Metabolic Acidosis: Causes

Pathogenesis (disease development)

Metabolic acidosis is defined as a metabolic decrease in blood pH <7.36. Possible causes of metabolic acidosis include:

  • Addition Acidosis and Subtraction Acidosis Metabolic acidosis can result either from increased metabolic uptake or production of acids (addition acidosis) or from increased losses of bases (HCO3; hydrogen carbonates, obsoletely also bicarbonates) (subtraction acidosis). During the degradation of dietary protein (protein), acid valencies, so-called “fixed” acids (sulfate and phosphate from sulfuric and basic amino acids) are formed, which the organism cannot “exhale”. These acids are urinary and are excreted by healthy kidneys – but in old age, they can overload the buffer system in the long term.
  • Renal (belonging to the kidney) acidosis Renal acidosis occurs when the kidney is no longer able to excrete enough acids or increased excretion of bases (HCO3). A distinction is made between metabolic acidosis with a large or small anion gap. The anion – a negatively charged ion – is chloride. A small anion gap indicates organic causes, such as keto or lactic acidosis – acidosis caused by ketone bodies or lactate (lactic acid). The large anion gap indicates rather poisoning, for example, with alcohol.

Etiology (causes)

Biographical causes

  • Genetic burden
    • Genetic diseases
      • Renal tubular acidosis (RTA) – genetic disorder with autosomal recessive inheritance that leads to a defect defect H+ ion secretion in the tubular system of the kidney and consequently to demineralization of bone (hypercalciuria and hyperphosphaturia/increased excretion of calcium and phosphate in the urine) and hypokalemia (potassium deficiency).

Behavioral causes

  • Nutrition
    • Starvation state – increased acid production
    • Overeating – increased acid production

Causes due to disease

  • Gastrointestinal (gastrointestinal tract related:
    • Diarrhea (diarrhea) – increased losses of HCO3.
  • Ketoacidosis (diabetic (diabetic ketoacidosis, DKA), hunger, alcohol)Note: Approximately 6-7% of pregnant women suffer from diabetes mellitus (DM); this is about 90% of cases are gestational diabetes.
  • Lactic acidosis:
    • Hypoxia (lack of oxygen supply to the tissues) in the context of shock.
    • Liver and kidney failure
    • Sepsis (blood poisoning)
    • Intoxications by alcohol, biguanides (metformin: inhibition of hepatic gluconeogenesis), salicylates.
  • Renal (kidney related):
    • Renal insufficiency (chronic renal impairment) → hyperkalemia (excess potassium).
    • Renal tubular acidosis (RTA).
    • Uremia (increased occurrence of urinary substances in the blood due to lack of or insufficient renal function) – due toreduced ability to adequately excrete daily dietary intake of acids with severely reduced glomerular filtration rate (GFR).
  • Alcohol abuse (alcohol abuse)
  • Diabetes mellitus
  • Diarrhea (diarrhea) → gastrointestinal bicarbonate loss.
  • Cachexia (emaciation; emaciation).

Medication

Operations

Environmental exposure – intoxications (poisonings).

  • Alcohol
  • Ethylene glucole – used as an antifreeze.
  • Methanol
  • Toluene