Acid-Base Balance in Physiology
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Questions and Answers

Which acid is associated with environmental exposure and can lead to vision loss if not treated promptly?

  • Salicylic acid
  • Acetoacetic acid
  • Formic acid (correct)
  • Glycolic acid

    • What condition is primarily caused by the ingestion of NH4Cl?

  • Proximal renal tubular acidosis (RIA)
  • Distal renal tubular acidosis (RTA) (correct)
  • Acidosis due to toxins
  • Hyperkalemic renal tubular acidosis (RTA)

    • Which alcohol does not produce acidosis but rather leads to a condition characterized by 'acetone breath'?

  • Methanol
  • Acetone (correct)
  • Ethanol
  • Isopropanol

    • Which of the following is a consequence of glycolic acid and oxalic acid toxicity?

    <p>Decreased cardiac contractility</p> Signup and view all the answers

    What clinical feature is commonly observed in hospital-acquired lactic acidosis?

    <p>Minimal clinical manifestations</p> Signup and view all the answers

    What is the corrected anion gap formula?

    <p>AG corrected = AG + 2.5 (4 - serum albumin)</p> Signup and view all the answers

    What indicates a high osmolar gap?

    <p>Osmolar gap (measured - calc) is &gt; 10</p> Signup and view all the answers

    In acid-base measurements, how is the bicarbonate concentration derived?

    <p>Calculated from pH and pCO2 using the Henderson-Hasselbach equation</p> Signup and view all the answers

    What is the significance of the base excess measurement

    <p>It helps interpret changes in HCO3- levels</p> Signup and view all the answers

    How is base excess defined?

    <p>The difference between normal HCO3- and observed HCO3-</p> Signup and view all the answers

    What does a base excess greater than +2 indicate?

    <p>Presence of metabolic alkalosis</p> Signup and view all the answers

    What are the components that constitute the total buffer negative ion of blood?

    <p>Plasma proteins, Hemoglobin, and Phosphate</p> Signup and view all the answers

    What should the osmolal gap be to not indicate the presence of toxic substances?

    <p>&lt;= 10</p> Signup and view all the answers

    What is the expected increase in [HCO3] for every 10 mmHg increase in PCO2 above 40 mmHg?

    <p>4 mmol/L</p> Signup and view all the answers

    Which formula gives the expected pCO2 when [HCO3] is known?

    <p>Expected pCO2 = 1.5 x [HCO3] + 8</p> Signup and view all the answers

    What does a change in actual pCO2 or [HCO3] from the predicted values suggest?

    <p>The presence of secondary acid-base disorder</p> Signup and view all the answers

    How much will [HCO3] decrease for every 10 mmHg decrease in PCO2 below 40 mmHg?

    <p>5 mmol/L</p> Signup and view all the answers

    For acute conditions, what is the change in [HCO3] when PCO2 changes?

    <p>0.2 Δ PCO2</p> Signup and view all the answers

    What will happen to [HCO3] for every 10 mmHg increase in PCO2 below 40 mmHg in chronic conditions?

    <p>Increase by 4 mmol/L</p> Signup and view all the answers

    What does the equation Δ PCO2 = 0.6 Δ HCO3 indicate?

    <p>Chronic metabolic alkalosis</p> Signup and view all the answers

    Which statement is true regarding the expected [HCO3] calculations?

    <p>Assumes a normal temperature and pH</p> Signup and view all the answers

    What is the maximum rate of administration for alkali replacement?

    <p>1 Meq/kg/hour</p> Signup and view all the answers

    What is often the primary cause of a primary increase in serum [HCO3-]?

    <p>Loss of H+ from the body</p> Signup and view all the answers

    Which compensatory mechanism occurs with increased serum bicarbonate levels?

    <p>Decreased ventilation leading to hypercapnia</p> Signup and view all the answers

    What condition is commonly associated with metabolic alkalosis due to chloride loss?

    <p>Vomiting</p> Signup and view all the answers

    Which drug is considered a potassium-sparing diuretic that can be used for primary hyperaldosteronism?

    <p>Spironolactone</p> Signup and view all the answers

    What can cause a decrease in ionized calcium after the administration of alkali?

    <p>Hypocalcemia</p> Signup and view all the answers

    Which syndrome is characterized by the need for potassium supplementation and is often linked to metabolic alkalosis?

    <p>Bartter syndrome</p> Signup and view all the answers

    What is a potential consequence of administration of exogenous alkali such as NaHCO3?

    <p>Fall in ionized calcium</p> Signup and view all the answers

    What is the primary cause of hypoaldosteronism in the context described?

    <p>Adrenal gland destruction by viruses and bacteria</p> Signup and view all the answers

    Which condition is characterized by the inability to acidify urine even after an acid load?

    <p>Incomplete renal tubular acidosis</p> Signup and view all the answers

    What type of metabolic acidosis does a patient exhibit upon admission after the rave?

