Clinical meaning
Hypertensive crisis is defined as severe blood pressure elevation (systolic above 180 mmHg and/or diastolic above 120 mmHg) that may or may not be associated with acute end-organ damage. It is classified into two categories: hypertensive URGENCY (severe elevation WITHOUT end-organ damage) and hypertensive EMERGENCY (severe elevation WITH acute end-organ damage). End-organ damage targets include the brain (hypertensive encephalopathy, stroke, intracranial hemorrhage), heart (acute MI, aortic dissection, acute heart failure/pulmonary edema), kidneys (acute kidney injury with proteinuria and hematuria), eyes (papilledema, retinal hemorrhages), and vasculature (microangiopathic hemolytic anemia). The pathophysiology involves a critical point where the body's normal autoregulatory mechanisms fail. Under normal conditions, cerebral and renal blood flow remain constant across a wide range of systemic pressures through vasoconstriction and vasodilation (autoregulation). In hypertensive crisis, pressure exceeds the upper limit of autoregulation (typically MAP above 150-160 mmHg), causing forced dilatation of arterioles, breakdown of the blood-brain barrier, endothelial damage, fibrinoid necrosis of arteriolar walls, and end-organ ischemia. A vicious cycle develops: endothelial damage activates the RAAS and causes further vasoconstriction, worsening hypertension. The practical nurse monitors blood pressure frequently, administers prescribed antihypertensives, and recognizes signs of end-organ damage requiring emergency intervention.