General Principles

General Principles is a topic covered in the Washington Manual of Medical Therapeutics.

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  • The normal ECF pH is 7.40 ± 0.03. Perturbations in pH can occur with changes in the ratio of Descriptive text is not available for this image to partial pressure of carbon dioxide (pCO2) as described by the Henderson–Hasselbalch equation:Descriptive text is not available for this image
  • Maintenance of pH is essential for normal cellular function. Three general mechanisms exist to keep it within a narrow window:
    • Chemical buffering is mediated by Descriptive text is not available for this image in the ECF and by protein and phosphate buffers in the ICF. The normal Descriptive text is not available for this image is 24 ± 2 mEq/L.
    • Alveolar ventilation minimizes variations in the pH by altering the pCO2. The normal pCO2 is 40 ± 5 mm Hg.
    • Renal H+ handling allows the kidney to adapt to changes in acid–base status via Descriptive text is not available for this image reabsorption and excretion of titratable acid (e.g., Descriptive text is not available for this image) and Descriptive text is not available for this image.
  • Acidemia and alkalemia refer to processes that lower and raise pH regardless of mechanism. They can be caused by metabolic or respiratory disturbances:
    • Metabolic acidosis is characterized by a decrease in the plasma Descriptive text is not available for this image due to either Descriptive text is not available for this image loss or the accumulation of acid.
    • Metabolic alkalosis is characterized by an elevation in the plasma Descriptive text is not available for this image due to either H+ loss or Descriptive text is not available for this image gain.
    • Respiratory acidosis is characterized by an elevation in pCO2 resulting from alveolar hypoventilation.
    • Respiratory alkalosis is characterized by a decrease in pCO2 resulting from hyperventilation.

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