(Non) Malignant Hyperthermia

angeldaisy

Can anyone explain to me the difference between Non Malignant Hyperthermia and Malignant Hyperthermia in plain english.

I've tried googling it and ended up even more confused. I know that it is a reaction to certain anaesthesia, but after that ...

DrIndy

Hyperthermia is by definition a temperature over 41.1C.

Up to this point, fever is permissible because it does not harm humans and in fact helps to fight a number of infections, which is why we evolved to have a fever when an infection is present.

Temperatures above this can damage the human body and particularily the brain is injured first at sustained temperatures above 41.1C.

Hyperthermia is seen primarily as a result of heat stroke, but gram negative sepsis can induce very high temperatures as the gram negative bacteria (like E.coli and other bowel bugs) contain proteins internally which leach out when they break down that artificially induce a fever. These endogenous pyrogens (fever producing proteins) mimic the normal proteins the immune system produce that reset the hypothalamus (part of the brain which controls temperature as well as other functions) to a higher temperature. This is why people shiver before a fever - the body thinks you are hypothermic like on a cool day and tries to increase your body temperature to a new level. Too much thyroid hormone and drugs like ecstacy and cocaine can cause this too.

Malignant hyperthermia is a different condition. It can be caused by anti-schizophrenic drugs (neuroleptic malignant syndrome). This is related to dopamine receptors (D2) in the hypothalamus. These are the ones that want to be augmented in the rest of the brain when you treat psychosis or schizophrenia but in a small subset of the population can cause neuroleptic malignant syndrome which is fever and muscle rigidity amongst other effects.

The other form of malignant hyperthermia is directly related to anaesthesia - this is where there is an directly inherited gene defect (autosomal dominant - meaning if you inherit the gene - you will always have it and a carrier has a 1 in 2 chance of passing it on - so if one of your parents has this - please tell the anaethetist!). Here excess calcium is released in response to halothane and other drugs in the muscles and results in excessive muscle contraction causing this syndrome. There is treatment - but an anaethetist hates complications so it is better to know ahead.

hope this helps - tell me if I used too much medical speak!

angeldaisy

thanks for that, it makes it a bit clearer, but what I still don't understand is why is there Malignant Hyperthermia and Non Malignant Hyperthermia?