Conn Syndrome

An endocrine disorder caused by hyperaldosteronism presenting with symptoms associated with hypertension and hypokalemia.

Primary Hyperaldosteronism; Aldosteronoma.

Previously thought to be rare; however, the detection rate has increased tremendously with more sensitive screening options now available. Prevalence rates in hypertensive patients now vary between 3 and 32%, depending on the patient selection and the diagnostic criteria used.

Most cases are sporadic; however, a genetic basis for the disorder has been identified in some patients. An autosomal dominant inherited form is known as familial hyperaldosteronism, which is caused by an abnormal hybrid gene encoding an enzyme that has 11-β-hydroxylase and aldosterone synthase activity and is regulated by adrenocorticotropic hormone instead of angiotensin II.

Primary hyperaldosteronism results from adrenal cortical hyperplasia (diffuse or nodular), adrenal adenoma, or rarely adrenal carcinoma. This results not only in excessive sodium reabsorption in the distal nephron with hypertension and suppression of the renin-angiotensin II system, but also in increased urinary losses of potassium and hydrogen ions (in exchange with sodium) leading to hypokalemia and metabolic alkalosis.

Based on clinical findings (hypertension, polyuria, polydipsia, fatigue, tinnitus, paresthesia, paralysis of variable duration, failure to thrive, muscle loss). Hypokalemia (<3.5 mmol/liter; present in approximately 20% of patients), metabolic alkalosis associated with inappropriate kaliuresis, increased plasma levels of aldosterone (>40 ng/dl), decreased plasma renin activity (<0.3 ng/ml/hour), nonsuppressible aldosterone response to ambulation, and a pathologic fludrocortisone suppression test confirm the diagnosis. Dexamethasone does not suppress aldosterone levels (except in familial hyperaldosteronism, where small doses of dexamethasone are used therapeutically). Magnetic resonance imaging is the diagnostic imaging tool of choice. It shows that the adrenal gland on the left side is involved four times more often than the gland on the right.

Morbidity in Conn syndrome results mainly from hypertension, which can range from mild to severe and be associated with significant headache. Increasing evidence indicates aldosterone in excess can trigger adverse cardiovascular sequelae (myocardial remodeling and fibrosis) independent of hypertension. Hypervolemia and hyperglycemia may occur. Renal failure as a result of acute rhabdomyolysis because of severe hypokalemia has been reported, as well as a lumbar plexopathy. Visual disturbances are less frequent. Severe growth retardation has been reported as a result of severe potassium depletion.

Evaluate serum electrolyte status and correct hypokalemia. Restrict sodium intake. Administer spironolactone and stop captopril or enalapril (if used) 24 hours before general anesthesia. Check cardiovascular status. Check for signs of long-standing arterial hypertension (left ventricular hypertrophy, peripheral arterial and coronary artery sclerosis, heart failure). Obtain a chest radiograph, an electrocardiogram, and potentially an echocardiogram. Check renal function (creatinine, urea, serum electrolytes).

If hypokalemia is not corrected prior to anesthesia, hyperventilation could be very dangerous by further decreasing potassium plasma levels. In young children, regional anesthesia techniques may be preferred because of the absence of hemodynamic effects. In older patients, however, significant drops in arterial blood pressure can occur in combination with spinal anesthesia. No specific anesthetic agents can be recommended or are contraindicated considering the risk of acute hypotension. Depending on the procedure, invasive arterial blood pressure and central venous pressure monitoring should be considered. Hypokalemia may prolong the action of neuromuscular blockers, so reduced doses should be used and monitoring with a peripheral nerve stimulator is recommended.

Close attention should be paid to the possible interaction between the antihypertensive drugs that are used in these patients (e.g., captopril, enalapril, spironolactone) and the risk of hyperkalemia. Clonidine should be avoided because it decreases plasma renin activity. The use of enflurane may be questionable if signs of nephropathy exist preoperatively. Supplementation with exogenous cortisol is indicated only in patients with excision of multiple adenomas with bilateral mobilization of adrenal glands.

Liddle Syndrome: Renal tubular defect causing severe hypertension with hypokalemia and metabolic alkalosis.