Acid-Base Balance

Acid-Base History

• Introduction to the History
• Principal Historical Events
  

Introduction to History

The history has been summarized in a series of review-essays by two of the best known investigators in this fascinating and complex field, John Severinghaus and Poul Astrup (1985, 1986). Some of the critical events and participants that they mention are summarized in the historical summary which serves several purposes: the time required for ideas and equipment to reach their present state is evident; the names of the more prominent investigators are recorded; some of the many attempts to measure metabolic disturbances are mentioned; and the controversy which surrounded the introduction of "base excess" is described.

Interest in acid base balance stems from its physiologic importance, from fascination in a subject which has exercised and challenged scientific interest during the last century, and from the requirement to set and pass examinations

Principal Historical Events

Boyle (1627-1691)

"Pressure is inversely proportional to volume."

Benjamin Franklin (1706-1790)

Called "vitreous" charges "positive" which later necessitated the labeling of excess electrons with the adjective "negative".

Dalton (1801)

Proposed law of partial pressures.

Henry (1802)

"Dissolved gas proportional to partial pressure."

Gay-Lussac (1808)

"Pressure proportional to 'absolute' temperature". Law of combining volumes.

Avagadro (1811)

Equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules

Faraday (1833)

Coined terminology (ion, anion, anode, etc.) and established laws of electrolysis.

Lord Kelvin (1848)

Combined known gas laws to permit calculation of the universal gas constant, R, in:
PV=nRT (P = pressure, V = volume, n = number of moles, and T = temperature).

Claussius (1857)

Concluded that ions already exist in solutions.

Van't Hoff (1887)

Linked the "gas laws" to the behavior of osmotic pressure in solutions.

Arrhenius (1887)

Proved that dissolved salts and acids are ionized.

Ostwald (1887)

Made first electrical measurement of hydrogen ion concentration.

Nernst (1889)

Derived equation which related change in voltage to the universal gas constant (R), the absolute temperature (T), the valence (n), the faraday (F) and the activity (a):
E = E^o + [RT/nF] log(a/a^o ). (note: RT/nF = 61.5 mV at 37^o C)

Nernst (1889)

Also recommended selecting salts with ions having similar diffusion rates to avoid error voltages at liquid junctions.

Bjerrum (1905)

Adopted Nernst's recommendation; introduced now standard potassium chloride salt bridge.

Cremer (1906)

Discovered that a pH difference can cause a potential difference across the glass membrane.

Henderson (1908)

Discovered buffering power of CO₂ and applied law of mass action:
K = [H⁺] [HCO₃^-] / [dCO₂] (where dCO₂ = dissolved CO₂)

Sorensen (1909)

Suggested the pH terminology. Also developed the hydrogen electrode for biologic use.

Hasselbach (1916)

Used Sorensen's terminology for Henderson's equation in logarithmic form:
pH = pK + log(HCO₃^-/dCO₂)

Hasselbach (1916)

Proposed measuring metabolic acidosis using "standard" pH at 38^oC with PCO₂ = 40 mm Hg (analogous to the 'standard' bicarbonate later introduced by Jorgensen and Astrup).

Van Slyke (1921)

Published acid-base diagram using, as axes, log(H⁺):log(PCO₂) the forerunner of the in-vivo Siggaard- Andersen diagram (1971).

Van Slyke (1924)

Originated manometric Van Slyke apparatus to measure gas quantities released from blood.

Eisenman (1927)

Derived pH by interpolation on a graph using log(CO₂ content):log(PCO₂) axes. Measurements of CO₂ content were made using Van Slyke measurement at known PCO₂.

MacInnes and Dole (1929)

Perfected glass composition for pH electrodes (later known as 015 pH glass - Corning).

MacInnes and Belcher (1933)

Designed the first commercial electrode to measure blood pH.

Poul Astrup (1952)

Encountered the need to measure PCO₂ in his clinical laboratory during the Copenhagen polio epidemic, and derived PCO₂ by interpolation on a graph of log (PCO₂): pH. Measurements of pH were made at known PCO₂ levels.

Stow (1954)

Covered pH and reference electrode with rubber to make a practical PCO₂ electrode, later modified and improved by Severinghaus.

Astrup (1956)

Designed practical thermostatically controlled glass electrode in a CO₂ equilibration chamber.

Jorgensen and Astrup (1957)

Introduced "standard bicarbonate" (the bicarbonate level at PCO₂ = 40 mmHg) as the "best available measure of non-respiratory disturbances".

Astrup and Siggard-Andersen (1958)

Introduced the capillary microelectrode and the concept "base-excess" as a measure of treatment required to correct metabolic disturbances. The "in-vitro" base excess was dependent on the hemoglobin level - subsequently a source of criticism and debate.

Severinghaus and Bradley (1958)

Demonstrated blood-gas apparatus which contained both PCO₂ and PO₂ electrodes.

Siggaard-Andersen (1962)

Published acid-base nomogram using log(PCO₂):pH axes for calculating, by interpolation, the PCO₂, the bicarbonate, the standard bicarbonate and the base-excess. The technique required pH to be measured at known PCO₂ levels.

Siggaard-Andersen (1963)

Published alignment nomogram.

Schwartz and Relman (1963)

Critically reviewed the concept "base-excess" and proposed the use of linear equations to characterize acid-base syndromes. By this means they avoided describing the adaptation to chronic hypercapnia as "metabolic alkalosis" but, rather, they regarded the patient as being compensated to chronic hypercapnia if he fitted their equation.

Severinghaus (1966)

Developed blood-gas slide rule.

Siggaard-Andersen (1971)

Published In-Vivo Diagram (see Van Slyke 1921)

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