Content Reviewers:Antonella Melani, MD, Lisa Miklush, PhD, RNC, CNS, Ashley Mauldin MSN, APRN, FNP-BC, Gabrielle Proper, RN, BScN, MN
Now, let’s quickly review the physiology of consciousness. Normal consciousness is composed of alertness and awareness while awake, as well as arousal or the ability to be woken up from sleep. Consciousness and arousal are believed to be regulated by the reticular activating system, which is a network of neurons that’s located in the brainstem. Normally, these neurons ultimately act by activating parts of the brain cortex involved in wakefulness, attention, behavior, and thinking.
So, altered levels of consciousness can have many causes and risk factors, which can be broadly categorized as structural, metabolic, infectious, toxic, or other. Structural causes include cerebral edema, increased intracranial pressure, stroke, or traumatic brain injury; while metabolic causes include dehydration, hypo- or hyperthermia, hypo- or hyperglycemia, hypo- or hypernatremia, hypoxia, hypercapnia, or uremic encephalopathy. Infectious causes include meningitis, encephalitis, or sepsis. Toxic causes include carbon monoxide, alcohol, or medications, such as opiates, salicylates, barbiturates or benzodiazepines. Lastly, other causes include syncope, seizures, sleep deprivation, serious illness, sensory impairment, or intense pain.
The underlying pathology leading to an altered level of consciousness depends on the cause. Some cases seem to be associated with dysfunction or damage of the reticular activating system; while other cases seem to result from direct dysfunction or damage to the brain, as well as reduced delivery of oxygen or glucose. Ultimately, neural activity is disrupted, leading to impaired wakefulness and attention, and sometimes even altered behavior and thinking.
So the typical clinical manifestations may have gradual or sudden onset, and include clouded consciousness and confusion. The client may also appear disoriented or speak incoherently. Some clients may present with delirium, which is characterized by mental confusion, disorientation, as well as hypo- or hyperactivity, and even hallucinations.
Alternatively, the client may become lethargic, feeling fatigued, sleepy, or sluggish. If a client begins to have obtundation, their interest in their surroundings may decrease, as well as their stimulus response time, which is defined as the quickness or their response to a given stimulus. Some cases may progress to stupor, where the client becomes primarily unresponsive, only arousing after repeated stimulation. Finally, clients that progress into a coma can become completely unresponsive and unarousable.
Diagnosis begins with the client’s history and physical assessment, which includes a thorough neurological exam. The client’s level of consciousness in response to stimuli is assessed with the Glasgow Coma Scale, or GCS for short, which evaluates verbal, motor, and eye-opening responses. In the urgent care setting, a quicker exam to assess the client’s level of consciousness is the AVPU assessment, which rates the client as either Alert, Verbally responsive, Painfully responsive, or Unresponsive. In addition, the pupils in both eyes should be assessed for size, shape, and symmetry; and if the client is awake, orientation should be checked by asking their name, what day it is, and if they know where they are and why.
If the client presents with delirium, they should be assessed for potential causes. These can be summarized with the mnemonic PINCH ME, which stands for Pain, Infection, Nutritional deficiency, Constipation, Hydration deficit or dehydration, Medications like opioids or benzodiazepines, and Environmental factors like isolation, decreased sensory stimulation, and unfamiliar places.
Additionally, laboratory tests are often performed, including a complete blood count, comprehensive metabolic panel, and toxicology screening. Imaging, such as X-rays and CT scans can help assess for brain injury or damage. In severe cases, cerebral spinal fluid can be collected to assess for infections like acute meningitis.
Treatment for clients with an altered level of consciousness varies depending on the cause and severity, so the main goal is to identify any reversible cause as quickly as possible. Treatment often includes an empiric reversal agent, commonly dextrose and, in the case of opioid overdoses, naloxone. Less commonly, flumazenil can be given to reverse the sedative effects of benzodiazepines. Additionally, some clients may require supplemental oxygen therapy and cardiac monitoring; and clients with hypothermia require warming with blankets or warm fluids, which can be given intravenously, or in some cases orally if the client is awake.