Definitions, and approach to Coma

COMA

Dr. Valmiki Salema,Med Officer, Gen Medicine

Definitions and Approach to:

Normal Brain Anatomy

Cerebral Cortex

Reticular

Activating

System

Consciousness is defined as a state of

full awareness of the self and one’s

relationship to the environment.

It has 2 components:

• Arousal (RAS)

• Awareness (Cortex)

Consciousness

Anatomy of Consciousness

Ascending Reticular Activating System (RAS) is

a system of fibers which arises from the reticular

formation of the brainstem and projects to the

thalamus.

Neurons in the reticular formation

receive collaterals from the

ascending spinothalamic pathways

and then projects diffusely to the

entire cerebral cortex .

Sensory stimuli are involved not only with sensory perceptionbut also play role in the maintenance of consciousness through their connections with the RAS.

Stimulation of RAS produces arousal and destruction of RAS produces coma.

Hypothalamus is an important component of consciousness, Stimulation of posterior hypothalamic region causes arousal.

The degree of alteration in consciousness is roughly proportional to the volume of brain tissue involved in the process.

Few Loosely Used Terms in Medical Practice, and their

Definitions

• Mild form of altered mental status.

• Patient has reduced wakefulness or awareness.

• Include hyper- excitibility or irritability alternating

with drowsiness.

Clouding of Consciousness:

Confusional State:

More profound deficit including disorientation and

difficulty in following commands due to focal deficit

of cognitive function.

Obtundation:Patient has a lessened interest in the environment,

slowed responses to stimulation, and tends to sleep

more than normal with drowsiness in between sleep

states .

Stupor:Only vigorous and repeated stimuli will arouse the

individual, and when left undisturbed, the patient will

immediately lapse back to the unresponsive state .

Coma:State of unresponsiveness , patient cannot be

aroused by stimuli even with vigorous stimulation.

Locked in Syndrome:Ventral brainstem destruction sparing the RAS.

Patient is mute and quadriplegic but not comatose,

with variable preservation of consciousness. Patient

is awake but speechless & motionless with little

response to stimuli and Sustained eye opening along

with aphonia or hypophonia.

Persistant Vegetative state:Vegetative describes an organic body capable of

growth and development but devoid of sensation and

thought. Patient have massive bilateral hemisphere

damage with intact brainstem. In PVS, patient is

awake but unaware of environment.

Minimally Conscious state:Patients shows limited but clear evidence of

awareness of themselves or their environment by at

least following simple commands, gestural or verbal

yes/ no response. Further improvement is more likely

than patients in a vegetative state.

Akinetic Mutism: Sub category of minimally conscious state in which

patient neither tend to move nor speak, lack motor

functions such as speech, facial expression, gestures

but demonstrate alertness. They can move their eyes

in response to auditory stimulus or move after

repeated commands.

Causes of COMA

Structural Non- Structural(Focal) (Diffuse or metabolic)

Structural brain injuries causing Coma

Compressive lesions Destructive lesions

Non Structural (Diffuse, Metabolic or Multifocal

causes of Coma)

A. Deprivation of oxygen, substrate or metabolic

cofactors

1. Hypoxia

2. Ischaemia

3. Hypoglycemia

4. Cofactor deficiency (thiamine, niacin, pyridoxine)

B. Toxicity of Endogenous products

1. Due to organ failure (hepatic coma, uremic coma)

2. Due to hyper or hypofunction of endocrine organs

C. Toxicity of Exogenous poisoning

1. Sedative drugs

2. Acid poisons/ poisons with acid breakdown

3. Psychotropic drugs

D. Infections or inflammation of CNS:

1.Meningitis

2.Encephalitis

3.Vasculitis

Approach to An Unconscious Patient..

History.. (Whenever possible from relatives, friends, reliable attenders)

Make sure to ask:

• Onset: (abrupt, gradual)

• Recent complaints: (headache, weight gain/ loss, fever, depression (suicidal ideas), focal weakness, trauma)

• Previous medical illness: (diabetes, hypertension, chronic lung diseases, renal failure, thyroid disease, heart disease)

• Drug intake history: (prescription drugs, insulin, thyroxine, recreational drugs)

• Family History: (similar complains, to r/o environmental toxicity/ food poisoning etc.)

• Travel History: (to malaria/ Japanese encephalitis etc. endemic regions. or contact with STD’s)

Examination.. (Brief but thorough)

• Vital signs: Pulse, BP, Temperature, RR

• GPE:

• Habitus, Pallor, Icterus, Cyanosis, Clubbing, Lymphadenopathy,

Oedema, Thyroid swelling.

• Evidence of Trauma: bruises/ laverations/ fracures/ bleeding

from ear or nose/ abd distension

• Evidence of Drug use: Needle marks/ smell from breath/ pupils/

unkempt and poor hygiene/ parasympathetic symptoms

• Evidence of previous suicide attempts: cut marks

• Systemic Exam: Respiratory/ Cardiac/ Abdomen/ Neurological.

