Bicarbonate Administration Effects in Animals
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Bicarbonate Administration Effects in Animals

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Questions and Answers

What is a potential consequence of bicarbonate administration related to volume status?

  • Volume expansion into the intravascular space (correct)
  • Hypovolemia due to fluid loss
  • Decreased serum sodium levels
  • Increased red blood cell production

    • What does a high anion gap indicate in terms of metabolic acidosis?

  • Loss of bicarbonate with increased chloride
  • Bicarbonate consumption due to unmeasured anion accumulation (correct)
  • Dilution of bicarbonate concentration
  • Increased bicarbonate production

    • Which physiological change occurs as a result of high pH from bicarbonate administration?

  • Increased release of ionized calcium from proteins
  • Decreased ionized calcium binding to albumin
  • Increased potassium retention
  • Increased binding of ionized calcium to albumin (correct)

    • Which of the following best describes the normal anion gap in dogs?

    <p>12 – 25 mmol/L</p> Signup and view all the answers

    What could cause a hyperchloraemic metabolic acidosis?

    <p>Excessive bicarbonate loss due to renal failure</p> Signup and view all the answers

    Which condition is likely to result in normal anion gap metabolic acidosis?

    <p>GI loss of bicarbonate</p> Signup and view all the answers

    What effect does bicarbonate administration have on potassium levels?

    <p>Hypokalemia from H+/K+ exchange</p> Signup and view all the answers

    Which of the following conditions could indicate a decreased bicarbonate concentration?

    <p>Both A and B</p> Signup and view all the answers

    What is typically true when PaCO2 increases in relation to bicarbonate levels?

    <p>Bicarbonate levels should increase.</p> Signup and view all the answers

    When is bicarbonate administration indicated?

    <p>When base excess is more negative than – 7 mmol/L.</p> Signup and view all the answers

    Which of the following best describes the actual base excess?

    <p>It is the dose of acid or alkali needed to achieve a pH of 7.4 in 1L of blood.</p> Signup and view all the answers

    What should the ideal PaCO2:bicarbonate ratio be?

    <p>1:20</p> Signup and view all the answers

    In the case of metabolic acidosis, what would you expect the base excess to be?

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

    What effect does a decrease in H+ concentration have on pH?

    <p>It increases the pH.</p> Signup and view all the answers

    Which condition might necessitate caution against bicarbonate administration?

    <p>Lactic acidosis due to acute hypovolaemia.</p> Signup and view all the answers

    What happens to cerebral blood flow when PaCO2 levels rise?

    <p>Cerebral vasodilation occurs, increasing blood flow.</p> Signup and view all the answers

    What happens to HCO3- levels in acute respiratory acidosis when PaCO2 increases by 10 mmHg?

    <p>HCO3- increases by 1.5 mmol/L</p> Signup and view all the answers

    In a case of chronic respiratory alkalosis, how does a decrease of 10 mmHg PaCO2 impact HCO3- levels?

    <p>HCO3- decreases by 5.5 mmol/L</p> Signup and view all the answers

    What is the pH change associated with an increase of 10 mmHg in PaCO2?

    <p>Decrease by 0.08 units</p> Signup and view all the answers

    How does metabolic acidosis affect PaCO2 in response to a decrease in HCO3-?

    <p>PaCO2 decreases by 0.7 mmHg for each 1 mmol decrease in HCO3-</p> Signup and view all the answers

    What does a low base excess indicate in a clinical scenario?

    <p>Metabolic acidosis process</p> Signup and view all the answers

    What does a normal anion gap coupled with hyperchloraemia indicate?

    <p>Metabolic acidosis due to loss of bicarbonate</p> Signup and view all the answers

    What effect does an increase of 1 mmol HCO3- have on PaCO2 levels?

    <p>PaCO2 increases by 0.7 mmHg</p> Signup and view all the answers

    In the provided clinical case, the bicarbonate level indicates which of the following conditions?

    <p>Low levels indicating loss or consumption</p> Signup and view all the answers

    Study Notes

    Bicarbonate Administration Problems

    • Haemodilution
      • Decreases packed cell volume (PCV), total proteins, platelets, and clotting factors.
      • Important to consider if the animal is already anemic.
    • Hypochloremia
    • Hypernatremia
      • Bicarbonate is administered as sodium bicarbonate, which can lead to high sodium levels.
    • Volume Expansion
      • Bicarbonate is hyperosmolar, which can cause fluid to move from the extravascular space into the intravascular space.
    • Hypercapnia
      • Bicarbonate administration pushes the reaction to produce CO2, particularly intracellularly, due to high levels of carbonic anhydrase.
      • This can worsen the acidotic process.
      • Requires frequent monitoring of ventilation when administering bicarbonate.
    • Alkalosis
    • Ionized Hypocalcemia
      • Increased pH increases the binding of ionized calcium to albumin.
    • Hypokalaemia
      • Increased pH stimulates the movement of H+ from intracellular to extracellular with simultaneous potassium movement in the opposite direction (H+/K+ exchanger).

