MLAB 2401: Clinical Chemistry Keri Brophy-Martinez

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MLAB 2401 Clinical ChemistryKeri Brophy-Martinez

• Disorders of Acid-Base Imbalance

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Acid-Base Imbalances

• pHlt 7.35 acidosis/acidemia
• pHgt 7.45 alkalosis/alkalemia
• The body responds to imbalances by compensation
• If balance is fully restored to 201 , it is
  termed complete
• If balance is still outside of normal limits it
  is termed partial

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Compensation

• Respiratory compensation
• Occurs when underlying problem is metabolic
• See changes in pCO2
• Body responds by hyper or hypoventilation
• Metabolic Compensation
• Occurs when underlying problem is respiratory
• See changes in bicarbonate concentration
• Body responds by activating renal mechanisms

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Acid-Base Imbalance

• Four categories
• Metabolic Acidosis
• Metabolic Alkalosis
• Respiratory Acidosis
• Respiratory Alkalosis

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Metabolic vs Respiratory

• Metabolic
• KIDNEY
• Effects base bicarbonate
• Respiratory
• LUNGS
• Effects acid carbonic acid

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Metabolic Acidosis

• Bicarbonate deficit blood concentrations of
  bicarb drop below 22mEq/L
• Results in pH drop
• Decrease in 201 ratio
• Causes of
• Loss of bicarbonate through diarrhea or renal
  dysfunction
• Accumulation of acids (lactic acid or ketones)
  that exceed rate of elimination
• Failure of kidneys to excrete H

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Symptoms of Metabolic Acidosis

• Headache,
• Rapid and deep breathing
• Lethargy
• Nausea, vomiting, diarrhea
• Coma
• Death

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Compensation for Metabolic Acidosis

• Respiratory
• Primary mechanism
• Increased ventilation
• CO2 blown off
• Renal
• Excretion of hydrogen ions if possible
• Reabsorption of bicarbonate

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Metabolic Alkalosis

• Bicarbonate excess - concentration in blood is
  greater than 26 mEq/L
• Results in pH increase
• Causes of
• Loss of acid-rich fluids
• Excess vomiting loss of stomach acid
• Certain diuretics
• Addition of base to the body
• Excessive use of alkaline drugs
• Heavy ingestion of antacids
• Decrease of base elimination
• Endocrine disorders ( Cushings syndrome)

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Compensation for Metabolic Alkalosis

• Respiratory
• Primary mechanism
• Hypoventilation
• Increased retention of CO2
• Limited by hypoxia ( no oxygen)
• Alkalosis most commonly occurs with renal
  dysfunction, so cant count on kidneys to excrete
  excess bicarbonate

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Symptoms of Metabolic Alkalosis

• Respiration slow and shallow
• Hyperactive reflexes tetany
• Often related to depletion of electrolytes
• Atrial tachycardia
• Dysrhythmias

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Respiratory Acidosis

• Increased carbonic acid as indicated by increased
  pCO2
• Results in decreased pH
• Causes of
• Problems within the respiratory system
• Organs- lungs
• Obstruction in the airway or restriction of gas
  exchange
• Obstructive emphysema
• Pulmonary edema/ pulmonary disease
• Depression of respiratory center in brain that
  controls the breathing rate
• Drugs
• Stroke, Coma

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Compensation for respiratory acidosis

• Kidneys
• Primary mechanism
• Eliminate hydrogen ions
• Retain bicarbonate ions

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Signs and Symptoms of Respiratory Acidosis

• Breathlessness
• Restlessness
• Lethargy and disorientation
• Tremors, convulsions, coma
• Respiratory rate rapid, then gradually depressed
• Skin warm and flushed due to vasodilation caused
  by excess CO2

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Respiratory Alkalosis

• Decrease carbonic acid indicated by decreased
  pCO2
• Most common acid-base imbalance
• Results in increased pH
• Causes of
• Hypoxemia
• Stimulation of the Respiratory Center

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Respiratory Alkalosis

• Hypoxemia
• Pulmonary disease
• Congestive heart disease
• Severe anemia
• High-altitude exposure
• Conditions that stimulate respiratory center
• Acute anxiety
• Salicylate intoxication
• Cirrhosis
• Gram-negative sepsis
• Hyperventilation syndrome

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Compensation for respiratory Alkalosis

• Kidneys
• Primary mechanism
• Conserve hydrogen ion
• Excretion of bicarbonate ion

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Summary of acid-base disorders
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Primary Acid/Base Disorders
pCO2 pH HCO3 Base Excess
Uncompensated acidosis N D D D
Uncompensated alkalosis N I I I
Partially compensated acidosis D D D D
Partially compensated alkalosis I I I I
Compensated Acidosis/alkalosis I/D N I/D I/D
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Disturbance Primary Abnormality Compensation Cause
Metabolic Acidosis Excess endogenous acid depletes bicarbonate Hyperventilation lowers pCO2, Kidney excretes excess H and forms more HCO3- Renal failure Ketosis Increased lactic acid Diarrhea
Respiratory Acidosis Inefficient excretion of CO2 by the lungs Formation of excess HCO3- by kidney Chronic pulmonary Diseases (COPD), such as emphysema Acute problems, such as pneumonia, airway obstruction, drugs such as opiates, congestive heart failure
Metabolic Alkalosis Excess plasma bicarbonate Kidneys excrete excess HCO3- and form less HCO3- and NH4, Lungs hypoventilate Loss of gastric juice Chloride depletion Hypokalemia Increased corticosteroid Increased ingestion of antacids
Respiratory Alkalosis Hyperventilation lowers pCO2 Increased excretion of bicarbonate by kidney Hyperventilation, such as with severe anxiety, fever, head injuries Stimulation of resp. center by drugs Central nervous system diseases
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References

• Bishop, M., Fody, E., Schoeff, l. (2010).
  Clinical Chemistry Techniques, principles,
  Correlations. Baltimore Wolters Kluwer
  Lippincott Williams Wilkins.
• Carreiro-Lewandowski, E. (2008). Blood Gas
  Analysis and Interpretation. Denver, Colorado
  Colorado Association for Continuing Medical
  Laboratory Education, Inc.
• Jarreau, P. (2005). Clinical Laboratory Science
  Review (3rd ed.). New Orleans, LA LSU Health
  Science Center.
• Sunheimer, R., Graves, L. (2010). Clinical
  Laboratory Chemistry. Upper Saddle River Pearson
  .