Malignant Hyperthermia Flashcards
MH is
a life-threatening clinical hypermetabolic syndrome involving skeletal muscle
MH is triggered by
- volatile IA
- succinylcholine
- stressors such as vigorous exercise and heat
T/F MH is an allergy
False!
it is an inherited disorder
__ genetic defects are associated with MH
(PPT)
80
on average a patient requires how many anesthetics before a triggering event occurs?
3
but this crisis may delevlop at first exposure to anesthesia
MH complicates 1 in how many surgical procedures in adults? and 1 in how many surgeries of children?
100,000
30,000
(pg. 841)
children under what age approximate 52% of all reactions
15 years of age
MH is more sustible in males or females?
males
3 co-existing disease are defineitly associated with MH
- King-Denborough syndrome
- central core disease
- Multiminicore disease
factors that increase risk
- geography: Wisconsin, Nebraska, West Virginia, Michigan
- male sex
- youth (peds accounts for 52% of cases)
what is the most common myopathy that triggers MH
Evans myopthay
What other genes are linked with MH suceptibility ?
CACNA1S
STAC3
all myopathies have what gene dysfunction?
RYR1
MH-associated genetic variants are found within what gene?
RYR1
RYR1
encodes the ryanodine receptor, the major calcium release channel of the SR
STAC3
gene variants are manifested most as native american myopathy in the Lumbee Native American tribe of North Cariolina
CACNA1S
encodes a subunit of a dihydropyridine calcium channel located in the skeletal muscle T tubule
the elevated IC calcium results in
muscle contraction and abnormal muscle metabolism
energy-dependent reuptake mechanisms attempt to remove excess calcium from the myoplasm, increasing muscle metabolism how many folds?
2-3
this accelerated cellular process does what?
- increase oxygen consumption
- increase CO2
- increases heat production
- depletes ATP
- generates LA
what lab values markedly increase in the EC?
- potassium
- myoglobin
- CK
what 3 things cause saroplama destruction?
- acidosis
- hyperthermia
- ATP depletion
Patients with DMD have an absence of __ which stabilizes the sarcolemma during muscle contraction & increases membrane permeability
dystrophin
what happens at the cellular level with DMD
- EC calcium is free to enter the cell, increases metabolism
- IC K is free to exit the cell, can lead to hyperkalemic cardiac arrest
- myoglobin is free to the cell, which can cause RF
- halogenated agents/succ can initiate MH-like syndrome – avoid and use TIVA
this MH-like syndrom is associated with DMD d/t
rhabomyolysis
give TIVA for these conditions (5) because they hold calcium in their msucles
- becker MD (progressive muscle weakness)
- neuoleptic malignant syndrome (neuro emergency associated with use of antipsychotic agent causing mental staus change, rigidity and fever)
- myotonia congenita (delayed relexation of the muscles after contraction- rigidity)
- myotonic dystrophy (in ability to relax muscles at will)
- osteogensis impeerfecta (fragile bones that break easily)
pathophysiology of MH causes
- respiratory acidosis
- metabolic acidosis
- rigidity
- altered cell permeability
- hyperkalemia
MH risk may increase up to how many times higher when succ is used along with VIA?
20 times higher
MH symptoms may occur when?
- immediatley after induction
- several hours into surgery
- even after surgery is completed
- recovery room or ICU within 1 hour after GA
what is the most relaible sign that MH is occuring?
ETCO rise rapidly > 55
what is the other common sign with MH?
tachycardia
what are other common signs of MH?
- tachypnea
- skin mottling
- total body or jaw muscle rigisity
how often does hyperthermia climb?
1 to 2 degrees celcius every 5 mins till averaging out at 39.3
hyperthermia can occur?
early or late
myoglobin appears in the __ and puts the patient at risk for __ __ & __ __
urine
tubular obstruction & renal failure
even with treatment, individuals are at risk for complications including:
- cerebral edema
- consumptive coagulopathy
- myoglobinuric renal failure
- compartment syndrome
- hepatic dysfunction
- pulmonary edema
what can also share several of the same characteristics with MH that makes it difficult to diagnose?
- insufficient anesthetic depth
- hypoxia
- neuroleptic malignantnt syndrome
- thyrotoxicosis
- pheochromocytoma
- sepsis
every surgical patient should be asked the following:
- FH of unexpected intraop complications or deaths?
- family or personal hx of MH, muscle rigidity/stiffness, and or high fever under anesthesia?
- personal hx of dark/cola-colored urine after surgery or exercise?
- personal or family hx of high temps or death during exercise?
lab findings consistent with MH
- ABG: MA/RA
- Potassium > 6 mEq/L
- CK > 20,000 units/L
- serum myoglobin > 170 mcg/L
- urine myoglobin > 60 mcg/L
Clinical events during MH
- rapid unexplainable rise in ETCO2 > 55
- unexplained tachy
- masseter muscle or generalized muscle rigidity
- rising patient temp
- cola-colored urine
- mottled cyanotic skin
- decreased SaO2
- Tachypnea
- labile BP
- arrhythmias
dantrolene works how
not at the NMJ, works by binding to the ryanodine calcium channel and reducing calcium efflux from the SR, counteracting the abnormal IC calcium levels
Dantrolene can have what side effects?
- significant muscle weakness
- respiratory insufficiency
what would happen if you gave CCB to a patient with MH?
