Acid–BaseDisordersintheICU
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anion gap, however if the AG is > 20 mEq/L there is a metabolic acidosis present regardless of the pH or the bicarbonate concentration
Steps in Evaluating Acid-Base Disorders
metabolic acidosis. If the PaCO2 his high, respiratory
acidosis.
pH
If the pH is > 7.40, an alkalemia is present.
If the CO2 content (HCO3-) is high, metabolic alkalosis.
mEq/L a non-anion gap metabolic acidosis is present.
Effect of Unmeasured Acid wk.baidu.comn HCO3Concentration
160 140 120 100
80 60 40 20
0 Cation
Anion 1
Anion 2
Na+ Cl- HC03- AG Excess AG
Acid–Base Disorders in the ICU
William D. Hoffman, M.D.
Primary Determinants of Acid-Base Status
PCO2
Ventilation CO2 production
Buffering capacity
Isohydric principle – All buffer systems are in equilibrium with the carbonic acid-bicarbonate buffer pair.
Strong ions
Glycolysis Ketogenesis (DKA, AKA, Starvation)
Steps in Evaluating Acid-Base Disorders
pH CO2 content (HCO3-) Anion Gap Potential Bicarbonate
PB = HCO3- + Excess AG
Summary
pH is the key to the primary disorder. If HCO3- < 15 mEq/L, a metabolic acidosis is
present. A HCO3- > 30 mEq/L cannot be due to an
pH
If abnormal, always tells you the primary disorder.
The body never completely compensates or overcompensates for and acid-base disorder.
pH
pH < 7.4 an acidemia is present. If the CO2 content (HCO3-) is low,
If the PaCO2 is low, respiratory alkalosis.
Steps in Evaluating Acid-Base Disorders
pH CO2 content (HCO3-) Anion Gap Potential Bicarbonate
HCO3-
If the HCO3- is high (> 26 mEq/L), respiratory acidosis or metabolic alkalosis.
pH CO2 content (HCO3-) Anion Gap Potential Bicarbonate
Potential Bicarbonate
PB = AG – 8 + HCO3 If the potential bicarbonate > 30 mEq/L
a metabolic alkalosis is present. If the potential bicarbonate is < 22
acute respiratory acidosis. If the AG is > 20 mEq/L, a metabolic acidosis
is present. If PB < 20 mEq/L, a non-anion gap metabolic
acidosis is present. If PB > 30 mEq/L, metabolic alkalosis.
If HCO3- is low (< 22 mEq/L) then metabolic acidosis or respiratory alkalosis.
The lowest the HCO3- will go with respiratory alkalosis is 15 mEq/L.
If the HCO3- is < 15 mEq/L, a metabolic acidosis must be present.
It requires 3-4 days for the kidney to compensate for CO2 retention.
Acute respiratory acidosis does not increase the HCO3- to more than 30 mEq/L.
HCO3-
Steps in Evaluating Acid-Base Disorders
pH CO2 content (HCO3-) Anion Gap Potential Bicarbonate
Anion Gap
AG = [Na+] - [Cl-] – [HCO3-] Normal value is 8-12 mEq/L. Many acid-base disorders will alter the
Steps in Evaluating Acid-Base Disorders
metabolic acidosis. If the PaCO2 his high, respiratory
acidosis.
pH
If the pH is > 7.40, an alkalemia is present.
If the CO2 content (HCO3-) is high, metabolic alkalosis.
mEq/L a non-anion gap metabolic acidosis is present.
Effect of Unmeasured Acid wk.baidu.comn HCO3Concentration
160 140 120 100
80 60 40 20
0 Cation
Anion 1
Anion 2
Na+ Cl- HC03- AG Excess AG
Acid–Base Disorders in the ICU
William D. Hoffman, M.D.
Primary Determinants of Acid-Base Status
PCO2
Ventilation CO2 production
Buffering capacity
Isohydric principle – All buffer systems are in equilibrium with the carbonic acid-bicarbonate buffer pair.
Strong ions
Glycolysis Ketogenesis (DKA, AKA, Starvation)
Steps in Evaluating Acid-Base Disorders
pH CO2 content (HCO3-) Anion Gap Potential Bicarbonate
PB = HCO3- + Excess AG
Summary
pH is the key to the primary disorder. If HCO3- < 15 mEq/L, a metabolic acidosis is
present. A HCO3- > 30 mEq/L cannot be due to an
pH
If abnormal, always tells you the primary disorder.
The body never completely compensates or overcompensates for and acid-base disorder.
pH
pH < 7.4 an acidemia is present. If the CO2 content (HCO3-) is low,
If the PaCO2 is low, respiratory alkalosis.
Steps in Evaluating Acid-Base Disorders
pH CO2 content (HCO3-) Anion Gap Potential Bicarbonate
HCO3-
If the HCO3- is high (> 26 mEq/L), respiratory acidosis or metabolic alkalosis.
pH CO2 content (HCO3-) Anion Gap Potential Bicarbonate
Potential Bicarbonate
PB = AG – 8 + HCO3 If the potential bicarbonate > 30 mEq/L
a metabolic alkalosis is present. If the potential bicarbonate is < 22
acute respiratory acidosis. If the AG is > 20 mEq/L, a metabolic acidosis
is present. If PB < 20 mEq/L, a non-anion gap metabolic
acidosis is present. If PB > 30 mEq/L, metabolic alkalosis.
If HCO3- is low (< 22 mEq/L) then metabolic acidosis or respiratory alkalosis.
The lowest the HCO3- will go with respiratory alkalosis is 15 mEq/L.
If the HCO3- is < 15 mEq/L, a metabolic acidosis must be present.
It requires 3-4 days for the kidney to compensate for CO2 retention.
Acute respiratory acidosis does not increase the HCO3- to more than 30 mEq/L.
HCO3-
Steps in Evaluating Acid-Base Disorders
pH CO2 content (HCO3-) Anion Gap Potential Bicarbonate
Anion Gap
AG = [Na+] - [Cl-] – [HCO3-] Normal value is 8-12 mEq/L. Many acid-base disorders will alter the