malignant hyperthermia
DESCRIPTION
MALIGNANT HYPERTHERMIA. A brief History of Malignant Hyperthermia. 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 - PowerPoint PPT PresentationTRANSCRIPT
A brief Historyof
Malignant Hyperthermia 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?
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.
EARLY
Prolonged masseter spasm after suxamethonium
Inappropriately raised end tidal carbon dioxide or tachypnoea during spontaneous respiration
Inappropriate tachycardia
Cardiac arrhythmias, particularly ventricular ectopic beats
DEVELOPING
Rapid rise in temperature (0.5oC per 15 min)
Progressive respiratory and later metabolic acidosis (ABG)
Hyperkalaemia
Profuse sweating
Cardiovascular instability
Decreased SpO2 or mottling of skin
Generalised muscular rigidity
LATE
Coloured urine – due to myoglobinuria
Generalised muscle ache (in an awake patient)
Grossly raised serum CK
Coagulopathy
Cardiac arrest
Key signs and symptoms of Malignant Hyperthermia
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 MH-
susceptible 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
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
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 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 CUse IV saline from the fridgeSurface cooling with ICE bagsConsider 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
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? 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
Referenceshttp://www.anaesthesia.mh.org.au/malignant-hyperthermia/w1/i1001286/
http://www.anaesthesiawa.org/mh.html
www.anzca.edu.au/resources/endorsed-guidelines