Rightly nicknamed the "silent killer," hypertension, or high blood pressure, may go undetected for years. Still, the "Primary Care" journal associates it with progressive or sudden damage of such target organs as the brain, kidney or heart. The damage occurs as hypertension overworks your heart and injures blood vessels. Though relatively rare, very low blood pressure, or hypotension, also may damage organs--by depriving them of blood.
Blood Pressure Basics
Your heart and blood vessels work like a hydraulic system. In this system, your heart receives blood from some blood vessels and pumps it into others in a continuous, pulsating manner. Your blood vessels essentially act as pipes that connect the heart to various organs. As your heart contracts to push the blood out, it exerts pressure on blood vessels: this is the systolic pressure. In contrast, when the heart relaxes to let blood in, pressure levels in blood vessels falls: this is the diastolic pressure. Both pressures are expressed in millimeters of mercury, or mm/Hg.
Ideally, your blood pressure should be lower than 120/80 mm Hg. The Family Practice Handbook defines hypertension as blood pressure that consistently exceeds 140/90 mm Hg. Mild, or stage 1, hypertension features a systolic pressure between 140 mm Hg and 159 mm Hg, or a diastolic pressure between 90 mm Hg and 99 mm Hg. A systolic pressure above 160 mm Hg, or diastolic pressure exceeding 100 mm Hg, would put you in a stage 2 category, which is moderate-to-severe hypertension. Pre-hypertension defines blood pressure readings that consistently fall between 120/80 mm Hg and 139/89 mm Hg.
In "Reversing Hypertension," physician Julian Whitaker describes important factors that can lead to hypertension. For instance, your heart may pump blood with too much force, or your blood vessels may narrow, causing blood flow to apply more pressure against vessel walls. A blood pressure above 180/110 mm Hg is considered severe, even if you experience no symptoms other than a mild or moderate headache and no sign of organ damage.
Clinicians speak of "hypertensive urgency" when your blood pressure exceeds 180/110 mm Hg with symptoms such as severe headache, shortness of breath or edema, but with little or no organ damage. Physicians Christopher Hebert and Donald Vidt also associate hypertensive urgencies with elevated blood creatinine. Creatinine is a breakdown product of an important muscle component called creatine. Because healthy kidneys normally clear excess creatinine, high blood levels are a sign of kidney malfunction.
Very high blood pressure, usually above 220/140 mm Hg, can lead to life-threatening organ damage. Physicians consider this a "hypertensive emergency." A 2008 issue of the "Primary Care" journal describes many sources of hypertensive emergency, including hemorrhagic stroke, hypertensive brain disorders, severe nosebleeds, hemorrhage, heart attack, acute heart failure, eclampsia, head injury, cocaine use or surgical complications. A state of hypertensive emergency can cause chest pain, severe shortness of breath, altered mental status and decreased function of the brain, muscles or nerves..
Treatment & Prevention
All hypertensive crises require medical treatment, according to the "Primary Care" journal. Hypertensive emergencies are particularly dangerous, and require hospital admission. If you know you have high blood pressure, you may avoid a crisis by carefully following your treatment plan, consulting your healthcare provider regularly and by monitoring your blood pressure at home. Beyond medical treatment and home monitoring, however, the 2006 "Harvard Medical School Guide to Lowering Your Blood Pressure" recommends addressing important risk factors, such as: obesity, smoking, lack of exercise, poor diet, excessive dietary salt, caffeine use, heavy drinking and stress.
Although a low blood pressure is desirable, it is possible for its value to consistently drop to such low levels that key organs no longer receive enough blood to function normally. In "Cecil Medicine," physicians describe the resulting, life-threatening, condition as "shock." Shock can occur because of severe illness or injury. However, the authors remark that, if you chronically have low blood pressure, you may not develop shock until the average of your systolic and diastolic pressures falls to less than 50 mm Hg.