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Altered Level of Consciousness
An altered level of consciousness (LOC) is apparent in the pa-tient who is not oriented, does not follow commands, or needs persistent stimuli to achieve a state of alertness. LOC is gauged on a continuum with a normal state of alertness and full cognition (consciousness) on one end and coma on the other end. Coma is a clinical state of unconsciousness in which the patient is unaware of self or the environment for prolonged periods (days to months or even years). Akinetic mutism is a state of unresponsiveness to the environment in which the patient makes no movement or sound but sometimes opens the eyes. Persistent vegetative state is a condition in which the patient is described as wakeful but devoid of conscious content, without cognitive or affective mental function. The level of responsiveness and consciousness is the most important indicator of the patient’s condition.
Altered LOC is not a disorder itself; rather, it is a function and symptom of multiple pathophysiologic phenomena. The cause may be neurologic (head injury, stroke), toxicologic (drug over-dose, alcohol intoxication), or metabolic (hepatic or renal failure, diabetic ketoacidosis).
The underlying causes of neurologic dysfunction are disrup-tion in the cells of the nervous system, neurotransmitters, or brain anatomy.
A disruption in the basic functional units (neurons) or neuro-transmitters results in faulty impulse transmission, impeding communication within the brain or from the brain to other parts of the body. These disruptions are caused by cellular edema and other mechanisms such as antibodies disrupting chemical trans-mission at receptor sites.
Intact anatomic structures of the brain are needed for proper function. The two hemispheres of the cerebrum must communi-cate, via an intact corpus callosum, and the lobes of the brain (frontal, parietal, temporal, and occipital) must communicate and coordinate their specific functions. Additional anatomic structures of importance are the cerebellum and the brain stem. The cerebellum has both excitatory and inhibitory ac-tions and is largely responsible for coordination of movement. The brain stem contains areas that control the heart, respiration, and blood pressure. Disruptions in the anatomic structures are caused by trauma, edema, pressure from tumors as well as other mechanisms such as an increase or decrease in blood or cerebro-spinal fluid (CSF) circulation.
Alterations in LOC occur along a continuum, and the clinical manifestations depend on where the patient is along this con-tinuum. As the patient’s state of alertness and consciousness decreases, there will be changes in the pupillary response, eye open-ing response, verbal response, and motor response. Initial changes may be reflected by subtle behavioral changes such as restlessness or increased anxiety. The pupils, normally round and quickly re-active to light, become sluggish (response is slower); as the patient becomes comatose, the pupils become fixed (no response to light). The patient in a coma does not open the eyes, respond verbally, or move the extremities in response to a request to do so.
The patient with an altered LOC is at risk for alterations in every body system. A complete assessment is performed, with particu-lar attention to the neurologic system. The neurologic examina-tion should be as complete as the LOC allows. It includes an evaluation of mental status, cranial nerve function, cerebellar function (balance and coordination), reflexes, and motor and sen-sory function. LOC, a sensitive indicator of neurologic function, is assessed based on the criteria in the Glasgow Coma Scale: eye opening, verbal response, and motor response (Bateman, 2001). The patient’s responses are rated on a scale from 3 to 15. A score of 3 indicates severe impairment of neurologic function; a score of 15 indicates that the patient is fully responsive. If the patient is comatose, with localized signs such as abnor-mal pupillary and motor responses, it is assumed that neurologic disease is present until proven otherwise. If the patient is comatose and pupillary light reflexes are preserved, a toxic or metabolic dis-order is suspected.
Procedures used to identify the cause of unconsciousness in-clude scanning, imaging, tomography (eg, computed tomogra-phy, magnetic resonance imaging, positron emission tomography), and electroencephalography. Laboratory tests include analysis of blood glucose, electrolytes, serum ammonia, and blood urea ni-trogen levels, as well as serum osmolality, calcium level, and par-tial thromboplastin and prothrombin times. Other studies may be used to evaluate serum ketones and alcohol, drug levels, and arterial blood gas levels.
Potential complications for the patient with altered LOC include respiratory failure, pneumonia, pressure ulcers, and aspiration. Respiratory failure may develop shortly after the patient becomes unconscious. If the patient cannot maintain effective respirations, supportive care is initiated to provide adequate ventilation. Pneu-monia is common in patients receiving mechanical ventilation or in those who cannot maintain and clear the airway. The patient with altered LOC is subject to all the complications associated with immobility, such as pressure ulcers, venous stasis, muscu-loskeletal deterioration, and disturbed gastrointestinal function-ing. Pressure ulcers may become infected and act as a source of sepsis. Aspiration of gastric contents or feedings may occur, pre-cipitating the development of pneumonia or airway occlusion.
The first priority of treatment for the patient with altered LOC is to obtain and maintain a patent airway. The patient may be orally or nasally intubated, or a tracheostomy may be performed. Until the patient’s ability to breathe on his or her own is deter-mined, a mechanical ventilator is used to maintain adequate oxy-genation. The circulatory status (blood pressure, heart rate) is monitored to ensure adequate perfusion to the body and brain. An intravenous catheter is inserted to provide access for fluids and intravenous medications. Neurologic care focuses on the specific neurologic pathology, if any. Nutritional support, using either a feeding tube or a gastrostomy tube, is initiated as soon as possi-ble. In addition to measures to determine and treat the under-lying causes of altered LOC, other medical interventions are aimed at pharmacologic management of complications and strategies to prevent complications.
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