Malignant Hyperthermia Flashcards
Malignant Hyperthermia
Potentially lethal disorder triggered by Succinylcholine and/or volatile anesthetics in susceptible individuals with resulting hypermetabolism, skeletal muscle damage, hyperthermia, acidosis, dysrhythmias
inhaled anesthetics
all potential triggers except NO
paralytic trigger
succinycholine
Gene mutation
most common RYR1 (ryanodine receptor gene)
50 DNA variants
Ryanodine receptor
Major calcium release channel in sarcoplasmic reticulum
Ryanodine receptor dysfunction results
Leads to UNCONTROLLED release of calcium from the sarcoplasmic reticulum in muscle (sustained contractions)
Reuptake mechanism attempt to remove excess calcium
Depletion of ATP stores
Increased metabolism (increase oxygen consumption)
Accelerate heat and carbon dioxide production
Increasing lactic acid production
Acidosis, Hyperthermia & ATP depletion results
Sarcolemma destruction
Marked increased in potassium levels
Myoglobin
Increased creatine kinase levels
Marked increased intracellular calcium
Clinical signs
-First signs: Sinus Tachycardia, Hypercarbia, Masseter spasm (sometimes)
-Elevated end-tidal CO2 (increased PaCO2)
-Most common pattern: Respiratory acidosis with muscular abnormalities
Tachypnea in spontaneously breathing patient
Overbreathing (if not paralyzed) with mechanical ventilation
Rapid exhaustion of CO2 absorbent (Hot canister)
-Trunk or total body muscle rigidity
-Elevated temperature (may be early MH sign)
-Hypercalcemia
-Myoglobinuria
Core body temperature
Core body temperature can be as high as 45 ° C. Can increase 1 ° C every 5 minutes.
Lab results
-hyperkalemia
-hypercalcemia
-mixed respiratory & metabolic acidosis
-lactic acidosis
-marked increase CK levels
-myoglobinuria (due to rhabdo)
Complications of MH
Hyperthermia (excessive cooling)
DIC
renal failure (d/t myoglobinuria)
Drug interactions
Death
Preparation for MH crisis
Knowledge (assessment and interventions)
Dantrolene: on MH cart, backpack, and supply box
Crisis management though teamwork
-MH hotline
-cognitive aids
-adequate personnel to help during crisis
-simulation for preparedness
Supplies needed for MH Crisis
-Dantrolene (IV access), Anesthesia drugs, emergency medications, Oxygen/airway, CODE CART
-MH App, MH Hotline, Cognitive Aids
-Team Communication System
-IVFs, IV supplies, IV pumps
-Supplies for multiple lab draws (istat, transporter)
-Bags of ice, Cooling blanket
-NG Tube with cool fluids for lavage
-Foley catheter
-Arterial line equipment, central line
Emergency treatment of acute MH even
call for help
1: notify surgeon to halt procedure ASAP
2: discontinue volatile agents and succinylcholine triggers
3. get dantrolene/MH cart
4. hyperventilate with 100% O2 at flows of 10L/min to flush volatile anesthetics and lower ETCO2
5. insert activated charcoal filters
Vapor-Clean (activated charcoal filters)
The Vapor-Clean™filter may become saturated after one hour; therefore, a replacement set of filters should be substituted after each hour of use.
Filters contain granules of activated charcoal to capture volatile anesthetic vapor molecules
concentration of vapor <5ppm in less than 2 minutes
Dantrolene
Skeletal muscle relaxant
Acts within the muscle cell, reduces calcium release by the SR
Half-life of intravenous Dantrolene ~12 hours
Use with caution with neuromuscular disease
Give every 6 hours after MH clinical crisis episode
Muscle weakness can last for 24 hours
Side effects: muscle weakness, double vision, dizziness, nausea, diarrhea
Ryanodex
250mg vial reconstituted w/ 5mls of sterile water
Loading dose 2.5mg/kg IV (actual weight) for either formulation
3 vialsshould be available in each institution where MH can occur, each to be diluted at the time of use with 5 ml of sterile water for injection, USP (without a bacteriostatic agent).
Other adjunct medications
Obtain blood gas (venous or arterial) to determine degree of metabolic acidosis. Consider administration of sodium bicarbonate, 1-2 mEq/kg dose, for base excess greater than -8 (maximum dose 50 mEq).
cooling the patient
Cool the patient if core temperature is >39°C or less if rapidly rising. Stop cooling when the temperature has decreased to <38°C.
Dantrolene MHAUS requirement
Dantrolene must be available for all anesthetizing locations within 10 minutes of the decision to treat for MH.
Should have at least 36 vials readily available at your institution
Dantrolene must be available for all anesthetizing locations where MH trigger agents are used
Dantrolene formulations
2.5mg/kg (actual weight) rapidly though large-bore IV - repeat until patient responds with decrease in ETCO2, decreased muscle rigidity, and/or lowered HR
. Large doses (>10mg/kg) may be required for patients with persistent contractures or rigidity (MHAUS). No ceiling dose of Dantrolene
Dantrium/Revono: each 20mg vial needs 60mls of sterile water for injection (36 vials - 15min prep)
Ryanodex MH Protocol
Less than 1 minute for reconstitution and administration of a loading dose (2.5 mg/kg) in an MH crisis
Fewer vials required to treat MH (1 vial contains 250 mg of dantrolene sodium)
1 vial of RYANODEX® contains the same amount of dantrolene sodium as 12.5 vials of other approved dantrolene sodium formulations
Over 99% less sterile water for injection than otherdantrolene sodium IV treatments
1 vial provides a loading dose (2.5 mg/kg) for patients up to 100 kg
Hyperkalemia treatment for MH
If hyperkalemia (K > 5.9 or less with ECG changes) is present, treat with:
Calcium chloride 10 mg/kg (maximum dose 2,000 mg) or calcium gluconate 30 mg/kg (maximum dose 3,000 mg) for life-threatening hyperkalemia
Sodium bicarbonate: 1-2 mEq/kg IV (maximum dose 50 mEq)
Glucose/insulin
– For pediatric patients: 0.1 units regular insulin/kg IV and 0.5 grams/kg dextrose (% in formulation not important)
– For adult patients: 10 units regular insulin IV and 50 ml 50% dextrose
–Check glucose levels hourly
For refractory hyperkalemia, consider albuterol (or other beta-agonist), kayexelate, dialysis, or ECMO if patient is in cardiac arrest.
