Podcast
Questions and Answers
What is the condition characterized by a blood pH lower than 7.35?
What is the condition characterized by a blood pH lower than 7.35?
Which of the following conditions can lead to respiratory acidosis?
Which of the following conditions can lead to respiratory acidosis?
If pH and bicarbonate (HCO₃⁻) levels are directly related, what type of disorder is it likely to be?
If pH and bicarbonate (HCO₃⁻) levels are directly related, what type of disorder is it likely to be?
Which statement correctly describes compensations in acid-base disorders?
Which statement correctly describes compensations in acid-base disorders?
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What is the normal range for bicarbonate (HCO₃⁻) in arterial blood gas measurements?
What is the normal range for bicarbonate (HCO₃⁻) in arterial blood gas measurements?
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Which condition is associated with high anion gap metabolic acidosis?
Which condition is associated with high anion gap metabolic acidosis?
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What does a normal anion gap indicate in the context of metabolic acidosis?
What does a normal anion gap indicate in the context of metabolic acidosis?
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Which of the following is NOT a cause of metabolic alkalosis?
Which of the following is NOT a cause of metabolic alkalosis?
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What is the primary reason for metabolic alkalosis related to chloride-sensitive conditions?
What is the primary reason for metabolic alkalosis related to chloride-sensitive conditions?
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Which diuretic works primarily by inhibiting the Na⁺/K⁺/2Cl⁻ transporter?
Which diuretic works primarily by inhibiting the Na⁺/K⁺/2Cl⁻ transporter?
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Which type of metabolic alkalosis does not respond to saline infusion?
Which type of metabolic alkalosis does not respond to saline infusion?
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What common adverse effect is associated with thiazide diuretics?
What common adverse effect is associated with thiazide diuretics?
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In which part of the nephron do potassium-sparing diuretics primarily act?
In which part of the nephron do potassium-sparing diuretics primarily act?
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What mechanism underlies the action of osmotic diuretics like mannitol?
What mechanism underlies the action of osmotic diuretics like mannitol?
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Which of the following diuretics can potentially lead to ototoxicity when used with aminoglycosides?
Which of the following diuretics can potentially lead to ototoxicity when used with aminoglycosides?
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Study Notes
Acid-Base Disorders
- Acidosis: Blood pH below 7.35, excess hydrogen ions.
- Alkalosis: Blood pH above 7.45, deficit of hydrogen ions.
Respiratory Disturbances
- Respiratory acidosis: Caused by hypoventilation, CO₂ retention. Example: COPD
- Respiratory alkalosis: Caused by hyperventilation, CO₂ depletion. Example: anxiety, altitude.
Arterial Blood Gas (ABG) Interpretation
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Normal values:
- pH: 7.35-7.45
- PaCO₂: 35-45 mmHg
- HCO₃⁻: 22-26 mEq/L
- PaO₂: 80-100 mmHg
- O₂ saturation: 95-100%
Diagnosing Acidosis or Alkalosis
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Primary respiratory disturbances: Involve changes in pH and PaCO₂
- Inverse relationship: Respiratory disorder
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Primary metabolic disturbances: Involve changes in pH and HCO₃⁻
- Direct relationship: Metabolic disorder
Compensation in Acid-Base Disorders
- Compensated: Body corrects pH near normal, while CO₂ or HCO₃⁻ may be abnormal.
- Uncompensated: Body hasn't corrected the pH.
- Mixed disorders: Both respiratory and metabolic components are abnormal, but in opposite directions.
Metabolic Acidosis
- Definition: Excess acid production or decreased acid excretion, or bicarbonate loss.
- Causes: Diabetic ketoacidosis, renal failure, diarrhea.
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Anion Gap: Calculation used to differentiate causes.
- Normal: 8-12 mEq/L.
- High: Caused by acid accumulation (lactic acid, ketones). MUDPILES mnemonic.
