Coma

Key Differential Diagnoses

Drunk, asleep
Hysterical coma

Key Investigations

Glucose (BM), CSU
ABG
FBC, ESR, CRP
U+E, LFT/GGT, Bone, Glucose, TFT
BC
CXR
± CT head (± LP)

Key Treatment

If GCS <8, or unwell, ABC + Call Senior
OXYGEN, high flow, if hypoxic
IV BENZYLPENICILLIN 1.2 g qds + IV GENTAMICIN 5 mg/kg od, if infected (and source unclear)
± IV GLUCOSE, 20 mls 50%
± IV NALOXONE 400 mcg
± IV FLUMAZENIL 200 mcg, over 15 secs
± NEUROSURGICAL (eg SDH); other Rx (see below)

Key Management Decision

CT head ± LP (encephalitis)
Neurosurgery

Introduction

• The mechanism involves dysfunction of both cerebral hemispheres or of the reticular activating system (also known as the ascending arousal system). Causes may be structural or nonstructural (eg, toxic or metabolic disturbances). Damage may be focal or diffuse
• Head injury, diabetes, sepsis and drug/alcohol (excess/withdrawal) are the most important causes of comas
• First of all check the Glucose (DM) and do a quick neurological examination, including fundi; and record glasgow coma score (GCS)
• If it is not possible to obtain a history from the patient, a collateral history should be sought from a relative or carer. Talk to the GP or ambulanceman. Pick up the phone if necessary. The 'poor historian' is you
• TIA/CVA rarely presents as coma. Don't forget encephalitis and psychiatric
• Do a CT head (± LP) immediately if no obvious cause, or if no better at 24 hrs

Definitions

Unrousable unresponsiveness: GCS <8 = coma; GCS 8 or more = reduced conscious level. Ie, coma is unresponsiveness from which the patient cannot be aroused. Similar, but less severe disturbances of consciousness may also occur

Causes

HIDEMAP (from GP notebook)
2Hs = hypoxia (CCF, Resp F, ARF) + head trouble (head injury, hypertensive encephalopathy, cerebral vasculitis, cerebral vein thrombosis (CVT), SOL (SDH? Brain abscess?), meningitis (rarely), encephalitis: [Ref] , eclampsia, cerebral malaria: [Ref] )
I = infection (UTI, chest, wound, line, post-op, neutropenic sepsis, especially if immunosuppressed)
D = drugs = recreational (opiate?)/prescribed (excess or withdrawal; benzodiazepine?)
E = endocrine (hyper/hypoglycaemia, hypothroidism (especially elderly))
M = metabolic (ARF, ALF, hypercalcaemia, hyponatraemia)
A = alcohol (excess or withdrawal)
3Ps = psychiatric (hysterical coma) + postictal + postop (especially post #NOF; often multifactorial, eg septic, dry and drugs)
Notes: TIA/CVA does not usually present as coma unless major cerebral haemorrhage, or brainstem); steroids can cause 'steroid psychosis'
[Ref]

Risk factors

DM
Epilepsy
Alcohol + recreational drugs
Recent surgery (especially neurosurgery)
Pregnancy (eclampsia)

Symptoms

History limited value

Key questions

History limited value
If possible, ask re headache (and time of onset)
Vital to get history from witnesses (family, ambulanceman):
Depression (?overdose); suicide note; epilepsy; drug/medical history; recent head and neck infection (brain abscess); recent surgery (especially neurosurgery); cerebral shunt?; recent travel to malarial countries

Signs

Record conscious level of comatose patient, with Glasgow Coma Score (GCS)
Look for needle tracks, and signs of head injury and alcohol
Look at fundi (hypertensive encephalopathy, papilloedema or subhyaloid haemorrhage)
After an immediate blood glucose, perform a tip-to-toe physical examination, including the breasts (brain metastases), abdomen (unknown pregnancy)
What is the BP? Severe hypotension and severe hypertension are rare causes of coma, but record BP anyway

Blood

Glucose (BM)
FBC, ESR, CRP
U+E, LFT/GGT, Bone (?calcium), Glucose, TFTs
ABG
BC
± CK, if has been on floor for long
± Thick/thin films (malaria)
± SLE serology

Other

Urinalysis: leucocytes? nitrites? protein (renal disease); catheterise if cannot get sample
Urinary toxin screen (overdose?)
MSU
ECG
CXR (pneumonia, ?carcinoma if pt hyponatraemic)
CT head ± LP immediately if no obvious cause, or no better at 24h
Cervical XR, if suspect neck injury (care with neck)

Subdural haematoma

Key investigation

Glucose
CT head ± LP

Specialist investigation

EEG

Differential diagnosis

Drunk or asleep
Hysterical loss of consciousness

Treatment
(first line)

Drugs:
IV GLUCOSE 20 mls 50%, if BG < 4 mmol/L
Note: GLUCOSE increases risk of Wernicke's encephalopathy, so give IV PABRINEX first, if suspect patient is alcohol dependent and hypoglycaemic
IV NALOXONE 400 mcg, if small pupils (?opiate OD)
IV FLUMAZENIL 200 mcg, over 15 secs, if ?benzodiazepine OD; then 100 mcg, every 60 secs; max 1 mg (2 mg ITU)
Note: flumazenil is contraindicated in patients with epilepsy on longterm benzodiazepines; you may need to give further doses of naloxone and flumazenil (see BNF)

Procedures:
Assess ABC (care with neck)
Vital signs are vital, look at them
Call ITU and consider intubation if GCS <8
IV (+IV fluids if dry)
OXYGEN, if hypoxic
Warm up/cool down, if necessary

[Ref]

Stop

Alcohol
Any sedative drug (if in doubt, stop almost everything)

Treatment
(second line)

Drugs:
Have low threshold for broad spectrum IV AB (± antivirals ± antimalarials):
IV BENZYLPENICILLIN 1.2 g qds + IV GENTAMICIN 5 mg/kg od; before CT ± LP, if meningitis possible
± IV ACICLOVIR 10 mg/kg tds (infused over 60 mins) for 10-14 days, if encephalitis possibility (reduced dose in renal insufficiency)
± IV QUININE DIHYDROCHLORIDE: loading dose 20 mg/kg (max 1.4 g) over 4h; then 8 hrs after loading dose, 10 mg/kg tds (also infused over 4h); doses diluted in 250 mls N Saline, if cerebral malaria possible; watch for toxicity (QT prolongation)

If ?Wernickes, give IV PABRINEX 2 vials tds
If ?fitting, give IV LORAZEPAM 4 mg slowly (over 2 min); can repeat after 10 mins

Procedures:
If unwell, urinary catheter, CVP, arterial line

Admit?

Always

Bed plan

Medical admission ward
± ITU

Referrals

Medical:
Depends on cause (neurology, neurosurgery may be important)
± ITU

Complications

Brain damage, especially if prolonged hypoxia

Prognosis 

Very variable (depends on cause)
If deep coma, most patients die: 25% in 1hour, 65% in 1week, 75% within 1 month, 90% at 1 year
Only 0.6% make full recovery
Severe head injury: 25% dead in 1 year
[Ref]

2° Prevention
+ Health promotion

If alcohol or recreational drugs all/part of problem, refer to appropriate community services

Don't forget

1. Blood glucose
2. Look at vital signs and fundi
3. Check the drug chart (if in doubt, stop almost everything); look on the back of it
4. Encephalitis and psychiatric
5. DO CT head/LP immediately if no obvious cause, or if no better at 24 hrs

Red flags

Call ITU, and consider intubation, if GCS 8 or less, or falling