CLINICAL CASES
167
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Figure 18-3. Structure of dantrolene (1-[[[5-(4-nitrophenyl)-2 furanyl]-
methylene]amino]-2, 4 imidazolidinedione).
Treatment of MH depends on cessation of anesthesia, mechanical means
to reduce the temperature, and the correction of blood electrolyte and gas
parameters to normal. In addition, dantrolene (Figure 18-3) is infused initially
intravenously and then may be given orally. Dantrolene brings about the
reduction in contraction of skeletal muscles by decreasing the amount of
Ca2+ released from the sarcoplasmic reticulum. A serious side effect of
dantrolene use is its potential hepatotoxicity. The hepatotoxicity is fatal to 0.1
to 0.2 percent of patients treated for 60 days or longer. Thus, use of dantrolene
for longer than 45 days requires monitoring of hepatic markers.
C O M P R E H E N SIO N Q U E ST IO N S
A young and otherwise healthy student undergoing preparation for a simple sur-
gical procedure was noticed to have an elevating temperature and respiratory
rate with muscle rigidity following the onset of anesthesia using halothane and
succinylcholine. Laboratory findings revealed elevated levels of calcium, hydro-
gen ion, pyruvate, and lactate. The diagnosis was malignant hyperthermia.
[18.1] The muscle rigidity observed in this patient is most likely prompted by
which of the following?
A. The patient’s fear of surgery
B. Increased levels of hydrogen ion, causing the muscles to become
immobile
C. Increased Ca2+ levels in muscle tissue, triggering muscle contraction
D. Increased pyruvate and lactate, causing precipitation of muscle
protein
E. Increased body temperature
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