NURSING BULLETS: Hypertension

• Blood pressure is blood flow, the volume of blood pumped out of the heart per beat, multiplied by arteriolar resistance to the blood flow.

• Blood flow depends on the rate of heart beats and the volume of blood pumped out with each beat. If rate or volume increases, blood pressure goes up. Likewise, increased resistance raises blood pressure, as when arteries downstream from the heart constrict. Over time, high blood pressure, or hypertension, damages many organs.

• First, the heart works harder to pump out more blood or against higher resistance.

• The heart then requires more oxygen, and is more susceptible to angina or a heart attack.

• Second, arteries and arterioles can be damaged.

• Arteriosclerosis results when blood moves through arteries and arterioles at high pressure, damaging the vessel.

• White blood cells are drawn to the damaged area to form a plaque.

• Third, kidneys can be damaged.

• The capillaries of the kidney are delicate. Continually subjected to high blood pressure, they break down, becoming permeable to proteins and other molecules.

• The kidney’s tubules can become clogged, decreasing the kidney’s ability to make urine. Also, the proteins injure the capillaries’ membranes, causing more damage and worsening the situation.

• Fourth, the retina of the eye can be damaged if its delicate capillaries are damaged.

• Localized hemorrhages can occur, causing scarring and formation of new, imperfect capillaries to replace the old ones.

• Finally, the blood vessels of the brain can be injured.

• High blood pressure can cause clots to break off from atherosclerotic plaques, blocking blood flow to the rest of the brain. This is called a thrombotic stroke.

• Continual exposure to high pressure may also cause a blood vessel to burst, leading to a hemorrhagic stroke.