High Temperature in Pediatric Cardiac Patient
A 9 months old male, 7.1 Kg, presented for mitral valve replacement. The patient has been treated since birth with captopril, furosemide, and spironolactone. He was appropriate developmentally without any other abnormality. Family history was negative for MH.
Anesthesia was induced with fentanyl, etomidate and the muscles were paralyzed with atracurium. Anesthesia was maintained with isoflurane. Thirty minutes following incision, esophageal temperature increased to 38.2 °C without elevation in heart rate, end tidal CO2, or potassium. Muscles rigidity or acidosis did not occur. Active warming with forced air was stopped but the temperature stayed elevated.
Cardiopulmonary bypass without inhalation agent was instituted and the patient was actively cooled to 33-34 °C.
1) Do you think this is MH?
A) Likely
B) Unlikely
C) I’m not sure
D) Need more information
2) All of the following trigger an MH episode in susceptible patients Except:
A) Sevoflurane
B) Halothane
C) Succinylcholine
D) Nitrous oxide
Following separation from cardiopulmonary bypass and administration of isoflurane, temperature was elevated again to 42 °C associated with tachycardia and hemodynamic instability requiring vasoactive medications. Urine was clear and PaCO2, potassium, PH, and muscle tone were all within normal limits. Patient has not received platelets. Active cooling with cold saline in the pericardium and with nasogastric lavag was performed.
3) 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
D) Dantrolene is not indicated.
Follow up
Patient was transferred to ICU with vasoactive drugs dobutamine and noradrenaline. Temperature was still high at 39.2 °C. Hyperthermia continued postoperatively for 10 days, with elevated CPK. No apparent source of infection, negative cultures. The patient received broad spectrum antibiotics.
The patient was discharged from ICU on the 15th postoperative day with improvement in general condition.
4) Do you still think this is MH?
A) Likely
B) Unlikely
C) I’m not sure
D) Need more information
5) 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) 3-fold rise in CK following a rapid intraoperative temperature elevation
6) What diseases are associated with MH?
A) King-Denborough Syndrome
B) Minicore myopathy
C) Central Core Disease
D) All of the above
Answers
Narrative:
1) Hyperthermia can be the first presenting sign of malignant hyperthermia. However, other signs of hypermetabolism such as increased ETCO2 and heart rat usually accompany increased temperature. So far, the diagnosis is unclear.
Answer B
2) Halogenated agents and succinylcholine are the only pharmacological triggering agents of MH episode. Nitrous oxide, propofol and narcotics are considered safe.
Answer D
3) When suspicious of MH episode, dantrolene could be a life saver. It is always recommended to start early treatment with dantrolene (2.5 mg/kg) that delaying the treatment waiting for more signs of MH to develop. However, this patient does not show signs of hypermetabolism such as increased in ETCO2. It is common for patients separating from cardiopulmonary bypass to become unstable and require vasoactive support. Other causes of hyperthermia should be ruled out first.
Answer D
4) MH-like reactions can occur in patients with subclinical myopathies. This patient must be referred for neurological evaluation.
Answer B
5) Currently, halothane-caffeine contracture testing is considered the best test with regard to sensitivity and specificity for diagnosing MH susceptibility. However, since only 6 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
6) All three diseases are associated with MH as all of them have defect on the same gene (RYR1) just like MH.
Answer D
Assistant Professor, Anesthesiology
Children’s
Talitha G. Lelis, Anesthesiology Resident, and
Helga C. A. Silva, MD, PhD, Post-Graduation Professor.
CEDHIMA (
Dept. Surgery. Discipline Anaesthesia, Pain and Intensive Care.
UNIFESP (University Federal São Paulo).
