When blood pressure is chronically high, the condition is called hypertension (HTN). In 90% of hypertension cases, the cause is unknown, and the condition is called essential, or primary, hypertension. The other 10% of the cases are called secondary hypertension because the condition is caused by another problem. Some causes of secondary hypertension include kidney disease, prob-lems of the adrenal glands, and use of oral contraceptives.
The blood pressure commonly measured is that of the artery in the upper arm. This measurement is made with an instrument called the sphygmoma-nometer. The top number is the systolic pressure, taken as the heart contracts. The lower number is the diastolic pressure, taken when the heart is resting. The pressure is measured in millimeters of mercury (mm Hg). Hypertension can be diagnosed when, on several occasions, the systolic pressure is 140 mm Hg or more and the diastolic pressure is 90 mm Hg or more. The blood pressure categories are the following:
• Normal—less than 120/less than 80 mm Hg
• Prehypertension—120–139/80–88 mm Hg
• Stage 1 hypertension—140–159/90–99 mm Hg
• Stage 2 hypertension—160/100 mm Hg
Hypertension contributes to heart attack, stroke, heart failure, and kidney failure. It is sometimes called the silent disease because sufferers can be asymptomatic (without symptoms). Its frequency increases with age, and it is more prevalent among African Americans than others.
Heredity and obesity are predisposing factors in hypertension. Smoking and stress also contribute to hypertension. Weight loss usually lowers the blood pressure and, consequently, clients are often placed on weight reduction diets.
Excessive use of ordinary table salt also is considered a contributory factor in hypertension. Table salt consists of over 40% sodium plus chloride. Both are essential in maintaining fluid balance and thus blood pressure. When consumed in normal quantities by healthy people, they are beneficial.
When the fluid balance is upset and sodium and fluid collect in body tissue, causing edema, extra pressure is placed on the blood vessels. A sodium-restricted diet, often accompanied by diuretics, can be prescribed to alleviate this condition. When the sodium content in the diet is reduced, the water and salts in the tissues flow back into the blood to be excreted by the kidneys. In this way, the edema is relieved. The amount of sodium restricted is determined by the physician on the basis of the client’s condition.
Previous research focused primarily on sodium as a primary factor in the development of hypertension, but as research continues, the effects of chloride also are receiving increasing scrutiny. In addition, the particular roles of calcium and magnesium in relation to hypertension are being studied. Knowing that sodium raises blood pressure and that potassium lowers blood pressure, the NIH (National Institutes of Health) created the DASH (Dietary Approaches to Stop Hypertension) eating plan. The DASH plan has been clini-cally shown to reduce high blood pressure while increasing the serving of fruits and vegetables to 8 to 12 servings per day, depending upon calorie intake. See Appendix C-1. Many fruits and vegetables are high in potassium levels, which will lower blood pressure. The newest guideline for potassium intake is 4.7 grams, or 4,700 mg, per day to lower blood pressure. It is recommended that a physician be consulted if the DASH eating plan is undertaken and one is already on blood pressure–lowering medication.