Coma & Brain stem death

Coma

• Definition
• A state of prolonged unconsciousness characterized by loss of reaction to external stimuli or, a state of unrousable unresponsiveness.
• Differentiate from:
• Stupor
• Unconscious but can be aroused with repeated stimuli.
• Delirium
• Confused state often with restlessness and hallucinations.
• ‘Locked-in’ syndrome
• actually conscious but unable to speak or move
• may move eyes (massive brainstem damage)
• Vegetative state
• apparently awake but unresponsive (brainstem intact but widespread cortical damage)
• may breath spontaneously.

The Reticular Activating System

• Consciousness is determined by the reticular activating system
• which is located in the brainstem
• and its ascending connections

Coma is considered a medical emergency:

• Keep the patient alive
• resuscitate if necessary
• Exclude obvious factors
• head injuries
• hypogylcaemia, etc.
• Obtain history
• eyewitnesses
• medical information cards
• eg. MedicAlert
• Do general and neurological examination
• Do appropriate investigations

Causes of Coma

• Neurological
• Lesions within the brainstem
• affecting the reticular activating system
• Lesions in other parts of the brain
• compressing the brainstem
• Traumatic Brain Injury
• Diffuse brain injury
• Extradural (epidural) haemorrhage
• Haematoma – blood collection between the skull and the dura
• This is due to trauma resulting in rupture of arteries or veins
• commonly the middle meningeal artery
• Treatment is to evacuate the haematoma by drilling a burr hole.
• Subdural haemorrhage
• The haematoma is between the arachnoid and the dura
• They are due to rupture of the bridging veins between the cerebral cortex and the venous sinuses
• Mid-line shift
• Ipsilateral ventricle effaced
• Acute or chronic
• chronic subdural haematomas become isodense (darker appearance) 
• Vascular (eg. stroke)
• majority do not result in coma
• large strokes can act as mass lesions
• Infections (eg. encephalitis)
• Intracranial tumours
• Epilepsy/Post-Ictal states
• Hypertensive encephalopathy
• Toxic, metabolic, inflammatory or vascular conditions diffusely affecting the brain
• Hypoxia, CO2 Narcosis
• Drugs / Poisons
• Hypoglycaemia, Hyperglycaemia
• Hepatic Encephalopathy
• Electrolyte Abnormalities /Uraemia
• Endocrine: Myxoedema, Addisonian
• Liver Failure (portosystemic encephalopathy)

Types of coma

Coma due to mass lesions

• Hematoma, large strokes ( a type of mass lesion)
• compress brain tissue causing:
• herniation of brain tissue from one compartment to another

Hypoglycaemic coma

• Signs & Symptoms
• blood glucose < 3.0 mmol/L
• Sympathetic:
• sweating
• tremors
• palpitations
• anxiety
• Neuroglycopenia
• confusion
• abnormal behaviour
• coma
• death
• Causes
• oral hypoglycaemic agent/insulin in treatment of diabetes
• Give glucose immediately
• IV if patient drowsy or unconscious
• Whipple’s Triad

1. Symptoms known or likely to be caused by hypoglycemia
2. A low plasma glucose measured at the time of the symptoms
3. Relief of symptoms when the glucose is raised to normal

Hyperglycaemic comas

• There are two types of hyperglycaemic comas in diabetes:
• Diabetic Ketoacidosis (DKA)
• Type 1 diabetes
• Hyperosmolar Hypergylcaemic Non-Ketotic Coma (HHNC)
• Type 2 diabetes
• The new term is: HHS or Hyperosmolar Hyperglycaemic State. However only about 20% of HHS have coma

Drugs & Coma

• Drug overdose may be accidental or intentional
• Diagnosis
• History important
• Suspect if
• IV needle marks
• pin-point pupils

Liver Failure (Portosystemic Encephalopathy)

