MH Flashcards
Signs of MH
most specific sign of impending MH
increased ETCO2 (hot/blue absorbent)
esp: acute increase
less specific:
tachy<3
HTN
tachyRR
increase Mv
expected lab findings
resp & metab. acidosis
(lactic acidosis)
increase a-v pCO2 gradient
Hyper K
Hyper CK
↑ serum & urine myoglobin
abnormal coags
how to adjust vent settings when MH is expected
1.0 FiO2 (100%)
High gas flows
dysrhythmias are d/t ____ so we must treat them with ….
acidosis & hyperK
bicarb (NaHCO3)
When cooling the pt, we should cease measures once pt reaches ____ C
37.5-38
pt will continue to cool once active measures are ceased
which drug class should be avoided when treating MH? why?
Ca channel blockers
adversely interact w/ dantrolene
hyperK mgmt
Post acute phase mgmt
sedation
monitor core temp
maintain U/O (IVF, diuretics)
ICU
serial CK labs x 24H
Dantrolene 1mg/kg Q6H x 24-48H (25% reoccurrence)
kidney protection: saline & bicarb
MH reoccurs in ___% of pts in the first 24H following the incident
25
whats why we give Dantrolene 1mg/kg Q6H x 24-48H
Differential diagnosis
muscle Dzs
neuroleptic malig. synd
myotonic synd
cereb ischemia
ascending tonic-clonic synd
rhabdo (statins, hypoperfusn)
exertional heat illness
Autosomal dominant means…
only requires 1 abnormal gene to manifest symptoms
variable penetrance
does not trigger with every exposure
Ryanodine receptor
embedded in SR wall
Ca release channel
Gene for encoding RYR1 protein location
chromosome 19
dihydropyridine receptor
mutations in the corresponding gene can lead to MH
T/F
Genetic testing is the gold standard for diagnosing MH
False
multiple proteins are likely involved in Ca release that have not yet been discovered
Caffeine-Halothane Contracture Test (CHCT)
not widely available
CHCT statistics
low specificity: many false +
high sensitivity: low false -
T/F
N2O can trigger MH
False
the volatiles do
(non/depolarizing) agents trigger MH
depolarizing (suxx)
Mgmt of pt with MH history
shut off VAs for 15 mins
T/F
Pretreat MH history pt with dantrolene.
False
avoid triggering agents, but do not pretreat
Flushing machine of VA’s
may take over 60 min
charcoal filter
contact manufacturer
- Remove the vaporizers
- Replace CO2 absorbent canisters
- Replace the bellows and fresh gas hose
- Flush machine for 20 min. with O2 @ 10 L/min.
T/F
In susceptible/suspected MH pts, a CHCT test is not needed if we do not use triggering agents.
True
Pretreating with Dantrolene
not recommended
can worsen muscle weakness if muscle Dz
MH patients:
Postop monitoring
uneventful Sx: d/c same day
1H+ PACU; VS Q15min
1H phase 2 PACU/step down
T/F
Dantrolene is necessary for pts susceptible to MH
False
use non-triggering agent
recc core T monitoring
T/F
Ca Cl/gluconate can be used to treat the hyperK in MH crisis.
True
Diseases linked to MH
Central Core Dz
King Denborough Synd
T/F
Neuromalignant Syndrome makes pts susceptible to MH.
False
not at increased risk for MH susceptibility
similar presentation (fever, muscle rigidity)
MH kit contents
Occurrence rate
MH may be more common in which gender?
males
T/F
MH monitoring is important for PACU as well
True
may occur minutes after induction
or
several hours after triggering agent
Steps of contraction and MH
- Nerve signals muscle to contract
- Na into muscle cell
- induces electric current
- current: down T tubule thru DiHydroP & ryanodine receptor –> SR
- SR release Ca thru channel in ryanodine rcptr –> cell interior
- contractile proteins overlap to contract & signals mito to make more ATP
- after contraction, Ca uptaken back into SR
- relaxation
MH: abnormally high Ca release; actinomysin contracture
cascde of abnormal events in MH
abnormally high Ca release:
1. actin-myosin contracture
2. heat
3. O2 consumed
4. CO2 (from mito making energy)
5. lactic acid (runs out of O2)
6. cell brkdn & release contents (out of energy)
the release of contents causes downstream effects of MH
T/F
elevated T is a late sign of MH
true
T/F
Before treating a pt with history of MH, its wise to change the CO2 absorber.
True
Preparing Dantrolene
20 mg into 60 ml STERILE WATER
goal: 2.5 mg/kg
MH is a ____ disorder
myopathic
Triggers outside of the OR
○ heat exhaustion
○ Caffeine
○ strenuous exercise
○ other medical conditions
One parent with the trait means the child will have a __% chance of having the
trait as well.
