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Zorluk: ZorNephrology

Match each set of arterial blood gas (ABG) and basic metabolic panel (BMP) results with the most likely clinical scenario. Assume all values were obtained simultaneously on room air. Reference ranges: Na+Na^+ 135-145 mEq/L, Cl−Cl^- 98-106 mEq/L, HCO3−HCO_3^- 22-28 mEq/L, pCO2pCO_2 35-45 mmHg, pH 7.35-7.45.

  • pH 7.25, pCO2pCO_2 20 mmHg, HCO3−HCO_3^- 9 mEq/L, Na+Na^+ 140 mEq/L, Cl−Cl^- 105 mEq/LDiabetic ketoacidosis due to medication nonadherence
  • pH 7.40, pCO2pCO_2 40 mmHg, HCO3−HCO_3^- 24 mEq/L, Na+Na^+ 140 mEq/L, Cl−Cl^- 96 mEq/LAdvanced chronic kidney disease complicated by profuse vomiting
  • pH 7.44, pCO2pCO_2 28 mmHg, HCO3−HCO_3^- 19 mEq/L, Na+Na^+ 138 mEq/L, Cl−Cl^- 108 mEq/LNormal physiologic changes of third-trimester pregnancy
  • pH 7.30, pCO2pCO_2 35 mmHg, HCO3−HCO_3^- 17 mEq/L, Na+Na^+ 140 mEq/L, Cl−Cl^- 115 mEq/LSevere, large-volume secretory diarrhea
  • pH 7.55, pCO2pCO_2 50 mmHg, HCO3−HCO_3^- 42 mEq/L, Na+Na^+ 140 mEq/L, Cl−Cl^- 90 mEq/LAggressive loop diuretic therapy for decompensated heart failure

Cevap

Profile 1 matches Diabetic ketoacidosis; Profile 2 matches Advanced chronic kidney disease complicated by profuse vomiting; Profile 3 matches Normal physiologic changes of third-trimester pregnancy; Profile 4 matches Severe, large-volume secretory diarrhea; and Profile 5 matches Aggressive loop diuretic therapy.
Each acid-base profile uniquely aligns with a specific clinical pathophysiology. Methodically calculating the anion gap, expected respiratory compensation, and the delta-delta ratio reveals the underlying single or mixed acid-base disorders, which are required to match the corresponding clinical scenarios accurately.

Adım Adım Çözüm

1
Calculate the anion gap (AG=Na+−[Cl−+HCO3−]AG = Na^+ - [Cl^- + HCO_3^-]) for each profile to rapidly differentiate gap from non-gap metabolic acidosis.
Profile 1 (AG=26AG = 26) and Profile 2 (AG=20AG = 20) have high anion gaps. Profiles 3, 4, and 5 have normal gaps (<12< 12).
Calculating the anion gap is the essential first step in evaluating any acid-base disorder, even if the pH is entirely normal.
2
Verify appropriate respiratory compensation for primary metabolic disorders using Winter's formula (pCO2=1.5×HCO3−+8±2pCO_2 = 1.5 \times HCO_3^- + 8 \pm 2) for acidosis and the alkalosis multiplier (pCO2=0.7×ΔHCO3−+40pCO_2 = 0.7 \times \Delta HCO_3^- + 40).
Profile 1, 4, and 5 represent fully compensated primary metabolic disorders without a secondary respiratory process.
To rule out mixed respiratory-metabolic disorders in patients with clear primary metabolic derangements.
3
Calculate the delta-delta gap (ΔΔ=[AG−12]+measured HCO3−\Delta\Delta = [AG - 12] + measured\ HCO_3^-) for patients with an elevated anion gap to check for hidden mixed disorders.
For Profile 2, the adjusted HCO3−HCO_3^- is 3232 mEq/L (which is >26>26), confirming a superimposed metabolic alkalosis despite a normal measured HCO3−HCO_3^-.
A high anion gap always represents a metabolic acidosis; a normal pH and HCO3−HCO_3^- in this setting guarantees the presence of a neutralizing metabolic alkalosis.

Anahtar Kavram

Acid-base interpretation utilizing the anion gap, expected respiratory compensation, and delta-delta gap.
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Konular

Nephrology

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