Bartter Syndrome

Chronically volume depleted, not hypertensive - Renin and aldosterone are both high, but the patient still runs a normal-to-low blood pressure because they are salt- and water-depleted. Long-standing cases can drift hypertensive, so read the number against their own baseline. Load volume before induction and have a vasopressor drawn up.

Hypokalemia is the headline - Hypokalemia and metabolic alkalosis are present in almost all cases, so this is a chronic baseline rather than an acute derangement. Get a potassium and a 12-lead: the classic findings are a U wave and a prolonged QT, and hypokalemia is one of the major causes of perioperative dysrhythmias. See the Hypokalemia entry for correction detail.

Replacing potassium - Oral KCl 25 to 100 mmol/day is the chronic mainstay. Acutely, IV potassium 10 to 20 mEq/hr with continuous ECG monitoring throughout, and use repletion solutions without glucose - glucose drives potassium straight back into the cell.

Check a magnesium too - Hypomagnesemia aggravates potassium wasting, and magnesium supplementation is part of the standard regimen. Repleting potassium while the magnesium is low tends to fail.

Don't hyperventilate - Respiratory alkalosis from hyperventilation drives potassium intracellularly and stacks on top of an existing metabolic alkalosis. These patients are already compensating with a raised pCO2, so ventilate toward their baseline CO2 rather than a textbook ETCO2.

Neuromuscular blockade - Hypokalemia prolongs blockade and interferes with reversal, and chronic weakness means baseline strength is already down. Use quantitative train-of-four monitoring rather than clinical assessment and confirm a train-of-four ratio of at least 0.9 before extubation (2023 ASA neuromuscular blockade guideline).

This is a chloride-resistant alkalosis - Urine chloride is typically above 35 mEq/L in Bartter; a spot urine chloride under 25 mEq/L points to surreptitious vomiting instead. Chloride-resistant means saline alone will not correct the alkalosis the way it does after NG suction - treatment goes after aldosterone with potassium-sparing agents such as amiloride 5 to 40 mg/day or spironolactone.

Home meds worth knowing - Many are on an ACE inhibitor or ARB, prescribed here to lower angiotensin II and aldosterone and raise serum potassium, and on indomethacin 1 to 3 mg/kg/24 hours to antagonize the elevated urinary PGE2. The potassium you measure is a treated number; holding those drugs perioperatively can unmask worse hypokalemia.

Avoid aminoglycosides - Aminoglycosides produce a Bartter-like picture of hypokalemic metabolic alkalosis with hypomagnesemia and hypocalcemia that persists 2 to 6 weeks after the antibiotic stops. In a patient who already has the disease, choose different surgical prophylaxis.

What the alkalosis costs you - Metabolic alkalosis shifts the oxyhemoglobin dissociation curve left and impairs peripheral oxygen unloading, decreases myocardial contractility, decreases cerebral blood flow, and increases neuromuscular excitability. The net result is a patient who tolerates hypoxia badly.

Keep the fast short - Concentrating ability is impaired and polyuria is obligate, so these patients keep losing free water through an NPO period a normal kidney would ride out. Schedule early, allow clear fluids to the usual cutoff, and start maintenance fluid when the IV goes in.

Renal reserve - Chronic kidney disease is the major contributor to morbidity and nephrocalcinosis is common. Get a baseline creatinine and check whether prior renal ultrasound or CT documented nephrocalcinosis, then dose renally cleared drugs against that.

The pediatric patient - Classic and antenatal forms present in infancy with failure to thrive, polyuria, vomiting and dehydration; antenatal cases follow polyhydramnios and are often delivered prematurely. Patients are typically emaciated, so pad pressure points deliberately, and note that sensorineural deafness is described in this population when you plan induction and emergence.

Bartter syndrome is an autosomal recessive salt-wasting tubulopathy - functionally a patient born on a permanent loop diuretic. Defects in the NKCC2 cotransporter, the ROMK potassium channel, or the thick ascending limb chloride channel block sodium and chloride reabsorption there. Salt and water are lost, extracellular volume stays chronically depleted, and the renin-angiotensin-aldosterone system runs wide open with high renin and secondary hyperaldosteronism - yet blood pressure sits normal or low, because the patient is dry.

The sodium delivered distally is reabsorbed in exchange for potassium and hydrogen, producing the hypokalemic metabolic alkalosis present in almost all cases. Loss of the lumen-positive charge in the thick ascending limb also strips paracellular calcium and magnesium reabsorption, giving hypercalciuria, nephrocalcinosis, and hypomagnesemia in some patients. Concentrating ability is impaired, so polyuria is obligate. Presentation is usually in infancy with failure to thrive, polyuria, polydipsia, vomiting and dehydration.