What common laboratory finding would you expect in a patient with increased sympathetic tone and renal artery stenosis?

In a patient with increased sympathetic tone and renal artery stenosis, one would expect to find high levels of aldosterone. This is due to the fact that renal artery stenosis can lead to decreased renal perfusion and consequently the activation of the renin-angiotensin-aldosterone system (RAAS). As renin levels increase in response to the perceived decrease in blood flow, it stimulates the formation of angiotensin II, leading to an increase in the secretion of aldosterone. Aldosterone promotes sodium retention, potassium excretion, and water retention, which can result in hypernatremia instead of hypokalemia.

Additionally, the increased sympathetic tone often contributes to sodium retention through various mechanisms, but in the context of renal artery stenosis, it's the activation of the RAAS that predominantly causes the various electrolyte imbalances. Therefore, the correct response indicates that the pathological interplay leads to an increase in aldosterone levels, with subsequent effects on potassium and sodium levels.