Extra Topic 1.3 -- Masseter Muscle Spasm

Question 1

What information do you want to know?

(A 14-year-old male with a history of masseter muscle spasm is scheduled for tonsillectomy the following day. You are seeing him in pre-op clinic.)

Answer 1

Along with a complete history and physical examination,

I would wish to know about the circumstances related to the masseter spasm, including –

• the type of anesthesia provided,
• the severity of the spasm,
• how it was treated, and
• the results of any subsequent work up related to the incident.

I would also attempt to determine if there was –

• any family history of anesthetic complications, particularly masseter spasm or malignant hyperthermia.

It may also be helpful to review the anesthetic record or talk with the physician involved in the case.

Question 2

The mother says she has never had surgery and she isn’t aware of her husband or family members experiencing any anesthetic complications.

What type of anesthesia will you provide?

(A 14-year-old male with a history of masseter muscle spasm is scheduled for tonsillectomy the following day. You are seeing him in pre-op clinic.)

Answer 2

Masseter muscle rigidity has been reported after halothane or succinylcholine in children and may indicate susceptibility to malignant hyperthermia (MH).

If no follow up testing were performed to show otherwise, I would proceed under the assumption that the patient is susceptible to MH and provide a non-triggering anesthetic.

Agents known to trigger MH include – succinylcholine and volatile anesthetics.

Therefore, I would provide a total intravenous anesthetic with fentanyl and a propofol infusion.

Question 3

During induction, the first year resident administers succinylcholine before you can stop him.

Now, you are unable to open the patient’s jaw.

What will you do?

(A 14-year-old male with a history of masseter muscle spasm is scheduled for tonsillectomy the following day. You are seeing him in pre-op clinic.)

Answer 3

I would – attempt to ask ventilate with 100% oxygen.

If ventilation were difficult, I would – call for help, place a nasal airway, attempt nasal intubation, and prepare for a possible surgical airway.

After securing the airway, I would – look for pigmenturia, place an arterial line, and monitor end-expired CO2, creatine kinase (CK), acid-base status, and electrolyte levels.

If the trismus was severe and prolonged, I would – cancel the case and admit the patient to the hospital for 12-24 hours of monitoring for myoglobinuria (can lead to acute tubular necrosis and obstructive nephropathy), generalized rigidity (rigidity of the chest and/or extremities increases the risk of progression to MH), and/or signs of hypermetabolism.

I would also – order a neurology (? or nephrology?) consult to evaluate the patient for the presence of occult myopathy, continue to monitor serum electrolytes (rhabdomyolysis can lead to hyperkalemia), temperature, and creatine kinase levels (in the absence of a myopathy, a CK level > 20,000 IU increases the likelihood that the patient is MH susceptible), and recommend testing for MH susceptibility.

UBP Notes –

• if you know the algorithm, continue on (e.g. neonatal resuscitation)
• How would you monitor this patient?
• admit patient and observe for 12-24 hours to make sure he does not develop MH

Question 4

Why would you cancel the case?

(A 14-year-old male with a history of masseter muscle spasm is scheduled for tonsillectomy the following day. You are seeing him in pre-op clinic.)

Answer 4

GREAT DISCUSSION ONLINE UBP

When the succinylcholine-induced trismus is intense and/or prolonged the likelihood of MH susceptibility is as high as 50%.

Therefore, all triggering agents should be discontinued, the case should be cancelled, and the patient should be monitored closely for 12-24 hours.

If the masseter spasm had been less intense and prolonged, I may have continued the case using a non-triggering anesthetic and careful monitoring.

In the case of severe MMR, or mild to moderate MMR with evidence of rhabdomyolysis, I would recommend a Caffeine Halothane Contracture Test (CHCT) to further evaluate the patient for MH susceptibility. (Recommended by MHAUS).

• —*
• Xtra Q –*
• Would you recommend follow-up testing?
• Would you be comfortable providing anesthesia w/ triggering anesthetics if demonstrate negative caffeine halothane contracture test?