Is bicarbonate solution tolerated better than Shohl’s solution in neonatal renal tubular acidosis?

Abstract

Sirs, Distal renal tubular acidosis (dRTA) was first recognized by Albright et al. as a distinct entity in 1946 [1]. The clinical syndrome described hypokalemia, hyperchloremic metabolic acidosis, inability to lower urine pH below 5.5, nephrocalcinosis, nephrolithiasis and potassium depletion. Additional features included osteomalacia or rickets. The syndrome was designated as “distal renal tubular acidosis” because the establishment of a large pH gradient between urine and blood is the function of the distal nephron. Distal RTA is almost always observed in children as a primary entity inherited in both autosomal dominant and recessive patterns [2]. If detected early in life, therapeutic correction of the acidosis by continuous alkali administration may induce resumption of normal growth, arrest of nephrocalcinosis, and preservation of renal function [2]. We describe the case of a 20-day-old girl with dRTA associated with hypokalemia, metabolic acidosis and dehydration. The girl was born at 40 weeks of gestation, weighing 3,250 g. Her parents described a sister diagnosed with dRTA and treated with Shohl’s (potassium or sodium citrate) solution in the neonatal period. The sister could not tolerate the solution and suffered persistent vomiting and diarrhea, which resulted in death at 4 months. At 20 days of age, the patient was admitted to our outpatient clinic for weight loss (body weight loss 110 g), dehydration, and generalized weakness. Laboratory examination on admission revealed severe acidemia (pH 7.27, PCO2 27 mmHg, plasma bicarbonate 12 mmol/l, base excess −12.4 mmol/l) and a high urine pH (pH=8). Serum analysis revealed sodium 138 mmol/l, chloride 118 mmol/l, total calcium 11.6 mmol/l, ionized calcium 1,26 mmol/l, phosphorus 6.4 mmol/l, urea 58 mg/dl, creatinine 0.6 mg/dl, glucose 83 mg/dl and serum alkaline phosphatase 537 IU/l. Pyuria was noted. However, urine cultures on two occasions showed no growth. No significant protein, glucose, or amino acid was detected in the urine. The urine anion gap (Na + K Cl) was +86 mmol/l [normal range: −10 to +10 mmol/l]. The urinary calcium/creatinine ratio was 0.52 (normal values for infants are below 0.6). Renal ultrasonography was normal. A diagnosis of distal RTA was made, and treatment with sodium bicarbonate infusion was initiated. Two days after admission, infusion was stopped. Shohl’s solution was initiated at a dose of 2 mEq kg day and increased to 16 mEq kg day. Oral potassium citrate, about 2 mEq body weight per day, was added to treat hypokalemia. Vomiting and diarrhea were observed under treatment with Shohl’s solution. Plasma bicarbonate concentrations decreased from 17 to 9 mmol/l and serum pH was 7.1. Metabolic acidosis was treated with bicarbonate infusion and thereafter per oral 2 mmol kg day sodium bicarbonate was initiated. Under sodium bicarbonate and potassium citrate therapies, pH increased to 7.44, PCO2 to 40 mmHg, plasma bicarbonate to 27 mmol/l, base excess to +3.2 mmol/l and potassium to 3.7 mmol/l. No vomiting or diarrhea was observed. In the second month her body weight was 4,450 g, pH 7.42, PCO2 40 mmHg, plasma bicarbonate 28 mmol/l, base excess +3 and potassium 4 mmol/l. Pediatr Nephrol (2007) 22:152–153 DOI 10.1007/s00467-006-0249-5