Page 1143 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

782 PART 6: Neurologic Disorders

Brain-injured patients may suffer from so-called “hypothalamic seizures.” focal and generalized seizures 57,58 ; epilepsia partialis continua was the
Tetanus patients do not lose consciousness during their spasms, and most common type seen in a recent series. Seizure activity infrequently
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describe excruciating pain associated with the sustained whole-body may be the first presenting sign of diabetes mellitus. Both severe, rapidly
contractions. Psychiatric disturbances in the ICU occasionally resemble developing hyponatremia and hypoglycemia can cause seizures. The
complex partial seizures. If doubt about the nature of abnormal move- patient’s blood glucose concentration should be measured immedi-
ments persists, an EEG should be performed. ately upon presentation, and dextrose and thiamine administered if
hypoglycemia is present. Hypocalcemia rarely causes seizures beyond
the neonatal period; identifying even moderate hypocalcemia must
DIAGNOSTIC APPROACH not signal the end of the diagnostic work-up. Hypomagnesemia has an

The initial approach to seizure management is the same as that for any equally unwarranted reputation as the cause of seizures in malnourished
other acute medical problem: circulation, airway, and breathing. As alcoholic patients.
described above, generalized convulsive status epilepticus often causes In recent years, the importance of autoimmune and paraneoplastic
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apnea and/or poor oxygen saturation. Hypertension and tachycardia disorders has become clearer. Empiric immunologic therapy may be
may be marked. However, respiratory and hemodynamic dysfunction necessary when these conditions are suspected, as diagnosis may require
is transient, and with seizure termination rapidly returns to normal. weeks of specialized testing. 61
Padded tongue blades or similar items should not be placed inside the The physical examination should emphasize assessment for both
mouth; they are more likely to obstruct the airway than to preserve it. global and focal abnormalities of the CNS. Evidence of cardiovascular
Medication to treat tachycardia and hypertension before the seizure disease or systemic infection should be sought and the skin and fundi
activity stops is not warranted. examined closely. Particular attention should be given to the fundu-
When a patient has a seizure, one has a natural tendency to try to stop scopic examination of infants presenting from the community with sei-
the event. This leads to both diagnostic confusion and iatrogenic com- zures, as retinal hemorrhages may be the only evidence of brain trauma
plications. Beyond protecting the patient from harm, very little can be induced by child abuse (the “shaken baby syndrome”).
done rapidly to influence the course of the seizure. The seizures of most New-onset seizures almost always warrant brain imaging. Considering
patients stop before any medication can reach the brain in an effective the large number of critically ill patients with neurologic pathology as a
concentration. Observation is the most important activity to perform primary or contributing cause for seizures, acute brain processes must be
when a patient has a single seizure. This is the time to collect evidence ruled out. Computed tomography (CT) scanning is a rapid modality with
of a partial onset in order to implicate structural brain disease. The which the trained clinician can detect acute blood, swelling, large tumors
postictal examination is similarly valuable; language, motor, sensory, or or abscesses, and subacute or remote ischemic strokes. With current
reflex abnormalities after an apparently generalized seizure are evidence technology, there are exceptionally few patients who cannot undergo CT
of focal pathology. scanning. Magnetic resonance imaging (MRI) is particularly helpful in
Seizures in ICU patients have many potential causes that must be detecting evidence of acute ischemic stroke, encephalitis, small tumors,
investigated. Medical conditions such as hepatic encephalopathy or subdural empyemas, and cerebral edema. Most cardiac pacemakers are
acute hypothyroidism have been associated with seizures, particu- a contraindication to MRI, but many other medical devices, such as
larly nonconvulsive status epilepticus. 44,45 Drugs are a major cause of inferior vena cava filters, intracranial pressure monitors, and cerebral
seizures in critically ill patients, especially in the setting of renal or aneurysm clips, are now manufactured using MRI-compatible material.
hepatic dysfunction. Imipenem-cilastatin and fluoroquinolones have Patients with altered mental status who need cerebrospinal fluid analysis
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the potential to lower the seizure threshold, particularly in patients require imaging of the brain first, to rule out a mass, swelling, or other
with impaired renal function. Similarly, cephalosporins, particularly cause of impending brain herniation. When CNS infection is suspected,
cefepime, have been associated with NCSE, especially in adult patients empiric antibiotic treatment should be started while imaging studies are
with impaired renal function. Theophylline can provoke seizures or SE being obtained.
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if it has been rapidly loaded or if high concentrations of the drug occur; In contrast to the patient with a single or a few seizures, the SE patient
however, these complications can also arise with normal serum drug requires simultaneous diagnostic and therapeutic efforts. Most seizures
levels. Immunosuppressant agents such as cyclosporine or tacrolimus in critically ill patients stop within 2 to 3 minutes. However, if the devel-
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are known culprits for seizures, and as etiology for posterior revers- opment of SE is suspected based on a seizure duration of greater than
ible leucoencephalopathy, which may manifest primarily with seizures, 5 minutes, or absence of recovery in between seizures episodes, one
but status epilepticus seems to arise only rarely. 50,51 Accumulation of should not wait, but rather initiate immediate treatment.
patients with normal renal function. Sevoflurane, a volatile anesthetic ■ THE ELECTROENCEPHALOGRAM
a metabolite of meperidine, normeperidine, causes seizures, even in
agent, also causes electrographic and clinical seizures without a his- Treatment for recognized SE should not be delayed to obtain an EEG,
tory of epilepsy or CNS pathology. Other, less conventional etiologies but such recognition is not always straightforward. A prospective evalu-
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include the use of tranexamic acid in cardiac surgery, which was found ation of 164 patients demonstrated that nearly half manifested persistent
to be associated with postoperative seizures in patients with renal electrographic seizures in the 24 hours after clinical control of convul-
dysfunction. 53 sive SE, and 14% went into electrographic status epilepticus. Therefore,
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Recreational drugs are frequently-overlooked offenders in patients continuous EEG monitoring should be initiated within 1 hour of SE
presenting to the ICU. Acute cocaine or methamphetamine intoxica- onset if ongoing seizures are suspected. Subclinical seizures have been
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tion is characterized by a state of hypersympathetic activity followed by observed during aggressive treatment for SE, even in patients treated
seizures. Ethanol withdrawal is a common cause of seizures between with high-dose barbiturates to produce a burst-suppression pattern on
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6 and 96 hours after the patient’s last drink, but concomitant causes EEG. These data suggest that EEG monitoring after control of convul-
must not be overlooked. Narcotic withdrawal may produce seizures in sive SE can be essential in directing the course of treatment. Emergent
the critically ill and in newborns of opioid-dependent mothers. Both EEG is necessary to exclude NCSE in those patients who do not begin
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bupropion hydrochloride and tricyclic antidepressants are associated to awaken soon after visible seizure activity has stopped. Patients who
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with seizure in overdose and occasionally at therapeutic doses. In the develop refractory SE or receive neuromuscular junction blockade
absence of other clear causes for seizure, a complete toxicology screen require continuous EEG monitoring, since ongoing seizure activity can
should be performed upon admission. cause neuronal injury via excitotoxic mechanisms as outlined above.
Serum glucose, electrolyte concentrations, and serum osmolality A variety of findings may be present in the EEG, depending on
should also be measured. Nonketotic hyperglycemia can precipitate both the seizure type, duration, and level of pharmacologic intervention.

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