Solved Go through the Acid/Base balance review sheet listed ... - Free Printable

Let's solve each of the acid-base balance problems using the provided blood gas values and interpret them based on pH, pCO₂ (partial pressure of carbon dioxide), and HCO₃⁻ (bicarbonate). We'll determine:

a. Type of acidosis or alkalosis (Respiratory or Metabolic)
b. Presence or absence of compensation

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🔍 Normal Values:

- pH: 7.35–7.45
- pCO₂: 35–45 mm Hg
- HCO₃⁻: 22–26 mEq/L

We use the following rules:
- pH < 7.35 → Acidosis
- pH > 7.45 → Alkalosis
- If pCO₂ is abnormal → Respiratory cause
- If HCO₃⁻ is abnormal → Metabolic cause
- Compensation: The body tries to correct pH via opposite changes in pCO₂ or HCO₃⁻.

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✔ Problem 1:

pH: 7.48
pCO₂: 48 mm Hg
HCO₃⁻: 32 mEq/L

- pH ↑ → Alkalosis
- pCO₂ ↑ → Respiratory acidosis? No! Wait: pCO₂ is elevated, but pH is high → not respiratory acidosis.
- Actually: Elevated pCO₂ would cause respiratory acidosis, but here pH is high, so it’s inconsistent.
- But wait: pCO₂ = 48 (slightly high), HCO₃⁻ = 32 (high), pH = 7.48 (alkalotic)

→ This is metabolic alkalosis with partial respiratory compensation.

Explanation:
- High HCO₃⁻ → Metabolic alkalosis
- pCO₂ is slightly elevated (48) → the body retains CO₂ to compensate for alkalosis (hypoventilation)
- pH is still high → uncompensated or partially compensated metabolic alkalosis

✔ Answer:
a. Metabolic Alkalosis
b. Partial Compensation (pCO₂ is elevated as a compensatory mechanism)

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✔ Problem 2:

pH: 7.31
pCO₂: 50 mm Hg
HCO₃⁻: 32 mEq/L

- pH ↓ → Acidosis
- pCO₂ ↑ → Respiratory acidosis
- HCO₃⁻ ↑ → Metabolic compensation

→ Primary problem: Respiratory acidosis (low pH + high pCO₂)
→ HCO₃⁻ is elevated → renal compensation (kidneys retain HCO₃⁻ to buffer acid)

✔ Answer:
a. Respiratory Acidosis
b. Compensated (HCO₃⁻ is increased as compensation)

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✔ Problem 3:

pH: 7.30
pCO₂: 41 mm Hg
HCO₃⁻: 18 mEq/L

- pH ↓ → Acidosis
- pCO₂ → Normal (41) → Not respiratory
- HCO₃⁻ ↓ → Metabolic acidosis

→ Metabolic acidosis (low HCO₃⁻, low pH)
→ pCO₂ is normal — but should be low in compensation (hypoventilation to retain CO₂)
→ Here, pCO₂ is normal → no compensation yet

✔ Answer:
a. Metabolic Acidosis
b. No Compensation (pCO₂ not decreased)

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✔ Problem 4:

pH: 7.50
pCO₂: 30 mm Hg
HCO₃⁻: 24 mEq/L

- pH ↑ → Alkalosis
- pCO₂ ↓ → Respiratory alkalosis
- HCO₃⁻ → Normal (24) → Slight increase possible?

Wait: HCO₃⁻ is normal, but pH is high and pCO₂ is low → primary respiratory alkalosis

→ Respiratory alkalosis (hyperventilation → low pCO₂ → high pH)
→ HCO₃⁻ is normal → no metabolic compensation yet (or minimal)

✔ Answer:
a. Respiratory Alkalosis
b. No Compensation (HCO₃⁻ is within normal range; not decreased)

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✔ Problem 5:

pH: 7.20
pCO₂: 46 mm Hg
HCO₃⁻: 27 mEq/L

- pH ↓ → Acidosis
- pCO₂ ↑ → Respiratory acidosis
- HCO₃⁻ ↑ → Metabolic compensation

→ Primary: Respiratory acidosis (pH down, pCO₂ up)
→ HCO₃⁻ is elevated (27) → renal compensation (retention of bicarbonate)
→ pH is still very low → incomplete compensation

✔ Answer:
a. Respiratory Acidosis
b. Compensated (partially) — HCO₃⁻ is increased, but pH is still acidic

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✔ Problem 6:

pH: 7.60
pCO₂: 47 mm Hg
HCO₃⁻: 28 mEq/L

- pH ↑ → Alkalosis
- pCO₂ ↑ → Respiratory acidosis? No — this would lower pH
- But here, pCO₂ is high, and pH is high → contradiction?
- Wait: High pCO₂ causes acidosis, but here pH is alkalotic → must be metabolic alkalosis overriding

→ HCO₃⁻ = 28 → Elevated → Metabolic alkalosis
→ pCO₂ = 47 → elevated, which is compensatory (hypoventilation to retain CO₂ and lower pH)

So: Metabolic alkalosis with respiratory compensation

✔ Answer:
a. Metabolic Alkalosis
b. Compensated (pCO₂ is elevated as compensation)

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📌 Final Answers Summary:

| # | pH | pCO₂ | HCO₃⁻ | Type | Compensation |
|---|------|------|--------|---------------------------|--------------|
| 1 | 7.48 | 48 | 32 | Metabolic Alkalosis | Partial |
| 2 | 7.31 | 50 | 32 | Respiratory Acidosis | Yes |
| 3 | 7.30 | 41 | 18 | Metabolic Acidosis | No |
| 4 | 7.50 | 30 | 24 | Respiratory Alkalosis | No |
| 5 | 7.20 | 46 | 27 | Respiratory Acidosis | Yes |
| 6 | 7.60 | 47 | 28 | Metabolic Alkalosis | Yes |

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✔ Key Takeaways:

- Look at pH first to determine acidosis/alkalosis.
- Then check pCO₂ and HCO₃⁻ to find primary cause.
- Opposite direction changes indicate compensation.
- Use the "Rule of Thumb":
- For acute respiratory acidosis, pCO₂ ↑ → pH ↓, HCO₃⁻ unchanged initially.
- For chronic, kidneys compensate → HCO₃⁻ ↑.
- In metabolic acidosis, pCO₂ ↓ (compensatory hyperventilation).
- In metabolic alkalosis, pCO₂ ↑ (compensatory hypoventilation).

Let me know if you want a mnemonic or chart!