(Esp. look for Meningeal signs, Pupils, Fundus)

Changes in Pupils with lesions at different levels

of brain that can cause Coma

Diencephalon:• Thalamus• Hypothalamus• Pituitary

Pretectum:• Lies at the junction of

mid and fore brain.• Made up of atleast 7

nuclei• Main role: initiation of

optokinetic reflexes, also nociception and REM sleep.

Hippus:Pupillary athetosis. Irregular alternating dilation and contraction of the pupil in response to light.

Coma Evaluation Scales

Glasgow Coma Scale• Graham Teasdale and Bryan Jennet, Neurosurgery

professors, at the University of Glasgow, Developed this

scale in 1974

• 15 point scale, used to test best motor response (6), best

verbal response (5) and best eye response (4).

• Score ranges from 3 (deep coma or death) to 15 (fully

awake).

• Limitations:• Failure to assess verbal score in intubated patients.

• Inability to test brainstem reflexes

• Person to person variation (a 2005 trial in the US, showed only 30% ER

docs, 38% Neurosurgeons Concur)

• Does not take physical debility into account ( eg. eyes swollen shut after

head injury, broken bones causing painful movements)

Newer Scales for Prognosis of Coma:

• FOUR (Full Outline of UnResponsiveness) SCALENew Coma Scale is devised in 2005, Four components (Eye,

Motor, Brainstem, Respiration)

Each component has maximum of score of Four.

• AVPU Alertness, response to Verbal stimuli, response to Painful

stimuli, or Unresponsive

• ACDU Alertness, Confusion, Drowsiness, and Unresponsiveness

• Grady Scale: Scale of I to V along a scale of Confusion, Stupor, Deep

stupor, abnormal Posturing, and Coma.

Wijdicks E, Bamlet WR et al. Validation of New Coma Scale: The Four Scale. Ann Neurol 2005; 58: 585 – 593.

Investigations.. (But don’t wait to start stabilising the patient)

• Laboratory:

• Routine: CBC, LFT, RFT, U/E, CRP, ESR

• Specific: ABG’s, Amylase, TFT, Calcium, Lactate, Cultures,

CSF, Toxicology screen

• Radiological:

• X- Rays: Chest/ Abdomen/ Skull/ Bones

• Ultrasound: Abdomen

• CT Brain: Plain/ With Contrast

• MRI: If CT inconclusive

Stages of Coma

Grade I - Individuals who respond with recognition when their

name is called and do not lapse into sleep when left

undisturbed.

Grade II - The person lapses into sleep when undisturbed and is

aroused only when a pin is tapped gently over the chest wall.

Grade III - Patient who winces in response to deep pain

stimulus. Deep pain stimulus may result in abnormal postural

reflexes either unilateral or bilateral.

Grade IV – Deep pain stimulus may result in decorticate or

decerebrate posturing.

Grade V - The patient who maintains a state of flaccid

unresponsiveness inspite of deep pain stimulation.

Consisting of High Flow Oxygen, dextrose,

flumazenil, naloxone , thiamine, activated

charcoal is sometimes used in the

management of an orphan comatose patient.

Coma cocktail

TO RECAP...

TAKE HOME MESSAGES....

Even before detailed history & examination, it is

important to start emergency measures such as

correction of possible deficiencies in glucose,

oxygenation and blood pressure.

After determination of vital signs, attention should

be towards ensuring an adequate airway, oxygenation

and intravenous access.

Immediately after obtaining blood samples, 50 cc of

50% glucose followed by 100 mg of thiamine should

be given.

Naloxone and flumazenil may be given if there is

suspicion of opiate or benzodiazepine overdose.

Preparation for intubation, respiratory support, and

for use of pressor agents should be made, as it may

become necessary.

Always assume a cervical spine injury may be

present, and immobilise the neck until a fracture can

be ruled out.

Never forget to check ECG/RBS/ TFT’s in an

unconscious patient.

Eye response ( Score – 4)

4 - eyelids open , tracking, or blinking to command

3 - eyelids open but not tracking

2 - eyelids closed but open to loud voice

1 - eyelids closed but open to pain

0 - eyelids remain closed with pain

Motor response (Score – 4)

4 - thumbs-up, fist, or peace sign

3 - localizing to pain

2 - flexion response to pain

1 - extension response to pain

0 - no response to pain

Brainstem reflexes ( Score – 4)

4 - pupil and corneal reflexes present

3 - one pupil wide and fixed

2 - pupil or corneal reflexes absent

1 - pupil and corneal reflexes both absent

0 - absent pupil, corneal, and cough reflex

Respiration (Score – 4)

4 - not intubated, regular breathing pattern

3 - not intubated, Cheyne–Stokes breathing pattern

2 - not intubated, irregular breathing

1 - breathes above ventilator rate

0 - breathes at ventilator rate or apnea