The Journal of the Arkansas Medical Society Med Journal Aug 2019 Final 2 | Page 18
Malignant Hyperthermia: When You Least Expect It
Benjamin K. Woodle, MD; Daniel Bingham, MD;
Tolga Suvar, MD; Jill Ramsey, MD; Alvin Stewart, MD
Background
M
alignant hyperthermia (MH) is
a rare genetic condition that
predisposes 1:15,000 pediatric
patients and 1:40,000 adult patients
to a hyper-metabolic state resulting in
abnormal muscle contraction predominant
after exposure to an offending agent such
as volatile anesthetics or succinylcholine.
Other manifestations of MH include rising
EtCO 2 , acidosis, hyperkalemia, rhabdomyolysis,
myoglobinuria (“Coca-Cola colored urine”), and
hyperpyrexia. Onset of symptoms vary, from
immediate to several hours after exposure.
Early efforts attempting to determine the
mechanisms of MH focused on the gene for
the ryanodine (Ryr1) receptor. This particular
receptor is an ion channel responsible for calcium
release from the sarcoplasmic reticulum, and it
plays an important role in muscle depolarization.
Subsequent genetic studies in humans have
revealed at least five different chromosomes and
more than 180 individual mutations associated
with MH. Most patients with an episode of MH have
an indicative family history that includes a relative
who has an “anesthetic allergy” or possible death
resulting from a reaction to anesthesia. Thus, a
pre-op evaluation consisting of a family history
There are not many side
effects to treating MH with
dantrolene; whereas, the
end result of not treating MH
promptly is death.
of anesthetic complications is always important
prior to surgery. With high clinical suspicion, a
proper diagnosis can be made with a muscle
biopsy and a halothane-caffeine contracture test.
In many of the early reported cases, both
succinylcholine and a halogenated anesthetic
agent were used. Of note, and interestingly,
nearly 50% of patients who experience an epi-
sode of MH have had at least one previous un-
eventful exposure to anesthesia, during which
they received a recognized triggering agent. MH
is most commonly triggered by inhaled, haloge-
nated volatile anesthetics such as sevoflurane,
isoflurane, desflurane, and halothane; but it can
also be triggered by the depolarizing muscle re-
laxant succinylcholine. A halogenated anesthetic
agent alone may trigger an episode of MH; how-
ever, the prevalence of MH with exposure to suc-
cinylcholine only, has been controversial. There
has been doubt that succinylcholine, alone,
causes MH crisis in susceptible individuals. 1,2
However, data from the MH registry and new
data from the Canadian MH experience show
that MH crisis can be induced by succinylcholine
administration alone. 3-5
Case Report
A 20-year-old Caucasian male, with an un-
known past medical history, was a restrained
driver involved in a MVC. Upon EMS arrival, his
GCS was 5, interosseous access was obtained,
and the patient was intubated with succinylcho-
line and ketamine for airway protection at the
scene. A level-one trauma was activated, and
the patient was transported to the trauma center
via med flight. On arrival to the trauma bay, vital
signs were GCS 6T, HR 163, BP 70/32, sp02 99%
and EtCO2 45, with no obvious injuries on pri-
42 • THE JOURNAL OF THE ARKANSAS MEDICAL SOCIETY
mary or secondary survey. Vital signs were Temp
40.8C, HR 130, BP 144/34, spO2 100, etCO2 53.
iSTAT showed a pH of 7.30, PCO2 28, and HCO3
of 14.3. The patient was given 650mg Tylenol
via NG tube and started on Propofol and fentanyl
for sedation. A CT scan was then obtained and
showed no intracranial or intraabdominal injury
and was only significant for a transverse fracture
of L1 vertebrae. Patient was taken back to the
trauma bay, where a Foley catheter was inserted
revealing dark urine. The patient’s temperature
continued to rise to 41.3C. The first set of labs
returned and were significant for potassium of
6.0, Cr 2.2, Lactate 6.0, CK 1688, and tropo-
nin 2.99. ABG 7.06/58/92/16.8 on (SIMV 90%
600/20/11). A cooling blanket was placed over
the intubated patient, with ice packs placed
around his head and extremities; cold intrave-
nous fluids were started. The patient continued
to have hypercarbia, with EtCO2 peak at 100.
The decision was made to initiate dantrolene
therapy for suspected malignant hyperthermia.
The patient received a total of four doses of dan-
trolene, dosed at 2.5mg/kg, with improvement
in both temperature and etCO2. The patient was
transferred to the ICU, where dantrolene admin-
istration was continued at 1mg/kg/hr. The pa-
tient later developed multi-system organ failure
due to rhabdomyolysis and severe acidosis. The
family elected to make the patient DNR, and he
was pronounced shortly thereafter.
Discussion
Attributing to the rarity of malignant hyper-
thermia, most health care providers do not have
a high clinical suspicion to make this diagnosis.
However, in the presence of an offending agent
such as succinylcholine and/or halogenated-vol-
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