MALIGNANT HYPERTHERMIA A brief History of Malignant Hyperthermia

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 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.

Key signs and symptoms of Malignant Hyperthermia EARLY DEVELOPING LATE Prolonged masseter spasm after suxamethonium Rapid rise in temperature (0. 5 o. C 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 Sp. O 2 or mottling of skin Generalised muscular rigidity

Preparation for a known or suspected MH-Susceptible Patient Remover vaporisers and turn the oxygen to 10 L 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 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 4 mcg/ml or 30 -50 mls/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. 5 mg/kg IV initial bolus and repeat as necessary (same dosing adult and peads) Mix each amp with 60 ml 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. 5 mmol/kg IV as required to maintain p. H>7. 2 Treat arrhythmias Lignocaine 1 -2 mg/kg Amiodarone 2 -3 mg/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 2 mls/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 3 way 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/w 1/i 1001286/ http: //www. anaesthesiawa. org/mh. html www. anzca. edu. au/resources/endorsedguidelines