Chapter 14: Observations
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Source: Reproduced from Fuller ([66]) with permission of Elsevier.
Related theory
Changes in neurological status can be rapid and dramatic or subtle, developing over minutes, hours, days, weeks or even longer (Wilkinson et al. [215]). The frequency of neurological observations will depend upon the patient's condition and the rapidity with which changes are occurring or expected to occur, and should include:
- assessment of level of consciousness
- pupil size and reaction to light
- limb assessments (including both motor and sensory function)
- vital signs (Adam et al. [2]).
Assessment of level of consciousness
Level of consciousness is the most sensitive indicator of neurological deterioration and is therefore the most important aspect of any neurological assessment (Brain Trauma Foundation [25]). Consciousness is a state of awareness of self and the environment and is dependent on two components: arousal and awareness (Baumann [16]). These correspond to two brain structures: the reticular activating system (RAS) and the cerebral cortex (Tortora and Derrickson [199]). Consciousness depends on the interaction between the neurones in the RAS in the brainstem and the neurones in the cerebral cortex (Adam et al. [2]).
Arousal
Arousal is a primitive state managed by the RAS. The core of nuclei that make up the RAS extends from the brainstem with projections upwards to the cortex and downwards to the spinal cord (Tortora and Derrickson [199]). The RAS receives auditory, visual and sensory impulses (such as pain, touch, movement of limbs, bright light or noise), and because of its connections is ideal for governing arousal of the brain as a whole (Adam et al. [2]). Unless inhibited by other areas of the brain, the reticular neurones send a continuous stream of impulses to the cerebral cortex, maintaining the cortex in an alert, conscious state; the RAS is selective, however, forwarding only essential information to the cortex and filtering out unnecessary information (Tortora and Derrickson [199]). Certain drugs have a direct effect on the RAS; alcohol, sleep‐inducing drugs and tranquillizers depress the RAS and drugs such as lysergic acid diethylamide (LSD) remove the RAS's filter system, leading to heightened sensory arousal (Adam et al. [2]).
Awareness
Awareness is the more sophisticated part of consciousness and requires an intact cerebral cortex to interpret sensory input and respond accordingly (Adam et al. [2]).
Assessing consciousness
Consciousness cannot be measured directly but is assessed by observing behaviour in response to different stimuli. The response indicates the level at which the sensory information has been translated within the central nervous system (Adam et al. [2]).
Assessment of arousal focuses on the patient's ability to respond appropriately to verbal and non‐verbal stimuli. It begins with verbal stimuli in a normal tone; if there is no response, the stimulus is progressively increased, initially by raising the voice, then by gently shaking the patient and finally by applying noxious (painful) stimuli (see section on application of painful stimuli below).
Assessment of awareness is concerned with the patient's orientation to person, place and time. Changes in this may be the first sign of neurological deterioration leading to confusion and disorientation (Baumann [16]).
Previous and/or co‐existing problems should be considered when assessing levels of consciousness, for example deafness, hemiparesis or hemiplegia, as a manifestation of altered consciousness implies an underlying brain dysfunction (Adam et al. [2]). Its onset may be sudden, for example following an acute head injury, or it may occur more gradually, such as in hypoglycaemia (Wilkinson et al. [215]). Similarly, alterations in level of consciousness can vary from slight to severe, indicating the degree of brain dysfunction (Adam et al. [2]). For a full assessment, it is essential to take a detailed history and to involve family and/or friends to describe the patient's usual function (Adam et al. [2]).
Consciousness ranges across a continuum from alert wakefulness to deep coma with no apparent responsiveness (Baumann [16]). Level of consciousness can be measured using the Glasgow Coma Scale (GCS) or, during a rapid assessment of an acutely unwell patient, the AVPU (alert, verbal, pain, unresponsive) scale (see the section below on assessment and recording tools) (Adam et al. [2], Brain Trauma Foundation [25], Braine and Cook [26]).
Application of painful stimuli
Painful stimuli should be employed only if the patient does not respond to firm and clear commands (Braine and Cook [26]). The stimulus should be applied in a standard way, increasing from light pressure and being maintained until a response is elicited, for a maximum of 10 seconds, to avoid soft tissue injury and unnecessary pain (Adam et al. [2], Brain Trauma Foundation [25], Braine and Cook [26]).
As the ability to localize pain is lost, various responses may be observed when painful stimuli are applied (Baumann [16]). It is important to note, when applying a painful stimulus peripherally, that it may only elicit a spinal reflex that does not involve cerebral function; therefore, evaluation of cerebral function requires the application of central stimuli (Braine and Cook [26]).
