Acid-base and Electrolyte Disorders

7/24/2019 Acid-base and Electrolyte Disorders

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Method of analyzing acidbase

disorders

Traditional

(bicarbonate-centered)model

The Stewart

(strong ion) model


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Traditional Approach

(Bicarbonate centered)

The traditional model use easily

measured concentrations of blood

carbon dioxide [CO2] andbicarbonate [HCO3-]. As in any

chemical reaction in equilibrium, a

change in the concentration of the

reactant or product will move the

reaction in the direction that would

reestablish equilibrium (Le

Chateliersprinciple).


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Retention of CO2

Production nonvolatile acid from protein and

organic molecule metabolism Losses bicarbonate pass through feces and urine

Intake acid or acid precursor

Cause the

equilibriumshift:

Consumption of hydrogen in several organic

anion metabolism Depletion acid from vomiting and urine

Losses of ions due to diarrhea

Depletion CO2 from hyperventilation

Cause ofacid

deficiency :


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Compensation:Acid-base equilibrium is regulated by buffering

agent that linked with Hydrogen to regulation pHalteration

Extracellular buffer

Bicarbonate andammonia

Intracellular buffer

Protein andphosphate


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Bicarbonatebuffering system isthe primary keys

CO2 can movethrough H2CO3 tohydrogen and

bicarbonate


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Anion Gap

Is the different between (positive charged ion) and(negative charged ion) in serum, plasma, or urine and thelarge of different assumed as Gap

Measured cation : Na, K, Ca, Mg

Unmeasured cation: protein, H, paraprotein di myeloma

Measured anion : Cl, HCO3, PO43-

Unmeasured anion : sulfat dan protein

If Gap higher than the normalvalue indicated as high anion

gap metabolic acidosis


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Anion Gap

The anion gap, consisting of the sum total of all

unmeasured charged specie (predominantly

albumin) in plasma, is calculated below as :

Normal value < 11mEq/L


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Anion Gap Classification

High

Anion Gap

Normal

Anion Gap

Low Anion

Gap


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The Stewart (or strong ion) model

The method to estimate acid-base balance with mathematics

models it is relevant because it is a powerful construct that can

shed light on an important biologic system

variables:

a. Dependent :H, OH, HCO3, CO3, HA, A

b. Independent: PCO2, A tot, SID

All the variable will construct a complex mathematics model

SID (strong ion difference) : the difference between total

concentration of strong cation and strong anion


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& STRONGION

Metabolic

disturbance

Gastrointestinal

Losses

Urinary Charge

Gap

Compensation

for respiratory

disorder and

Urinary

Intravenous

Fluids and

Content


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Metabolic disturbance & STRONG ION


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Gastrointestinal Losses & STRONG ION

Losses of ions due to diarrhea are associated withthe development of metabolic acidosis or metabolicalkalosis.

Diarrhea is the cause of metabolic alkalosis, rather thanacidosis. Large losses of chloride may occur in patients whohave villous adenomas or other secretory diarrheas that causedepletion of chloride. Na, K, and Cl concentration would be lessthan the normal plasma bicarbonate concentration.

High losses of chloride from vomiting or after theuse of loop diuretics, cause hypocloremic alkalosis


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Urinary Charge Gap& STRONG ION

Measurements of urinary electrolyte concentrations and flow rate

indicate renal acidbase function even without measurement of

urinary bicarbonate.

A negative value for the urinary netcharge gap indicates the presence of theunmeasured cation, ammonium (excretionof ammonium chloride).

. NegativeUrinary ChargeGap

A positive value for the urinary net chargegap indicates excretion of an unmeasuredanion.

. Positive UrinaryCharge Gap


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Compensation for respiratory disorder and Urinary &STRONG ION

Respiratory alkalosis : The

hyperchloremic renalcompensation for respiratoryalkalosis is the excretion offiltered sodium and potassiumwith bicarbonate, because lowPaCO2 decreases proximal and

distal hydrogen secretion.

Respiratory acidosis : high PaCO2increases production of ammoniaby the kidney, results inhypochloremia. The elevated PaCO2increases the renal reabsorption ofsodium and bicarbonate, so thecompensation is maintained.


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Intravenous Fluids and Content &STRONG ION

The insufficient urinary excretion of the extra chloride as

ammonium chloride leads to metabolic acidosis.

Saline-induced acidosis, which

develops because the infusion of

aproportionately high sodium

chloridecontaining solution, onewith a sodium-to-chloride ratio of

less than 140:100, will decrease the

plasma strong ion difference and the

bicarbonate concentration.

Figure 1 (facing page) Renal Tubular Cells with Transporters That Are Targets


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Figure 1 (facing page). Renal Tubular Cells with Transporters That Are Targetsof Hormones, Diuretics, and Mutations Affecting AcidBase Balance.


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Conclusion

Clinical evidence can be interpreted with the use of

both the strong ion theory and the traditional

bicarbonate centered approach to provide an optimal

understanding of acidbase disorders.

An understanding of the consequences of thesedisturbances helps in the diagnosis and treatment of

the associated acidbase disorders.


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References

Julian L. Seifter, M.D. 2014. Disorders of Fluids and

Electrolytes : Integration of Acid-Base and Electrolyte

Disorders. Review. N Engl J Med. 371: 1821-31


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Acid-base and Electrolyte Disorders