2. Malignant Hyperthermia Flashcards
MH genetics mutations (2)
mutation in either:
- RyR1
- CaV1.1
RYR1 receptor
Ca2+ release channel
on sarcoplasmic reticulum
RYR1 known mutaions
110
CAV1.1 receptor
DHP receptor
L-type Ca2+ channel
in T-tubule
CAV1.1 known mutations
2
MH chromosome locations
1
15
19
MH genetic pattern
autosomal dominant
w/ variable penetrance
MH genetic prevalance
1:3000
MH genetic concentration
scandinavian descent
higher inicidence of occurrence in wisconsin and upper midwest
_____% of pts who develop MG have have previous uneventful anesthetics with triggering medications
50%
krebs cycle
glucose —>
ATP + CO2 + heat
normal physiology responses
transient hyponatremia
transient hyperkalemia
ATP hydrolysis (incr heat)
SERCA activation (incr heat)
how does MH occur
sustained RyR activation
= sustained Ca2+ release (need more ATP)
Mg2+ inhibition of Ca2+ release is blocked
– Ca2+ release continues
MH most potent trigger
halothane
MH triggers
volatile agents (iso, sevo, des)
sux
MH awake triggers
high intensity exercise
heat
anoxia
apprehension
exercise ____ min prior to trigger _____ severity and _____ onset
exercise <60 min prior to trigger increased severity and hastened onset
MH general clinical signs
incr metabolism
incr sympathetics
muscle damage
hyperthermia
incr metabolism signs 7
incr CO2 production
incr O2 consumption
decr MVO2 tension
metabolic acidosis
respiratory acidosis
cyanosis
mottling
incr sympathetics
tachycardia
hypertension
arrhythmias
MH arrythmia progression
PVCs
bigeminy
VTACH
VFIB
asystole
3 ways to correct hyperkalemia
membrane stabilization
transfer of K+ INTO cells
incr K+ excretion
correct hyperkalemia: membrane stabilization
hyperventilation
give CaCl (500-1000mg) or Ca gluconate (1000mg)
correct hyperkalemia: transfer of extracellular K+ INTO cells
give 5-10 units insulin w/25-50g glucose
(10 units insulin w.50 mL of 50% dextrose)
give beta agonist (albuterol)
when do you just give insulin in MH treatment
if glucose levels are > 250
correct hyperkalemia: incr K+ excretion
give loop /thiazide diuretic (furosemide 20-40mg)
give GI cation exchange resins (kayexalate)
start hemodialysis
give sodium bicarb
what do GI cation exchange resins do
bind K+ in GI tract
MH clinical signs: muscle damage (7)
masseter spasm
rigidity
incr creatine kinase (CK)
hyperkalemia
hyperphosphatemia
myoglobinemia
myoglobinuria
what indicates muscle breakdown
myoglobin release
clinical signs: hyperthermia
fever (1 degree in 5-15 mins)
sweating
hyperthermia is the first sign of MH in _____ of cases
4%
hyperthermia is one of the first signs of MH in ____ of cases
8%
is there a dependable early sign in MH presentation
not really
common early MH signs (4)
hypercarbia
tachycardia
generalized muscle rigidity
MMR
what should be an immediate assumption of MH
MMR after exposure to trigger
above ____ degrees C causes:
above 41.5C causes:
- organ dysfunction
- DIC
late MH signs
rhabdo
myoglobinuria
MH arterial blood gas
elevated base deficit
MH BMP
hyperkalemia
MH Mag
hypermagnesemia
MH venous blood gas
decr MVO2
MH serum myoglobin
incr myoglobin
MH serum CK
incr CK
MH serum lactate dehydrogenase
incr lactic dehydrogenase
when does CK peak after acute MH
14 hours
differential diagnosis
list of all potential diagnoses based on
- signs
- symptoms
- lab results
MH DDX (10)
neuroleptic maliignant syndrome
thyroid storm
pheochromocytoma
serotonin syndrome
iatrogenic hyperhtermia
brainstem/hypothalamic injury
transfusion reaction
sepsis
anaphylaxis
drug abuse
baclofen withdrawal
MH iatrogenic DDx
inadequate anesthesia/analgesia
hypoventilation/CO2 rebreathing
incr CO2 absorption
NMS differing from MH
