June 2008 Case Of The Month

High temperature and rigidity, is it MH?

 

66 y/o woman s/p mitral valve replacement who presented to the ICU with trachea intubated. Her ABG on ICU admission and FIO2 of 50% was: Ph 7.12, PO2 210, PCO2 61, HCO3 21, BE -5 with vital signs stable except for temperature of 38.6°C. Half an hour following ICU admission, the nurse noted that the patient has rigid extremities and the temperature was still elevated despite acetaminophen administration. Patient was still sedated with HR of 115. Family history is negative for MH and this is the first general anesthetic the patient received in her life.

 

1) Do you think this is MH?

A)    Likely

B)     Unlikely

C)    I’m not sure

D)    Need more information

 

2) Based on the above information, will you treat with dantrolene?

            A) Dantrolene is contraindicated in this patient

            B) I will start with 1 mg/kg and titrate to effect

            C) Dantrolene 2.5 mg/kg is indicated immediately

 

3) Following administration of dantrolene (2.5 mg/kg), rigidity and elevated temperature did not improve. Can MH be ruled out?

            A) Certainly yes

            B) Certainly no

            C) Another dose should be administered

 

4) 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

 

5) 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

Answers:

1)      A.

2)      C.

3)      C.

High temperature that is accompanied by rigidity is highly likely to be an MH episode. Although it is very difficult to confirm the diagnosis in this patient, administering dantrolene at 2.5 mg/kg is indicated. Improvement in clinical signs by either improving rigidity or decrease in temperature indicates the likelihood of MH episode. However, if the clinical signs do not improve following dantrolene administration, it still difficult to role out MH.

4)      C.

5)      D.

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 approximately 10 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.

Mohanad Shukry, MD
Children's Hospital of Oklahoma
Oklahoma City, OK