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Zorluk: ZorNephrology

A 24-year-old woman with a history of type 1 diabetes mellitus presents to the emergency department with a 3-day history of intractable nausea, vomiting, and diffuse abdominal pain. She reports that her insulin pump malfunctioned four days ago. On physical examination, she appears lethargic and has dry mucous membranes. Her pulse is 118/min, blood pressure is 98/60 mm Hg, and respirations are 26/min and deep.

Laboratory studies show:
Serum:
Sodium: 140 mEq/L140 \text{ mEq/L}
Potassium: 4.8 mEq/L4.8 \text{ mEq/L}
Chloride: 88 mEq/L88 \text{ mEq/L}
Bicarbonate: 16 mEq/L16 \text{ mEq/L}
Blood urea nitrogen: 42 mg/dL42 \text{ mg/dL}
Creatinine: 1.6 mg/dL1.6 \text{ mg/dL}
Glucose: 520 mg/dL520 \text{ mg/dL}

Arterial blood gas (room air):
pH: 7.34
pCO2\text{pCO}_2: 31 mm Hg31 \text{ mm Hg}
pO2\text{pO}_2: 95 mm Hg95 \text{ mm Hg}

Assume a normal serum anion gap of 12 mEq/L12 \text{ mEq/L} and a normal serum bicarbonate of 24 mEq/L24 \text{ mEq/L}.

What is this patient's delta-delta ratio (ΔAGΔHCO3−\frac{\Delta \text{AG}}{\Delta \text{HCO}_3^-})?

Cevap: 3

Cevap

3.0
The correct answer is 3.0. The patient has a calculated anion gap of 36 mEq/L (140 - [88 + 16]). The change in anion gap (Δ\Delta AG) is 24 mEq/L (36 - 12). The change in bicarbonate (ΔHCO3−\Delta\text{HCO}_3^-) is 8 mEq/L (24 - 16). The delta-delta ratio is ΔAG/ΔHCO3−=24/8=3.0\Delta\text{AG} / \Delta\text{HCO}_3^- = 24 / 8 = 3.0. In an uncomplicated high anion gap metabolic acidosis (HAGMA), the drop in bicarbonate should roughly equal the rise in the anion gap, yielding a ratio between 1.0 and 2.0. A ratio greater than 2.0 indicates that the bicarbonate level is higher than expected, signaling a concurrent metabolic alkalosis. This is consistent with the patient's history of intractable vomiting (loss of gastric HCl) in the setting of diabetic ketoacidosis.

Adım Adım Çözüm

1
Calculate the serum anion gap.
36 mEq/L
To identify the presence and magnitude of an unmeasured anion accumulation (high anion gap metabolic acidosis).
2
Calculate the delta anion gap (ΔAG\Delta\text{AG}).
24 mEq/L
To determine how much the anion gap has increased above the normal baseline.
3
Calculate the delta bicarbonate (ΔHCO3−\Delta\text{HCO}_3^-).
8 mEq/L
To determine how much the serum bicarbonate has decreased from the normal baseline.
4
Calculate the delta-delta ratio (ΔAGΔHCO3−\frac{\Delta\text{AG}}{\Delta\text{HCO}_3^-}).
3.0
To evaluate for the presence of a concurrent mixed acid-base disorder.

Anahtar Kavram

Delta-delta ratio in the evaluation of mixed acid-base disorders
Tahmini Süre:1m 30s
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Nephrology

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