COMA- A CLINICAL APPRAISAL

                                    COMA- A  clinical appraisal

Coma in its simplest definition is loss o f consciousness

Consciousness is awareness of self and environment and ability to respond

 To external stimuli and inner needs

Intact consciousness depends upon

2 anatomical structures

I .Cerebral cortex

II. .ARAS-Ascending Reticular Activating System

 Medulla

Pons

Thalamus

Hypothalamus

Importance of ARAS: that is essential for arousal and wakefulness

A diffuse lesion of cerebral cortex only causes Coma

A focal  lesion of ARAS can cause Coma

Etiology

Mnemonic to remember the causes-I₅,M D

I-Injury,ICT (raised).Intoxication,infection,ischemia

M-Metabolic

D-drugs and intoxication

1/3 rd cases are due to trauma,stroke

1/3^rd cases are due to metabolic causes,

1/3^rd case are due to drugs and intoxication

In our tropicl country specially remember the possibility of

 cerebral malaria

Heat stroke

Leptospirosis

Typhoid encephalitis

Another way of classifying the lesions

1. Supra tentorial

2. Infra tentorial

3. Diffuse lesions

History

Points to be noted

1.H/o sudden onset

2.H/o chronic illness-Diabetes,epilepsy

3.Substance abuse

4.H/o taking prescription drugs

5.H/o head injury –Most important

Clinical Examination

Before doing detailed examination

First check ABC-Airway,Breathing,Circulation

And ensure adequate ventilation

For practical purpose initially itself exclude Hypoglycemia and Hypothermia

Administer Glucose and Thiamine Intravenously.

Next step is examination of

Pulse,BP.respiration skin temperature

This will help to diagnose

Raised ICT/Hypertensive encephalopathy CVA/Metabolic conditions

Examination of level of consciousness is important

This is of importance in assessing progress and prognosis

For this Glaxco coma scale is useful

A score between 0-7 has very poor prognosis

A score above 11 has only less than 5% chances.

Next step simple order of examination-of practical value

Examination of head

Examination of neck

Examination of limbs and

Detailed examination of CNS with special reference to exam

Pupils and

Eye movements

Examination of the Head

Look for signs of head injury

1.Wounds and contusion

2.Black eye

3.Battles sign-discoloration behind the ears due to blood pigments(mastoid ecchymosis)

-in fracture of middle cranial fossa.

4.ENT bleed

5.Ear discharge

CSF rhinorrhea

Examination of the neck:

Note-neck stiffness can occur in local neck injury

Note-when neck injury is suspected Intubation is contra indicated; only tracheostomy  has to be done.

Neck retraction can occur in meningitis/tetanus/hysteria

Examination of Limbs

1.Note general  posture of the body

.curled up position in-

decorticate rigidity

Decerebrate rigidity

Catatonia

2. Note movements of the limbs in response to pain

If asymmetrical-sign of focal deficit

Fundus examination

-Is of special importance in raised intracranial tension

Examination of pupils

Note size, shape, inequality of reaction to light

Specially look for

1. Fixed dilated pupil on one side -3^rdnerve involvement or uncal herniation

2. Fixed mid position of the pupil-in midbrain lesion

3. Pinpoint pupils occur in:-

Pontine hemorrhage/pilocarpine installation/Barbiturate poisoning or morphine overdose

Eye movements

1. Conjugate deviation of the eye:-

towards the side of the lesion-in supra tentorial lesion

away from the side of the lesion-pontine lesion

2.Dolls eye phenomenon-if intact indicates metablic cause/if not brain stem lesion

3.inter nuclear ophthalmoplegia-is sign ofMedial longitudinal bundle lesion

4.impaired upward gaze-sign of damage to midbrain/pretectal region.

Metaboic disorders

Early signs of metabolic disorder

Confusion

Lack of concentration

Impaired memory

Respiratory changes:

1.Cheyne stocks breathing(common in metabolic disorder)

2.Hyper ventilation-hysteria,metabolic acidosis

3.Hypoventilation-in metabolic alkalosis

Pupils are usually normal and reacting in metabolic disorder

Ocular movements are normal

No focal neurological signs are present

Psychiatric conditions and coma

Respiration and pupils are normal

Muscle tone and DTR are normal

Patient resists eye opening

INVESTIGATIONS

To be very precise perform the following

Xray skull,CT scan,MRI and arteriography-if head injury or mss leion is suspected.

Xray skull –take basal view if basal skull fracture is suspected because CT will not show this.

Undertake CSF analysis –to confirm infective cause or sub arachnoid  hemorrhage.

General investigation:

Complete hemogram

Biochemical parameters

LFT

Urine exam

Xray chest

ALGORITHMIC APPROACH TO  DIAGNOSIS OF COMA

Perform CT scan (if h/o trauma)

If normal-  ECG to rule out arrhythmias

If normal-ABG to r/o hypoxia/hypercapnea/Corbon monoxide poisoning

If ABG normal-Check body temperature to r/o  hypo or hyperthermia

If temperature normal   do biochemical profile, electrolytes to r/o metabolic conditions

If above normal               do CSF analysis to r/o infection/Sub arachnoid hemorrhage

If CSF normal-     do toxin screen to r/o drugs / toxins

If above test normal-do thyroid function to r/o thyroid disease

If thyroid test normal-look for ANA to r/o vasculitis

If all above tests are normal think of vitamin deficiency,drug withdrawal,porphyria,psychiatric condition

TREATMENT highlights

Basic principles:

Maintain effective respiration by ensuring airway clearance,O2 administrationmechanical ventilation

Maintain BP

Administer IV fluids

restoreAcid base balanceGive IV glucose/Thiamine on emergency basis

careful attendance to skin,bladder and bowel

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