BIOCHEMICAL INVESTIGATION OF COMA

Question 1

CAUSES

Answer 1

Supratentoral
Infratentoral
Metabolic
Diffuse

This lecture is concerned with Metabolic Comas

Question 2

AETIOLOGY

Answer 2

Classified as Structural and Non structural

Mnemonic is AEIOUTIPPS
Alcohol
Epilepsy
Insulin
Opiates
Urea
Trauma
Infection
Poisoning
Psychogenic
Shock
Stroke

Question 3

CLINICAL ASSESSMENT

Answer 3

History and Physical Examinations

WARNING SIGNS ON GPE

• Severe dehydration, acidotic breathing and acetone breath suggests DKA
• Bullous lesions characterise Barbiturate poisoning
• Jaundice could indicate liver disease
• Cherry red colour of lips and mucous membranes suggest Carbon Monoxide Poisoning
• Needle tracks suggests Drug abuse

Radio diagnostic modalities ( CT scan, MRI) to elucidate intracranial structural abnormalities

BIOCHEMICAL INVESTIGATIONS 
Required to rule out metabolic, endocrine, toxicologic causes and complications 
—Metablolic causes include
1. Hyper/hypoglycemia 
2. DKA
3. Addison’s disease
4. Hypoxia
5. Hypercapnia
6. Hepatic encephalopathy 
7. Hyper/hyponatremia
8. Hypercalcemia
9. Uraemia
10. Hypothyroidism 

Toxic encephalopathy
Due to toxins, poison, drugs
Wernicke encephalopathy

SEQUENCE OF TESTS;
—serum glucose, e, u and cr ( Is a must in all cases of Coma)
— Serum Calcium
— Serum alcohol levels
— LFT
— Arterial blood gases, Carboxyhemoglobin levels( in suspected CO poisoning)
— Urinalysis and Urine toxicologic studies
— Urinary electrolytes in suspected addisonian crisis
— Thyroid function tests
— Drug screening

Question 4

METABOLIC COMAS

Answer 4

A cardinal feature is the absence of lateralizing signs, neurological deficits are bilaterally symmetrical in metabolic comas

Tremors, Asterixis and Multifocal Myoclonus strongly suggest metabolic coma ( organ failure)

Question 5

URINALYSIS AND BASIC METABOLIC PROFILE

Answer 5

Offers rapid semi quantitative assays for glucose, ketone, bilirubin, pH, S.G , RBC e.t.c
— capillary blood glucose can be estimated by a finger prick using glucometer
— pulse oximeter to estimate arterial oxygen tension also reveals presence or absence of hypoxia
— Moderate to severe glucosuria with ketonuria suggest DKA/Hyperglycemia
— ABG ( Arterial Blood gases) required to confirm Hypercapnia

Always correct Calcium if need

Question 6

THYROID FUNCTION TEST RESULTS

Answer 6

Medical history and Examination reveal suggestive features

— TSH is high in Myxoedema coma with low freeT3, freeT4 or both

— FreeT4 alone is better than FreeT3 alone

Question 7

ADDISON’S DISEASE

Answer 7

Hyponatremia, Hyperkalemia and Mild non anion gap metabolic acidosis

Low cortisol with High ACTH ( Assay cortisol and Aldosterone after ACTH injection)

Acetone breath, hypoglycemia and high AG acidosis suggests alcohol, normal ph from vomitting may mask acidemia

Question 8

Drug abuse

Answer 8

History and Exam

Specific drug metabolites can be assayed using HPLC or GLC

Naloxane may be given when opiates is suspected

Stabilize patient and refer for better assessment and management