Malignant Hyperthermia - 11
MMR is part of a spectrum of responses to intravenous succinylcholine.
Masseter Muscle Rigidity (Spasm) (MMR, MMS)
- Some slight, subclinical increase in masseter muscle tone may be normal.
- Jaw stiffness that interferes with mouth opening for direct laryngoscopy and orotracheal intubation occurs in about 2% of children. This may include an unknown number at risk for MH.
- "True MMR" occurs when "jaws of steel" make mouth opening impossible. This is relatively rare. In one series of children referred for biospy, 50% proved to be MHS.
- not enough time
- not enough succinylcholine (use a peripheral nerve stimulator to test for block)
- temporomandibular joint dysfunction (Could patient open mouth before induction?)
- amyotonic myotonia
If succinylcholine has caused marked MMR, then
- patient may be MHS
- consideration should be given to canceling an elective case
- emergent case may be continued with nontriggering agents (patient may require flexible fiberoptic nasotracheal intubation)
- observe closely for (additional) signs of MH
- be prepared to treat with dantrolene
- extend postoperative observation period
- consider referral for muscle biopsy after discussion with family