Malignant Hyperthermia is autosomal dominant. It means 50% of the offspring will be affected. This disorder can be lethal. If anything you need to remember about this topic is the Dantrolene. The Dantrolene is a life-saving drug that stops the release of calcium from the sarcoplasmic reticulum into the cell, which means the blocks the calcium blocker. So, it decreases the intracellular calcium and stabilizes the sarcoplasmic reticulum.
You can do other things like you can call the patient, you can hydrate the patient, you can try to get the right balance but the most important thing is the use of Dantrolene Sodium. So, what happens here is the patient will get succinylcholine or halothane, or other inhalation agent and that would trigger the initiation of malignant hyperthermia.
So these anesthetic agents basically impair the function of the sarcoplasmic reticulum and calcium homeostasis and we're going to discuss how this happens but the condition associated with malignant hyperthermia are usually the central core disease Duchenne Muscular Dystrophy, Arthrogryposis, or Osteogenesis Imperfecta usually diagnosed during anesthesia or by family history with no really special symbol test for it. You can do muscle biopsy and testing. It's only done in certain few centers.
So because there is a problem in ryanodine receptor, will be an uncontrolled release of calcium. So you get sustained muscle contraction, rigidity, spasms, muscle damage, myoglobinuria, rhabdomyolysis and acute renal failure. Because of all this hypermetabolic activity, you would get classic hyperthermia. That's why they call it malignant hyperthermia. It is a classic finding. That's not a good sign because it is late.
You can also find metabolic acidosis hyperkalemia, which may give the patient dysrhythmia. You can have marked CO2 production. The CO2 production increases, you can have an increase end-tidal CO2 which you can explain. It is unexplained.
It is the earliest sign and probably the most specific and sensitive finding so that is the one that anesthesia will find and that will probably dare list when that will indicate the patient may have malignant hyperthermia.
How does this condition happen? What's going on? What is the physiology of that?
You probably need to know three things,
1- the sarcolemma, which is the membrane of the cell
2- the t-tubule which is like it David into the cell or a clef
3- the sarcoplasmic reticulum is the storage for calcium. It's a container of calcium when the muscle is relaxed a debt circle plasmic reticulum.
There is a large routine embedded into the wall of the circle plasmic reticulum and serves as a calcium release channel for the sarcoplasmic reticulum. So after the muscle contracts, the calcium is taken up by the circle plasmic reticulum. At that point, the muscle relaxants don't need any more calcium. The calcium is picked up by the sarcoplasmic reticulum the storage site. So when this disabled action of this fascist because the uh, Nadine receptor is defective then ran again triggers the release of calcium to the inside of the cell and the calcium is released in large quantities than normal.
So the interest or concentration of calcium increased substantially and you'll have sustained contracture of these muscles and that's how you get the malignant hyperthermia.
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