Editing Anatomy and Physiology (section)

=== Baroreceptors and the Renin-Angiotensin-Aldosterone System ===

Baroreceptors in the carotid sinus and aortic arch detect pressure changes within seconds and adjust sympathetic and parasympathetic output. Over hours to days, low renal perfusion triggers renin release, which produces angiotensin I, converted by angiotensin-converting enzyme to angiotensin II, a potent vasoconstrictor that also stimulates aldosterone release and sodium and water retention.

'''Nursing application:'''
* This system explains the mechanism of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, and explains why they can cause hyperkalemia.
* Baroreceptor sensitivity declines with age, which is why orthostatic hypotension and falls are common in older adults. Teach patients to change position slowly and dangle their legs before standing.
* '''Left-sided heart failure''' backs blood into the pulmonary circulation: dyspnea, orthopnea, paroxysmal nocturnal dyspnea, crackles, cough, and pink frothy sputum. '''Right-sided heart failure''' backs blood into systemic veins: jugular venous distention, peripheral edema, hepatomegaly, ascites, and weight gain. Daily weight is the most reliable indicator of fluid status; about 1 kilogram equals about 1 liter of fluid.