The client asks the nurse what the 'rule of nines' is. Which explanation by the nurse is accurate regarding the rule of nines?

Rationale:

A. Increased cardiac output leading to muscle fatigue is incorrect. Intermittent claudication is not caused by cardiac output. While the heart supplies blood to the muscles, the issue in claudication is localized arterial insufficiency, not systemic cardiac function.

B. Atherosclerosis leading to reduced blood flow to the muscles is correct. Intermittent claudication occurs when arterial blood flow to the leg muscles is insufficient during exercise. Atherosclerotic plaques narrow or occlude peripheral arteries, reducing oxygen delivery to the muscles during increased activity. This oxygen deficit results in pain, cramping, and fatigue, which typically resolves with rest when oxygen demand decreases. Claudication is a hallmark symptom of peripheral artery disease (PAD).

C. Decreased oxygen demand in the leg muscles is incorrect. The symptom arises because oxygen demand exceeds supply, not because demand decreases. The muscles are actively working during exercise, which increases oxygen requirements, revealing the underlying ischemia caused by arterial obstruction.

D. Increased venous pressure causing fluid accumulation in the legs is incorrect. Venous insufficiency can cause edema and heaviness, but it does not produce the characteristic exercise-induced pain of intermittent claudication. Claudication is primarily an arterial problem rather than a venous one.

Rationale:

A. By promoting vasoconstriction, aldosterone release, and increasing blood volume is correct. The renin-angiotensin-aldosterone system (RAAS) is activated in response to low blood pressure, decreased renal perfusion, or low sodium levels. Renin, released by the juxtaglomerular cells of the kidney, converts angiotensinogen to angiotensin I, which is then converted to angiotensin II by angiotensin-converting enzyme (ACE). Angiotensin II is a potent vasoconstrictor, increasing systemic vascular resistance and blood pressure. It also stimulates aldosterone release from the adrenal cortex, which promotes sodium and water reabsorption in the distal tubules and collecting ducts of the kidney, thereby increasing blood volume and further raising blood pressure.

B. By blocking angiotensin II from binding to its receptors, reducing vasoconstriction is incorrect. This describes the action of angiotensin receptor blockers (ARBs), which lower blood pressure by preventing angiotensin II from exerting its effects. This is the opposite of the RAAS’s natural compensatory mechanism during hypotension.

C. By decreasing blood volume through promoting sodium and water excretion is incorrect. RAAS activation conserves sodium and water, increasing blood volume. Promoting excretion would lower blood volume and exacerbate hypotension, which is contrary to the system’s function.

D. By inhibiting aldosterone production and promoting sodium excretion is incorrect. RAAS stimulates aldosterone production, not inhibits it. Inhibiting aldosterone would lead to sodium and water loss, reducing blood volume and failing to restore blood pressure.