Potassium Presentation in Bartter Syndrome
Bartter syndrome characteristically presents with hypokalemia (low serum potassium) due to excessive renal potassium wasting, typically accompanied by hypochloremic metabolic alkalosis and normal blood pressure despite elevated renin and aldosterone levels. 1, 2
Pathophysiology of Hypokalemia
The hypokalemia in Bartter syndrome results from two primary mechanisms:
- Impaired sodium, potassium, and chloride reabsorption in the thick ascending limb of Henle's loop due to dysfunction of the Na+-K+-2Cl- cotransporter (NKCC2) or associated ion channels 2, 3
- Enhanced aldosterone-mediated potassium secretion in the collecting duct, driven by secondary hyperreninaemic hyperaldosteronism from chronic volume depletion 2, 4
Clinical Manifestations Related to Hypokalemia
Patients with Bartter syndrome commonly present with:
- Muscle cramps and weakness from the neuromuscular effects of hypokalemia 2
- Salt craving as a compensatory mechanism for renal salt wasting 2
- Growth failure, particularly in untreated cases during childhood 1, 2
- Cardiac complications including QT prolongation and risk of arrhythmias or sudden death 1, 2
Laboratory Findings
The characteristic electrolyte pattern includes:
- Hypokalemia with inappropriately high urinary potassium excretion (typically >20-40 mEq/L) 5, 6
- Hypochloremic metabolic alkalosis 4, 5, 3
- Normal or low serum sodium and chloride 6, 7
- Elevated plasma renin and aldosterone despite normal blood pressure 5, 3
Management of Hypokalemia
Potassium chloride supplementation (5-10 mEq/kg/day in children) is the cornerstone of treatment, though complete normalization is often not achievable. 1, 2
Key management principles include:
- Target potassium level of 3.0 mmol/L is reasonable, with explicit acknowledgment that this may not be achievable in all patients 1, 2
- Use potassium chloride specifically, not other potassium salts like citrate, which may worsen metabolic alkalosis 2
- Divide supplements throughout the day to maintain steady levels rather than large fluctuations 1
- Check and correct magnesium first before supplementing potassium, as hypomagnesemia is the most common reason for treatment failure 8
Additional Therapeutic Considerations
- NSAIDs (particularly indomethacin) address the underlying pathophysiology by suppressing prostaglandin formation and improve both electrolyte profile and growth 1, 8, 2
- Sodium chloride supplementation (5-10 mmol/kg/day) is recommended as foundational therapy for the salt-wasting component 1, 8
- Avoid potassium-sparing diuretics, ACE inhibitors, and ARBs as they risk life-threatening hypovolemia in this salt-wasting condition 1, 8