ABG Values at a Glance

Step-by-Step ABG Interpretation

1. pH - Normal (7.43)

2. Primary Disorder

• pCO2 is 35 mmHg (low-normal) and HCO3- is 23.2 mmol/L (normal).
• BE is -1.1 (essentially normal).
• This is a compensated/normal ABG - no overt primary acid-base disorder.
• However, the slightly low pCO2 with a high-normal pH hints at mild respiratory alkalosis (hyperventilation), which is fully compensated.

3. Oxygenation

• pO2 = 190 mmHg (markedly elevated) - patient is clearly on supplemental oxygen.
• SO2 = 100% - fully saturated.

Critical Abnormalities - Require Urgent Attention

🔴 Severe Hyponatremia: Na+ = 124 mmol/L

• Normal: 135-145 mmol/L. This is critically low (severe hyponatremia).
• Symptoms risk: confusion, seizures, cerebral edema.
• Requires urgent evaluation for cause (SIADH, hypovolemia, hyperglycemia correction, etc.)
• Correction must be slow - max 8-10 mEq/L per 24h to avoid osmotic demyelination syndrome.

🔴 Severe Hypocalcemia (Ionized): Ca++ = 0.66 mmol/L

• Normal ionized calcium: 1.12 - 1.32 mmol/L. This is critically low (roughly half of normal).
• Corrected to pH 7.4: still only 0.67 mmol/L.
• Risk of: tetany, laryngospasm, seizures, cardiac arrhythmias.
• Requires urgent IV calcium supplementation.

🟠 Hyperglycemia: Glucose = 277 mg/dL

• Significantly elevated. Consistent with poorly controlled diabetes mellitus or stress hyperglycemia.
• Note: Hyperglycemia lowers measured sodium. Corrected Na = 124 + 1.6 × [(277 - 100)/100] = 124 + 2.8 ≈ 127 mmol/L - still severely hyponatremic.

🟠 Elevated Lactate: 3.9 mmol/L

• Normal: < 2.0 mmol/L. This is moderately elevated (type A or B lactic acidosis range).
• Could reflect tissue hypoperfusion, sepsis, or hepatic dysfunction.
• Despite normal pH/BE, the elevated lactate may be masked by concurrent respiratory alkalosis.
• Requires clinical correlation.

🟡 Hypokalemia: K+ = 3.1 mmol/L

• Mildly low (normal 3.5-5.0 mmol/L). Needs monitoring and replacement, especially in the context of severe hypocalcemia (both can provoke arrhythmias).

🟡 Elevated Hematocrit: Hct = 55%

• Normal for females: 36-46%. This is elevated, suggesting polycythemia or dehydration/hemoconcentration.

🟡 Elevated Hemoglobin: THbc = 17.1 g/dL

• Corroborates the elevated Hct. Likely hemoconcentration in this clinical context.

Summary Diagnosis

Clinical Picture

• SIADH or pseudohyponatremia workup
• Hypoparathyroidism or vitamin D deficiency for the hypocalcemia
• Sepsis workup given elevated lactate
• The respiratory alkalosis may be a pain/anxiety response or early compensation for metabolic acidosis not yet apparent