Pathophysiology
Malignant Hyperthermia Definition
•A rare genetic disorder of the skeletal muscles, that can be triggered by inhalation of anesthetic gases and succinylcholine administration in susceptible individuals.
•Mutation of RYR1 gene
•Ca overload of cells
ETCO2 of 60
Early (elevated).
WNL 35-45 mmHg
Medication used to treat MH
Dantrolene
Different formulations are available.
Revonto/Dantrium-older
Ryanodex-newer
The next steps after identifying an MH Crisis and anesthesia is stopping any triggering agents.
•Get Help! Get Dantrolene!
•Retrieve the MH Cart
•Where is your MH Cart Located?
•Call Code Blue
•If not in the OR, Call OR and get an anesthesiologist
•Call MHAUS
•Call Lab and Pharmacy
•Call for additional support if needed- House Supervisor, Rapid Response Team
Test is used to diagnose MH
•Gold Standard- Caffeine Halothane Contracture Study
Expensive
Muscle Biopsy
80% Specific
•Genetic Testing
If a defect is identified- deemed susceptible
If neg- Move to biopsy
Individuals at risk
•Individuals with a genetic predisposition receiving triggering agents…
•Rare Autosomal Dominant
•Male > Female
•Child>Adult
•Hx Muscle Disorders- Muscular Dystrophy, Central core disease, King-Denborough syndrome, Evans Myopathy, Rhabdomyolysis
Temperature of 102.2 F/39 C
Late
How Dantrolene is reconstituted
With 60 ml of sterile WATER. Mixed till fully dissolved. (Warming the water can help)
3 priority actions for MH
•Discontinue volatile agents & succinylcholine
•Hyperventilate with 100% Oxygen at flow of 10 liters or more
•Timely administration of Dantrolene
Form needed to be filled out post-crisis
•AMRA- Adverse Metabolic Reaction to Anesthesia for
Triggering Agents
Succinylcholine and/or Inhalation Anesthetics- (Ex: Isoflurane, Desflurane, Halothane, Enflurane, Ether, Isoflurane, Sevoflurane)
Unexplained Tachycardia/Tachypnea
Early
Timeframe Dantrolene should be administered in
Within 10 minutes of the decision to treat via Rapid IV Push
Your patient’s core temperature is 40 C/104 F. What are your next steps.
Start cooling when the patient's temperature is above 39 C (102.2 F)
Stop cooling when the temp drops to 38 C/100 F (they will continue to cool)
•Chilled IV Saline
•Ice packs externally (axilla, groin, neck)
Be careful of the patient's skin
When should MH susceptible patients be scheduled in the case line up
•First case of the day-Less risk of being exposed to triggering anesthesia gases.
Due to the increase in calcium being stuck in the intracellular space what might you see as a result
•Increase Metabolism (aerobic & anaerobic) > Increase C02 Production
•Increase 02 consumption & aerobic activity= Heat Production
•Sustained muscle contraction > Ca is stuck and overloading cells telling it to continually contract- leads to depletion of ATP
•Rhabdomyosis-Cellular Death- Myoglobin in urine, K+ release
Muscle Rigidity
Early
Can be trunk/whole body
The most common is Masseter muscle
Dantrolene decreases what in the cells
Calcium- Decreases release of Ca from the Sarcoplasmic Reticulum and increase its uptake by SR
Other nursing interventions that should be implemented during an MH Crisis.
•Place a Foley –Temp is best
I & O
Cola Colored Urine?
•Additional Lines- Central Line and PIVs
•Need ETCO2 Monitoring
•EKG- When treating arrhythmias do not use Ca Channel Blockers- They may cause hyperkalemia or cardiac arrest in the presence of Dantrolene.
•Labs
ABGs or VBGs
Glucose
Electrolytes & K+
Creatine Kinase- Muscle Damage Indicator
Coagulation Studies
•Yes- While dantrolene can be given to a pregnant woman, it does cross the placenta and there are side effects in the neonate. This again is just a risk and would have to be weighed against the expected benefit. Weakness in the neonate might be expected and must be looked for and treated appropriately.
3-5 signs and symptoms of MH
•**Increase end-tidal CO2 (Hallmark)
•Unexplained Tachycardia
•Muscle Rigidity (Masseter/Trunk/Whole Body)
•Tachypnea
•Increase in body temp (Late Sign)
Hyperkalemia
Late
You would see Hyperkalemia due to cells releasing potassium as they expire
Vials of Dantrolene you would initially give a 100kg patient
13 vials
Dose = 2.5 mg/kg
2.5mg x 100kg = 250 mg
250mg / 20mg = 12.5 Vials
Vials come in 20 mg
Following an MH event, staff members should
•Notify the PACU and/or ICU of the impending transfer
•Ensure that dantrolene sodium is available for administration for up to 24-48 hours following the initial MH crisis
•Be aware that s/s can reoccur up to 72 hours following the initial MH event, and are most common in the initial 24 hours after the onset of MH
How long a patient should be monitored for a relapse of MH
For at least 24 hours following cessation of signs of MH. 25% of MH events relapse and relapses can be fatal. Treat immediately if relapse occurs. Signs of MH relapse include:
•Increasing muscular rigidity in the absence of shivering
•Inappropriate hypercarbia with respiratory acidosis
•Metabolic acidosis without other cause
•Inappropriate temperature rise