- Normal: Caused by bicarbonate loss or chloride retention. Examples: diarrhea, renal tubular acidosis.
Metabolic Alkalosis
- Definition: Excessive loss of acidic substances or gain of bicarbonate.
- Causes: Vomiting, nasogastric suctioning, diuretics, excess bicarbonate administration.
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Classification:
- Chloride-sensitive: Responds to saline infusion. Urine Chloride < 20 mEq/L
- Chloride-resistant: Does not respond to saline. Urine Chloride > 20 mEq/L. Hyperaldosteronism or Cushing's syndrome are examples.
Diuretic Agents
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Thiazides:
- Site: Distal convoluted tubule.
- Mechanism: Inhibits Na⁺/Cl⁻ symporter, reducing sodium reabsorption.
- Uses: Hypertension, edema.
- Adverse effects: Hypokalemia, hyperglycemia, hyperuricemia.
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Loop Diuretics:
- Site: Ascending loop of Henle.
- Mechanism: Inhibits Na⁺/K⁺/2Cl⁻ transporter, leading to sodium, potassium, and water excretion.
- Uses: Pulmonary edema, heart failure, kidney disease.
- Adverse effects: Hypokalemia, ototoxicity, dehydration.
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Potassium-Sparing Diuretics:
- Site: Collecting ducts.
- Mechanism: Inhibit aldosterone (spironolactone) or block sodium channels (amiloride, triamterene).
- Uses: Counteract potassium loss from other diuretics.
- Adverse effects: Hyperkalemia, gynecomastia (spironolactone).
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Osmotic Diuretics:
- Site: Proximal tubule and descending loop of Henle.
- Mechanism: Increase filtrate osmolarity, preventing water reabsorption.
- Uses: Reducing intracranial pressure, acute glaucoma.
- Adverse effects: Dehydration, electrolyte imbalance.
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Carbonic Anhydrase Inhibitors:
- Site: Proximal tubule.
- Mechanism: Inhibit carbonic anhydrase, decreasing bicarbonate reabsorption.
- Uses: Glaucoma, altitude sickness, metabolic alkalosis.
- Adverse effects: Metabolic acidosis, hypokalemia.
Diuretic Site of Action in the Nephron
- Thiazides: Distal convoluted tubule.
- Loop diuretics: Ascending loop of Henle.
- Potassium-sparing: Collecting ducts.
- Osmotic diuretics: Proximal tubule and descending loop of Henle.
- Carbonic anhydrase inhibitors: Proximal tubule.
Diuretic Mechanism of Action
- Thiazides: Inhibit Na⁺/Cl⁻ symporter, decreasing sodium reabsorption in the distal tubule.
- Loop diuretics: Inhibit Na⁺/K⁺/2Cl⁻ transporter in the loop of Henle, leading to large amounts of water and salt excretion.
- Potassium-sparing: Inhibit sodium reabsorption and potassium excretion in the collecting duct.
- Osmotic diuretics: Create an osmotic gradient to retain water in the renal tubules.
- Carbonic anhydrase inhibitors: Block bicarbonate reabsorption, leading to diuresis.
Adverse Effects and Drug Interactions
- Thiazides: Hypokalemia, hyperglycemia, increased uric acid (gout risk), potentiates digitalis toxicity.
- Loop diuretics: Electrolyte imbalances (hypokalemia, hypomagnesemia), ototoxicity with aminoglycosides.
- Potassium-sparing: Hyperkalemia, especially with ACE inhibitors or ARBs.
- Osmotic diuretics: Can worsen heart failure due to fluid shifts.
- Carbonic anhydrase inhibitors: Metabolic acidosis due to bicarbonate loss.
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Description
Test your knowledge on acid-base disorders, including acidosis and alkalosis. This quiz covers respiratory disturbances, arterial blood gas interpretation, and the compensation mechanisms involved in these conditions. Perfect for students studying physiology or medicine.
