Evaluation of coma and brain death

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Abstract

Coma is a nonspecific sign of widespread central nervous system impairment resulting from various metabolic and structural etiologies. The rapid recognition of this neurologic emergency and results from the history, physical examination, and early investigative studies are key to the identification and treatment of its underlying cause. The prognosis for recovery depends greatly on the underlying etiology as well as on its optimal treatment, which seeks to preserve neurologic function and maximize the potential for recovery by reversing the primary cause of brain injury, if known, and preventing secondary brain injury from anoxia, ischemia, hypoglycemia, cerebral edema, seizures, infections, and electrolyte and temperature disturbances. Brain death must be diagnosed with similar care and precision, and families approached compassionately about the diagnosis and their decisions regarding organ donation.

Section snippets

Impairment of consciousness

Numerous descriptive terms for states of acute altered awareness, spanning a continuum between normal consciousness and coma, are frequently used, although this is often done without precision. One principal distinction between these various states is whether alertness is heightened or reduced. A heightened mental state, occasionally with hypervigilance, is seen in patients with delirium, delusions, and hallucinations. Mental states with reduced alertness range from lethargy, in which patients

Causes of coma

Coma is a nonspecific consequence of various CNS insults, but generally is seen only in conditions that either cause widespread dysfunction of both cerebral hemispheres or disrupt the ascending brainstem and diencephalon activating systems. The functional impairment itself may be caused by destructive or compressive lesions, which most commonly result from severe head trauma, or metabolic disturbances, which typically result from nontraumatic causes and have diffuse effects.2

Traumatic and

Diagnostic testing of coma

Routine laboratory testing of a patient with coma of unknown etiology should include an immediate bedside test for serum glucose level, a complete blood count, and a complete metabolic profile, including serum calcium, ammonia, and lactate levels. The blood count may show evidence of infection, anemia, or leukemia. The complete metabolic profile may disclose the presence of an electrolyte imbalance, a disorder of osmolality, renal or hepatic dysfunction, or an inborn error of metabolism.

Management of coma

The primary brain insult, regardless of etiology, may cause irreversible cellular energy failure, leading to early and delayed cell death along necrotic and apoptotic pathways. The mechanisms for injury include excessive release of excitatory neurotransmitters, loss of ion homeostasis, elevated intracellular calcium, and mitochondrial and inflammatory free-radical production, DNA cleavage, proteolysis, and lipid peroxidation.33 Laboratory research into experimental therapies to address these

Outcome of coma

The prognosis for neurologic recovery depends greatly on the etiology and severity of the primary brain injury and on the success of treatments to minimize secondary brain injury. There is an high overall mortality rate, with traumatic brain injury consistently one of the most common causes of childhood mortality and neurologic morbidity.49 Outcomes from coma are commonly reported using one of several scales. The five-point Glasgow Outcome Scale (GOS) emphasizes functional independence, as

Brain death

The concept of brain death and guidelines for its clinical determination were originally proposed by an ad hoc committee of the Harvard Medical School faculty in 1968.73 The need for an alternative definition of death arose from the technological advances that allowed preservation of the cardiorespiratory functions that had previously been used to define life and death. Two important motivations were the desire to avoid prolonged suffering for families of patients in a coma who had no hope for

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