Examkin

Soru

Zorluk: KolayNephrology

A 28-year-old daycare worker comes to the urgent care center complaining of severe, watery diarrhea for the past four days. She reports drinking only tap water since her symptoms began and has been unable to keep solid food down. On physical examination, her blood pressure is 105/65 mmHg and her pulse is 112/min. Her mucous membranes are dry. Laboratory studies show:

LabValue
Sodium138 mEq/L
Potassium3.2 mEq/L
Chloride113 mEq/L
Bicarbonate14 mEq/L
Blood urea nitrogen35 mg/dL
Creatinine1.1 mg/dL

Which of the following is the expected arterial partial pressure of carbon dioxide (PaCO2PaCO_2) for this patient if appropriate respiratory compensation has occurred?

  1. A
    14 mmHg
  2. B
    21 mmHg
  3. 29 mmHgCevap
  4. D
    40 mmHg
  5. E
    48 mmHg

Cevap

29 mmHg
The patient has a normal anion gap metabolic acidosis secondary to severe diarrhea (loss of bicarbonate in the stool). To determine if her lungs are appropriately compensating by blowing off carbon dioxide, Winter's formula must be applied. The formula is: Expected PaCO2=1.5×[HCO3−]+8±2PaCO_2 = 1.5 \times [HCO_3^-] + 8 \pm 2. Given a bicarbonate of 14 mEq/L, the calculation is 1.5×14+8=21+8=291.5 \times 14 + 8 = 21 + 8 = 29. Therefore, the expected PaCO2PaCO_2 is 29±229 \pm 2 mmHg. A measured PaCO2PaCO_2 exactly in this range indicates appropriate respiratory compensation.

Adım Adım Çözüm

1
Calculate the anion gap to characterize the primary acid-base disturbance.
Anion Gap = 138−(113+14)=11138 - (113 + 14) = 11 mEq/L.
An anion gap between 8 and 12 mEq/L indicates a normal anion gap metabolic acidosis (NAGMA), consistent with severe gastrointestinal bicarbonate loss from diarrhea.
2
Calculate the expected respiratory compensation using Winter's formula.
Expected PaCO2=(1.5×14)+8=21+8=29PaCO_2 = (1.5 \times 14) + 8 = 21 + 8 = 29 mmHg.
Winter's formula (1.5×[HCO3−]+8±21.5 \times [HCO_3^-] + 8 \pm 2) is used to determine if the respiratory response to a metabolic acidosis is appropriate, inadequate, or excessive.

Anahtar Kavram

In patients with metabolic acidosis, the expected compensatory respiratory response (decrease in PaCO2PaCO_2) is calculated using Winter's formula: Expected PaCO2=1.5×[HCO3−]+8±2PaCO_2 = 1.5 \times [HCO_3^-] + 8 \pm 2.
Bu soruyu puanla

Konular

Nephrology

Bu konudan daha fazla soru