The Acidosis of Exogenous Phosphate Intoxication

Background Severe hyperphosphatemia resulting from the use of laxatives and enemas with high levels of phosphate has been the subject of many case reports. These have generally focused on the hypernatremia and hypocalcemia that develop and become life-threatening. Less attention has been paid to the metabolic acidosis of phosphate intoxication. Methods In-depth analysis of a case of severe hyperphosphatemia and review of the literature for cases with sufficient data to permit correlation between the phosphate concentration, acidosis, and anion gap. Results Marked metabolic acidosis with a large increase in the anion gap was present in our patient. The correlation between these parameters and the plasma phosphate concentration was highly significant. Despite a paucity of data in most case reports, we did uncover other cases of anion gap–positive metabolic acidosis in patients with hyperphosphatemia. Conclusions Among high-risk patients, including the elderly and debilitated, the presence of metabolic acidosis, hypernatremia, an increased anion gap, and low plasma calcium levels or a prolonged QT interval on the electrocardiogram should raise suspicion of phosphate intoxication.