Central stimuli include the trapezium squeeze (Figure 14.49), supraorbital pressure and the sternal rub (Baumann [16]), which are described below (although the sternal rub is no longer advocated). Local policies and guidelines should be followed as some practices are not recommended in some organizations.
- Trapezium squeeze: using the thumb and two fingers, hold 5 cm of the trapezius muscle where the neck meets the shoulder and twist the muscle.
- Supraorbital pressure: run a finger along the supraorbital margin (the bony ridge along the top of the eye) to feel a notch. Apply pressure to the notch to stimulate the supraorbital nerve and cause an ipsilateral (on that side) sinus headache‐type pain. This method should not be used if the facial or cranial bones are unstable, if facial fractures are suspected or after facial surgery. Using supraorbital pressure as a painful stimulus may also make the patient grimace and lead to them closing the eye rather than opening it (Fairley et al. [62]).
- Sternal rub: the use of a sternal rub is no longer recommended as it has been shown to cause excessive bruising and discomfort to the patient (Dawes and Durham [51], Naalla et al. [123]).
Figure 14.49 Trapezium squeeze.
If there is no response to central stimuli (e.g. flexion, eye movement or verbal response) then a peripheral stimulus should be applied (Adam et al. [2]). One technique is to place the patient's finger between the assessor's thumb and a pencil or pen, apply pressure gradually and increase it over a few seconds or until the slightest response is seen (Braine and Cook [26]). Due to the risk of bruising, pressure should not be applied to the nail bed and, again, local policies and guidelines should be followed.
Assessment of pupillary activity
Careful examination of the reactions of the pupils to light is an important part of the neurological assessment and can lead to important findings, as listed in Table 14.19 (Fuller [66]). The size (Figure 14.50), shape, equality, reaction to light (in both the eye directly exposed to light (direct) and the eye not directly exposed to it (consensual)) and position of the eyes should be noted as well as whether the eyes are deviated upwards or downwards, and whether the eyes are conjugate (moving together) or dysconjugate (not moving together) (Bickley [18]). Pupillary response to light relies on unimpaired afferent and efferent function (which respectively rely on the optic and oculomotor nerves), which allow the retina to communicate the light impulse to the pupillary musculature and to the midbrain (Adam et al. [2]). Due to its resistance to metabolic changes, the pupillary pathway reaction to light aids in the differentiation of a metabolic coma from a structural one (Wilkinson et al. [215]). When a brain mass is suspected, compromised pupillary response to light is likely due to the midbrain being under pressure; in these cases, changes in the constriction and dilation of the pupils may reflect pressure on the oculomotor nerve (cranial nerve III) or brainstem damage (Adam et al. [2]).
Table 14.19 Examination of pupils
| Observation | Pupil size | Pupil reactiveness | Possible indication |
|---|---|---|---|
| Pupils equal | Pinpoint | – | Opiates or pontine lesion |
| Small | Reactive | Metabolic encephalopathy | |
| Mid‐sized | Fixed | Midbrain lesion | |
| Reactive | Metabolic lesion | ||
| Pupils unequal | Dilated | Unreactive | Third nerve palsy |
| Small | Reactive | Horner's syndrome |
Figure 14.50 Pupil size guide.
Assessment of limb function
Motor function
Damage to any part of the motor nervous system can affect the ability to move (Baumann [16]). After assessing motor function on one side of the body, the contralateral muscle group should also be evaluated to detect asymmetry (Adam et al. [2]). Motor function assessment involves evaluation of the following:
- muscle strength
- muscle tone
- muscle co‐ordination
- reflexes
- abnormal movements (Bickley [18]).
Muscle strength
This involves testing the patient's muscle strength against the pull of gravity and then against resistance applied by another person. Changes in motor strength, especially between the right and left sides, may indicate imminent or existing neurological failure (Baumann [16]).
Muscle tone
Muscle co‐ordination
Reflexes
Among the most important reflexes are blink, gag and swallow, oculocephalic and plantar:
- Blink (corneal): this is a protective reflex and can be affected by damage to the fifth cranial nerve (trigeminal) and the seventh cranial nerve (facial). Facial weakness (seventh cranial nerve) will affect eye closure, and absence of the corneal reflex may result in corneal damage (Fuller [66]).
- Gag and swallow: damage to the ninth cranial nerve (glossopharyngeal) and 10th cranial nerve (vagus) may impair protective reflexes. These two cranial nerves are always assessed together as their functions overlap. Muscle innervation of the palate is from the vagus, while sensation is supplied by the glossopharyngeal nerves (Wilkinson et al. [215]).
