Page 1187 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

824 PART 6: Neurologic Disorders

patients with neuromuscular disease would be intubated and managed hypertension or hypotension, develop in 20% of patients with GBS. 12,22,24
without the use of neuromuscular blockade. However, if neuromuscular Although bowel and bladder function are usually preserved, ileus and
blockade is necessary the following important pharmacologic principles urinary retention can occur.
need to be carefully considered. Succinylcholine should not be used to Variants of the typical GBS presentation may be encountered, includ-
facilitate intubation of patients whose neuromuscular disease involves ing the Miller-Fischer variant, with ataxia, ophthalmoparesis, and
denervation. This would include patients with GBS, multiple scle- areflexia. 12,23,24 Overall, ophthalmoparesis develops in approximately
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rosis, amyotrophic lateral sclerosis, and those with a stroke or spinal 15% of patients. Acute inflammatory demyelinating polyradiculopathy
cord injury more than 24 hours before intubation. In these patients, (AIDP) is the most common presentation in the United States and
an upregulation of fetal-type acetylcholine receptors may result in Europe. However, variants of AIDP are encountered in 10% to 15% of
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life- threatening hyperkalemia after administration of succinylcholine. patients. Primary axonal form of GBS, acute motor axonal neuropathy,
Patients with MG are commonly resistant to succinylcholine secondary and acute sensorimotor axonal neuropathy are more commonly seen in
to a reduction in the number of acetylcholine receptors or functional southeast Asia and Mexico. 24
antibody-induced receptor blockade. In addition, secondary to signifi- For unclear reasons, GBS appears to be more common in young adults
21
cant reduction in functional receptors, patients with MG may be very and in the elderly. A preceding infectious syndrome with respiratory or
sensitive to nondepolarizing agents. Although nondepolarizing neuro- gastrointestinal symptoms, usually occurring 1 to 4 weeks prior to the
21
muscular blocking agents may be used in patients with GBS, an increase onset of neurologic symptoms, has been noted in approximately two-thirds
in sensitivity to these agents has been reported. 21 of patients. 12,23,25 Campylobacter jejuni and cytomegalovirus infections are
Supportive care of critically ill patients with neuromuscular disease the most commonly identified triggers for GBS. In addition, Epstein-Barr
remains a central component of their management strategy in the ICU, virus, varicella virus, HIV, and Mycoplasma pneumoniae infections have
including attention to deep venous thrombosis and stress ulcer prophy- also been associated with the development of GBS. A diverse and seem-
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laxis, nutritional support, and skin care. In addition to speech therapy ingly unrelated group of triggers have been identified, including infections,
22
consultation, early consultation and close follow-up by physical and vaccination (eg, 1976 influenza vaccination), general surgery, epidural
occupational therapists are also recommended. Patients should also be anesthesia, thrombolytic agents, drugs, neoplastic disease (Hodgkin dis-
regularly assessed for pain, dyspnea, anxiety, and depression. Psychiatry ease), sarcoidosis, and connective tissue diseases. 5,12,24 An autoimmune
consultation should be requested when appropriate. Daily communica- mechanism is strongly suspected in the pathogenesis of GBS; however, the
tion with all members of the care team remains essential in optimizing immunopathology has not been fully defined.
clinical outcomes in this challenging patient population. A diagnosis of GBS is based on the clinical presentation and electrodi-
Weaning from mechanical ventilation should be considered only agnostic studies compatible with a demyelinating polyneuropathy. 5,12,23,24
after clear evidence of improvement in general and respiratory muscle- Elevated cerebrospinal fluid (CSF) protein levels are commonly noted
specific weakness has been demonstrated. As muscle strength in patients after the first week of symptoms and is typically accompanied by a
with neuromuscular disorders may fluctuate, a durable improvement in normal cell count or limited mononuclear pleocytosis (<10 cells/cm ).
3
respiratory muscle strength should be confirmed. Prospective studies Pleocytosis in the CSF fluid appears to be more common in patients with
are not available to clearly guide bedside decision making in patients human immunodeficiency virus infection and GBS. Diagnoses other
