Metabolic Disorders in Hypoxia

Energy collapse as a trigger

Any form of oxygen deprivation begins with the suppression of biological oxidation processes. Since the aerobic pathway is blocked, its coupling with phosphorylation is disrupted.

• High-energy phosphate deficit: The concentration of ATP and creatine phosphate in cells drops rapidly. This is characteristic of both acute and chronic hypoxia.
• Excess phosphates: Simultaneously, inorganic phosphate accumulates in tissues. This occurs due to the accelerated hydrolysis of remaining high-energy compounds (ATP, ADP, AMP) against the background of impossible resynthesis.

ATP restoration stops not only due to the direct lack of oxygen, but also as a result of a shortage of metabolic substrates and the suppression of tissue respiration enzyme activity.

Carbohydrate and lipid metabolism: the path to acidosis

Trying to compensate for the energy deficit, the cell reorganizes its metabolism, which inevitably leads to uncompensated acidosis.

1. Glycolysis dynamics. Initially, anaerobic carbohydrate breakdown is sharply activated. Lactate is released into the tissue, and the concentration of hydrogen ions increases. As the acidification of the environment increases, the excess of protons begins to inhibit the enzymes of glycolysis itself, and the process slows down.
2. Lipid metabolism. Due to the energy deficit, the synthesis of new lipids stops, while lipolysis is activated (under the action of lipases and an acidic environment). Ketone bodies (acetone, acetoacetic, and β-hydroxybutyric acids) and higher fatty acids (HFAs) accumulate in plasma and cells.

Important: The accumulation of HFAs further uncouples oxidation and phosphorylation processes, closing the vicious circle and exacerbating the ATP deficit.

Protein metabolism and ion imbalance

Against the background of energy starvation and environmental acidification, profound structural changes occur within the cells.

• Protein breakdown: The synthesis of nucleic acids and proteins halts. At the same time, the acidic environment activates cellular proteases, initiating non-enzymatic hydrolysis of the cell's own proteins. A negative nitrogen balance is formed, ammonia accumulates in tissues, and the blood residual nitrogen level rises (azotemia develops).
• Cell swelling: Without ATP, key membrane ion pumps (Na⁺, K⁺-ATPase, Ca²⁺-dependent ATPase) stop working. Ions distribute according to their concentration gradient, water rushes into the cell, causing its hyperhydration. The situation is aggravated by damage to the membranes themselves and shifts in the production of hormones regulating water-salt metabolism (mineralocorticoids, calcitonin).

Systemic consequences of acute hypoxia

The severity of systemic disorders depends on four factors: the type of hypoxia, its degree, the rate of development, and the initial reactivity of the organism. Nervous tissue has the lowest resistance; the outcome for the patient is often determined by the degree of damage to cerebral cortex neurons.

In acute hypoxia, the metabolic catastrophe quickly leads to organ dysfunction:

• Nervous system: Critical thinking decreases, coordination is impaired, and consciousness is depressed up to bulbar disorders.
• Blood circulation: Cardiac output drops, arrhythmias, coronary insufficiency, and microcirculatory disorders develop.
• Respiration: Hypoventilation occurs, gas diffusion across the blood-air barrier is impaired, leading to acute respiratory failure.
• Internal organs: Acute renal failure develops, the liver loses its antitoxic function, and erosions and ulcers form in the gastrointestinal mucosa.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Mechanisms of adaptation in chronic moderate hypoxia (COPD, heart defects, anemias).
• Etiology of acute (fulminant) hypoxia: cyanide poisoning, ventricular fibrillation.
• Effect of hypoxia on higher nervous activity and bulbar centers.
• Ventilation-perfusion ratio disorders in the lungs and the development of acute respiratory failure.
• Pathogenesis of acute renal failure and gastrointestinal lesions during oxygen deprivation.

Other topics in "Chapter 15. HYPOXIA. HYPEROXYGENATION"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.