Malignant Hyperthemia Flashcards
How to manage MH
CLINICAL MANAGEMENT
1. Discontinue all triggering agents and call for HELP
and for the MH cart STAT!!! Inform surgeon to stop
surgery ASAP
2. Hyperventilate (3-4X’s normal minute volume) with
100% O2 at high flow rates (10L/min) via a “clean”
source. Even small amounts of gas in circuit can be
detrimental; can insert activated charcoal filter on
inspiratory and expiratory limbs (Vapor-Clean)
3. Give Dantrolene 2.5 mg/kg rapid IV push, repeat Q
5-30 minutes until EtCO2 decreases, decreased
muscle rigidity, or HR decreases. May require large
doses (>10 mg/kg)
What is MH?
○ Malignant hyperthermia is an inherited disorder
of skeletal muscles triggered in susceptible
individuals when exposed to certain anesthetic
agents that results in hypermetabolism, skeletal
muscle damage, hyperthermia and eventual
death if untreated
Pathophysiology of MH
what are the genes involves?
What are the two hall marks or this disorder?
○A trigger agent is administered to a susceptible
individual.
○A generalized derangement of processes which
regulate skeletal muscle contraction results
○There is a marked increase in intracellular
ionized calcium-up to 8X’s normal
○Calcium reuptake is blocked ○“Triggering agents” for MH release calcium from storage sites in the muscle (sarcoplasmic
reticulum) leading to elevated concentrations of
calcium in the muscle
- Elevated calcium results in increased metabolism and
causes the muscles to contract and become rigid
resulting in heat production, acidosis, and muscle cell
breakdown
○Untreated, this results in ATP depletion, acidosis,
membrane destruction, cell edema and death
○The heat production is not regulated by the
hypothalamus, but is peripheral in origin because of
hypermetabolism in the muscles
○Hyperthermia is the result, not the cause of this
metabolic disturbance in the muscles
○2 hallmarks of this disorder are increased O 2
consumption and CO2 production
What is the mode for transmission of MH?
Autosomal dominant inheritance
Therefore, children and siblings of a patient
with MH have a 50% chance of inheriting the
gene for MH
T/F
MH can have immediate or delayed onset
TRUE
○Can have immediate or delayed onset
○MH does not only occur in the OR, but can happen
anywhere that triggers are given such as succinlycholine
used to secure an airway in the ED, ICU ○Or it can have delayed onset and present in the PACU
What are the triggering agents for MH?
○ All Halogenated inhalational agents:
• Forane
• Halothane
• Sevoflurane
• Desflurane
○Succinylcholine (Anectine)
T/F
Heatstroke may occur more often in MH susceptible patients
TRUE
○ Heat stroke may occur more often in MH
susceptible patients
○Even though caffeine is not a trigger, one should be highly suspicious of patients with caffeine
sensitivity
○In the past Lidocaine wasn’t used as it was
thought to be a trigger agent, it is now
considered safe and has been administered to
many patients with documented MH
What is the earliest and most consistent sign of MH?
1. Unexplained tachycardia (earliest and most
consistent sign, seen in 96% of MH cases)
- Sudden increased and rising ETCO2 (2-3X’s normal, despite seemingly adequateventilation)
- Increased PaCO2 (possibly > 100 mmHg)
and decreased pH (possibly < 7.0)
ADDITIONAL CLUES…
- Generalized muscle rigidity (75-80%)
- Masseter muscle rigidity or trismus (50%)
- Unexplained tachypnea (or trying to over-
breath the vent if paralyzed) 7. Rhabdomyolysis (tea or cola colored urine) - Cyanosis (70%), from inadequate O 2 supply
- Hemodynamic instability (85%), initially
hypertension, then hypotension 2* to cardiac
depression
a very specific late sign for MH
Marked temperature elevation
How much can skin temp rise in MH?
○Can rise 1° Celsius Q 5 mins, may reach 43° C
(110° F)
How is Dantrolene given?
Dantrolene 2.5 mg/kg rapid IV push, repeat Q
5-30 minutes until EtCO2 decreases, decreased
muscle rigidity, or HR decreases. May require large
doses (>10 mg/kg)
what do you give for base excess >-8
Bicarb 1-2 mEq/kg even in absence of ABG’s or for
base excess > -8, metabolic acidosis; max dose 50
mEq
What can you give for lethal or refractory ventricualr dysrhythmias?
Procainamide for lethal or refractory ventricular
dysrhythmias (1.5 mg/kg over 1 min) repeat Q 5 min
until resolves or total of 15 mg/kg given.
What medication is absolutely contraindicated in MH- this can be lethal (not MH triggers)
Calcium Channel Blockers
Some Hot Dude Better Give Iced Fluids Fast
Where does Dantrolene work?
Dantrolene Sodium preparation
Works on the muscles directly, not on the neuromuscular junction
➢Packaged 20 mg per vial, reconstituted with 60 ml of
sterile water. Shake vigorously until clear. Each vial
contains 3 gms of Mannitol to increase solubility of
drug
➢Protect from light once mixed and use within 6 hours
of reconstitution.
➢Immediate administration is mainstay of therapy.
➢Warm medication or sterile water to help dissolve the
drug
➢Dose: 2.5 mg/kg rapid IV push, repeat Q 5-30 mins
based on ongoing S & S of MH. Decreased ETCO 2
followed by decreased temp are signs of effective
therapy. Total dose usually < 10 mg/kg
What is the shelf life of Dantrolene?
What is Ryanodex?
What is the dose?
How is it reconstituted?
How much Dantrolene is 1 vial of Ryanodex?
Comparison of Dantrolene formulation chart
What do you need to becareful when using Dantrolene and Ryanodex when using as preTx?
NMS???
What is the minimum PACU stay for MHS?
Difference between NMS and MH
The underlying defect in _NMS is central in nature, where
as in MH it is peripheral_
MH VS. NMS
○Although NMS is a separate entity, it may predispose
patients to MH
○Patients with NMS should not receive MH triggers,
conversely, patients with MH can safely receive
phenothiazines
○Treatment of NMS consists of drug withdrawal and
symptomatic treatment.
○Bromocriptine and Amantadine (dopamine agonists)
may be effective in treating NMS
○Consider benzodiazepines like Lorazepam
○Mortality in NMS is 20-30% with deaths usually
resulting from renal failure or dysrhythmias
NMS vs MH
Chart