Treat dysrhythmias - standard medication but avoid calcium channel blockers.
Diurese to >1ml/kg/hr urine output. If CK or K+rise, assume myoglobinuria and give bicarbonate infusion of 1 mEq/kg/hr, to alkalinize urine (more mannitol in Dantrium dosing vs. Ryanodex)
indicators of stability
When stable, transfer to post anesthesia care unit or intensive care unit for at least 24 hours.
Key indicators of stability include:
ETCO2is declining or normal
Heart rate is stable or decreasing with no signs of ominous dysrhythmias
Hyperthermia is resolving
If present, generalized muscular rigidity has resolved
Masseter muscle rigidity
Marked difficulty in manual mouth opening that interferes with and impedes direct laryngoscopy and tracheal intubation without the presence of temporomandibular joint dysfunction. When MMR occurs in response to administration of succinylcholine in the absence of an underlying temporomandibular joint disorder or myotonia, it may be an initial sign of MH. More common in children & young adults” (MHAUS)
Not relieved by additional Sux or NMBDs
Differential diagnosis
Myotonic syndrome, TMJ, underdosing of Sux, insufficient time allowed for Sux onset, increasing resting tone after Sux associated with fever or elevated plasma epinephrine, MH
MH cart contents
Dantrolene
sterile water
NaHCO3
D50
Calcium chloride
Regular Insulin
Charcoal filters
syringes
IV catheters
NGT
Toomy irrigation syringes
MH testing
muscle biopsy (halothane-caffeine contracture test)
genetic testing
Conditions resembling MH
Neuroleptic malignant syndrome - Symptoms include high fever, sweating, unstable blood pressure, stupor, muscular rigidity, and autonomic dysfunction.
Pheochromocytoma
Thyrotoxicosis
Sepsis
Hypoxic encephalopathy
Mitochondrial myopathies
predisposing conditions
Central core disease
Central core disease is a disorder that affects muscles used for movement (skeletal muscles).Most people with central core disease experience persistent, mild muscle weakness (hypotonia, floppy) that does not worsen with time. This weakness affects the muscles near the center of the body (proximal muscles).
Multiminicore disease
Multiminicore disease is a disorder that primarily affects muscles used for movement (skeletal muscles). This condition causes muscle weakness and related health problems that range from mild to life-threatening.
King Denborough Syndrome
TheKing-Denboroughsyndrome(KDS) is acongenitalmyopathy associated withsusceptibilitytomalignant hyperthermia, skeletal abnormalities and dysmorphic features with characteristic facial appearance. Although the cause of King-Denborough syndrome is not fully understood, at least some cases have been attributed to theryanodine receptor gene(RYR1), which has been tied to malignant hyperthermia andcentral core disease.
Safe anesthetic drugs for MH patient
Intravenous anesthetics, nitrous oxide, local anesthetics, opioids, benzodiazepines, and/or non-depolarizing muscle relaxants
TIVA with Propofol (general), regional, MAC, or local anesthesia technique
Recommend first case of the day
Change CO2 absorbent & breathing circuit
Use charcoal filters
Notify team of plan and increase MH risk
**Remove Succinylcholine from area. Remove or tape off Vaporizers to avoid accidental use.
Have Dantrolene and all necessary equipment readily available. Alert pharmacist and staff of MH or MH susceptible patient.
Preparation for the MHS patient
Disable vaporizers (remove or tape in “OFF” position)
Attach new breathing circuit and reservoir bag. Place bag on circuit & set ventilator to inflate bag periodically [flush anesthetic gases from the system]
New machines: 10L/min FGF for up to 104 minutes
Older machines: 10L/min FGF for up to 20 minutes
Option: add activated charcoal filters to circuit to remove anesthetic gases (eliminates need to purge the system).
NOTE: Anesthesia machine will still need to be flushed with high fresh gas flows (≥ 10 L/min) for 90 seconds prior to placing the activated charcoal filters onboththe inspiratory and expiratory ports.
Preparation for the MHS patient
Disable vaporizers (remove or tape in “OFF” position)
Attach new breathing circuit and reservoir bag. Place bag on circuit & set ventilator to inflate bag periodically [flush anesthetic gases from the system]
New machines: 10L/min FGF for up to 104 minutes
Older machines: 10L/min FGF for up to 20 minutes
Option: add activated charcoal filters to circuit to remove anesthetic gases (eliminates need to purge the system).
NOTE: Anesthesia machine will still need to be flushed with high fresh gas flows (≥ 10 L/min) for 90 seconds prior to placing the activated charcoal filters onboththe inspiratory and expiratory ports.
