Malignant Hyperthermia Crisis

Phase 1 of 6

Recognise the pattern

1. Critical action

   Start treatment as soon as a malignant hyperthermia crisis is suspected.

   Clinical presentation varies; adapt treatment to the findings without waiting for every sign to appear.

Suspect malignant hyperthermia when a pattern of unexplained hypermetabolism develops during or shortly after exposure to a volatile inhalation anaesthetic or succinylcholine. Early findings include rising carbon dioxide production, increased oxygen consumption, mixed acidosis, sweating or mottling, unexplained tachycardia or arrhythmia, unstable arterial pressure, masseter spasm after succinylcholine, or generalised rigidity. Hyperkalaemia, a rapid rise in core temperature, marked creatine kinase or myoglobin elevation, dark urine, severe arrhythmia, cardiac arrest, and disseminated intravascular coagulation are later findings; do not wait for temperature rise before treating a convincing pattern.

For adult and paediatric perioperative patients. Begin the urgent actions concurrently where clinically possible and follow current local emergency procedures, clinical judgement, and specialist advice.

Phase 2 of 6

Act immediately

1. Critical action

   Stop all triggering agents immediately.

2. Critical action

   Hyperventilate with 100% oxygen at high flow.

   Use a minute volume 2–3 times normal.

   Clinical values

   Minute volume relative to normal

   2–3 × baseline

   Inspired oxygen

   100 %

3. Critical action

   Declare an emergency and call for help.

4. Change to non-trigger anaesthesia using total intravenous anaesthesia.

5. Inform the surgeon and ask for the operation to be terminated or postponed.

6. Remove the vaporiser.

   Do not delay treatment to change the breathing circuit or anaesthesia machine.

7. If:Activated-charcoal filters are available.

   Place activated-charcoal filters in both the inspiratory and expiratory limbs.

Phase 3 of 6

Give dantrolene

1. Critical action

   Give dantrolene.

   Dantrolene

   Dose

   2–2.5 mg/kg

   Weight basis

   Actual body weight

   Route

   Intravenous

   Maximum per dose

   300 mg

   Timing and condition

   Give promptly once the crisis is suspected.

2. Critical action

   Repeat the initial dantrolene dose every 10 min, or as often as possible if administration takes longer than 10 min.

   Continue until PaCO2 is below 6 kPa with normal minute ventilation and core temperature is decreasing.

   Clinical values

   Standard repeat interval

   10 min

   If administration takes longer than this, repeat as often as possible

   > 10 min

   PaCO2 target with normal minute ventilation and decreasing core temperature

   < 6 kPa

3. Arrange additional dantrolene supply without interrupting treatment.

   A total supply of 1200 mg may be needed to treat an adult; this is an availability warning, not a dose target.

   Clinical values

   Possible total adult supply need

   1,200 mg

   Population: Adult

4. Reconsider differential diagnoses when the total dose reaches 10 mg/kg.

   The 10 mg/kg reference is not a hard maximum and may need to be exceeded when the clinical response still supports malignant hyperthermia.

   Clinical values

   Reassessment reference; may need to be exceeded

   ≥ 10 mg/kg

Phase 4 of 6

Monitor and investigate

1. Continue routine anaesthetic monitoring.

   Continue oxygen saturation, electrocardiography, non-invasive blood pressure, and end-tidal carbon dioxide monitoring.

2. Monitor core temperature continuously.

3. Establish reliable intravenous access with wide-bore cannulas.

4. Insert an arterial line and a urinary catheter.

5. Consider central venous access.

6. Check arterial blood gases, potassium, creatine kinase, myoglobin, and glucose frequently.

7. Check renal function, hepatic function, and coagulation.

8. Check for signs of compartment syndrome.

Phase 5 of 6

Treat secondary features

1. If:An adult patient has hyperthermia.

   Give 2000–3000 mL of crystalloid chilled to 4–8 °C intravenously.

   Clinical values

   Adult chilled-crystalloid volume

   2,000–3,000 mL

   Population: Adult

   Adult crystalloid temperature

   4–8 °C

   Population: Adult

2. If:A paediatric patient has hyperthermia.

   Give chilled saline intravenously; maximum volume 50–60 mL/kg.

   Clinical values

   Paediatric maximum chilled-fluid volume

   50–60 mL/kg

   Population: Paediatric

3. If:The patient has hyperthermia.

   Use surface cooling or another available cooling device.

4. Stop cooling once core temperature is below 38.5 °C.

   Clinical values

   Stop cooling below this core temperature

   < 38.5 °C

5. If:Hyperkalaemia is present.

   Treat hyperkalaemia using the current local emergency protocol.

   EMHG options include intravenous insulin with dextrose, intravenous calcium chloride or calcium gluconate when calcium chloride is unavailable, a beta-2 agonist, and dialysis. No dose is specified here.

6. If:Acidosis is present.

   Treat acidosis and ventilate to normocapnia.

   Give intravenous sodium bicarbonate or another buffer when pH is below 7.2; use the current local protocol for agent selection and dosing.

   Clinical values

   Give intravenous buffer below this pH

   < 7.2

7. If:An arrhythmia or persistent tachycardia is present.

   Treat arrhythmias using the current local emergency protocol.

   EMHG options include amiodarone or magnesium, and a beta-adrenergic blocker if tachycardia persists. No dose is specified here.

8. If:Urine output requires support.

   Monitor urine output closely and support it when clinically indicated.

   Depending on the clinical situation, use crystalloid or furosemide according to the current local protocol.

Phase 6 of 6

Continue post-crisis care

1. Monitor the patient for a minimum of 24 h.

   Continue monitoring in critical care or a recovery unit.

   Clinical values

   Minimum observation duration

   ≥ 24 hours

2. If:Signs of malignant hyperthermia recur.

   Give dantrolene for recurrence.

   Dantrolene

   Dose

   2–2.5 mg/kg

   Weight basis

   Actual body weight

   Route

   Intravenous

   Maximum per dose

   300 mg

   Timing and condition

   Every 10 min until the recurrent signs regress.

3. Consult a malignant hyperthermia investigation unit and arrange specialist referral.

   Refer patients suspected of malignant hyperthermia susceptibility to a designated laboratory for diagnostic confirmation.