January 2007 Case of the Month

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Topic: Is this MH or do common things occur commonly?

A 4-year-old child is scheduled for a redo Nissen fundoplication due to GERD and recurrent aspiration pneumonia. He has a history of a meningomyelocoele and Chiari malformation, which necessitated a VP shunt. He also has a history of tracheomalacia and is status post tracheostomy. He has multiple inhalational anesthetics without problems. Family history is unremarkable for neuromuscular diseases, high temperatures or rhabdomyolysis. Meds include antibiotics, antacids and ranitidine.

Child had an inhalation induction. After 2 hours there is a sudden increase in temp (39.6 C), ETCO2 (54), HR (140). Surgeon is pushing on abdomen and retracting on chest and abdomen causing decreased compliance and making ventilation difficult. Inhalational anesthetic D/C’ed and passive cooling started. Surgeon stops pushing on the chest. Ventilation improves. T resolves. ABG at this time ph 7.3 pCO2 38 HCO3 18.

Transported to ICU where ABG nl, T normal, lytes nl. LFTs elevated. CK max 700. CXRay nl. After several days LFTs normalize.

1. Is this MH?

A. Yes
B. No
C. Maybe

2. Should Dantrolene have been given?

A. Yes
B. No

3. Are ABGs consistent with MH?

A. Yes
B. No
C. Maybe

4. What is differential diagnosis?

A. MH
B. Aspiration
C. Infection
D. Overheating of patient
E. Inaccurate T monitoring

5. Is the amount and speed of increase T and CO2 consistent with MH?

A. Yes
B. No

6. Are the LFTs most likely due to MH in this patient?

A. Yes
B. No

7. Further work up (ms Bx, genetic testing)?

A. Yes
B. No
C. Maybe

Answers and Narrative

1. B. This child has many reasons for an increased T and CO2 without immediately thinking it is MH. Aspiration is very common in these patients even if the CXR is normal. The CO2 is probably due to retraction.

2. B. This child quickly improved without treatment. Careful monitoring of ABGs, T, and muscle rigidity can guide treatment in this case.

3. B. A sudden rise in temp from any cause will result in an increase in basal metabolic rate, which will increase CO2 production (10% per degree centigrade). Thus, a temp of 39.6 from infection would cause a 25% rise in CO2 production, which would cause a moderate rise in arterial CO2 similar to what was seen in this patient. MH is a hypermetabolic state of skeletal muscle where CO2 production dramatically increases. The increase should be greater then what one would expect from other causes of fever. If skeletal muscle hypermetabolism was driving this temperature to increase quickly, then one would expect a much higher CO2, unless minute ventilation was changed. The relatively slight elevation in CO2 is more consistent with a fever from other origins. Further, MH does not cause a change in pulmonary compliance. The child’s difficulty ventilating was probably due to surgical retraction on the abdomen and lungs.

4. C. Most probably infection, but all other diagnoses must be reviewed.

5. B. See #3 for details.

6. B. Although LFTs can increase in severe MH episodes, in this case liver retraction probably is at fault.

7. B. Muscle biopsy in patients with underlying neuromuscular disease is very difficult to interpret since our normal values are based on otherwise healthy patients. Although genetic testing could be done, this child’s clinical course is not MH and the chances of finding one of the 15 abnormal MH genes is no greater then anyone else in the normal population.

In this case, it seems the diagnosis of MH was appropriate to entertain at the time of the problem; but, in retrospect, this was due to other factors (surgeon pushing on abdomen, excessive covers, drugs reaction or infection causing increased temperature.

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Richard F. Kaplan, MD
Professor and Chief
Division of Anesthesiology and Pain Medicine
Children's National Medical Center
111 Michigan Ave N.W.
Washington, DC 20010
Tele: 202-884-2025
Fax: 202-884-4922 or 202-884-5999