T/F It is important to never give calcium-containing drugs when a pt is experiencing MH!
False
-avoid calcium channel blockers but give calcium chloride or calcium gluconate for hyperkalemia to stabilize the myocardial membrane!!!!
Hyperkalemia treatment for MH
-Calcium Chloride or Calcium Gluconate doses
Calcium Chloride: 10mg/kg (MAX=2000mg)
Calcium Gluconate: 30mg/kg (MAX= 3000mg)
Hyperkalemia treatment for MH
-bicarb dose
1-2mEq/kg (MAX= 50mEq)
Hyperkalemia treatment for MH
-glucose and insulin (peds and adult doses)
Peds:
-Regular insulin: 0.1 unit/kg
-Dextrose: 0.5mg/kg
Adults:
-Regular insulin: 10units
-Dextrose: 50mL (50% Dextrose amp)
Hyperkalemia treatment for MH
-refractory hyper K options
-albuterol (or another beta receptor agonist)
-kayexalate
-dialysis
-ECMO (if pt is in cardiac arrest)
UO goal for MH is _mL/kg/hr.
1mL/kg/hr
-give lots of fluids!
MHAUS recommends that dantrolene be available to give within _ mins of the decision to treat with it
10
3 preparations of dantrolene are called:
-Dantrium
-Revonto
-Ryanodex
Dantrium and Revonto are packaged as _ mg vials and must be reconstituted with _ mL of sterile water. They each contain _g of mannitol in each vial as well.
20mg vials
60mL sterile water
3g mannitol
Which formulations of dantrolene must be shaken vigorously until the solution is clear prior to admin and which are supposed to be opaque and orange?
Dantrium and Revonto=clear
Ryanodex=orange and opaque
Ryanodex comes as _mg vials, must be reconstituted with _mL of sterile water. It only contains _mg of mannitol, so a supp might be needed.
250mg vials
5mL sterile water
0.125mg mannitol
What is needed in the documentation of a MH event?
-pt responses
-staff involved
-meds given
-other interventions
-pt outcomes
T/F LA, especially esters can trigger MH
False, neither can, LA is safe
Which medications are safe for MHS patients?
Anything that isn’t a volatile anesthetic or sux
-no CCB if there’s a reaction already happening
Possible link between _-induced myopathy and MHS
statin
Things that should be changed on the AGM if the pt is having MH:
-circuit, including bag
-CO2 absorber
-remove vaporizer
-20+min(AGM dependent) of O2 flush to remove volatile anesthetic from silicone parts of AGM
-charcoal filters Q 1hr
Before charcoal filters are placed, flush AGM on high FGF (>_L/min) for _ s
> 10L/min
90s
Charcoal filters keep anesthetic agent concentration < _ppm for up to _hrs with FGF of at least _L/min and eliminate need to purge system.
<5ppm
12hrs
at least 3L/min
A full complement of dantrolene includes _ vials of Dantrium or Revonto or _ vials of Ryanodex
36 vials
3 vials
At least _mL of cold IV fluid must be available for MH pts
3000mL
MHS pts with uneventful cases should have assiduous monitoring in PACU for _hr.
1
A same-day discharge MHS pt can be discharged from the hospital if their case was uneventful after:
-1hr PACU monitoring Q 15mins
-1hr in phase 2 PACU/stepdown
-can use myoglobin urine test to make sure they’re good too
Pts who have survived an unequivocal episode of MH are considered _
MHS
Muscle biopsies for CHCT can have _ or _ anesthetic for the procedure
regional or local
People who should have CHCT done per MHAUS:
-pt with MHS family member
-pt with past MH event (wait 6mo postop depending on degree of rhabdo)
-pt with severe masseter muscle rigidity (MMR) during anesthesia with triggering agent
-pt with moderate to mild MMR with evidence of rhabdo
-pt with unexplained rhabdo during or after surgery
-pt with exercise-induced rhabdo after a negative rhabdo workup
-signs of, but not definitive for MH
Alternatives to CHCT for confirmation of MH:
-genetic testing
-DNA-based mutation analysis
Most gene tests focus on mutations encoding for which receptors for MH?
-ryanodine receptor (RYR1)-most common
-dihydropyridine receptor
-associated proteins
After an acute MH episode, pts should be sent to ICU and monitored for complications such as:
-recrudescence
-DIC
-pulm edema
-compartment syndrome (from rhabdo)
-myoglobinuric renal failure
Dantrolene
-infusion
after episode, continue IV Dantrolene
1mg/kg Q 4-6hr for 24hr
or
0.25mg/kg/hr continuously for 24hr
OK to stop or decrease intervals of dantrolene if ALL of the following criteria are met:
-metabolic stability for 24hr
-core temp<38*C
-CK decreasing
-no evidence of myoglobinuria
-muscular rigidity resolved
Recrudescence of MH can occur in _% of cases with an average time from initial reaction to recrudescence in _ hrs
25%
13hr
MMR or _ is sustained and forceful contracture of the _ muscle.
trismus
masseter
Your pt develops some masseter muscle tension after giving sux, but you can still open their jaw. You choose not to open the MH kit. Why?
-mild rigidity is normal with sux and you can open their jaw still so it’s probably not MH
MMR progresses to MH in -% of cases
20-30%
-not often but not ignorable
Your pt develops MMR and you also notice peripheral muscle rigidity. What is your next step?
DC triggering agent and assume it is MH and immediately begin treatment
-also if pt has MMR and their jaw can’t open
MH hotline is ___-___-____ and is open _hr a day.
1-800-MH-HYPER
1-800-644-9737
-maybe put this in your phone? God forbid you ever need it, but MI is a common MH state, and this way, you won’t have to look for the number in the MH kit or on the poster. You can call them on speakerphone, and they’ll walk you through everything
