Malignant Hyperthermia Clinical Information

Emergency Management of a Malignant Hyperthermia Reaction

1. Discontinue potent inhalational agents, hyperventilate with 100% oxygen (full oxygen flow)
2. Call for assistance
3. Prepare and administer dantrolene. An initial dose of 2.5mg/kg should be administered. and repeated every 5-10 minutes until ETCO2, tachycardia and temperature start to fall (the latter may lag). There is no limit to a maximum dose. 44mg/kg have been used. The starting dose for children is 2.5mg/kg

Treat life threatening complications

1. Intravenous saline at 4oC – 1 litre/10mins. 4-5 litres can be administered in a young adult. 1 litre reduces mean body temperature approx 0.5oC.
2. Surface cooling – crushed ice most effective. Ice cubes (in bags) applied extensively to exposed surfaces also effective.
3. Peritoneal lavage if temperature reduction is resistant. (1 litre Normal Saline at 4oC with 10 min cycles)
4. Badder lavage for young children only
   Note: gastric lavage, forced air cooling not advised

Acidosis

1. Hyperventilate
2. Sodium bicarbonate 1-2mmol/kg. To a ph of 7.1

Hyperkalaemia

1. Sodium bicarbonate
2. 10 mmol i/v calcium chloride
3. Insulin/glucose (1unit insulin/5gm glucose)

Arrhythmias – usually respond to the treatment of acidosis and hyperkalaemia

1. Lignocaine 1-2mg/kg
2. Amiodarone 2mg/kg
3. Procainamide 7mg/kg (30mg/min)
4. Verapamil – avoid similtaneous administration with dantrolene

Monitoring and further management

1. Observe the patient in an ICU for at least 24hrs. Recrudescence develops in 25% patients and can be associated with mortality.
2. SpO2, ECG, arterial BP monitoring, temperature, ETCO2
3. Measure ABGs, electrolytes, CK, coagulation
4. Maintain urinary output (uo) > 1ml/kg/hr. Mannitol in the dantrolene assists uo

Other

• An infusion of dantrolene (1-2mg/kg/6hrs) is recommended by some units. Other units treat recrudesence with bolus doses (2.5mg/kg)
• Avoid an afterdrop in temperature

Do not waste time in:

• Changing the circuit. Use high flows of 100% oxygen. As an alternative to ventilation use a self-inflating resuscitation bag and separate oxygen source
• Changing the anaesthetic machine – this can be done if necessary after the acute phase. Advisable to remove vaporizer
• Attempting central line placement at the expense of the above measures.

Maintain anaesthesia for completion of the surgical procedure with TIVA
 

• Patients who have survived an MH reaction and/or have a positive in vitro contracture test (IVCT).
• Relatives of such patients.
• Patients with suspected MH reactions.
• Associated muscle disorders, e.g. central core disease.

Pre-operative Preparation:

• Inform Consultant Anaesthetist.
• Discuss options.
• Benzodiazepine premedication.

Operating Theatre:

• Unused theatre 15 minutes (>14 fresh air exchanges/hour).
• Agent-free/’clean machine’ (see technician page).
• Dantrolene available.
• MH trolley (see technician page).

Monitoring:

• ECG
• Temperature/nasal/axillary
• SpO2
• ETCO2
• ABGs checked intraoperatively only if indicated. E.g. unexplained tachycardia

For Neuraxial/Regional Anaesthesia:

• ECG- Temperature (axillary)
• SpO2
• ETCO2 via nasal prongs

Induction/Maintenance/Reversal:

• Thiopentone/Propofol are safe. Ketamine may cause confusing signs
• Suxamethonium and potent inhalation agents are contra-indicated
• Non-depolarising muscle relaxants/narcotics are safe
• Neostigmine is safe (avoid atropine during an MH reaction – tachycardia, reduced temperature loss)
• IV fluids – normal saline

Management Post-operatively:

• Continue monitoring temperature, SpO2, ECG, respiratory rate, PR, BP and ETCO2 (if available)
• Take four measurements of the above over an hour, i.e. each 15 minutes
• ABGs measured only if abnormal intraoperatively, or abnormal signs in recovery
• Monitor in standard recovery area. Safe concentrations of inhalational agents are <5ppm. Not achieved in a well ventilated recovery
• For a regional procedure standard monitoring period – approximately 30 minutes

Inform Anaesthetist if:

• HR > 130 bpm
• SpO2 < 94%
• Temperature >38.5oC
• Base deficit > -6mmol/L
• ETCO2 >55mm Hg

Ward:

• Discharge to the DOSA ward after one hour if the above measurements are stable
• Three groups of measurements at half-hourly intervals, RR, PR, BP, Temperature
• Contact anaesthetist if PR >130bpm and temperature >38.5oC

Discharge:

• Patient can then be discharged home if stable
• Next day contact home/ward to check that there were no complications

Drug Use

• Depolarising muscle relaxants.
• Potent inhalational agents (excludes N2O).
• Long acting cholinergic drugs (Neostigmine is safe).
• Calcium channel antagonists with simultaneous Dantrolene use.

