Page 1191 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

828 PART 6: Neurologic Disorders

may be confused with the Miller-Fischer variant of GBS (see above). Mitochondria produce adenosine triphosphate (ATP) from oxidative
12
Botulism is not typically accompanied by fever, altered mental status, phosphorylation, a critical element in cell biology. Clues to the pos-
100
or sensory abnormalities. Foodborne botulism should be considered sible presence of this interesting group of disorders in the ICU include
in patients presenting with three or more of the “Dozen Ds” of signs unexplained dyspnea progressing to respiratory failure; sedative-related
and symptoms. 87,88 Botulism in adults is most often foodborne, but respiratory failure out of proportion to the sedative dose administered;
wound-related illness has been increasingly recognized, especially in respiratory failure with persistent unexplained lactic acidosis; prolonged
parenteral “black tar” heroin users. Inhalational botulism due to bio- paralysis following limited use of neuromuscular blockade; unexplained
89
terrorism remains a concern. Early treatment with an antitoxin directed difficulty with weaning from mechanical ventilation; multisystem
against the neurotoxin derived from Clostridium botulinum remains disease with myopathy; and a family history of mitochondrial dis-
the most important therapeutic intervention and appears to reduce ease. 99,100,102 In addition, multisystem disease of unexplained etiology
mortality. Antibiotic therapy with penicillin or metronidazole is also with features of central and/or peripheral nervous system dysfunction,
recommended. Progressive respiratory failure with need for mechani- and retinal abnormalities may suggest the possibility of mitochondrial
cal ventilation occurs in approximately 25% of patients with botulism. disease. Muscle biopsies are usually diagnostic, demonstrating charac-
103
90
In common with other progressive neuromuscular disorders, respira- teristic findings on light and electron microscopy. Care for patients with
tory failure remains the principal cause of mortality in patients with these unique disorders is primarily supportive, including treatment of
botulism. Fortunately, survivors of botulism typically achieve complete precipitating infections and withholding sedatives and neuromuscular
recovery of neuromuscular function. 90 blockers. The use of pharmacologic agents that interfere with the mito-
Tick paralysis affects children more often than adults and is mani- chondrial respiratory chain should be avoided. In addition, patients
100
fested by an ascending paresis or paralysis caused by a tick-borne with mitochondrial disease appear to have an increased sensitivity to
neurotoxin. 91,92 Most cases of tick paralysis have been identified in succinylcholine and nondepolarizing agents. 21
North America and Australia in the spring or early summer. Ascending
paralysis with lack of deep tendon reflexes may result in diagnostic
confusion with GBS. Atypical presentations include unilateral or asym-
metric extremity weakness, and isolated facial or bulbar involvement. 93,94
A high index of clinical suspicion is critical for establishing a diagnosis KEY REFERENCES
of tick paralysis. Treatment of tick paralysis is centered on a very careful • American Thoracic Society/European Respiratory Society. ATS/
physical examination (including scalp, ears, axilla, buttocks, perianal ERS statement on respiratory muscle testing. Am J Respir Crit Care
skin, and labia) to identify and remove all ticks and their body parts, Med. 2002;166:518.
along with close observation and supportive care. Significant improve- • Dalakas MC, Hohlfeld R. Polymyositis and dermatomyositis.
ment in neuromuscular strength usually occurs within several hours of Lancet. 2003;362:971.
tick removal.
Acute drug-induced myopathies may be associated with neuromuscular • Drachman DB. Myasthenia gravis. N Engl J Med. 1994;330:1797.
weakness. Alcohol intoxication and cocaine use have been associated • Elovaara I, Apostolski S, VanDoorn P, et al. EFNS guidelines for
95
with the development of rhabdomyolysis and acute myopathy. 96,97 In addi- the use of intravenous immogulobulin in treatment of neurologi-
tion, their combined use appears to more than summate in the degree of cal diseases. Eur J Neurol. 2008;15:893.
myotoxicity observed. Other potentially myotoxic drugs include statins, • Hughes RAC, Swan AV, Raphael JC, et al. Immunotherapy
nucleoside reverse transciptase inhibitors ( zidovudine), neuroleptic for Guillain-Barre syndrome: a systematic review. Brain. 2007;
malignant syndrome from antipsychotics, malignant hyperthermia from 130:2245.
anesthetic agents or succinylcholine, high-dose corticosteroid therapy,
and therapy with chloroquine or hydroxychloroquine. 95 • Laghi F, Tobin MJ. Disorders of the respiratory muscles. Am J
Respir Crit Care Med. 2003;168:10.
Electrolyte abnormalities must be considered in the differential of
progressive neuromuscular weakness. Marked hypokalemia can lead • Maramatton BV, Wijdicks EFM. Acute neuromuscular weakness
2
to generalized muscle weakness. Most causes of hypokalemia develop in the intensive care unit. Crit Care Med. 2006;34:2835.
gradually and weakness is uncommon at potassium levels above • McCool FD, Tzelepis GE. Dysfunction of the diaphragm. N Eng
2.5 mEq/L. With familial hypokalemic familial periodic paralysis, potas- Med. 2012;366:932.
sium levels fall abruptly and clinical manifestations may be evident at • Naguib M, Flood P, McArdle J, Brenner HR. Advances in neuro-
higher values. Hyperkalemia can also lead to weakness, as can hypo- biology of the neuromuscular junction: implications for the anes-
phosphatemia. Finally, marked elevation in serum magnesium levels thesiologist. Anesthesiology. 2002;96(1):202.
or severe hypocalcemia may impair neuromuscular transmission by
inhibiting the release of acetycholine. • Rezania K, Goldenberg FD, White S. Neuromuscular disorders
Organophosphate toxicity inhibits acetylcholinesterase resulting in and acute respiratory failure: diagnosis and management. Neurol
markedly elevated acetylcholine concentrations in the neuromuscu- Clin. 2012;30:161.
lar junction. Organophosphate toxicity may result from ingestion • Skeie GO, Apostolski S, Evoli A, et al. Guidelines for treatment of
98
(accidental or intentional), skin contact with absorption, or inhalation autoimmune neuromuscular transmission disorders. Eur J Neurol.
(eg, Sarin nerve gas). Patients typically present with both muscarinic 2010;17:893.
(bradycardia, bronchospasm, lacrimation) and nicotinic (hypertension, • Ropper AH. The Guillain-Barré syndrome. N Engl J Med. 1992;
mydriasis, tachycardia, weakness) symptoms. Delirium is also common. 326:1130.
Treatment with atropine targets the muscarinic manifestations, and
pralidoxime (hydrolyzes organophosphate from acetylcholinesterase) • Yuki N, Hartung HP. Guillain-Barré syndrome. N Eng J Med. 2012;
treats both muscarinic and nicotinic manifestations. 366:2294.
Mitochondrial disease may present with diverse manifestations in
the critical care setting, including myopathy with respiratory mus-
cle impairment. 99,100 This rare but increasingly recognized metabolic
myopathy appears to result from acquired mutations of genes coding REFERENCES
for critical proteins in the mitochondrial respiratory chain involv-
ing glycolysis, fatty acid oxidation, or oxidative phosphorylation. 99-101 Complete references available online at www.mhprofessional.com/hall

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