Understanding Disorders of Consciousness

Encephalopathy, delirium, and coma are disorders of consciousness (DOCs) frequently encountered by critical care nurses. 

For nurses in the hospital setting being able to have knowledge of encephalopathy, delirium, and coma is important in improving patient outcomes. Furthermore, it is also vital to perform standardized assessments and interventions that are consistent with the cue-response theory. 

What is the State of Consciousness? 

Plum and Posner’s Diagnosis book define consciousness, that is, being fully aware of the self and the environment, as having 2 aspects, content and arousal. 

The content of consciousness is defined as “the sum of all functions mediated at a cerebral cortical level.” The content of consciousness includes cognition, which reflects how well information is processed and stored across the 2 cerebral hemispheres.

Arousal, on the other hand, refers to the level of consciousness or state of being awake. Consciousness and responsiveness are separate phenomena. Some patients may be aware but not able to respond (eg, locked-in syndrome), and patients may respond to stimuli but not be aware of their surroundings.

Based on current research the thalamocortical interactions are crucial for consciousness experience and voluntary action. The thalamocortical system is made up of the Thalamus and Cerebral Cortex.

For Refresher: 

Thalamus – the primary function of the thalamus is to relay motor and sensory signals to the cerebral cortex.

Cerebral cortex – many areas of the cerebral cortex process sensory information or coordinate motor output necessary for control of movement. 

The Brain

The brain, like other organs, has a limited capacity to withstand injury. The brain reacts to acute stress that can result from:

• Toxins
• Infections
• Inflammations
• Metabolic or nutritional derangements
• Use of nutrients, glucose, electrolyte level, hydration, or structural damage

 

A stress response results in multiple cellular-level processes and neurochemical changes that disrupt equilibrium.

This disequilibrium initiates multiple cascades that become a vicious cycle of competition between supply and demand, which are depicted as neuroelectrical changes on an electroencephalogram (EEG).

When the brain can no longer compensate, behavioral symptoms such as altered levels of arousal and disorganized thinking begin to develop.

Progression of Disorders of Consciousness

1. Delirium 
   1. Delirium is a neurocognitive disorder that presents as an acute change in behavior secondary to impairments in consciousness and cognition. There are 3 types of delirium: hyperactive, hypoactive, and mixed.
   2. Regardless of delirium type, individuals are often disoriented to place and time and have impairments in cognitive and visual-motor functions.
   3. Patients with hyperactive delirium tend to have greater disturbances in their circadian rhythm (ie, sleep-wake cycle) and mood lability. Conversely, patients with hypoactive delirium are more likely to be inattentive, have a flat affect, and face challenges with language.
2. Coma
   1. Like delirium, coma is on the continuum of altered states of consciousness. However, with a coma, there is a loss of both awareness and wakefulness
3. Minimal consciousness state
4. Persistent vegetative state 

ICU Synposis of Consciousness

When a patient has an altered consciousness, after 2 to 4 weeks, the individual will either progressively recover, die, or transition to a minimally conscious or more persistent vegetative state.

Encephalopathy 

The term encephalopathy is derived from 2 ancient Greek words: “enkephalin”, which means “brain,” and pathos, which means “suffering” and is associated with the disease.

Encephalopathy is defined as any diffuse disease of the brain that alters brain function or structure with the “hallmark feature being altered mental status.”

Although the phrases altered level of consciousness and altered mental status are often used interchangeably with encephalopathy, they are not the same. For example, sleep is an altered level of consciousness but is not caused by injury or disease.

Chronic Encephalopathy

Chronic encephalopathy is the result of permanent, usually irreversible, structural changes within the brain. The characteristics of chronic encephalopathy are prolonged alterations in mental status that usually progress slowly.

Examples of these are brain conditions such as Alzheimer’s disease and other dementias or anoxic brain injury. Acute encephalopathy results from the rapid development of abnormalities in cerebral structure and/or function.

Level of Function
Function	Coma	Minimally  conscious	Vegetative state
Self-aware	No	Very limited	No
Motor	Not purposeful	Severely limited	Not purposeful
Respiratory	Variable but depressed	Variable but Depressed	Normal
Sleep-wake cycles	No	Yes	Yes
Feels pain	No	No	Yes

 

 

The Mechanism Responsible (DOC’s)

• Interruptions in the delivery or use of oxygen
• Changes in neuronal excitability
• Signaling alterations and changes in brain volume. 

Potential Causes

• Hypoxia
• Ischemia
• Toxic and metabolic disturbances
• Acute organ failure
• Seizures
• Drugs and/or alcohol
• Infection
• Electrolyte imbalances.

Hypothalamic-pituitary-adrenal Axis 

Disorders of consciousness and illness severity are linked by the activity of the hypothalamic-pituitary-adrenal axis, which response to stress by impairing glucocorticoid and glucose metabolism.

The severity of the DOC is directly proportional to the levels of glucocorticoids and glucose in the blood that enters the brain (Stress response). In addition to that, the levels of these substances are directly proportional to the strength of the hypothalamic-pituitary-adrenal response, and that response is directly proportional to the severity of the illness.

Early  First Signs of Delirium Are Often:

• Subtle changes in focus and attention, including distractibility, 
• Delays in responding to stimuli
• Short-term memory deficits
• Disorientation

Prevention of Delirium in the Hospital

Nurses should pay particular attention to the following to prevent and resolve delirium:

• Resuming home medications
• Minimizing the use of chemical and physical restraints,
• Providing adequate pain management and high-quality basic nursing care. 
• Practice habits such as nighttime bathing, promoting uninterrupted sleep as well as day-time activity 
• Hydration
• Nutrition
• Early mobility

Nursing Care for Comatose Patients in the ICU

• Enteral tube feeding
• Promotion of regularity of bowel and bladder functions
• Airway management such as suctioning tracheostomy tube
• Management of muscle tone (excessive tightness of muscles)
• Prevention of infections such as pneumonia and urinary tract infection
• Management of other medical concerns such as fever, seizures, etc

 

Source:
https://www.aacn.org/docs/cemedia/c2161.pdf

If you want to know more about the disorders of consciousness, check out our full episode here 👇

TIME STAMPS:

00:00 Intro
00:44 Plugs
02:31 Episode Introduction
04:35 What exactly is consciousness?
06:37 What happens to the brain?
11:38 Progression of disorders of consciousness
17:24 What is encephalopathy?
19:58 The mechanism responsible for the disorder
20:37 The Potential Causes of Consciousness Disorder
24:57 FUN FACT: How does DOC severity determine?
25:52 What are the early signs of delirium
28:54 How to prevent and resolve delirium
32:23 Nursing care for comatose patients in the ICU
33:55 Area management
35:10 Wrapping up the episode