December 2006 Case of the Month

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Topic: A pulmonary problem that mimics MH.

An otherwise healthy, 90 kg five-feet-five inches tall woman was scheduled for breast reduction surgery. Anesthesia was induced with propofol and rocuronium and maintained with sevoflurane. One hour into the procedure with Fi 02 of 0.5 the Oxygen saturation dropped from 98% to 80%, without changes in BP or heart rate. The desaturation lasted a few moments and was corrected with hyperventilation and 100% Oxygen. Shortly thereafter it was noted that the patient’s ET CO2 was 60 despite adequate minute ventilation and bilateral breath sounds. Her temperature rose to 103 F and her heart rate was 120pbm.

The clinicians administered dantrolene 2.5mg/kg and cooled the patient until the temperature normalized. The procedure was not yet completed.

1. Would you advise the surgeons to stop?

a. Yes
b. No

2. Would you switch to non-trigger agents?

a. Yes
b. No

On 30% 02 in the PACU, the ABG was pH 7.39, pC02 37 and p02 132.

3. Would you extubate the patient?

a. Yes
b. No

4. What tests would you order at this time?

a. CK every 8 hours
b.  urine myoglobin
c.  electrolytes
d.  coagulation profile
e.  a chest X-ray
f. All of the above
g. A, B, C, and D

At 48 hours, the CK was 400 with the patient in ICU and still being ventilated. At 72 hours, the CK was 1165. A chest X-ray was normal.

5. What advice would you give regarding the dantrolene?

a. Discontinue
b. Continue

Ten hours later, the patient was awake and extubated, no complaints of weakness. Her temperature was 99.7 F and pC02 was 52 (patient had received narcotics for pain). However, her CK was now 1400.

6. Are these changes characteristic of MHS? What would you do?

a. Restart dantrolene
b. Would not restart dantrolene because the risk is high

Over the next day, CK stabilized and started trending down. Patient still in ICU.

7. What other test would you order, if any?

a. No additional tests needed
b. CT scan

Answers

1. b. Although all the signs are not characteristic of MH (i.e. the drop in saturation) because of the unexplained elevated pC02 and temperature, it was appropriate to administer dantrolene. Since this was not an emergency, the advice was to complete the surgery as rapidly as possible and, if necessary, complete the procedure at a later date.
Of course, the clinicians should assure themselves that there was no machine malfunction to explain the changes (i.e. ventilator malfunction, exhausted sodalyme, stuck valves).

2. a. During the completion of the procedure, the inhalation agent should be discontinued and the anesthesia switched to non-trigger agents.

3. b. Following an acute episode of MH, the patient should remain intubated for a period of time until the clinicians are assured that ABGs and vital signs are stable and there is no evidence of muscle weakness, myoglobinuria or DIC. This may be as soon as two hours or as long as 12 hours.

4. f. If CK is grossly elevated, liver function tests as well. In this case, a chest X-ray is in order.

5. a. Since the CK was not dramatically altered and the patient was stable, the dantrolene may be discontinued.

6. a. In general, CK levels decline after treatment with dantrolene, certainly after 36-48 hours of dantrolene. Temperature elevation has many causes and may not be related to MH. However, since the changes may be read as consistent with recrudescence of MH and since the risk of administering dantrolene is low, the consultant advised restarting dantrolene.

7. b. Because of the persistent elevation of CK and the brief period of hypoxia, a CT scan was done and revealed that the patient had sustained a pulmonary embolus.

Narrative

In retrospect, problems with Oxygenation are not common during an MH episode, except perhaps in the most fulminant cases, and should have alerted the clinicians and consultant to search for evidence of PE earlier especially since the patient’s Oxygenation was not normal despite supplemental Oxygen in the PACU.

As mentioned, the rising CK levels are not characteristic of MH.

The patient did not have a CT scan earlier in her course because the clinicians were concerned about moving this rather obese, intubated, ill patient.

The patient did well, however.

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Henry Rosenberg, MD, CPE
Director, Department of Medical Education and Clinical Research
Saint Barnabas Medical Center
94 Old Short Hills Road
Livingston, NJ 07039
Professor of Anesthesiology
Mount Sinai School of Medicine