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with neuromuscular disorders, but improvement in VC to >20 mL/kg than GBS should be more aggressively considered if (1) reflexes remain
and MIP to more negative than −30 cm H O are reasonable thresholds intact despite weakness (areflexia is present in ~90% of patients when
2
to achieve before considering extubation. Measurements of respiratory weakness is fully developed); (2) the distribution of weakness is highly
function (MIP, MEP, and VC) and ultrasound of the diaphragm may asymmetric; (3) fever is present during the initial presentation; or (4) the
be helpful in assessing the patient who exhibits difficulty in weaning electrodiagnostic features are not indicative of an acquired demyelinat-
from mechanical ventilation. Adequate oropharyngeal function is an ing polyneuropathy. A rapidly progressive spinal cord lesion is the most
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important element of successful extubation, and a thorough evaluation important potentially reversible process to be immediately excluded in
of oropharyngeal function should be performed following extubation a patient who presents with ascending weakness. The combination of
1
and prior to resuming oral intake. rapidly developing paralysis and urinary retention is highly suggestive of
Tracheostomy will be necessary in patients whose neuromuscular a compressive spinal cord lesion. Arsenic neurotoxicity may also pres-
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disorder does not improve sufficiently to allow safe extubation. ent with an ascending symmetrical sensorimotor neuropathy similar to
5,22
Timing of tracheostomy must be individualized, but is advisable when GBS and should be considered in the differential diagnosis. 27
prolonged (>2-3 weeks) mechanical ventilation will be required. Studies Respiratory failure occurs at the time of initial presentation in up to
involving patients with GBS and myasthenia gravis have identified cer- 10% of patients, and eventually develops in up to 43% of patients during
tain risk factors for prolonged mechanical ventilation (see below). the course of their disease. 22,24,28,29 All aspects of respiratory muscle func-
tion, including inspiratory strength, expiratory strength, and upper air-
Guillain-Barré Syndrome: Guillain-Barré syndrome is an acute inflamma- way protection may be impaired. Progression to respiratory failure was
tory demyelinating polyneuropathy that most often presents with ascend- predicted in one retrospective study by the presence of a VC <20 mL/kg,
ing symmetrical weakness beginning in the lower extremities. 5,12,23,24 MIP less negative than −30 cm H O, and MEP <40 cm H O (“20/30/40
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In approximately 10% of patients, weakness may be first noted in the rule”). Inability to cough markedly increases the risk for intubation.
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upper extremities or facial muscles. 12,25 Weakness typically evolves over In addition, multivariate analyses have indicated that the period of time
days to weeks, although a subset of patients experience a rapid decline from onset of symptoms to admission of less than 7 days, inability to
in function over hours. Excluding trauma, GBS is the most common stand, and inability to lift the head or elbows are all associated with
cause for acute flaccid paralysis in previously healthy people. The an increased risk for mechanical ventilation. A prospective cohort
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ascending weakness is accompanied by depressed or absent reflexes. study of patients with GBS identified three clinical characteristics
Sensory involvement is common, and the majority of patients experi- after multivariate analysis that were strongly associated with the need
ence peripheral paresthesias as their initial symptom. In addition, an for mechanical ventilation in the first week of hospitalization: rate
aching discomfort in the lower back and legs may also be seen in the of disease progression (days between onset of weakness and hospital
early phase of the syndrome. 24,26 Autonomic dysfunction is common admission); Medical Research Council (MRC) sum score on admission
in patients with GBS, occurring in 70% of patients. 5,22,24 Autonomic (measure of bilateral muscle strength); and presence of facial and/or
dysfunction may result in brady- or tachyarrhythmias, orthostatic bulbar weakness. In this study, 26% of the patients required intubation
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hypotension, hypertension, or abnormal sweating. Life-threatening with MV, with 22% intubated in the first week of their hospital admis-
alterations in autonomic function, including arrhythmias and extreme sion. The risk of intubation is increased by GBS-related dysautonomia,

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