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Assessment of consciousness - Part one

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VOL: 102, ISSUE: 04, PAGE NO: 26

Debra Fairley, MSc, PGDip, BSc, RGN is critical care nurse consultant, Leeds Teaching Hospitals NHS Trust

Amanda Pearce, BSc, RGN, DipN, is staff nurse, St Gemma’s Hospice, Leeds

Consciousness is a state of awareness of self and surroundings. Accurate, consistent assessment of a patient with impaired consciousness is crucial to determine deterioration or improvement.

The 14 or 15-point Glasgow coma scale (GCS) (Teasdale and Jennett, 1976; 1974) is the most widely used tool for measuring a patient’s level of consciousness.

Pupil size and reaction to light are important neurological examinations and are performed in conjunction with coma scale assessment (Fairley et al, 2005).

Influencing factors

Consciousness level can be influenced by a number of factors such as pathological disease, trauma, sedatives, narcotics, poisons, carbon monoxide and alcohol.

Important factors are:

- Patients who have hearing impairment may not respond to verbal questions;

- Non-reactive, pinpoint pupils are seen with opiate overdose and pontine haemorrhage;

- The parasympathetic nerve fibres of the third cranial nerve (oculomotor nerve) control constriction of the pupil. Compression of this nerve will result in fixed, dilated pupils;

- Antimuscarinics dilate the pupil. For example, the action of atropine sulphate one per cent (eye drops) lasts for 7-12 days after topical application. The effects of intravenous atropine sulphate on the pupil are dose-related and higher doses dilate the pupil further;

- Non-reactive pupils may also be caused by local damage;

- One dilated or fixed pupil may indicate an expanding/developing intracranial lesion, compressing the oculomotor nerve on the same side of the brain as the affected pupil.

Preparation

Within neurosurgical intensive care and high dependency units, a GCS assessment of the patient must be done at verbal handover or the beginning of the shift by both nurses (together) in order to avoid misinterpretation and facilitate continuity.

Collect all the necessary equipment:

- Neurological observation chart;

- Pupil scale (mm);

- Pen torch (bright light).

Consent should be obtained from the conscious patient and each step should be explained as required.

Pupil assessment

Pupillary changes may be a sign of pressure on oculomotor or optic nerves and increased intracranial pressure. Pupils are normally round and equal in size (2-5mm).

The procedure

For the purpose of neurological assessment:

- Reduce any external bright light so that pupil reaction can be monitored and position the patient so that you can see their eyes (Fig 1);

- The pupils should first be observed simultaneously to determine size and equality. A millimetre scale is used to record the size of each pupil (Fig 2);

- The shape of the pupil should also be assessed. An ovoid pupil may be an indication of intracranial hypertension;

- A bright light is shone into each eye (moving from the outer corner of each eye towards the pupil) (Figs 3-4);

- In normal eyes, both pupils contract when light is shone into either eye (Fig 5);

- If the pupil reacts briskly to light it is documented as ‘+’;

- If the pupil does not react to light it is documented as ‘-’;

- If the pupil is sluggish in response when compared with the other pupil it is documented as ‘S’;

- You may need to hold the patient’s eyes open (Fig 6);

- Unusual eye movements (such as nystagmus) must be reported;

- The shape of each pupil should be recorded. Abnormal pupil shapes may be described as ovoid, keyhole or irregular.

Reaction to light

When light is shone into the eye the pupil should contract immediately. The withdrawal of the light should produce an immediate and brisk dilatation of the pupil. This is called the direct light reflex.

Introducing the light into one pupil should cause a similar, simultaneous contraction in the other pupil. When the light is withdrawn from one eye, the opposite pupil should dilate simultaneously. This response is called the consensual light reflex.

A sluggish pupil may be difficult to distinguish from a fixed pupil and may be an early focal sign of an expanding intracranial lesion and increased intracranial pressure.

Glasgow coma scale

The procedure for the Glasgow coma scale is discussed in part two of this two-part series next week.

Professional responsibilities

All nurses who carry out clinical procedures must have undertaken a programme of education and demonstrated competence under supervision.

The practitioner is responsible for ensuring that her or his practice is compliant with NMC guidelines. The practitioner should also ensure that she or he is familiar with local trust policies.

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