Pathophysiology
What is Malignant Hyperthermia?
An inherited disorder (genetic mutation) of skeletal muscle resulting in an increase in intracellular calcium.
What is an early sign of MH?
An increase in end-tidal CO2.
What is the first thing that should be done by anesthesia if MH is suspected?
Stop the triggering agent (anesthetic gases and/or succinylcholine and hyperventilate the patient with 100% O2. Then, change the CO2 absorbent.
How many vials of Dantrolene are kept on the MH cart at all times?
36 vials
Does malignant hyperthermia only occur in the OR?
No, it can also occur wherever triggering anesthetics and depolarizing muscle relaxants are administered. As well as during heat stress, vigorous exercise and trauma.
What specific conditions should be noted as a potential trigger while performing a preoperative assessment?
History of heat stroke, rheumatoid arthritis, temperature instability, unexplained high fever/complications following anesthesia, history of dark/cola-colored urine following anesthesia or strenuous exercise.
What are additional signs of MH that may occur in a crisis?
Elevated temperature, generalized muscle rigidity, tachycardia, tachypnea, hypotension, and metabolic/respiratory acidosis.
What drug is the main treatment of a MH crisis?
Dantrolene
What irrigant is used to dilute Dantrolene? How much?
60 mls of preservative free sterile water for irrigation.
Where is the MH cart located?
In the holding area.
What can exposure to high environmental heat/strenuous exercise cause?
Abnormal release of calcium from its storage site which results in sustained muscle contraction and an abnormal increase in metabolism and heat production.
Shortly after anesthesia is given, and in rare cases, MH may occur as late as 24 hours after surgery.
Call for HELP. Administer Dantrolene. Cool the patient. Monitor and treat acidosis. Treat hyperkalemia. Treat dysrhythmias. Call MHAUS hotline.
What is the loading dose of Dantrolene that is used in the initial treatment of suspected MH?
2.5mg/kg IV until signs are controlled (9-12 vials will provide the initial dose).
Post crisis care should occur where?
ICU setting
What is the result of ATP depletion in the muscle cells of a patient in MH crisis?
This causes muscle cell death which releases large amounts of potassium into the bloodstream resulting in cardiac arrhythmias.
What are the later signs of MH?
Dark, cola-colored urine, heart arrythmias, bleeding, seizures...
What can you do while waiting for help during an MH crisis?
Place iced saline packs/ice packs on pressure points to cools patient. Infuse cold IVFs. Assist in mixing Dantrolene. Assist with CPR. Retrieve needed supplies/medications.
What is the subsequent bolus dose of Dantrolene?
1mg/kg
What are the triggering anesthetic agents?
Inhaled general anesthetics, depolarizing muscle relaxants, succinylcholine.
What is released from the muscle pigment during a MH crisis that is toxic to the kidneys?
Myoglobin
What severe complications occur as a result of untreated MH?
Cardiac arrest, kidney failure, blood coagulation problems, internal hemorrhage, brain injury, liver failure...death.
What drug is contraindicated during a MH crisis?
Calcium channel blockers. Use of these medications can worsen hyperkalemia, myocardial depression, and hypotension when co-administered with dantrolene.
What is the period of time that Dantrolene should be continued in the post-crisis treatment after the initial acute crisis dose?
24 hours
What hotline is notified and provides real-time assistance in the management of the patient during a MH crisis?
MHAUS (MH Hotline) at 800-644-9737 (800-MH-HYPER); available 24 hours.