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Revisions

February 2019 changes from October 2018

• the only change from 2018 is an update to the international MH Hotline Number

October 2018 changes from February 2015

*Other revisions, additions, or deletions were made but may not be noted below*

DIAGNOSIS

Signs of MH

•  Increasing  ETCO2 despite increasing (e.g. doubling) minute ventilation
•  Brown or cola colored urine (myoglobinuria)

Trismus or Masseter Spasm with Succinylcholine

• Check CK immediately and at 6-8 hour intervals until trending downward
• Measure CK at 6-8 hour intervals until trending downward
• Usually secondary to occult myopathy (e.g., muscular dystrophy)

 

ACUTE PHASE TREATMENT

Get Help. Get Dantrolene. Notify Surgeon. Call MH Hotline

• When you want urgent help managing the MH episode. Even if you’ve successfully treated the initial episode, we recommend speaking with a Hotline consultant regarding post-episode patient care and follow-up.
•   Hyperventilate with 100% oxygen with fresh gas flows at least 10L/min to flush volatile anesthetics and lower ET CO2.  If available, insert activated charcoal filters into the inspiratory and expiratory limbs of the breathing circuit.  If continuing to use the same anesthesia workstation, the activated charcoal filters should be replaced every hour.

 

Dantrium/Revonto/Ryanodex

•   Repeat until signs of MH are reversed. ETCO2 should significantly decrease, temperature should stop increasing and rigidity, if present, should resolve.
•  Sometimes more than 10 mg/kg (up to 30 mg/kg) of dantrolene is necessary. MH episodes that are promptly diagnosed and treated typically do not require dose of  dantrolene >10 mg/kg.

Cool the Patient

• Infuse cold or cool 0.9% saline (or Plasmalyte A) intravenously
•   Dysrhythmias
• EXCEPT avoid calcium channel blockers – may cause hyperkalemia or cardiac arrest in the presence of dantrolene. Do not withhold dantrolene therapy in patients on pre-anesthetic oral diltiazem,verapamil or dihydropyridine calcium channel blockers (e.g., nifedipine).
•  Avoid lidocaine or procainamide in hyperkalemic patients.

POST-ACUTE PHASE

(A)

• Increasing muscular rigidity in the absence of shivering or inadequate sedation. Can occur even with complete paralysis with conventional paralytics (e.g., vecuronium, cisatracurium)

 (D)

• Follow and maintain normal urine volume, check for urine myoglobin. If present, institute therapy to prevent myoglobinuric

• Renal failure. Follow standard intensive care therapy for acute rhabdomyolysis and myoglobinuria including hydration and diuretics (urine output >2 mL/kg/hr). Renal replacement therapy (CRRT) should be considered if conservative therapy of AKI fails.

• Counsel the patient and family regarding MH and further precautions; refer them to MHAUS. Fill out and send in the Adverse Metabolic or Muscular Reaction to Anesthesia (AMRA) form to the North American MH Registry of MHAUS (http://anest.ufl.edu/namhr/namhr-report-forms/) and send a letter to the patient and her/his physician. Refer patient to the North American MH Registry of MHAUS and the nearest MH Diagnostic Center (https://www.mhaus.org/testing/genetic- testing/genetic-testing-centers/) for follow-up .