50
(25 – 50%) of cases, MH occurs as a result of a mutation of …
the ryanodine receptor, type
1 (RYR1)
mutant ryanodine receptor is a ___ disorder
heterogenic
mutations in the ryanodine receptor (RYR) cause…
aberrant/abnormal calcium channel in the sarcoplasmic reticulum
RYR1
● encodes protein for calcium movement into muscle cell, (regulates muscle contraction & metabolism)
● defective RYR1= reduced reuptake of Ca++
increased Ca
↓
sustained muscle contraction
↓
hypermetabolic state
● To reverse the process, the SR must re-uptake the excess calcium.
thought to be induced by heat stress in children
“Awake-Triggered MH”
“Awake-Triggered MH”
similar to “Broken Heart Syndrome” (or “Takotsubo Syndrome” aka a
stressed-induced cardiomyopathy)
currently estimated that 1 in ___ have a defective ryanodine receptor.
1:500
higher incidence noted in ___
children
undiagnosed muscle disorders (i.e. Core Central Disease (CCD))
and first time exposure.
Approximately __ cases of anesthetic-induced MH occur in the United States each
year.
800
Introduction of treatment with dantrolene has caused the mortality rate to fall from __% in
the 1970s to less than __% today.
80
10
MH can occur by these 2 ways
excess calcium release
decreased calcium uptake
body temperature rises as
much as
1°C every 5 minutes
Why does Ca build up in MH?
the abnormal receptor does not close properly after having opened in response to a
stimulus
What generates the heat?
sustained, uncoordinated muscle contractions
What is happening to the brain and organs?
patient’s brain is frying like an egg – the proteins are denaturing
internal organs are destroyed in an acid bath
What happens as the muscle tissue breaks down?
(occurs d/t ATP depletion)
cells “leak” potassium, myoglobin,
creatine and creatine kinase
How did farmers find out if their pigs were MH-susceptible?
expose piglets to halothane
Those that die are MH-susceptible
Why is the pig model useful in MH research?
“awake trigger” in
stressful situations occurs in piglets
awake trigger is thought to be induced by heat stress in children
Early vs late signs
Dantrolene dosing
dantrolene sodium 2.5 mg/kg IV
every five minutes (up to 10 mg/kg)
use central vein
Diuresis
UO goal: >2 ml/kg/hr
mannitol 25 mg IV
furosimide 20 mg IV
IV fluids
○ mannitol 0.5 g/kg to force diuresis
○ Lasix will help bring down K+ levels.
Potassium management
insulin drip: 10 units/hr
100 ml of 50% glucose to (prevent hypoglycemia)
Albuterol
4 puffs MDI via ETT
arrhythmia mgmt
(10-30 mg/kg of calcium chloride)
antagonizes the cardiac effects of hyperkalemia
can also use procainamide
most common cause of death
VFIB
T/F
You must have confirmed diagnosis of MH to give Dantrolene
False
must be instituted rapidly on clinical suspicion of the onset of malignant
hyperthermia
Dantrolene MoA
muscle relaxant that works directly on the ryanodine receptor to prevent the
release of calcium from SR
Dantrolene HL
6 H
redosing is important!
only sure way to prevent MH
avoid the use of triggering agents
Azumolene
water-soluble analogue
less irritating
smaller volume for dilution
short shelf half life of only six months and more expensive
Dantrium/Revonto vs Ryanodex
Dantrium:
-36 vials on hand
-dilute w 60 ml sterile water
-3 g of mannitol in each vial of 20 mg of dantrolene
(0.15 g mannitol/ 1 mg dantrolene).
RYANODEX:
-3 vials on hand
-dilute w 5 ml sterile water
-0.125 grams of mannitol in each vial of 250 mg of Ryanodex
(0.0005 grams mannitol/1 mg dantrolene)
both: do not use bacteriostatic agent
During an MH code, the anesthesia provider will
run the code
How many people to prepare the Dantrium?
2 teams of 2 ppl
Patient history should include:
history of MH
adverse response to anesthesia
muscle disorders
strabismus
myalgia during exercise
caffeine intolerance
Prevention
Explore a persistent, elevated ___
creatinine kinase (an enzyme of skeletal muscle and the myocardium, which helps produce ATP)
Your patient is suspected to have MH by history. His CHCT biopsy was negative. How do you proceed with his anesthesia plan?
use non-triggering anesthetics (TIVA or regional)
Negative biopsies are not definitive
Sensitivity
probability that a symptom is present (or screening test is positive)
given that the person has the disease.
“True Positive Test”
Specificity
probability that a symptom is not present (or screening test is negative)
given that the person does not have the disease .
“True Negative Test”
its recommended to perform this test in addition to the CHCT to
make the test more specific
“Calcium Induced Calcium Releasing” (CIRC)
Any pt with suspected/confirmed MH should be the ___ case of the day
first
Notify ___ of any MH occurrence
MHAUS.org
(Malignant Hyperthermia Association of the United States )
T/F
A pt with history of MH must undergo anesthesia in an inpatient setting.
False
If the patient has a history of MH, but does not trigger, he or she is required to
stay in the PACU for observation before going home.
