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It's Getting Hot in Here

A patient is brought in for altered mental status and respiratory distress despite administration oxygen via cpap and medication. It is decided that the patient will be intubated. The patient is sedated and then given the depolarizing neuromuscular blocking agent, succinylcholine prior to intubation. The patient is stabilized and O2 sats are now in the high 90s. One hour later though you notice your patient is tachycardic, flushed, feels warm, has twitching in the jaw, and their ETCO2 is elevated despite being ventilated. Temperature reads 105.4 F.

What are your thoughts?

This patient is likely reacting to the anesthesia or more specifically in this case the paralytic. This rare but deadly condition is called malignant hyperthermia (MH), and treating it can be difficult.

MH occurs in people born with an abnormal protein within their skeletal muscle tissue. The triggering medications (generally inhaled anesthetics or depolarizing paralytics) signal the proteins to release calcium stored within the muscle resulting in a large increase in concentration within the cells and thus thousands upon thousands of muscle contractions. As we all know, when muscles contract, heat is generated, and when this happens thousands of times, the results can be dramatic. Temperatures have been seen as high as 114 and without aggressive treatment mortality rates are 80%.

In comes Dantrolene Sodium…a medication you are sure to see when studying for NCLEX and that can decrease that mortality rate to around 5%. Definitely worth it, but here is what they don’t tell you in nursing school.

Dantrolene Sodium is a postsynaptic muscle relaxant that decreases excitation-contraction coupling in muscle cells. In skeletal muscle, it specifically inhibits the release of calcium, thus preventing or lessening the severity of malignant hyperthemia by stopping the uncontrolled muscle contractions.

Dantrolene comes in 20mg vials that must be mixed with 60ml of sterile water, but dosing for MH starts at 2.5mg/kg rapid injection…and you increase the dose repetitively until symptoms subside. That means if your patient weighs 95kg then even at the minimum dose your will likely need 12 vials…. JUST FOR THE FIRST DOSE. If the patient’s symptoms persist after the first dose,

which they will, the dosage is increased to 4mg/kg…or 19 ADDITIONAL vials!!! Crazy huh? This goes on and some cases require up to 10mg/kg with literature showing some dramatic cases requiring 30mg/kg. This is why if your ER or ICU carries an MH kit, it is stocked with a minimum of 36 vials…because you will use them all and you better have a few nurses dedicated solely to mixing and drawing up the medication.

An alternative does exist. It is Dantrolene but is formulated at higher concentration of 250mg per vial as injectable suspension. Its called Ryanodex but the cost is much higher and thus you will still encounter the lower dose vials more often than not.

When the patient is no longer experiencing symptoms, they will still have to be monitored and given oral Dantrolene for a few days to ensure relapse does not occur.