2017 Volume 30 Issue 1 Pages 68-72
We experienced two cases showing the clinical usefulness of deviation from the normal difference between Na and Cl (Na-Cl=36) in the serum, raising suspicion of acid-base balance disorders and thus prompting blood gas analysis. Case 1, a 3-year-old girl, had developed a brain tumor at age 3 months and received multimodal therapy. When she developed gastroenteritis at age 3 years, she was diagnosed as having drug-induced Fanconi syndrome because of hypophosphatemia, low-molecular-weight proteinuria, metabolic acidosis and, rickets. Her serum Na-Cl levels were consistently 30 or lower, suggesting prolonged metabolic acidosis. Case 2, a 19-year-old woman, had suffered rhabdomyosarcoma at age 9 months and received multimodal therapy. After the end of treatment, her serum magnesium levels had gradually decreased. At age 19 years, she was diagnosed with hypocalcemia, hypokalemia, and metabolic alkalosis. While her serum magnesium levels decreased, her serum Na-Cl levels were consistently 40 or higher, suggesting prolonged metabolic alkalosis. When blood gas analysis is not performed, deviation from the Na-Cl=36 in the serum appears to be clinically useful as it raises suspicion of the presence of acid-base balance disorders.