• In liver failure
• there is accumulation of ammonia in the systemic circulation
• leading to coma
• It may occur in
• Acute liver failure
• acute fulminant hepatitis
• paracetamol overdose
• Chronic liver disease
• alcoholics
• chronic hepatitis B, C
• Specific signs to look for
• Early
• Drowsiness
• confusion
• altered sleep pattern
• fetor hepaticus
• Asterixis
• flapping tremor
• constructional apraxia
• loss of the ability to execute or carry out learned purposeful movements
• despite having the desire and the physical ability to perform the movements
• disorder of motor planning
• Late
• Coma
• +ve Babinski signs

CNS infection & Coma

• Serious Infections
• Encephalitis
• Meningitis
• Brain abscess
• Suspect if
• fever
• headache
• progressive drowsiness
• fits prior to coma
• Physical signs of neck stiffness
• meningism in meningitis
• Papilloedema
• may be present indicating raised intracranial pressure

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Postures found in comatose status

*Refer posture and balance lecture

Decerebrate Posture

• Brainstem Injury
• Extension of arms with internal rotation
• Pronation of wrists and flexion of fingers
• Legs extended with plantar flexion of feet

Decorticate Posture

• Lesions above brainstem
• Arms adducted and flexed across the chest
• Wrist and fingers flexed
• Legs extended with plantar flexion of feet

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Glasgow Coma Scale
Measure consciousness

• Based on 3 clinical responses: (EVM)
• Eye Opening
• Verbal Response
• Motor Response

• Record the best response
• Minimum Score 3
• Maximum Score 15
• Chart initial and subsequent scores
• The GCS record is the patient’s change in conscious level with time.

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Brain death

• Definition
• A condition in which there is:
• Permanent and irreversible loss of the functions of the brain
• together with irreversible loss of the capacity to breathe
• This person is supported by:
• Artificial mechanical ventilation
• Other supportive measures
• A person certified to be brain dead is considered to be legally dead
• Criteria
• Coma
• No spontaneous respiration
• No response to external stimulation
• Absence of brainstem reflexes
• Ethical issues
• Medicolegal
• who has the right to determine who should be kept alive by life support?
• Beneficence
• the duty of the doctor to do good
• Justice
• How is it justified?
• How is healthcare distributed under circumstances of limited human and financial resources and who / how determines
• ‘who gets what’?
• Dignity
• Everyone has a right to a dignified death
• Autonomy
• What would the patient have wanted?
• Many countries now have legal and medical definitions for brain death:
• The patient is in apnoeic coma on a ventilator
• There is evidence of a significant medical or CNS event that would result in brain death
• Formal tests of brainstem function confirm absent brainstem reflexes
• Before diagnosing brainstem death exclude:
• Hypothermia (T<35°C)
• Drug Intoxication
• Acid-Base Imbalance
• Electrolyte Abnormality
• Hypoglycaemia/Endocrine Disorder
• Tests of brainstem death:
• No pupillary response to light
• pupils fixed
• No oculocephalic reflex
• Doll’s Eye
• No vestibulo-ocular reflex
• No motor response within cranial nerve distribution
• No corneal reflex/gag reflex/grimacing to painful stimulus
• No cough response to pharyngeal/laryngeal/tracheal stimulation
• Apnoea with no respiratory effort when ventilator is switched off & PaCo2 rises to above 6.7kPa (50mmHg)
• Tests of brainstem death must be done twice at least 6-24 hours apart
• Tests must be done independently by 2 different senior doctors, one of whom must not be in the medical team managing the patient
• EEG is not routinely required
• Once the diagnosis is established, inform the next-of-kin and explain the diagnosis
• Allow adequate time for the family to understand and discuss the issue amongst themselves
• Informed consent must be obtained before withdrawing life support
• In suitable cases discuss and obtain informed consent from next-of-kin for organ donation
• Members of the surgical transplant team and the medical team looking after the potential recipient should not be involved in certification of brain death of the donor and in counselling / obtaining consent from the donor’s next-of-kin regarding organ transplantation