Neurological, Pain, Sedation, and Delirium Assessment
2.2 Neurological Assessment
There isn’t a single brain area responsible for consciousness, but its neuro-topical localization can be found in the ascending reticular activating system (ARAS). Whenever this system is functionally impaired bilaterally, one must anticipate distur- bances of consciousness ultimately attaining the degree of coma. The ARAS connects the thalamic and subthalamic nuclei with the reticular intermediary gray substance of the spinal cord.
The etiology and exact localization of the functional neuronal disturbance in the ARAS are not especially important: reversible
Table 2.1 Indications for neurological evaluation in ICU patients [5]
• Detect early neurological worsening before irreversible brain damage occurs
• Individualize patient care decisions
• Guide patient management
• Monitor the response to treatment, in order to avoid any adverse effects
• Allow clinicians to better understand the physiopathology of complex disorders
• Design and implement management protocols
• Improve neurological outcome and quality of life in survivors of severe brain injuries
• Through understanding disease physiopathology, begin to develop new mechanistically oriented therapies where treatments currently are lacking or are empiric in nature
metabolic CNS disease in a context of metabolic derangement is just as well possible as structural lesions along the thalamic loop structures.
Coma is a common clinical sign in ICU, and it is defined as a severe disturbance of consciousness, which precludes awaken- ing and the directed movement of limbs. The comatose person shows closed eyes and no purposeful reaction to painful stimuli.
The quantitative reduction of wakefulness, or better of arousal function, is the main feature of this condition [6].
Besides these signs we can also detect other cognitive and consciousness disorders before leading to a coma. If both events occur alternatively, or fluctuate, a delirium diagnosis should be considered. Following several brain damage, some patients can be awaken (the patient opens and moves its eyes), but still unre- sponsive (showing no voluntary movement) [7]; this syndrome is called vegetative/unresponsive state. A patient in this state has an alternated sleep-wake cycle, can swallow and breathe, and shows a response to pain stimuli and nonfinalized movement.
However he is not able to voluntarily move his eyes to visual stimuli and verbal response nor finalize movements. If this state continues for more than a month, this clinical syndrome, ini- tially termed “apallic syndrome” or “vigil coma,” will be defined as “persistent vegetative state” (PVS), although many neuroscientists prefer to describe this state of consciousness as
“unresponsive wakefulness syndrome” (UWS). This choice is due to ethical questions about whether a patient can be called
“vegetative” or not [8].
The minimally conscious state (MCS) is an impairment of consciousness; the patient shows awareness of self and/or the environment. Both actions and awareness are unstable during the day. If this condition is detected in acute stage, its outcome seems to improve.
Patients with MCS open their eyes spontaneously and show a response to visual stimuli, are able to show aware response to simple orders or imitate actions, and usually don’t speak and
pronounce unmeaning sounds instead. Patients are able to show finalized movement or emotional behaviors, and they usually swallow properly [8].
ICU nurses are skilled to assess patient’s consciousness; they evaluate and detect changes of neurological state and report them to medical staff in case early interventions are needed to improve the outcome and reduce the long-term sequelae [9].
Nursing care focuses on:
• Evaluation of awaken state using a score tool to define the level of consciousness and the stimuli needed to achieve a response from the patient
• Evaluation of the patient awareness of self and environment (testing orientation, ability to concentrate and speak) and per- forming test to assess presence of delirium
The most common scoring scale to assess the consciousness is the Glasgow Coma Scale (GCS) introduced in the 1970s [10].
An updated tool, the Full Outline of UnResponsiveness (FOUR), is also available (Table 2.2).
The GCS remains the most widely used in critical care set- tings. The assessment of motor, verbal, and eye responses of the GCS characterizes the level of consciousness. The picture pro- vided by these responses enables comparison both between patients and changes in patients over the time that crucially guides management. The three components can be scored sepa- rately or combined in a sum score, ranging from 3 to 15 [11].
This value must be associated to pupil diameter and reactiv- ity evaluation, arterial blood pressure, heart rate, body tempera- ture, breathing pattern and, when prescribed, CO2 (EtCO2) measurement, intracranial pressure (ICP), and cerebral perfu- sion pressure (CPP).
Its main limitations are that verbal responses are not assess- able in mechanically ventilated patients and that brainstem examination is not directly considered. The total GCS on ED arrival is a strong predictor of in-hospital mortality (area under
Table 2.2 Glasgow Coma Scale (GCS) and Full Outline of UnResponsiveness (FOUR) score
Glasgow Coma Scale (GCS)
Full Outline of
UnResponsiveness (FOUR) Eye response 4 = eyes open
spontaneously 3 = eyes opening to
verbal command 2 = eyes opening to pain 1 = no eyes opening
4 = eyelids open or opened, tracking, or blinking to command
3 = eyelids open but not tracking
2 = eyelids closed but open to loud voice
1 = eyelids closed but open to pain
0 = eyelids remain closed with pain
Motor response
6 = obeys commands 5 = localizing pain 4 = withdrawal from pain 3 = flexion response to
pain
2 = extension response to pain
1 = no motor response
4 = thumbs-up, fist, or peace sign
3 = localizing to pain 2 = flexion response to pain 1 = extension response to
pain
0 = no response to pain or generalized myoclonus status
Verbal response
5 = oriented 4 = confused
3 = inappropriate words 2 = incomprehensible
sounds
1 = no verbal response Brainstem
reflexes
4 = pupil and corneal reflexes present
3 = one pupil wide and fixed 2 = pupil or corneal reflexes
absent
1 = pupil and corneal reflexes absent
0 = absent pupil, corneal and cough reflex
(continued)
the ROC curve (AUC) of 0.91) and need for neurosurgical inter- vention (AUC of 0.87), with the eye score as the weakest predic- tor and sum score the best. An initial GCS sum score of 3 is associated with poor clinical outcomes in traumatic brain injury (TBI) (mortality 50–76%) [12].
The FOUR score, introduced in 2005, provides additional information not captured by the GCS including details about brainstem reflexes and respiratory drive and an opportunity to recognize the locked-in syndrome [13].
It assesses eye response, motor response, brainstem reflexes, and respiratory pattern. The FOUR score has been tested in a range of clinical settings and in different countries; moreover it has been further validated in the medical ICU, in the ED, and among ICU nurses well experienced in neurological care [12].
Patients with the lowest GCS score can be further differentiated using the FOUR score: among patients with GCS3, only 25% have FOUR = 0, while the others show scores from 1 to 8 [13].
The FOUR score showed good interrater reliability and prog- nostic content in a range of neurological conditions and may help to differentiate between several conditions when a patient is unresponsive [14]. However, experience with this instrument is still limited when compared to the GCS. Current evidence
Table 2.2 (continued)
Glasgow Coma Scale (GCS)
Full Outline of
UnResponsiveness (FOUR)
Respiration 4 = not intubated, regular
breathing pattern 3 = not intubated, Cheyne-
Stokes breathing pattern 2 = not intubated, irregular
breathing
1 = breathes above ventilator rate
0 = breathes at ventilator rate or apnea
Max–min 15–3 16–0
suggests that both the GCS and FOUR score provide useful and reproducible measures of neurological state and can be rou- tinely used to chart trends in clinical progress [5].
Sedation, major analgesics (e.g., opioids), and neuromuscular blockage remain a problem for any clinical scale of consciousness.