• Ketamine. Signs may be confused with an MH reaction.
• Aminophylline and Theophylline related compounds
• 5 H.T agonists.

• Opioids
• Local anaesthetics
• N2O
• Ecbolics
• Sympathomimetics
• NSAIDs
• Antibiotics 

Susceptibility Check

• As assistants to the anaesthetist, anaesthetic technicians are responsible for the checking of surnames of people having operations the next day, then all names that may be MH related are highlighted. Children have the father and mother's susceptibility checked.
• The anaesthetists are therefore made aware and obtain the necessary family history from the patient.
• MH names are found on a comprehensive computer database which is only accessible by the technicians and anaesthetists at Palmerston North Hospital.
• There is a manual systems still available of extensive family trees in relation to MH as back-up should the computer fail.

Acute Cases:

• Patients who come for acute surgery have their names checked by the Technician on duty and if the name is associated with MH, the Anaesthetist is informed and they check out susceptibility.
• If an association is suspected, and agent free Anaesthetic Machine is available and used.
• With monitoring the appropriate equipment a Trigger free anaesthetic is given.
• People with MH Negative Biopsies are given a normal anaesthetic.

Malignant Hyperthermia Susceptible:

• People who have positive muscle biopsy results have their medical notes labelled and a National Health Index alert is placed on their notes.
• Patients with positive muscle biopsy results are advised to contact their GP to obtain a medic alert bracelet.
• If any assistance is required in regard to Malignant Hyperthermia susceptibility, Contact: Palmerston North Hospital, Operating Theatre on (06) 350-8500 and ask for the Consultant Anaesthetist on call.

• Antenatal
• Specialist referral (anaesthetist/obstetrician). This applies even if the partner is MHS, and not the patient.
• Patient counselled by anaesthetic staff at the same or subsequent antenatal visit. Check family tree, discuss labour management, physical examination.
• Base Hospital management (ideally).
• Labour (Delivery Suite)
• Notify anaesthetic staff immediately patient is in labour or delivery proposed. Consultant Anaesthetist should be informed of any MHS patient in labour or undergoing surgical procedure.
• Preparation of theatre for possible use (anaesthetic technician):
  - unused for 15 minutes
  - vapour free machine available
  - MH trolley available
  - Dantrolene available
• Notify anaesthetic technician if patient in labour or delivery proposed.
• Paediatrician informed.

Management During Labour

• Blood tests - should be taken early in labour (Hb, urea & electrolytes, creatine kinase (CK), calcium).
• Pain relief - epidural early in labour as first option pain relief to minimise stress and activity – helpful for baby.
• Monitoring - pulse / BP hourly temperature (oral / axillary) hourly. If temp >38.5oC - radial line for ABG’s ? - Sp02
• Monitoring - the mother should have continuous CTG monitoring during labour.

Observations - see Table A

• Ranitidine - 150mg orally and repeat 8 hourly
• Fluids - use normal saline or Dextrose / Saline (avoid Hartmans).
• Post-partum maternal observations:
  - after delivery 1 hourly RR, pulse and temperature for 4 hours, then discontinue if satisfactory.
• Creatine Kinase - measure 14-24 hours postpartum
• Transfer - to another unit after 4 hours if required
• Note - Adrenalin containing solutions, syntocinon or ergometrine are not contraindicated.

At Risk Newborn

• Positive partner:
  If the father is positive and the mother is normal, intensive monitoring of the mother is not required. However, the foetus may be susceptible, so foetal monitoring is indicated, and continued after delivery (see below).
• Post-partum:
  All newborn of either a susceptible mother or father are to have vital signs recorded hourly for 4 hours after delivery (pulse, respiratory rate, temperature). Contact the anaesthetist on call if recordings are abnormal. (See table B)

TABLE B Frequency Notify Specialist Anaesthetist
Respiratory rate Hourly >60/min
Pulse Hourly >180 bpm
Temperature Hourly >37.5oC :
Measure SpO2
Measure ABG’s
 

• Notify anaesthetist.
• Operating theatre (see labour protocol for preparation).
• Notify paediatrician.
• Blood tests (FBC, renal profile, CK, Ca++) – not required for a woman whose partner is MHS.
• Dantrolene prophylaxis no longer used.
• Antacid prophylaxis (important for MHS women as risk may be increased without the use of Suxamethonium).
• Elective Caesarean patients receive Ranitidine 150mg orally at 2100 hours the night before, and 150mg orally at 0700 hours on the day of surgery.
• Emergency Caesarean patients receive 150mg orally 12-hourly or 50mg IV 8-hourly during labour, or 50mg IV once decision has been made to perform Caesarean section.
• 30mls Sodium Citrate 0.3 molar is given 10 minutes before surgery.
• IV fluids – Normal saline.

