Metabolic acidosis:

Definition:

It is a clinical condition which is developed due to accumulation of an acid other than carbonic acid in the body that causes reduction in the plasma bicarbonate.

Causes of metabolic acidosis:

1. Accumulation of excessive acids in plasma:

i) Lactic acidosis
ii) Ketoacidosis (e.g. Diabetic ketoacidosis)
iii) Salicylate poisoning
iv) Methanol poisoning

2. Decreased excretion of acids from plasma:

i) Acute renal failure
ii) Chronic renal failure
iii) Distal renal tubular acidosis

3. Bicarbonate loss:

i) Diarrhoea
ii) Uretero-sigmoidostomy
iii) Intestinal fistula.

Symptoms:

Symptoms of metabolic acidosis are-

i) Respiratory distress
ii) Thirst
iii) Dizziness
iv) Drowsiness
v) Confusion
vi) Fatigability
vii) Convulsion
viii) Muscle pain due to cramp.

Signs:

• Deep sighing breathing (Kussmaul respiration)
• Dryness of mouth
• Pulse rate – increased
• Blood pressure- decreased
• Postural hypotension
• Low JVP
• Reduced urine output
• Reflexes- depressed
• Coma.

Treatment of metabolic acidosis:

i) Identification and treatment of the underlying cause (if possible)
ii) If there is association with sodium and water depletion – correction accordingly
iii) IV infusion of Bicarbonate (1.26% NaHCO3) can be given if-

• Underlying cause cannot be corrected readily
• Severe acidosis (H⁺ concentration is more than 70 nmol/l, pH is less than 7.15)
• There is evidence of tissue dysfunction.

iv) Haemodialysis- is done as a part of treatment of metabolic acidosis in case of renal failure.