malignant hyperthermia 2

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A brief History
of
Malignant Hyperthermia
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MH was discovered in the Royal Melbourne Hospital By
anaesthetist Dr Jim Villiers in 1960
He was presented with a patient who was terrified as he had
10 family members die from minor procedures involving
general anaesthesia
He spent time talking to the patient and other colleagues to
devise a anaesthetic plan for the patient.
Although the patient did develop signs of what we now refer
to as MH, he was able to save him from death with his skilled
anaesthetic management.
Since 1972 the RMH has been providing advice, research
and a testing service for this rare, but important disease
which has major anaesthetic consequences.
What is
Malignant Hyperthermia?
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MH is an acute pharmacogenetic (autosomal dominant)
disorder
It develops during or after general anaesthesia
It is triggered by anaesthetic volatile agents and/or
depolarising muscle relaxants
It is a hereditary condition
The disorder is likely to be a result of a defect in calcium
channel regulation in the muscle cell.
Volatile anaesthetic agents and depolarising muscle
relaxants interact with the calcium channel resulting in the
clinical crisis.
Key signs and symptoms of Malignant
Hyperthermia
EARLY
DEVELOPING
LATE
Prolonged masseter spasm
after suxamethonium
Rapid rise in temperature
(0.5oC per 15 min)
Coloured urine – due to
myoglobinuria
Inappropriately raised end
tidal carbon dioxide or
tachypnoea during
spontaneous respiration
Progressive respiratory and
later metabolic acidosis
(ABG)
Generalised muscle ache
(in an awake patient)
Grossly raised serum CK
Hyperkalaemia
Coagulopathy
Inappropriate tachycardia
Profuse sweating
Cardiac arrhythmias,
particularly ventricular
ectopic beats
Cardiac arrest
Cardiovascular instability
Decreased SpO2 or mottling
of skin
Generalised muscular
rigidity
Preparation for a known or
suspected MH-Susceptible
Patient
Remover vaporisers and turn the oxygen to 10L per minute.
soda lime. Keep the oxygen flowing for a minimum of 10 minutes
OR
 If available, use a dedicated “vapour free” machine for MHsusceptible patients. The machine must be regularly maintained
and safety-checked
OR
 If appropriate, use an ICU ventilator that has never been exposed
to volatile anaesthetic agents
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Finally, make sure you have know where everything you would
need is kept.........just in case
Role of the Anaesthetic
Technician during an MH
crisis
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Provide immediate emergency/resuscitation skills
Facilitate profusion of Dantrolene, sodium bicarbonate, mannitol
insulin and frusemide
Facilitate immediate provision of cooling equipment and patient
monitoring
Insure availability of equipment uncontaminated by volatile
anaesthetic agents
It is imperative that the anaesthetic technician is aware of (a) the
location of dantrolene, (b) likely interventions, and (c) local
procedures for obtaining ice packs and cooling resources
MH initial
management
Guidelines from MHANZ
Stop the trigger
 Declare emergency and cease surgery if possible
 Call for more help
 Send for the MH trolley (located in Technicians room Level 4)
 Turn off volatile agents and remove vaporisers from
anaesthetic machines
 Hyperventilate with 100% oxygen and high fresh gas flows
 Do not waste time changing machine and circuit
 Commence TIVA, target 4mcg/ml or 30-50mls/hr
100% Oxygen/hyperventilate
Turn off and remove
volatile agents
An ambu bag can also be used to
deliver 100% oxygen eliminating any
chance of delivering volatile agents
An oxylog can also do the
same as above if you have
spare hands and time
Give Dantrolene
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2.5mg/kg IV initial bolus and repeat as necessary (same dosing adult and
peads)
Mix each amp with 60ml of STERILE WATER ONLY
You may require at least 36 ampoules
It is important to note that the administration of Dantrolene for injection
should be continuous until symptoms subside.
The effective dose to reverse the crisis is directly dependant upon the
individuals degree of susceptibility to malignant hyperthermia
If you require more Dantrolene, contact the pharmacy and if out of
hours contact the on call pharmacist
Simultaneously treat hyperkalaemia
 Hyperventilate and treat acidosis
Cool the patient if the temperature
>38.5 C
Use IV saline from the fridge
Surface cooling with ICE bags
Consider peritoneal lavage with cold fluids
(normal saline)
DO NOT OVER COOL, RISK OF SHOCK
Treat acidosis
 Hyperventilate to at least normocapnia
 Consider sodium bicarbonate 0.5mmol/kg IV as required to maintain
pH>7.2
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Treat arrhythmias
Lignocaine 1-2mg/kg
Amiodarone 2-3mg/kg over 15 minutes
Extra Monitoring
Monitor core temperature
Insert arterial line
Send urgent bloods
ABG, U+E. FBC, CK, COAG and myoglobin (repeat frequently)
Insert IDC (if has not already been done for cooling)
Maintain urine output above 2mls/kg/hour
Insert CVL
DO NOT DELAY DANTROLENE THERAPY WITH ATTEMPTED CVL
PLACEMENT
THE MALIGNANT
HYPERTHERMIA
TROLLEY IS
LOCATED IN THE
TECH ROOM ON
LEVEL 4
Dantrolene
What is Dantrolene?
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It’s a muscle relaxant acting specifically on skeletal muscles
It is thought to reduce muscle tone and metabolism by preventing the
ongoing release of calcium from the storage sites in muscle (the
sarcoplasmic reticulum)
In MH, intracellular calcium levels are elevated and therefore dantrolene
counteracts this abnormality
It is also used to treat muscle spasticity (stiffness and spasms) caused by
conditions such as, spinal cord injury, stroke, cerebral palsy and multiple
sclerosis
MHanz shows here
a recommended
way to draw up the
water and mix the
dantrolene
Another way that
water can be drawn
up is by using a
giving set with a
3way tap connected
at the end.
The bag can be pressurised
so that it is even easier to
draw the water into the
syringe
References
http://www.anaesthesia.mh.org.au/malign
ant-hyperthermia/w1/i1001286/
http://www.anaesthesiawa.org/mh.html
www.anzca.edu.au/resources/endorsedguidelines
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