Since NH 4 + salts are the major unmeasured osmoles in the urine, the osmolal gap is refl ective of urine ammonium excretion. If there is systemic acidemia, the appropriate renal response is generation of ammonium with a urinary ammonium value greater than 75 mEq/
dL. A urine NH 4 + which is less than 25 mEq/L is consistent with RTA with inadequate ammonium production.
7. A 2 year old male is transferred to the pediatric ICU from a referring institution with hypotension secondary to severe diarrhea and dehydration. His mother reports he has had diarrhea and fever for four days. He has had oral hydration with a pediatric rehydration solution and an appropriate dose of ibuprofen for fever every 6 hours. Vital sign are: pulse 167 beats per minute, blood pressure 109/67 mm Hg, respiratory rate of 44 breaths per minute. Examination reveals a lethargic child with cool extremities, delayed capillary refi ll and dry mucous membranes. Laboratory evaluation reveals:
Sodium 141 mEq/L Chloride 121 mEq/L Potassium 5.9 mEq/L BUN 44 mg/dL Creatinine 4.2 mg/dL Bicarbonate 7 mEq/L
Which of the following is most true regarding his decrement in renal function?
A. His BUN:creatinine ratio is refl ective of hypovolemia and not intrinsic renal injury
B. His increase in creatinine is mainly due to hemoconcentration
C. His increase in creatinine is refl ective of a 25% reduction in GFR
D. The acidosis is likely due to renal injury and renal loss of bicarbonate
E. The administration of ibuprofen likely impaired the kidney's ability to compensate for decreased perfusion
8. A 2 year old is admitted with pneumococcal sepsis and severe edema secondary to nephrotic syndrome. You are asked to estimate his GFR with the following information:
Dry weight - 12 kg Height - 85 cm
Plasma creatinine 1 mg/dl Urine output 2 ml/kg/hr
Which of the following is the most accurate estimate of GFR?
A. 10 ml/min/1.73 m2 B. 25 ml/min/1.73 m2 C. 30 ml/min/1.73 m2 D. 35 ml/min/1.73 m2A
E. An estimated GFR cannot be calculated with the above data
1. E 2. E 3. B 4. B
5. D 6. B 7. E 8. D
ANSWERS
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