A Toddler with Undiagnosed Muscle Disease Presenting for Head MRI
15 months old boy with hypotonia presented for head MRI. He has not been able to stand up on his own yet, and a neurologist is studying the possibility of muscle disease. The child’s family history is significant for a cousin with muscular dystrophy. However, problems with anesthesia are not reported in the family.
The mother reported that the patient had one previous anesthetic with some complication. The surgery took place in a rural hospital and the mother described it as “he almost died.” Previous records were unavailable and contacting the anesthesiologist who previously took care of the patient proved to be impossible.
On physical exam the child’s mental development was appropriate, but his muscular tone was weak and he could not stand up on his own. His calves were normal in size without hypertrophy. His other physical exam was unremarkable.
1) Knowing the above history, is this child at risk for MH episode?
A- Yes
B- No
2) Providing an anesthetic to this child, is avoiding halogenated agent necessary?
A- Yes
B- No
3) Providing an anesthetic to this child, is avoiding succinylcholine necessary?
A- Yes
B- No
4) Which of the following diseases is/are associated with MH?
A- King-Denborough Syndrome
B- Minicore myopathy
C- Central Core Disease
D- All of the above
5) Under anesthesia, the most sensitive and useful monitor for the early diagnosis of a hypermetabolic event is:
A- EKG
B- Temperature monitor
C- ETCO2
D- Pulse oximeter
E- Blood pressure monitor
6) What is currently considered to be the “gold standard” for diagnosing MH susceptibility?
A. Molecular genetic testing
B. Halothane-caffeine contracture testing
C. Masseter muscle rigidity with hypercarbia
D. Three fold rise in CK following a rapid intraoperative temperature elevation
7) Caffeine halothane contracture testing is indicated in all the following Except?
A. Clinical history suspicions for malignant hyperthermia
B. A first-degree relative of a patient with documented MH
C. Unexplained muscular rigidity with MH suspicion
D. Sudden cardiac arrest on induction of anesthesia
Narrative and Answers:
1) The child is being studied for a possible muscular dystrophy and has a family history of muscular dystrophy. Muscular dystrophy is not related to MH, although it was thought so in the past. However, the child has a vague history of life threatening complication during his last surgery. Thus he should be treated as MH susceptible (MHS) until proven otherwise.
Answer A
2) When a patient thought of as MHS, then anesthetic gases and succinylcholine should be avoided.
Answer A
3) See answer 2.
Answer A
4) All three diseases are associated with MH. Similar to MH, all of the three muscular diseases have defect on the same gene (RYR1).
Answer D
5) Early rise in ETCO2 is the most sensitive indicator for hypermetabolic state. All other monitors help in detecting MH episode, but they are not as sensitive as ETCO2. Increase in temperature is usually a late sign.
Answer C
6) Currently, halothane-caffeine contracture testing is considered the best test with regard to sensitivity and specificity for diagnosing MH susceptibility. However, since only five centers in North American currently administer the test, for which a fresh muscle specimen is required, the test is not available to most patients with suspected MH susceptibility.
Answer B
7) Currently, the in vitro contracture test (IVCT) is the gold standard for diagnosing MH. However, the IVCT is very expensive, requires a surgical procedure that can only be performed on-site in one of 5 specialized testing centers in the US, and has 97% sensitivity and 78% specificity. Consequently, IVCT is only indicated in patients who have had clinical episodes and (possibly) their immediate family members. Sudden cardiac arrest on induction of general anesthesia is most likely an indication for arrhythmias and not MH.
Answer D
Case Management: The child was brought into the MRI scanner and awake intravenous access was initiated in the right foot. Smooth propofol induction was performed with 1500 mcg/kg bolus followed with infusion of 200 mcg. kg-1. min-1. Oxygen at 1 L/min was administered via nasal cannula with ETCO2 monitoring capabilities. Axillary temperature was monitored continuously. The scanning was uneventful and the child was recovered in the PACU for 45 minutes then discharged home.
Mohanad Shukry, MD
Assistant Professor, Anesthesiology
Children’s Hospital of Oklahoma
Oklahoma University
750 NE 17th St. Suite 200
Oklahoma City, OK 73104
