So we're going to start off talking about
an extraordinary rare condition, but one that has
a very high mortality if it's not diagnosed early.
And this is malignant hyperthermia. This is
a genetic disorder that is transmitted in
an autosomal dominant genetic fashion.
But it's extremely rare. It occurs in less than
1:1,000,000 people. The problem is that,
when it does occur, it's highly lethal.
Has an 80-90% mortality, unless
it's rapidly diagnosed and aggressively
treated. When it is treated appropriately,
it has a 90% cure rate.
So the anesthesiologist who may go through a long
career, such as I have done, and never see this
disorder, must be able to diagnose it
instantly if it does occur.
It's only seen either after a vapour is used
on a patient, or Succinylcholine is used.
But it is probably the only truly
The cause is an abnormal sarcoplasmic reticulum calcium channel,
very complex. But the bottom line is that large
amounts of calcium are released into the muscle.
Muscle's going into spasm. Muscle fibers
are damaged and release myoglobin, which is
the color in muscle, the material that gives muscle
its orangish-reddish color. This can lead
to severe metabolic acidosis, renal failure,
cerebral edema, pulmonary edema,
and rapid death if treatment is not initiated.
Temperature is one of the signs of this disorder,
but it's a late sign. And nearly everybody
believes nowadays that temperature
is actually not a very good indicator of this problem,
and that we have to be aware of the problem and be able
to diagnose it long before temperature
becomes an issue. The early signs
of malignant hyperthermia are very non-specific unfortunately.
They include tachycardia, rapid heart rate
without apparent cause, and a sudden increase
in end-tidal carbon dioxide without apparent cause.
These signs in themselves may be enough to make
the diagnosis of malignant hyperthermia.
The problem is that both of these things
can occur in all kinds of other situations.
The good news is, if you start treatment and the patient
doesn't have malignant hyperthermia,
you really don't do any damage. So it's better to start
treatment on the assumption that it may be malignant
hyperthermia, further diagnose the situation, and if
it turns out not to be malignant hyperthermia,
you haven't done any damage. The only
real drug of use in the treatment
of malignant hyperthermia is a drug called
Dantrolene Sodium. This has to be mixed
and it's difficult to mix, and the usual
starting dose is 2 mg/kg, which is about
7 amps. And it takes a team of people
to mix the stuff, and you have to shake
it for ages to actually get it into a state
that will allow you to inject it. So you have
to think about it early. You have to get a team
of people working together really early on
in this condition, to reverse it and save
the patient. Start off with 2 mg/kg initially,
then 1-2 mg/kg, every 3-5 minutes,
until the patient
improves or you've hit 10 mg/kg.
If I ever see this condition, which
I'm thankful I haven't yet, I'm going
to carry on past 10 if I must, but hopefully,
and the evidence from the literature would suggest,
most people recover or start to show signs of recovery
before you hit 10 mg/kg.
You should also start active
cooling of the patient. Ice packs to the outside
of the body. Ice-cold solutions lavage
through the bladder and into
the peritoneal cavity. ICU
care is essential for these patients because
the condition can reactivate later on, so you
can get the patient under control, everything appears
to be great, but unfortunately, several hours later,
it may re-occur. So you have to have the patient
in a monitored environment, to make sure that you can
treat them again if necessary. Very rare,
but it must be diagnosed. This
URL to the Malignant Hyperthermia
Association of the US has
the best information on malignant hyperthermia
you can find anywhere. It's all there! So if you're
interested in this disorder and you want to know
more about it, go on to that web page, and all
the information you'll ever need to know about
MH is right there for you.