Editing Anatomy and Physiology – RN Flashcards (section)

== Cardiovascular ==

;Why does tachycardia worsen myocardial ischemia?
:The coronary arteries perfuse during diastole. As heart rate rises, diastole shortens disproportionately, so coronary perfusion and ventricular filling both fall at the moment myocardial oxygen demand is highest.

;Contrast the presentation of left-sided and right-sided heart failure and explain the mechanism.
:Left-sided failure backs blood into the pulmonary circulation, producing dyspnea, orthopnea, paroxysmal nocturnal dyspnea, crackles, and pink frothy sputum. Right-sided failure backs blood into the systemic venous system, producing jugular venous distention, peripheral edema, hepatomegaly, ascites, and weight gain.

;Trace the renin-angiotensin-aldosterone system and name two drug classes that interrupt it.
:Reduced renal perfusion triggers renin release, which cleaves angiotensinogen to angiotensin I; angiotensin-converting enzyme converts it to angiotensin II, a potent vasoconstrictor that stimulates aldosterone, causing sodium and water retention and potassium excretion. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers interrupt it, and both can cause hyperkalemia.

;Why does compensated shock present with a normal blood pressure?
:Baroreceptor-mediated sympathetic activation raises heart rate, contractility, and systemic vascular resistance, maintaining blood pressure until compensation fails. Tachycardia, narrowed pulse pressure, cool clammy skin, restlessness, and falling urine output appear before hypotension.