6th August 2024

The unconscious patient

Loss, or change in level, of consciousness is a common reason for presentation to healthcare providers, with a wide range of differentials including a number of serious pathologies and requires detailed evaluation and investigation.

This chapter will focus primarily on neurological causes, but initial attention will be paid to the general approach.

Causes of altered consciousness level

The table that follows is not an exhaustive list but touches upon the major differential diagnoses encountered in day-to-date clinical practice, as well as diagnoses favoured in the MRCP exams.

Assessment and management of the unconscious patient

Given the wide range of potential causes, it is necessary to cast a wide net when assessing unconscious patients. If the patient is unable to give a history, collateral is essential. It is important to capture the events leading up to, during, and, if applicable, after the episode.

All approaches should begin with ABCDE, with urgent input from critical care teams if appropriate. Intubation and ventilation may be required if there is the potential for airway compromise or evidence of inadequate ventilation, and there may be a need to support blood pressure with vasoactive drugs.

Examination should include a complete neurological examination, in particular assessing for:

• Meningism – the triad of photophobia, neck stiffness, and headache may guide towards a diagnosis
• Cranial nerve signs – especially those that can be passively detected, e.g. pupillary asymmetry
• Signs of head injury
• Evidence of raised intracranial pressure – pupillary or fundal abnormality, Cushing’s reflex (bradycardia, hypotension, and altered respiration), though keeping in mind that these are late signs
• Alteration of respiratory pattern – although if found, this may indicate either a ‘peripheral’ or central cause

A complete systems examination is essential and may indicate a potential aetiology; significant findings may include murmurs, jaundice, petechiae, and injection sites. Occupational and environmental causes may also reveal themselves on examination, for example, signs of lead or carbon monoxide poisoning.

Important baseline investigations include:

• FBC, U&Es, LFTs, blood gas analysis – for rapid assessment of Hb, lactate and carboxyhaemoglobin
• Blood glucose – this may give an early diagnosis, especially if presenting with seizures
• ECG – this may reveal an underlying rhythm disturbance or structural heart disease
• CT head – for identification of infarction, haemorrhage, infection, or mass effect
• Toxicology screening of blood and urine – if there is suggestive history or features on examination

There may be insufficient findings on preliminary investigations to identify a cause for altered consciousness levels. In these cases, more focused investigations should be carried out to identify a cause:

• Lumbar puncture – to diagnose infective and inflammatory causes of unconscious state, or if CT-negative subarachnoid haemorrhage is suspected
• EEG – this may reveal a diagnosis of seizure disorder, including non-convulsive status epilepticus
• MRI head – if CT imaging does not explain the clinical picture or if follow up imaging is required

Management of altered conscious level depends on the cause. Supportive management should be instigated and may include supporting the airway, ventilation and blood pressure, correction of metabolic and electrolyte abnormalities, maintenance of normothermia and management of seizure states. Often, it may be necessary to commence empirical treatments, for example for suspected meningoencephalitis, but once the patient is stabilised the underlying cause should be rapidly identified and targeted treatment started.

It may be useful to become familiar with the DVLA (Driver and Vehicle Licensing Agency) rules on driving following a loss of consciousness, available in the references.

References

• Blanchard G. Assessment of altered mental status. BMJ Best Practice [Internet]. 2020 [cited 29 November 2021]. Available from: https://bestpractice.bmj.com/topics/en-gb/843
• Dankiewicz J, Cronberg T, Lilja G, Jakobsen J, Levin H, Ullén S et al. Hypothermia versus Normothermia after Out-of-Hospital Cardiac Arrest. New England Journal of Medicine. 2021;384(24):2283-2294
• Driver and Vehicle Licensing Agency. Assessing fitness to drive – a guide for medical professionals [Internet]. London: HM Government; 2021 [cited 1 December 2021]. Available from: https://www.gov.uk/government/publications/assessing-fitness-to-drive-a-guide-for-medical-professionals
• Manji H, Connolly S, Kitchen N, Lambert C, Mehta A. Oxford Handbook of Neurology [Internet]. 2nd ed. Oxford: Oxford University Press; 2014 [cited 29 November 2021]. Available from: https://oxfordmedicine.com/view/10.1093/med/9780199601172.001.0001/med-9780199601172
• Young G. Stupor and coma in adults. UpToDate [Internet]. Eds: Aminoff M, Hockberger R, Wilterdink J. 2021 [cited 29 November 2021]. Available from: https://www.uptodate.com/contents/stupor-and-coma-in-adults