    Anion Gap (AG)

    • Represents the difference between measured cations and measured anions.
    • Normal range:
      • Dogs: 12 - 25 mmol/L
      • Cats: 13 - 27 mmol/L
    • Used to help differentiate the cause of metabolic acidosis.
    • High AG
      • Occurs due to accumulation of unmeasured anions (e.g., lactic acid, ketoacids, phosphates, sulfates, proteins).
      • Examples: Diabetic Ketoacidosis (DUEL), uremia, ethylene glycol intoxication, lactic acidosis.
    • Normal AG
      • Occurs due to loss of bicarbonate, which leads to an increase in chloride levels.
      • Examples Renal loss, GI loss, NaCl administration, hypoadrenocorticism.

    Compensatory Mechanisms

    • Acute Respiratory Acidosis: Increase in PaCO2 by 10 mmHg leads to an increase in HCO3- by 1.5 mmol/L.
    • Chronic Respiratory Acidosis: Increase in PaCO2 by 10 mmHg leads to an increase in HCO3- by 3.5 mmol/L.
    • Acute Respiratory Alkalosis: Decrease in PaCO2 by 10 mmHg leads to a decrease in HCO3- by 2.5 mmol/L.
    • Chronic Respiratory Alkalosis: Decrease in PaCO2 by 10 mmHg leads to a decrease in HCO3- by 5.5 mmol/L.
    • Metabolic Acidosis: Decrease in HCO3- by 1 mmol/L leads to a decrease in PaCO2 by 0.7 mmHg.
    • Metabolic Alkalosis: Increase in HCO3- by 1 mmol/L leads to an increase in PaCO2 by 0.7 mmHg.
    • Increase in PaCO2 by 10 mmHg leads to a decrease in pH by 0.08 units.

    Clinical Case Example

    • Acidaemia: pH=7.261 (Reference range 7.35-7.45), metabolic acidosis.
    • Hypocapnia: PCO2=26.9 mmHg (Reference range 27.8-47.2), hyperventilation, respiratory alkalosis compensating for metabolic acidosis.
    • Low Bicarbonate: HCO3-=14.6 mmol/L (Reference range 18.3-26.4), likely due to loss or consumption.
    • Low Base Excess: BEecf= -6 mmol/L (Reference range -5 to +5), indicates metabolic acidosis.
    • Normal Oxygenation: PO2=98 mmHg (Reference range 85-100).
    • Normal AG with hyperchloremia, suggesting metabolic acidosis due to bicarbonate loss.

    Interpretation of Arterial Blood Gas (ABG)

    • Bicarbonate
      • Should increase with increased PaCO2 (same direction).
      • Ratio of PaCO2: bicarbonate should be 1:20.
      • Decreased levels can be due to loss or consumption.
      • Anion gap can be used to determine the cause of decreased bicarbonate in metabolic acidosis.

    Base Excess

    • Actual Base Excess
      • Dose of acid or alkali (mmol) needed to bring blood pH to 7.4 in 1 L of blood.
      • Reflects the buffering capacity of all systems (bicarbonate, phosphate, hemoglobin, plasma proteins).
    • Standard Base Excess
      • Dose of acid/alkali (mmol) needed to bring pH to 7.4 in 1 L of anemic blood.
      • Reflects buffering capacity of all systems except hemoglobin (only ECF).
    • Normal value: -4 to 4 mmol/L.
    • Negative base excess indicates decreased buffering capacity, while positive base excess indicates increased buffering capacity.
    • Metabolic Acidosis: Negative base excess.
    • Metabolic Alkalosis: Positive base excess.

    Bicarbonate Administration Recommendations

    • Administer bicarbonate only when:
      • Base Excess (BE) is lower than -7 mmol/L.
      • pH is lower than 7.1.
      • Bicarbonate is low (due to bicarbonate loss).
    • Calculate bicarbonate dosage:
      • (BE x 0.3 x kg)
      • Administer first half slowly as a bolus; wait 20 minutes and re-evaluate ABG analysis. Administer the remaining half if needed.
    • Considerations:
      • If the acidaemia is due to acid accumulation (e.g., lactic acidosis from hypovolemia), correcting hypovolemia might be more effective than bicarbonate.
    • PaCO2
      • Range 45-60 mmHg.
      • Increase in PaCO2:
        • Increases sympathetic nervous system activity, increasing catecholamines.
        • Decreases hemoglobin's affinity for oxygen, facilitating oxygen delivery.
        • Causes cerebral vasodilation, leading to increased cerebral blood flow and intracranial pressure.
      • When PaCO2 increases, the carbonic acid reaction shifts towards the production of H+ and bicarbonate, leading to a decrease in pH.

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    Description

    This quiz covers the problems associated with bicarbonate administration in animals, including haemodilution, hypochloremia, hypernatremia, and more. Understanding these issues is critical for effective veterinary practice and animal care. Test your knowledge on the physiological impacts and necessary monitoring when using bicarbonate as a treatment.

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