Concept and classification of exogenous acid-base disorders
These disorders develop exclusively as a result of the entry of substances from the external environment capable of shifting the acid-base balance. Depending on the chemical nature of the incoming compounds, two main directions of disorders are distinguished:
- Exogenous acidosis is a consequence of an excess of compounds with acidic properties.
- Exogenous alkalosis is a rare condition that occurs when an excess of alkalis or bicarbonates enters the body.
Exogenous acidosis: etiology and pathogenesis
Acidosis develops with the excessive intake of compounds with acidic properties into the body. The main causes include:
- Accidental or intentional ingestion of non-volatile acid solutions, such as hydrochloric, sulfuric, or nitric acid.
- Alimentary factor associated with the prolonged consumption of foods or beverages with high levels of citric, malic, hydrochloric, or salicylic acids.
- Drug load from the intake of acids or their salts, including acetylsalicylic acid.
- Transfusion of donor blood preserved with sodium citrate.
Pathogenesis includes the dissociation of exogenous acids with an increase in hydrogen ion concentration, leading to the rapid depletion of buffer systems. Additionally, toxic effects on the liver and kidneys trigger metabolic disturbances, accumulating endogenous acidic metabolites and increasing the degree of acidosis.
Exogenous alkalosis: etiology and pathogenesis
This type of disorder is less common and is associated with an excess of alkaline compounds.
Causes of occurrence:
- Iatrogenic factor — rapid administration of solutions containing bicarbonate ions (e.g., during the incorrect treatment of lactic acidosis or ketoacidosis in patients with diabetes mellitus).
- Prolonged consumption of foods and liquids with a high alkali content. A classic example is patients with peptic ulcer disease who consume large volumes of milk and alkaline solutions.
Mechanisms of development: The main link is an increase in plasma bicarbonate concentration. The secondary link is increased production or impaired excretion of endogenous bicarbonate, often exacerbated by renal failure. The mechanisms of exogenous alkalosis are identical to those of conventional metabolic alkalosis.
Briefly: answers to topical questions
Through what respiratory mechanisms does compensation for exogenous metabolic acidosis occur?
Compensation for exogenous acidosis is carried out by mechanisms identical to those for metabolic acidosis compensation. The respiratory mechanism is pulmonary hyperventilation, which leads to a decrease in pCO2. A possible manifestation of such compensation is Kussmaul breathing.
Acidosis means acids (citric acid, aspirin, non-volatile acids), while alkalosis means alkalis and bicarbonates (milk for ulcers, excess soda).
Class and exam questions
What serves as the main cause of exogenous acidosis?
The main cause is the excessive intake of compounds with acidic properties into the body, such as solutions of non-volatile acids, acidic foods, certain drugs (e.g., acetylsalicylic acid), or sodium citrate during blood transfusion.
Why can a blood transfusion lead to exogenous acidosis?
Blood transfusion can cause acidosis if the blood was preserved using sodium citrate, which enters the recipient's body.
What is the pathogenesis of exogenous alkalosis?
The main link in pathogenesis is a sharp increase in plasma bicarbonate concentration, coupled with impaired excretion or increased production of endogenous bicarbonate.
What else to study on this topic
- Clinical examples of iatrogenic alkalosis manifestations during ketoacidosis correction
- The impact of toxic liver and kidney damage on the exacerbation of exogenous acidosis
- Comparison of the mechanisms of exogenous disorders with metabolic acid-base disturbances
- The role of the alimentary factor in the chronic shift of acid-base balance
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