American Medical Association Family Medical Guide - American Medical Association [337]
• Caffeine Although caffeine in coffee, tea, and soft drinks may raise blood pressure temporarily in some people, it quickly returns to its usual level. Limit your caffeine intake if your doctor recommends it.
• Stress management Stress can raise blood pressure temporarily and can aggravate existing high blood pressure, making it more difficult to control. Although stress management techniques—such as biofeedback, meditation, or relaxation training—do not help prevent high blood pressure, they may help you deal positively with the stress in your life. Getting enough sleep can also be helpful.
Shock
Shock is a life-threatening condition in which blood flow throughout the body suddenly becomes inadequate or is blocked, depriving body tissues of oxygen and other vital nutrients. Shock is usually caused by extremely low blood pressure, which prevents the heart muscle from pumping an adequate supply of blood to the tissues. If not treated quickly, shock can be fatal.
Very low blood pressure can result from conditions—such as a heart attack or arrhythmia—that interfere with the ability of the left ventricle of the heart to pump effectively. Another possible cause of extremely low blood pressure is severe blood loss resulting from an injury or from a disorder that causes internal bleeding, such as a perforated peptic ulcer (see page 755) or a ruptured aneurysm (see page 599). Tissue damage from a severe burn or severe dehydration caused by persistent vomiting, diarrhea, or inadequate fluid intake can decrease blood volume, resulting in very low blood pressure. Sometimes toxins from a severe infection get into the bloodstream and cause shock. Shock can also develop when a severe allergic reaction causes blood vessels to dilate (widen) and leak fluid, decreasing blood volume.
WARNING!
Shock
Shock is a medical emergency. Symptoms of shock are very low blood pressure combined with sweating, faintness, nausea, shallow breathing, rapid pulse, or pale, cold, clammy skin. Reduced blood flow to the kidneys causes urine production to stop. Inadequate blood supply to the brain leads to drowsiness, confusion, and loss of consciousness.
If you are with someone who has symptoms of shock, call 911 or your local emergency number, or take the person to the nearest hospital emergency department immediately. (For information on what to do while waiting for emergency help to arrive, see page 162.)
Heart Rate and Rhythm Disorders
The heart has four chambers: the left atrium and right atrium at the top, and the left ventricle and right ventricle at the bottom. Valves between the chambers keep blood moving in the proper direction, and electrical impulses produced by a group of cells in the right atrium help control the frequency and regularity of heart muscle contractions (the heartbeat). These electrical impulses move rapidly along specialized muscles that function like nerve pathways, branching out in all directions in all four chambers of the heart. For the heart to pump efficiently, all areas of the heart muscle must contract (beat) at the same time. If a problem develops anywhere along these pathways, the regular rhythm of the heartbeat is disrupted. A single irregular heartbeat is called an ectopic heartbeat (see page 583). A persistently irregular heartbeat is called an arrhythmia.
Arrhythmias
A normal heart rate for a person who is resting is between 60 and 100 beats per minute, with some minor variations. The two major types of arrhythmias are bradycardias, in which the resting heartbeat is slower than 60 beats per minute, and tachycardias, in which the resting heartbeat is faster than 100 beats per minute. An arrhythmia may be mild to severe and it may be continuous or alternate with periods in which the heart beats normally. A sudden, very rapid or very slow arrhythmia can reduce blood flow to the brain and may cause fainting or dizziness.
Risk Factors
In some cases,