Title: Scoliosis Surgery Without Triggering Agent
14 y/o boy with CP presented for spinal fusion (T6-L2) under general anesthesia and somatosensory and motor evoked potential monitoring. The boy was diagnosed with MH when he was exposed to GA for tonsillectomy, although the diagnosis was never confirmed with muscle biopsy or contracture test.
Following flushing the anesthesia machine for 20 minutes and disconnecting the gas vaporizers, anesthesia was induced with propofol and tracheal intubation was achieved. Anesthesia was maintained with propofol and sufentanil. Four hours later, ETCO2 was suddenly elevated with loss of motor evoked potential and tachycardia. Blood gas obtained was as follows: PH: 7.05, PCO2: 89 mmHg, PO2: 89 mmHg, HCO3: 18 mEq/dl, BE: -10. Temperature was normal.
1) What is your diagnosis?
A- Definitely MH
B- Probably MH
C- Definitely not MH as triggering agent was not used
D- I’m not sure
2) What action should be taken first?
A- Administer dantrolene 2.5 mg/kg IV
B- Actively cool the patient
C- Continue monitoring
D- Send CPK and liver enzyme
3) 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
4) What diseases are associated with MH?
A- King-Denborough Syndrome
B- Minicore myopathy
C- Central Core Disease
D- All of the above
5) Should dantrolene be administered following the initial dose and for how long?
A- Yes as 1 mg/kg every 6 hours for 24 hours at least
B- Yes, if the symptoms come back
C- No, first dose is usually enough
D- No as dantrolene is a long acting drug (24 hours half life)
Narrative and Answers:
1) Sudden rise in ETCO2 in a patient with previous history of anesthetic complication is MH until proven otherwise, especially if PCO2 does not improve with increasing ventilation. It is clear that stress and surgery may initiate an MH episode in MH susceptible individuals without pharmacological triggering agents.
Answer A
2) Actively cooling the patient and sending blood for blood work (CPK, BUN, Cr, and Liver enzymes) are part of the treatment for an MH episode. However, the first line of therapy is dantrolene @ 2.5 mg/Kg IV. The dose can be repeated at 1 mg/kg. Continue monitoring is always an option, but the early MH is treated the better the results are.
Answer A
3) Early rise in ETCO2 is the most sensitive indicator of a 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
4) All three diseases are associated with MH as all of them have defect on the same gene (RYR1) just like MH.
Answer D
5) Following administering an initial dose of dantrolene with good response, it is always advisable to administer it as 1 mg/kg every 6 hours as MH symptoms may reoccur. The decision is always difficult when the trachea is not intubated as dantrolene cause muscle weakness including respiratory muscles. Clinical judgment is always a key with close observation of the patient in ICU sittings.
Answer A
Assistant Professor, Anesthesiology
Children’s
