Metabolic Alkalosis Pathogenesis, Diagnosis, and Treatment: Core Curriculum 2022

Metabolic alkalosis is a widespread acid-base disturbance, especially in hospitalized patients. It is characterized by the primary elevation of serum bicarbonate and arterial pH, along with a compensatory increase in Pco2 consequent to adaptive hypoventilation. The pathogenesis of metabolic alkalosis involves either a loss of fixed acid or a net accumulation of bicarbonate within the extracellular fluid. The loss of acid may be via the gastrointestinal tract or the kidney, whereas the sources of excess alkali may be via oral or parenteral alkali intake. Severe metabolic alkalosis in critically ill patients-arterial blood pH of 7.55 or higher-is associated with significantly increased mortality rate. The kidney is equipped with sophisticated mechanisms to avert the generation or the persistence (maintenance) of metabolic alkalosis by enhancing bicarbonate excretion. These mechanisms include increased filtration as well as decreased absorption and enhanced secretion of bicarbonate by specialized transporters in specific nephron segments. Factors that interfere with these mechanisms will impair the ability of the kidney to eliminate excess bicarbonate, therefore promoting the generation or impairing the correction of metabolic alkalosis. These factors include volume contraction, low glomerular filtration rate, potassium deficiency, hypochloremia, aldosterone excess, and elevated arterial carbon dioxide. Major clinical states are associated with metabolic alkalosis, including vomiting, aldosterone or cortisol excess, licorice ingestion, chloruretic diuretics, excess calcium alkali ingestion, and genetic diseases such as Bartter syndrome, Gitelman syndrome, and cystic fibrosis. In this installment in the AJKD Core Curriculum in Nephrology, we will review the pathogenesis of metabolic alkalosis; appraise the precipitating events; and discuss clinical presentations, diagnoses, and treatments of metabolic alkalosis.

Purtscher-Like Retinopathy Secondary to Medication Induced Calcium-Alkali Syndrome and Acute Pancreatitis in a Pregnant Female

PURPOSE

To report a case of Purtscher-like retinopathy secondary to acute pancreatitis caused by medication-induced calcium-alkali syndrome in a pregnant woman.

METHODS

Case report.

RESULTS

A 39-year-old 23-week pregnant patient complained of visual disturbances during admission for acute pancreatitis precipitated by calcium-alkali syndrome. History revealed the acute ingestion of over 2,400 mg of elemental calcium from over the counter medication in the background of longstanding use. Visual acuity was counting fingers at 1 foot bilaterally. Posterior segment exam revealed Purtscher-flecken in the posterior pole with scattered dot hemorrhages. Optical coherence tomography (OCT) revealed inner retinal thickening and increased hyper-reflectivity. OCT angiography demonstrated loss of flow primarily in the superficial capillary plexuses. The patient was diagnosed with Purtscher-like retinopathy and observed. Two months follow up revealed resolution of the funduscopic findings and visual acuity improved minimally to 20/200 in the right eye and counting fingers in the left eye.

CONCLUSION

Common over the counter medication can potentiate a calcium-alkali syndrome capable of causing a Purtscher-like retinopathy.

Antacid-induced acute hypercalcemia: An increasingly common and potentially dangerous occurrence

Hypercalcemia is frequently encountered in both hospital wards and the primary care setting; 90% of cases can be attributed to primary hyperparathyroidism and malignancy. However, a minority are caused by medications, of which calcium supplements have been an increasingly common etiology. We are presenting a case of hypercalcemia resulted after acute oral intake of a moderate amount of antacids (calcium tablets) and normalized after supplement withdrawal.

Hypercalcemic crisis induced by calcium carbonate

We report a rare case of drug-induced hypercalcemic crisis in an elderly male resulting from calcium-containing supplements facilitated by thiazide diuretic and angiotensin-converting enzyme inhibitor. A 61-year-old male presented with hypercalcemic crisis along with renal insufficiency and metabolic alkalosis, mimicking the ‘calcium-alkali syndrome’. The patient responded to aggressive intravenous hydration along with emergent hemodialysis and salmon calcitonin. He did not have hyperparathyroidism or malignancy. History revealed an average daily intake of only 1200 mg of calcium carbonate along with vitamin D 1000 U/day over an extended period of time. The patient completely recovered in 3 days and had normal serum calcium, parathyroid hormone and phosphorous level at 3-month follow-up. The case highlights the life-threatening perils of indiscriminate and often excessive intake of calcium-containing supplements in an appropriate clinical setting. We also briefly discuss the epidemiology, clinical and laboratory features along with the recent advances in the understanding of the pathophysiology of calcium-alkali syndrome.

Calcium-alkali syndrome in the modern era

The ingestion of calcium, along with alkali, results in a well-described triad of hypercalcemia, metabolic alkalosis, and renal insufficiency. Over time, the epidemiology and root cause of the syndrome have shifted, such that the disorder, originally called the milk-alkali syndrome, is now better described as the calcium-alkali syndrome. The calcium-alkali syndrome is an important cause of morbidity that may be on the rise, an unintended consequence of shifts in calcium and vitamin D intake in segments of the population. We review the pathophysiology of the calcium-alkali syndrome.