- Oculocephalic: this reflex is an eye movement that occurs only in patients with a severely decreased level of consciousness (in conscious patients this reflex is not present). When the reflex is present, the patient's eyes will move in the opposite direction from the side to which the head is turned. However, in patients with absent brainstem reflexes, the eyes will appear to remain stationary in the centre. This reflex should not be assessed if there is suspected instability of the cervical spine as the necessary head movement could exacerbate any spinal injury (Baumann [16]).
- Plantar: abnormalities of the plantar reflex will help to locate the anatomical site of the lesion. The upgoing plantar (extension) reflex is termed ‘positive Babinski’ (dorsiflexion of the big toe and fanning of the other toes) and indicates an upper motor neurone lesion. Note that the upgoing plantar reflex is normal in children of less than 1 year of age (Baumann [16], Bickley [18]).
Abnormal movements
When carrying out neurological observations, any abnormal movements (such as seizures, tics and tremors) must be noted (Bickley [18]).
Sensory function
Constant sensory input enables individuals to alter their responses and behaviour to suit the environment. When disease or injury damages the sensory pathways, the sensory responses are always affected. Any assessment of sensory function should include an evaluation of the following:
Visual acuity
Clarity or clearness of vision may be tested with a Snellen chart, which uses decreasing letter sizes or newspaper prints. If the patient wears glasses, they should be worn during the test (Bickley [18]).
Visual fields
Lesions at various points in the visual pathways affect vision. It should be noted that loss of vision is always described with reference to the visual fields rather than the retinal fields (Bickley [18]).
Vital signs
It is recommended that assessment of vital signs should include respiration rate, oxygen saturation, temperature, and blood pressure and pulse.
Respiration and oxygen saturation
Respiratory patterns can give a clear indication of how the brain is functioning as the complex process of respiration is controlled by more than one area of the brain: the cerebral hemispheres, the cerebellum and the brainstem (Adam et al. [2]). Any disease or injury that affects these areas may produce respiratory changes (Wilkinson et al. [215]). The rate, character and pattern of a patient's respiration must be noted. Abnormal respiratory patterns are listed in Table 14.20 (Adam et al. [2], Wilkinson et al. [215]). Any change in respiration may lead to a change in oxygen saturation; this should therefore also be assessed.
Table 14.20 Abnormal respiratory patterns
| Type | Pattern | Significance |
|---|---|---|
| Apneustic breathing | Prolonged inspiration with a pause at full inspiration; there may also be expiratory pauses. | May indicate a lesion of the lower pons or upper medulla, hypoglycaemia or drug‐induced respiratory depression. |
| Ataxic breathing | A completely irregular pattern with random deep and shallow respirations; irregular pauses may also appear. | May indicate a lesion of the medulla. |
| Central neurogenic hyperventilation | Sustained, regular, rapid respirations, with forced inspiration and expiration. | May indicate a lesion of the low midbrain or upper pons areas of the brainstem. |
| Cheyne–Stokes breathing | Rhythmic waxing and waning of both rate and depth of respirations, alternating regularly with briefer periods of apnoea. Greater than normal rate of respiration (i.e. 16–24 breaths per minute). | May indicate deep cerebral or cerebellar lesions, usually bilateral; may occur with upper brainstem involvement. |
| Cluster breathing | Clusters of irregular respirations alternating with longer periods of apnoea. | May indicate a lesion of the lower pons or upper medulla. |
Constant re‐evaluation of the patient's ability to maintain and protect their airway is essential when there is evidence of reduced consciousness or coma (i.e. when the GCS score is less than 8) (Baumann [16]). At this stage, muscles often become flaccid and use of the recovery position may need to be considered (Adam et al. [2]). Patients whose neurological function has deteriorated may require adjuncts to protect the airway and possibly artificial ventilation (RCUK [173]). Close liaison with physiotherapists and speech and language therapists is important to minimize the danger of chest infections (due to the patient's inability to clear secretions) and the risk of aspiration (Adam et al. [2]).
Temperature
Damage to the hypothalamus (the temperature‐regulating centre) may result in grossly fluctuating temperatures (Adam et al. [2]).
Blood pressure and pulse
Hypertension with a widening pulse pressure, bradycardia and a fall in respiratory rate may be indicative of rising intracranial pressure and is part of the Cushing reflex (Adam et al. [2]). Abnormalities of blood pressure and pulse usually occur late (and may not appear at all in some patients); usually, the patient's level of consciousness will have begun to deteriorate before there is any alteration in their vital signs (Adam et al. [2]).