- myocardial depression
- hyperkalemia
once MH is identified it is important to
- disconnect triggering agents
- administer dantrolene
- hyperventilate with 100% FiO2
- cool the patient
- treat symptoms
Treatment sequence for MH
- call for help
- d/c VIA
- 2.5mg/kg dantrolene IV and repeat Q 5-10 mins until symptoms stop
- hyperventilate with 100% oxygen
- apply activated charcoal filters to each limb
- initiate cooling lavage (OG, bladder, open cavities)
- treat arrhythmias NOT w/ CCB
- check ABG, consider bicarb
- treat hyperkalemia: CaCl 10mg/kg, Ca gluconate 30mg/kg, bicarb 1-2mEq/kg, glucose/insulin
- maintain urine output
administer dantrolene through the __ vein possible
largest
can be very irritating to the vessels
replace charcoal filters how often?
every hour
original preparation of dantrolene is?
20mg reconstituted with 60 mL of sterile water
how many grams of mannitol are in each dantrolene vial?
3g
ryanodex preparation is?
250mg vial reconstituted with 5 mL of sterile water
how much mannitol in ryanodex?
.125 g
for MHS patients what else should you set up for the procedure along with standard monitoring equipment?
cooling water mattress
a link between statin-induced muscle toxicity and susceptibility to
MH
what do you do to AWS to prep for a MHS patient?
- remove trace anesthesia gas from the machine
- flush the anesthesia machine and vent with O2 set at 10L/min (20 mins at least) or more by attaching a new breathing circuit y-piece and reservoir bag
- apply charcoal filters
- dantrolene kit
- ice and at least 3L of cold IV solution
a full complement of dantrium is how vials?
36
what test is available for determining if someone has MH?
caffeine halothane contracture test (CHCT)
gold standard
a full complement of ryanodex is how vials
3
what does the test involve?
taking a biopsy of skeletal muscle and measuring its contractile response to caffeine, halothane, or both
where is this test avilable?
5 centers in North America
MHAUS recommends the CHCT test for the following patients
- MHS family member
- past suspected MH even
- severe masseter muscle rigidity during A
- pt with mild to moderate MMR with evidence of rhabdomyolysis
- unexplained rhabdomyolysis during or after surgery
- the patient with exercised-induced rhabdomyolysis after a neg rhabdomyolysis workup
- signs suggestive of MH but not definitive
IV dantrolene should be continued at least
24 hours
what is the dose of dantrolene post surgery
1mg/kg Q 4-6 hours
or
0.25/mg/kg/hour continuous infusion (.1-.3mg/kg/hr for 48-72 hours)
dantrolene can be stopped or the interval between doses increased if the following criteria are met:
- metabolic stability for 24 hours
- core temp is less that 38
- CK is decreasing
- no evidence of myoglobinuria
- muscular rigidity resolved
recrudescence of an MH episode may occur in up to __ % of cases with a mean time
25%
13 hours
MMR presages MH in how many % of cases?
20-30%
T/F a mild increase in masseter muscle tone or incomplete jaw relaxation after succ is fairly common
true
T/F is there a MH hotline?
true
available 24 hours a day
early S/S of MH
hypercarbia
tachycardia
masseter spasm/muscle rigidity
tachypnea
cyanosis
late S/S of MH
overt hyperthermia
irregular arrhythmias
cola-colored urine
coagulopathy
hyperkalemia
Trismus
describes a tight jaw that can still be opened –> can happen with succ (normal response)
whats the usual cause of death when temp exceeds 41 degrees celsius?
DIC
definition of rhabdomyolysis
breakdown of skeletal muscle
how many deaths are reported via the hotline each year?
1 to 2
mortality of MH currently?
less than 5%
used to be greater than 70% before the approval of dantrolene in the 1970’s
following conditions should be considered in your differential diagnosis for MH:
(PPT)
- thyroid storm
- MNS
- sepsis
- pheochromocytoma
- serotonin syndrome
- Heatstroke
- metastatic carcinoid
- cocaine intoxication
What do I do?
(PPT)
- d/c trigger
- TIVA
- call for help
- tell the surgeon finsih ASAP
- remove patient off circuit and hyperventilate with 100% fiO2 (min FGF 10L/min) — facilitates CO2 elimination, enhances O2 delivery, drives K into cells
- apply charcoal filters, change circuit, change bag (may place pt back on vent after 2 mins when the above is completed)
- administer dantrolene
dantrolene has two mechanisms of action
- it reduces Ca release from the RYR1 receptor in the skeletal myocyte
- it prevents Ca entry into the myocyte, which reduces the stimulus for Ca induced Ca release
max dose of Na Bicarb?
50mEq
glucose/insulin for adults
10 units of regular insulin IV and 50 mL 50% glucose
glucose/insulin for pediatric patients?
0.1 unit regular insulin/kg IV and 0.5 grams/kg dextrose
not so common sense steps for an MH event
- start new IVs
- arterial line for frequent ABGs
- turn off remove Bair Hugger
- turn off remove fluid warmer
- need foley
- need a team dedicated to mixing dantrolene
- dont delay placing pt back on vent
- assign help to change out soda lime canisters
- OGT insertion cool lavage
- central temp monitoring
- call MHAUS early for help/guidance
- stay calm, you have been trained and you know what to do :)
how long does the A gas machine need to be flushed with HFGF before placing activated charcoal filters on both inspiratory and expiratory ports?
90 seconds
