Liddle Syndrome

Renal tubular defect causing severe heritable hypertension with hypokalemia and metabolic alkalosis.

Pseudohyperaldosteronism.

Autosomal dominant trait with variable penetrance. The variability is particularly evident with regard to serum potassium concentration. Complete linkage of the disorder localized to gene 16p13-p12.

Liddle syndrome is the result of specific mutations that prevent the binding of a regulatory protein to a specific proline-rich region in the carboxyl terminal of the three subunits that compose the epithelial sodium channel SCNN1. This prevents normal degradation of the sodium channel so that the total number of channels is increased, giving rise to constitutive activation of the channel, which increases renal sodium absorption and excretes potassium despite the virtual absence of mineralocorticoids, accounting for the clinical and biochemical abnormalities.

Liddle syndrome is characterized by hypertension, hypokalemia, severe metabolic acidosis, decreased renin, and angiotensin. The hallmark is the finding of markedly suppressed serum aldosterone levels and the lack of response to administration of the mineralocorticoid receptor blocker spironolactone.

Clinically, patients resemble those with primary hyperaldosteronism. They may present with severe hypertension in their teenage years, and this is usually the presenting symptom. Amiloride and triamterene, but not spironolactone, are effective treatments for hypertension and hypokalemia in patients with this syndrome as long as dietary sodium intake is restricted. Hypokalemic metabolic alkalosis is present. Renal function is normal apart from the inability to conserve potassium. However, renal failure may occur secondary to hypertension. The metabolic defects are completely corrected with renal transplantation.

Evaluate the extent and severity of end-organ damage secondary to long-standing hypertension, in particular the cardiorespiratory and neurologic systems. Optimize antihypertensive therapy; addition of triamterene may help reverse the biochemical abnormalities. Treatment of any volume deficit helps in the correction of a persistent metabolic alkalosis and hypokalemia. Investigations: urea, creatinine, electrolytes, ECG, chest radiography, echocardiography. A sedative premedicant to reduce anxiety and its hypertensive response should be prescribed.

The anesthetic technique should avoid hypotensive and hypertensive events. Invasive arterial and central venous pressure monitoring should be determined by the severity of cardiovascular, neurologic, and renal impairment secondary to hypertension. Esmolol and labetalol are useful antihypertensive agents. Regional techniques, by itself or in conjunction with general anesthesia, offer excellent intraoperative and postoperative analgesia and reduce considerably the stress response to surgery. Capnography monitoring is essential as hyperventilation exacerbates a preexisting metabolic alkalosis.

Hypokalemia and metabolic acidosis may not only increase sensitivity to but may also prolong the duration of action with nondepolarizing muscle relaxants. These problems should be corrected before anesthesia.

Conn Syndrome: Potentially curable endocrine disorder resulting from hyperaldosteronism; presents with symptoms associated with hypertension and hypokalemia.