Coma Flashcards
Define coma
A state of unarousable psychological unresponsiveness in which the subjects lie with eyes closed and show no psychologically understandable response to external stimulus or inner need.
What does consciousness depend on?
- An intact ascending reticular activating system to act as the alerting or awakening element of consciousness
- A function cerebral cortex of both hemispheres which determines the content of that consciousness
What is consciousness?
- Arousal (reticular activating system)
* Awareness of environment (cerebral hemispheres)
Name four different states of consciousness
- Lethargy
- Stuporous
- Obtunded
- Coma
Name causes of a decreased GCS
• Toxic/metabolic states
o Hypoxia/hypercapnia/sepsis/hypotension
o Drug intoxication, renal failure or liver failure
o Hypoglycaemia, ketoacidosis
• Seizures
• Damage reticular activating system (arousal)
• Causes of raised intracranial pressure
o Tumour, stroke, epidural haematoma, subdural haematoma, subarachnoid haematoma, hydrocephalus
Define a persistent vegetative state
A state in which the brain stem recovers to a considerable extent but there is no evidence of recovery of cortical function.
There is arousal and wakefulness but the patient does not regain awareness or purposeful behaviour of any kind.
Define locked in syndrome
Patient has total paralysis below the level of the third nerve nuclei (oculomotor n.) and, although able to open, elevate and depress the eyes, has no horizontal eye movement and no other voluntary eye movements.
How do you diagnose locked in syndrome?
Depends on recognising that the patient can open their eyes voluntarily and signal numerically by eye closure
Describe the resuscitation after assessment of unconsciousness
• Airway
• Breathing
o Depressed respiration
o Increased respiration
o Fluctuating respiration
• Circulation
• Blood samples
o Glucose, biochemistry, haematology, blood gas
o Toxicology
• Establish baseline blood pressure, pulse, temperature, IV access and stabilise the neck
• Examine for evidence of mengingitis – treat on suspicion
What are causes of depressed respiration?
Drug overdose, metabolic disturbance
What are causes of increased respiration?
Hypoxia, hypercapnia, acidosis
What are causes of fluctuating respiration?
Brainstem lesion
What do you need to determine in the history?
• ? Predictable progression of underlying illness
• ? Unpredictable event in patient with previously known disease
• ? Totally unexpected event
o ? Head injury, sudden collapse, limb twitching, previous history of drug or alcohol abuse
What do you need to examine for and monitor?
- Temperature
- Heart rate, blood pressure, CVS
- Respiration
- Skin, breath
- Abdomen
- Meningism
- Fundal examination
Name three ways to carry out a neurological assessment of coma
- Glasgow coma scale
- Brainstem function
- Motor function + reflexes
What is the usual GCS of someone in a coma?
GCS <= 8
- Eye opening – 2 or less
- Verbal response – 2 or less
- Motor response – 4 or less
Describe the reason for GCS <= 8 in coma
Patient who fail to open eyes in response to voice, perform no better than weak flexion in response to pain, and make at best only unrecognisable grunting noises in response to pain are regarded as being in a coma
What CN are responsible for pupillary reactions?
II and III
What CN are responsible for corneal responses?
V + VII
What CN are responsible for spontaneous eye movements?
III, IV, VI
What CN are responsible for oculocephalic responses (doll’s eye)?
III, IV, VI, VIII
What CN are responsible for oculovestibular responses?
III, IV, VI, VIII
What CN are responsible for respiratory pattern?
Medullary centre
How do you test brainstem function?
Check function of cranial nerves
How do you test motor function?
- Motor response
- Muscle tone
- Tendon reflexes
- Seizures
What is a cause of coma, with no meningism and no focal brainstem or lateralising cerebral signs?
- Anoxic/ ischaemic conditions
- Metabolic disturbance
- Intoxications
- Systemic infections
- Hyperthermia/ hypothermia
- Epilepsy
What is a cause of coma, with meningism and no focal brainstem or lateralising cerebral signs?
- SAH
- Meningitis
- Encephalitis
What is a cause of coma, with or without meningism and with focal brainstem or lateralising cerebral signs?
Focal cerebral: • Tumour • Haemorrhage • Infarction • Abscess
What are the investigations used for a coma, with no meningism and no focal brainstem or lateralising cerebral signs?
- Toxicology screen including alcohol level
- Blood sugar and electrolytes
- Assess hepatic and renal function
- Acid – base assessment and blood gases
- Blood pressure
- Consider carbon monoxide poisoning
What are the investigations used for a coma, with meningism and no focal brainstem or lateralising cerebral signs?
• CT head scan • Lumbar puncture o Appearance o Cell count o Glucose level o Capsular antigen tests
What are the investigations used for a coma, with meningism and with focal brainstem or lateralising cerebral signs?
• CT or MRI • If CT/MRI not diagnostic, then investigate for other causes including o Metabolic screens o Lumbar puncture o EEG
Name five factors which fact the outcome in coma
- Age
- Cause of coma
- Depth of coma
- Duration of coma
- Certain clinical signs, the most important of which are the brain stem reflexes
What is the survival rate for patients in comas?
Only 15% of patients in non-traumatic coma for more than 6 hours will make a good or moderate recovery, the other 85% will die, remain vegetative or reach a state of severe disability in which they remain dependent
Name seven steps in the continuing management of patients in coma
- Maintenance of vital functions
- Care of skin, avoidance of pressure sores
- Attention to bladder and bowel function
- Control of seizures
- Prophylaxis of DVT, peptic ulceration
- Prevention of contractures
- Consider “locked-in” syndrome
How does a head injury cause focal neurological signs/epilepsy?
• Diffuse axonal injury • Contusion • Intracerebral haematoma • Extracerebral haematoma o Extra-dural haematoma o Sub-dural haematoma
What is the view of sub-dural/extra-dural haematoma on CT?
Subdural haematoma ellipse:
• Convex
Extradural haematoma:
• Concave/convex (lens)
What is the management of head injury?
- Stabilise cervical spine
- Airway/breathing/circulation
- If GCS ≤ 8 – intubation + ventilation
- Treat raised ICP
- Cranial imaging – may need decompressive surgery or removal of haematoma
- Neuro observation
What is the management of raised ICP?
- Surgery to relieve pressure
• Haematoma, ventricular shunt - Osmotic agents – mannitol
- Nurse with head at 30-45% (venous return)
- Reduce pain
- Maintain good PO2, reduce PCO2
- Reduce metabolism (reduce temp, barbituates)
