Examkin

Soru

Zorluk: ZorNephrology

A 24-year-old man is brought to the emergency department by his roommate due to confusion, rapid breathing, and ringing in his ears after intentionally ingesting an unknown quantity of pills. On physical examination, temperature is 37.8°C (100.0°F), blood pressure is 110/70 mm Hg, pulse is 112/min, and respiratory rate is 28/min. The lungs are clear to auscultation. Laboratory studies show the following:

Serum sodium: 142 mEq/L
Serum potassium: 4.1 mEq/L
Serum chloride: 104 mEq/L
Serum bicarbonate: 14 mEq/L

Arterial blood gas analysis on room air reveals:
pH: 7.43
pCO2: 21 mm Hg
pO2: 98 mm Hg

Based on these findings, which of the following best describes this patient's acid-base status?

  1. Mixed high anion gap metabolic acidosis and primary respiratory alkalosisCevap
  2. B
    High anion gap metabolic acidosis with appropriate respiratory compensation
  3. C
    Mixed high anion gap metabolic acidosis and primary respiratory acidosis
  4. D
    Mixed non-anion gap metabolic acidosis and primary respiratory alkalosis
  5. E
    Primary respiratory alkalosis with appropriate metabolic compensation

Cevap

Mixed high anion gap metabolic acidosis and primary respiratory alkalosis
This patient has a mixed high anion gap metabolic acidosis and primary respiratory alkalosis. The anion gap is calculated as 142−(104+14)=24142 - (104 + 14) = 24 mEq/L (normal: 8-12 mEq/L), indicating a primary high anion gap metabolic acidosis (HAGMA). In primary metabolic acidosis, the lungs compensate by hyperventilating to decrease pCO2. To determine if this respiratory compensation is appropriate, Winter's formula is used: Expected pCO2 = (1.5×14)+8±2=29±2(1.5 \times 14) + 8 \pm 2 = 29 \pm 2 mm Hg (range 27-31 mm Hg). The patient's actual pCO2 is 21 mm Hg, which is significantly lower than the expected range. A measured pCO2 lower than the expected compensatory pCO2 indicates the presence of a concurrent primary respiratory alkalosis. This mixed acid-base disorder is the classic presentation of salicylate toxicity (which causes a direct stimulation of the medullary respiratory center followed by an accumulation of organic acids).

Adım Adım Çözüm

1
Calculate the serum anion gap to identify if a metabolic acidosis is present.
Anion Gap = 142−(104+14)=24142 - (104 + 14) = 24 mEq/L.
An elevated anion gap (> 12 mEq/L) establishes the diagnosis of a primary high anion gap metabolic acidosis (HAGMA).
2
Calculate the expected pCO2 to evaluate the respiratory response to the metabolic acidosis.
Expected pCO2 = (1.5×14)+8±2=29±2(1.5 \times 14) + 8 \pm 2 = 29 \pm 2 mm Hg (range: 27-31 mm Hg).
Winter's formula determines the expected compensatory pCO2 for a given HCO3- in primary metabolic acidosis.
3
Compare the actual measured pCO2 with the expected pCO2.
Actual pCO2 (21 mm Hg) is less than the expected range (27-31 mm Hg).
When actual pCO2 is lower than the expected compensatory pCO2, it indicates the presence of an independent, concurrent primary respiratory alkalosis.

Anahtar Kavram

The evaluation of acid-base disorders requires calculating the anion gap to identify primary metabolic acidosis and applying Winter's formula to determine if the respiratory response is appropriate or if a concurrent primary respiratory disorder exists.
Bu soruyu puanla

Konular

Nephrology

Bu konudan daha fazla soru