    <p>High anion gap metabolic acidosis</p> Signup and view all the answers

    Which agent is associated with causing high anion gap metabolic acidosis initially?

    <p>Toluene</p> Signup and view all the answers

    What follows the initial high anion gap metabolic acidosis in the described patient?

    <p>Hypokalemic hyperchloremic metabolic acidosis</p> Signup and view all the answers

    What condition is unlikely due to the presence of hyponatremia and hyperkalemia?

    <p>Proximal renal tubular acidosis</p> Signup and view all the answers

    How does hypokalemia result from the metabolism of toluene?

    <p>Increased distal delivery of Na+ with hippurate</p> Signup and view all the answers

    Which of the following drugs does NOT typically cause proximal renal tubular acidosis?

    <p>Toluene</p> Signup and view all the answers

    Study Notes

    Acid-Base Physiology Overview

    • PCO2 and HCO3 levels are critical in determining acid-base balance.
    • Expected changes in HCO3 correlate to changes in PCO2:
      • Acute: Δ HCO3 = 0.1 Δ PCO2
      • Chronic: Δ HCO3 = 0.4 Δ PCO2
    • Blood gas calculations:
      • Expected pCO2 = 1.5 x [HCO3] + 8 (±2)
      • Alternate formula: Expected pCO2 = 0.7 [HCO3] + 20 (±5)
    • Primary compensatory responses should align in direction and magnitude to the primary disturbance.
    • Significant deviations from predicted pCO2 or HCO3 may indicate a secondary acid-base disorder.

    Bicarbonate Adjustments

    • Every 10 mmHg increase in PCO2 above 40 mmHg results in:
      • Increase in HCO3 by 1 mmol/L (common) or 4 mmol/L (less common).
    • Every 10 mmHg decrease in PCO2 below 40 mmHg results in:
      • Decrease in HCO3 by 2 mmol/L (common) or 5 mmol/L (less common).
    • Normal HCO3 is calculated as Expected [HCO3] = 24 + {(Actual PCO2 - 40) / 10}.
    • A balance in bicarbonate is crucial for maintaining physiological pH levels.

    Anion Gap and Osmolal Gap Calculations

    • Anion gap (AG) = Difference between measured cations and anions in serum (normal values provided).
    • Conditions such as renal failure, hyperlactatemia, and ketoacidosis influence AG readings.
    • AG corrected = AG + 2.5 (4 - serum albumin) for accurate assessment.
    • Osmolal gap calculation: Osm = 2 [Na+] + glucose/18 + BUN/2.8.
    • A high osmolal gap (>10) signifies possible toxicity (MUD PILES: methanol, uremia, diabetic ketoacidosis, propylene glycol, isopropyl alcohol, lactic acidosis, ethanol, salicylates).

    Acid-Base Disorders and Metabolic Impacts

    • Acidosis can result from various toxins (e.g., methanol, lactic acid).
    • Conditions leading to decreased serum bicarbonate include:
      • Loss of H+ or gain of HCO3; both lead to alkalemia.
      • Possible causes: vomiting, diuretics, primary hyperaldosteronism, renal tubular acidosis.
    • Base excess is the measure of bicarbonate in relation to pH; ranges indicate metabolic disorders:
      • -2 to +2: No metabolic disturbance.
      • < -2: Metabolic acidosis.

      • +2: Metabolic alkalosis.

    Case Studies Highlighting Acid-Base Disorders

    • Case 1: A 19-year-old female exhibited high AG metabolic acidosis post-party, shifting to hypokalemic hyperchloremic metabolic acidosis after 18 hours.
    • Possible agent causing initial disorder: Toluene. It metabolizes to hippurate causing high AG, then leads to hypokalemic metabolic acidosis.
    • Proximal renal tubular acidosis may occur with certain drugs (notably Ifosfamide, but others can induce it as well).

    Treatment and Management of Disorders

    • Corrective actions based on acid-base imbalances include electrolyte administration (e.g., NaCl) and potassium supplementation.
    • Specific conditions, like primary hyperaldosteronism or syndromes (Bartter, Gitelman), require tailored diuretic therapy or mineralocorticoid antagonists.
    • Monitoring and adjustment of bicarbonate levels critical in managing severe disturbances in acid-base equilibrium.

    General Concepts in Acid-Base Chemistry

    • Understand Henderson-Hasselbach equation for calculating pH based on bicarbonate and pCO2 levels.
    • Importance of distinguishing between respiratory and metabolic contributions to acid-base imbalances.
    • Recognize common clinical presentations of acid-base disorders for effective diagnosis and treatment strategies.

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    Description

    This quiz focuses on understanding the relationships between PCO2 and HCO3 levels in acute and chronic settings. Test your knowledge on the changes in these parameters and how they relate to acid-base imbalances. Gain insights into the physiological mechanisms behind these processes.

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