Regional Anaesthetic – Care in Operating Theatre / Recovery:

• Regional Anaesthesia
• Regional anaesthesia (spinal or epidural) is preferred
• Any local anaesthetic may be used
• Adrenalin containing solutions of local anaesthetic are not contraindicated.
• Other sympathomimetics are not contraindicated
• Ephedrine can be safely used if required for hypotension
• For a Woman who is herself at risk of Malignant Hyperthermia
• ECG, Non-invasive Blood Pressure (NIBP), Pulse Oximetry (SaO2) are always measured at Caesarean Section.
• Axillary/oral temperature measurement.
• End Tidal Carbon Dioxide (ETCO2) by nasal prongs is monitored intraoperatively.
• Ecbolics
• Syntocinon is safe, Ergometrine can be used if necessary
• Arterial Blood Gases (ABG’s)
• Taken during Caesarean Section if indicated by:
  - Sustained tachycardia >120 beats/min
  - Rising temperature >38.5oC
• Serial ABG’s indicated (site an arterial line), if abnormal signs/results at any stage, especially Base Deficit >8 mmol/L or temperature >38.5oC.
• Post-Anaesthetic Care Unit (Recovery Ward)
• Remains in Post-anaesthetic Care Unit for standard recovery time after Caesarean Section (monitor temperature, SpO2, NIBP and BP for thirty minutes)

General Anaesthetic – Care in Operating Theatre / Recovery:

• Suxamethonium and all volatile agents must be avoided in all MHS women and partners of MHS men,as these can cross the placenta to the foetus (Suxamethonium crosses the placenta in small quantities).
• There must be careful assessment of the airway and ability to intubate: - Awake oral fibreoptic intubation recommended if any difficulty anticipated.
• Rocuronium 1mg/kg can be given 30 seconds before induction agent to provide rapid intubating conditions:This will last a long time, so ventilation must be possible. Alternatively Atracurium 1mg/kg after induction has slower onset. Remifentanil 4mcg/kg can be used for intubation without any muscle relaxant. It may cause respiratory depression in the neonate, it may cause hypotension and bradycardia in the mother. It will wear off quickly if intubation fails.  
• For Woman who is Herself at Risk of Malignant Hyperthermia- ECG, SpO2, ETCO2, nasal temperature probe is placed for continuous temperature monitoring intraoperatively and for one hour afterwards in Recovery.
• Induction of Anaesthetic -Induction is with Propofol and non-depolarising muscle relaxant/remifentanil as above. Alfentanil and/or Fentanyl may also be used (notify Paediatrician)
• Maintenance of Anaesthetic - Maintenance is with Propofol infusion, Nitrous Oxide, and Opioids.
• Arterial Blood Gases (ABGs) - Taken during Caesarean Section if indicated by: - Sustained tachycardia > 120beats/min -Rising temperature > 38.50C. Serial ABGs indicated (site an arterial line), if abnormal signs/results at any stage, especially base deficit >8mmol/l or temperature >38.50C
• Ebolics - Syntocinon is safe. Ergometrine can be used if necessary
• Reversal - Neostigmine/atropine can be used
• Post-Anaesthetic Care Unit (Recovery Ward)- Observe for one hour with continuous ECG, temperature, SpO2, ETCO2 via nasal prongs, RR, BP (4 measurements over one hour). ABG’s indicated if abnormal signs/results at any stage, especially Base Excess >8mmol/L or temperature >38.50C. Repeat creatine kinase 14-24 hours post-delivery.
• For woman who herself is not at risk of Malignant Hyperthermia- Induction and intubation as above. Maintenance with propofol infusion, nitrous oxide and opioids as above. After delivery of the baby volatile agents can be used in the normal way. No extra monitoring is required after delivery or in the postoperative period.

• Infant -Monitor infant of Malignant Hyperthermia susceptible father or mother hourly for the first four hours following delivery:- Heart rate, Respiratory rate and Temperature.Notify on call Specialist Anaesthetist if there is an increasing trend or abnormal finding in any of the above (temp>37.50C, HR >180 bpm, RR > 60/min).
• MHS mother- Check creatine kinase 14-24 hours after delivery