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AVECCTN 2025 > Advanced Blood Gas Interpretation > Flashcards

Advanced Blood Gas Interpretation Flashcards

M. Brashear IVECCS MDR 2020

1
Q

What is measured to analyze a patient’s acid-base status?

A

Hydrogen content of blood

Hydrogen is produced by normal metabolism of protein and is necessary for enzyme function and cell structure.

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2
Q

What does a low pH indicate about hydrogen ion concentration?

A

Increased level of H+

A low pH indicates an acidic environment.

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3
Q

What is the main extracellular buffer in the body?

A

Bicarbonate (HCO3)

It is the main metabolic indicator of a patient’s acid-base status.

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4
Q

How does carbon dioxide (CO2) relate to pH?

A

Elevated CO2 contributes to acidosis, while lower than normal CO2 contributes to alkalosis

CO2 is a main respiratory indicator of acid-base status.

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5
Q

What are the two body systems involved with acid-base regulation?

A
  • Kidneys
  • Respiratory system
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6
Q

What is the primary acid-base problem determined from?

A

Blood gas results

This helps in determining the primary disorder and compensatory mechanisms.

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7
Q

What happens to potassium levels during acidosis?

A

Hyperkalemia may result

Potassium shifts out of cells in exchange for H+.

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8
Q

What is the most common disorder seen in patient populations?

A

Metabolic acidosis

Noted in patients with lactic acidosis, kidney failure, DKA, and GI losses.

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9
Q

What is a potential treatment for severe metabolic acidosis?

A

Sodium bicarbonate

It buffers the acid but must be administered cautiously.

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10
Q

What is a common cause of metabolic alkalosis?

A

GI outflow obstructions

Can also occur with low chloride levels and poor perfusion.

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11
Q

What occurs during respiratory acidosis?

A

Hypoventilation and CO2 retention

This leads to a drop in pH.

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12
Q

What indicates respiratory alkalosis?

A

Hyperventilation leading to excessive CO2 loss

This causes the pH to rise.

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13
Q

What happens to the body’s bicarbonate levels in respiratory acidosis?

A

Hang on to HCO3, excrete H+

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14
Q

What is the normal range of pH in blood?

A

7.35–7.45

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15
Q

What does a negative base excess indicate?

A

Primary metabolic acidosis

A positive BE points to primary metabolic alkalosis.

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16
Q

What is the formula for calculating the A-a gradient?

A

A = [FiO2 × (Pb − PH2O)] − (PaCO2/0.8)

Pb is barometric pressure and PH2O is saturated water vapor pressure.

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17
Q

What does the PaO2:FiO2 ratio indicate?

A

If the patient is responding appropriately to oxygen

A normal ratio is 300–500.

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18
Q

What is the expected compensation for metabolic acidosis?

A

Each 1 mEq/L ↓ HCO3 causes pCO2 ↓ by 0.7 mm Hg

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19
Q

What does a high PaCO2 value indicate?

A

The lungs’ inability to move air

High PaCO2 can be caused by various conditions such as neurologic disease and upper airway disease.

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20
Q

What does the 120 rule help determine?

A

Adequate lung function

If PaO2 + PaCO2 ≥ 120, lung function is adequate.

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21
Q

What is the significance of venous blood gas values?

A

Provide important information, but respiratory component is most accurately measured with an arterial sample.

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22
Q

What is a common effect of alkalosis on potassium levels?

A

Hypokalemia may result

Potassium shifts into cells in exchange for H+.

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23
Q

What are the normal values for PaCO2?

A

35–45 mm Hg

24
Q

What is a key consideration when interpreting blood gas results?

A

Determine the primary disorder and if the body is compensating

25
Q

What does a normal A-a gradient indicate?

A

Hypoxia is not due to significant pulmonary parenchymal disease or heart disease.

26
Q

What is the expected compensation for acute respiratory acidosis?

A

Each 1 mm Hg ↑ in pCO2 causes HCO3 ↑ by 0.15 mEq/L

27
Q

What happens to HCO3 for each 1 mm Hg decrease in PCO2 in chronic respiratory alkalosis?

A

HCO3 decreases by 0.25 mEq/L

28
Q

What happens to HCO3 for each 1 mm Hg decrease in PCO2 in acute respiratory alkalosis?

A

HCO3 decreases by 0.55 mEq/L

29
Q

What is the first step in assessing a mixed disorder in acid-base balance?

A

Calculate the compensatory response

30
Q

In respiratory disorders, which value changes to compensate?

A

HCO3 changes to compensate for CO2

31
Q

What is the formula to calculate expected HCO3 in respiratory alkalosis?

A

Expected HCO3 = (midpoint HCO3) − [(midpoint CO2 − patient CO2) × compensation rate]

32
Q

What is the formula to calculate expected HCO3 in respiratory acidosis?

A

Expected HCO3 = (midpoint HCO3) + [(patient CO2 − midpoint CO2) × compensation rate]

33
Q

What indicates a mixed disorder when comparing actual HCO3 to expected HCO3?

A

If actual HCO3 is much lower than expected HCO3

34
Q

What is the normal range for the anion gap?

A

Less than 20

35
Q

What does an anion gap greater than 20 indicate?

A

Primary metabolic acidosis

36
Q

What is the formula for calculating the anion gap?

A

Anion gap = (Na + K) − (HCO3 + Cl)

37
Q

Which conditions commonly present with mixed acid-base disorders?

A
  • DKA
  • GDV
  • Kidney failure
  • Cardiopulmonary arrest
  • CHF
  • Heatstroke
  • Sepsis
  • Parvovirus
38
Q

When treating a mixed acid-base disorder, which change should be addressed first?

A

Respiratory changes

39
Q

What does a negative base excess indicate?

A

Primary acidosis

40
Q

What does a positive base excess indicate?

A

Primary alkalosis

41
Q

What are the measured strong ions in plasma?

A
  • Sodium
  • Chloride
  • Potassium
  • Calcium
  • Magnesium
  • Lactate
42
Q

What is the normal strong ion difference (SID)?

A

∼40 mEq/L

43
Q

What happens to base excess for every 1 mEq/L change in SID?

A

Base excess changes in the same direction by 1 mEq/L

44
Q

What indicates acidosis in relation to SID?

A

A low SID

45
Q

What can increased serum sodium cause in terms of SID?

A

Increase in SID indicating alkalosis

46
Q

What effect does decreased serum chloride have on SID?

A

Increases SID indicating alkalosis

47
Q

What is the effect of hypovolemia on sodium and chloride levels?

A

Loss of sodium and chloride

48
Q

How does increased serum lactate affect acid-base status?

A

Contributes to acidosis

49
Q

What role do albumin and phosphorus play in acid-base balance?

A

They serve as buffers in the blood

50
Q

What happens to acid-base status with hypoalbuminemia?

A

Can worsen alkalosis

51
Q

What can elevated phosphorus levels due to kidney failure contribute to?

A

Worsening acidosis

52
Q

What is the limitation of the traditional acid-base approach in veterinary medicine?

A

Fails to consider the effect of electrolytes

53
Q

What is the strong ion approach primarily used for?

A

To evaluate acid-base status in critically ill patients

54
Q

What happens when compensation is not occurring as expected?

A

Look deeper into electrolyte changes and other factors

55
Q

What is the effect of hyperalbuminemia on acid-base status?

A

No change

AVECCTN 2025 (7 decks)

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