Pediatric emergency medicine trisk 2645 2645
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organism from the bowel or result in clinical improvement. Aminoglycosides,
which can cause neuromuscular blockade, should be avoided.
Periodic Paralysis
Familial periodic paralysis is a rare illness, inherited in an autosomal-dominant
fashion, which results in episodes of severe weakness associated with an
abnormality of circulating potassium during attacks. Two major forms of illness
—hyperkalemic and hypokalemic—are recognized. A third type, normokalemic,
has been described but most likely represents a rare variant of the hyperkalemic
variety. Other disorders that can produce weakness and electrolyte abnormalities,
such as use of corticosteroids or diuretics, thyrotoxicosis, hyperaldosteronism,
and renal insufficiency, may mimic the periodic paralyses. The serum potassium
abnormalities in familial periodic paralysis are believed to be epiphenomena of
yet undelineated muscle membrane abnormalities.
Characteristically, a previously well patient develops a flaccid weakness in his
or her trunk and upper thighs, and the weakness gradually involves the remainder
of the skeletal muscles. Deep tendon reflexes are diminished. The attacks last
from hours to days, and between the attacks, muscular strength is usually normal,
although a minority of patients have residual muscular weakness. In both forms
of periodic paralysis, ECG changes consistent with the serum potassium
abnormality may be noted and cardiac arrhythmias may rarely arise.
Hypokalemic periodic paralysis, the most common type, occurs primarily in
adolescents and young adults. Trigger factors include vigorous exercise, heavy
carbohydrate meals, alcohol, and the cold. During an attack, potassium levels are
usually 2 to 2.5 mEq/L. Emergency treatment of hypokalemic periodic paralysis
includes oral, or rarely IV, potassium. Prophylactically, patients should avoid
precipitants such as vigorous exercise or large carbohydrate loads. Recurrences
may be prevented with spironolactone or acetazolamide.
The hyperkalemic form usually begins in the first decade of life, and attacks
occur predominantly during the period of rest after vigorous exercise or after
fasting. Attacks are typically associated with myotonia. The episodes are more
common than in hypokalemic paralysis but often last less than a few hours.
During the attack, plasma potassium level can be moderately elevated, although it
is often in the upper normal range. Attacks of hyperkalemic periodic paralysis are
often brief enough that acute treatment is unnecessary. In severe attacks, inhaled
albuterol and IV calcium gluconate may be helpful. Acetazolamide, thiazide
diuretics, and albuterol have been used for prevention of recurrences.
