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Sudden deterioration in neurologic status


Patients admitted to the intensive care unit (ICU) with critical illness or injury are at risk for neurologic complications. A sudden or unexpected change in the neurologic condition of a critically ill patient often heralds a complication that may cause direct injury to the central nervous system (CNS). Alternatively, such changes may simply be neurologic manifestations of the underlying critical illness or treatment that necessitated ICU admission (e.g., sepsis). These complications can occur in patients admitted to the ICU without neurologic disease and in those admitted for management of primary CNS problems (e.g., stroke). Neurologic complications can also occur as a result of invasive procedures and therapeutic interventions. Commonly, recognition of neurologic complications is delayed or missed entirely because therapeutic interventions such as intubation and sedatives interfere with the physical examination or otherwise confound the clinical picture. In other cases, neurologic complications are not recognized because of a lack of sensitive methods to detect the problem (e.g., delirium). Morbidity and mortality are increased among patients who develop neurologic complications; therefore the intensivist must be vigilant in evaluating all critically ill patients for changes in neurologic status.

As the complexity of ICU care has increased over the course of time, so has the risk of neurologic complications. In studies of medical and surgical ICU patients, the incidence of neurologic complications has ranged from 12.3% to 54% , and is associated with increased morbidity, mortality, and ICU length of stay.

Sepsis is the most common clinical problem associated with development of neurologic complications (sepsis-associated encephalopathy). In addition to encephalopathy, other common neurologic complications include seizures and stroke. Neuromuscular disorders are now recognized as a major source of morbidity in severely ill patients. Recognized neurologic complications occurring in selected medical, surgical, and neurologic ICU populations are shown in Table 1.1 .

TABLE 1.1
Neurologic Complications in Selected Specialty Populations
Medical
Bone marrow transplantation , CNS infection, stroke, subdural hematoma, brainstem ischemia, hyperammonemia, Wernicke encephalopathy
Cancer , Stroke, intracranial hemorrhage, CNS infection, neurotoxicity from chimeric antigen receptor T-cell therapy (CAR T-cell)
Fulminant hepatic failure Encephalopathy, coma, brain edema, increased ICP
HIV/AIDS , Opportunistic CNS infection, stroke, vasculitis, delirium, seizures, progressive multifocal leukoencephalopathy
Pregnancy , Seizures, ischemic stroke, cerebral vasospasm, intracranial hemorrhage, cerebral venous thrombosis, hypertensive encephalopathy, pituitary apoplexy
Surgical
Cardiac surgery , Stroke, delirium, brachial plexus injury, phrenic nerve injury
Vascular surgery ,
Carotid Stroke, cranial nerve injuries (recurrent laryngeal, glossopharyngeal, hypoglossal, facial), seizures
Aortic Stroke, paraplegia
Peripheral Delirium
Transplantation ,
Heart Stroke
Liver Encephalopathy, seizures, opportunistic CNS infection, intracranial hemorrhage, Guillain-Barré syndrome, central pontine myelinolysis
Renal Stroke, opportunistic CNS infection, femoral neuropathy
Urologic surgery (TURP) Seizures and coma (hyponatremia)
Otolaryngologic surgery , Recurrent laryngeal nerve injury, stroke, delirium
Orthopedic surgery
Spine Myelopathy, radiculopathy, epidural abscess, meningitis
Knee and hip replacement Delirium (fat embolism)
Long-bone fracture/nailing Delirium (fat embolism)
Neurologic
Stroke Stroke progression or extension, reocclusion after thrombolysis, bleeding, seizures, delirium, brain edema, herniation
Intracranial surgery Bleeding, edema, seizures, CNS infection
Subarachnoid hemorrhage , Rebleeding, vasospasm, hydrocephalus, seizures
Traumatic brain injury Intracranial hypertension, bleeding, seizures, stroke (cerebrovascular injury), CNS infection
Cervical spinal cord injury Ascension of injury, stroke (vertebral artery injury)
CNS, Central nervous system; HIV/AIDS, human immunodeficiency virus/acquired immunodeficiency syndrome; ICP, intracranial pressure; TURP, transurethral prostatic resection.

Impairment in consciousness

Global changes in CNS function, best described in terms of impairment in consciousness, are generally referred to as encephalopathy or altered mental status . An acute change in the level of consciousness, undoubtedly, is the most common neurologic complication that occurs after ICU admission. Consciousness is defined as a state of awareness (arousal or wakefulness) and the ability to respond appropriately to changes in environment. For consciousness to be impaired, global hemispheric dysfunction or dysfunction of the brainstem reticular activating system must be present. The degree of impairment in consciousness may range from a sleeplike state (coma) to states characterized primarily by confusion and agitation (delirium). States and descriptions of acutely altered consciousness are listed in Table 1.2 .

TABLE 1.2
States of Acutely Altered Consciousness
State Description
Coma Closed eyes, sleeplike state with no response to external stimuli (pain)
Stupor Responsive only to vigorous or painful stimuli
Lethargy Drowsy, arouses easily and appropriately to stimuli
Delirium Acute state of confusion with or without behavioral disturbance
Catatonia Eyes open, unblinking, unresponsive

When an acute change in consciousness is observed, the patient should be evaluated in the clinical context with consideration of the age, presence or absence of coexisting organ system dysfunction, metabolic status, medications, and presence or absence of infection. In patients with a primary CNS disorder, deterioration in the level of consciousness frequently represents the development of brain edema, increasing intracranial pressure, new or worsening intracranial hemorrhage, hydrocephalus, CNS infection, or cerebral vasospasm. In patients without a primary CNS diagnosis, an acute change in consciousness is often the result of the development of infectious complications (i.e., sepsis-associated encephalopathy), drug toxicities, or the development or exacerbation of organ system failure. Nonconvulsive status epilepticus (NCSE) is increasingly being recognized as a cause of impaired consciousness in critically ill patients ( Box 1.1 ).

BOX 1.1
CNS, Central nervous system.
General Causes of Acutely Impaired Consciousness in the Critically Ill

Infection

  • Sepsis encephalopathy

  • CNS infection

Drugs

  • Narcotics

  • Benzodiazepines

  • Anticholinergics

  • Anticonvulsants

  • Tricyclic antidepressants

  • Selective serotonin uptake inhibitors

  • Phenothiazines

  • Steroids

  • Immunosuppressants (cyclosporine, FK506, OKT3)

  • Anesthetics

Electrolyte and acid-base disturbances

  • Hyponatremia

  • Hypernatremia

  • Hypercalcemia

  • Hypermagnesemia

  • Severe acidemia and alkalemia

Organ system failure

  • Shock (if severe)

  • Renal failure

  • Hepatic failure

  • Pancreatitis

  • Respiratory failure (hypoxia, hypercapnia)

Endocrine disorders

  • Hypoglycemia

  • Hyperglycemia

  • Hypothyroidism

  • Hyperthyroidism

  • Pituitary apoplexy

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