history is defining feature
trigger medication
thyroid storm difference from MH
no muscle rigidity
pheochromocytoma difference from MH
no muscle rigidity
serotonin syndrome difference from MH
clonus involvement present (not tonic which is found in MH)
transfusion reaction difference from MH
blood products are given
no muscle rigidity
sepsis difference from MH
no muscle rigidity
anaphylaxis difference from MH
no muscle rigidity
baclofen withdrawal difference from MH
lack of acidosis
common features within MH differential diagnosis
hypertension
tachycardia
tachypnea (non-paralyzed pts)
hypercarbia
fever
differentiating features within MH differential diagnosis
muscle rigidity
masseter spasm
rhabdo
hyperkalemia
metabolic acidosis
MH associated syndrome: strong
hypokalemic periodic paralysis
central core disease
multi-mini core myopathy
MH associated syndome: mild
muscular dystrophy
king-deborough syndrome
recent/frequent rhabdo
recent/frequent heat stroke
central core disease
myotonic dystrophy
deficiency of mitochondrial enzymes
central core disease SE
repiratory failure
cardiomyopathy
multiminicore myopathy
RyR gene cause weakness
SEPN gene causes stiffness
multiminicore SE
axial muscle weakness
rib/spine stiffness
arthogyroposis
king denborough
RyR mutation
king denborough phenotype
short stature
dysmorphic facial features
MH precautions
no Sux
no volatile agents
TIVA
remove vaporizer
tape off sux
flush anesthesia machine
use charcoal scrubbers
anesthesia machine flush MH
10L/min flow
20 mins
minimum flow needed for charcoal scrubbers
3L/min
how long do charcoal scrubbers last
12 hrs
MH treatment: oxygenation/ventilation
place ETT
incr flow >10L/min
incr MV
do you need to change out anesthesia machines when treating MH
no - just change out circuit
dantrolene MH dose
2.5 mg/kg
dantrolene trade names
dantrium
renovo
dantrolene reconstitution
20 mg powder into 60 ml sterile water
difference between dantrolene and ryanodex
ryanodex does not contain mannitol
how often do you dose dantrolene for MH
every 5 mins until symptoms cease
dantrolene max does
10 mg/kg
what labs should you draw off arterial line for MH case
BMPs – Red or Green tube
blood gases – ABG syringe
creatine kinase – green tube
coag/TEG – blue tube
BMP tests for
K+ levels
blood gases test for
acid base status
CK tests for
degree of muscle breakdown
Coag/TEG tests for
possible DIC
(functionality of cloitting factors)
when do you treat hyperkalemia with MH
with EKG abnormalities
or
K+ >6 mEq/L
hyperkalemia treatment for MH
10% CaCl - 5 mL
insulin/D50 - 10 units insulin / 30-50 dextrose
sodium bicarb - 1-2 mEq/kg
when do you treat metabolic acidosis in MH
base deficit > 8mEq/L
50 mEq of NaHCO3 produces ___ of CO2
50 mEq of NaHCO3 produces 1L of CO2
what cardiovascular drugs are contraindicated with MH pts
verapamil
diltiazem
when do you discontinue cooling measures
once pt is 38 degrees
cooling measures
cool saline
expose pt
ice packs - axilla, neck, groin
intraperitoneal lavage
urine output
1-2 mL/kg/hr
continued dantrolene dosing after acute epidose ends
1 mg/kg every 4-6 hrs for up to 24 hrs
0.25 mg/kg/hr for up to 24 hrs
DIC is associated in _____ of MH cases
7%
pts with rhabdo should be monitored for
compartment syndorme
rhabdo treatment
hydration
diuresis
dantrolene drug categoy
paralytic
(requires amnesia - background propofol)
why is mannitol in dantrolen
facilitate diuresis and renal protection
what IV should you be giving dantrolen through
14-16ga IV
MH testing
halothane-caffeine contracture test
– muscle biopsy from quads or rectus abdominus
what cells express MH mutations
WBC
caffeine
lowers threathold for spontaneous Ca2+ release
promotes contractions
