coma or decreased conscious state is a common presentation or occurrence within the ED, and most are transient due to syncope / near syncope or post-ictal states.

decreased conscious state will reliably occur when cerebral perfusion falls to low (eg. hypotension or raised intracranial pressure (ICP)), there is a lack of cerebral oxygenation (eg. hypoxia), or there is a severe metabolic disturbance (eg. hypoglycaemia, severe acidosis, etc).

the cause of the decreased conscious state may be immediately life-threatening (eg. ventricular fibrillation (VF), choking / respiratory arrest / cardiac arrest / BLS / ALS / CPR, raised intracranial pressure, hypoglycaemia, hypoxia, head trauma or the shocked hypotensive patient)

persistent decreased conscious state in itself may be immediately life-threatening as patient may not be able to support their airway, prevent aspiration or ventilate spontaneously.

check glucose level to exclude hypoglycaemia

if trauma possible, protect cervical spine

consider naloxone (Narcan) 0.1mg/kg (max 2mg) im/iv/intranasal in case opiate overdose, particularly if intravenous drug users (IVDU) or injection drug use (IDU) or pinpoint pupils

if evidence of seizures, Mx as per seizures, but be aware that hypoxia, shock, eclampsia and hypoglycaemia can all be the cause.

move to a resuscitation area as soon as possible for ongoing cardiorespiratory and neurologic monitoring

if persistent coma with GCS < 9 and no readily identifiable reversible cause, and no NFR status, consider intubation to protect airway and ensure adequate ventilation.

ECG

FBE

U&E

glucose

LFT

blood gas to exclude metabolic acidosis (eg. diabetic ketoacidosis (DKA) or toxicology) or alkalosis

coagulation screen - as there is a reasonable likelihood of need to do a lumbar puncture (LP)

CT brain

lumbar puncture (LP) if CT brain nad and no C/I

CXR

blood culture if possibly febrile illness

toxicology - eg. blood ethanol, salicylate, etc.

ammonia

metabolic screen in children

cortisol if possible adrenal crisis

if history of febrile illness and hypotensive or clinically in shock, consider septic shock

if high temperature, consider also, heat illness and heat stroke, neuroleptic malignant syndrome (NMS) or serotonin syndrome

if fever and young child with no sinister features, consider febrile convulsion

NOTE: many of the conditions below also cause a raised temperature, and some are often precipitated by infections (eg. hepatic and Wernicke's encephalopathy)

if evidence of trauma, Mx as per trauma including urgent CT scan of brain and cervical spine

if history of sudden headache preceding collapse, consider subarachnoid haemorrhage (SAH), thus urgent CT scan

if focal neurology then consider stroke (CVA) or other intracranial pathology, thus urgent CT scan

if known alcoholic, see ethanol intoxication/poisoning

if hypothermic, see hypothermia

consider raised intracranial pressure (ICP)