Hypotension

Hypotension is the medical term for low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries. As the heart pumps, it creates this pressure to move blood through the body. Doctors measure this using two specific numbers. The first is the systolic blood pressure, which is the maximum pressure during a heartbeat. The second is the diastolic blood pressure, which is the minimum pressure between beats.

Generally, hypotension is diagnosed if the systolic pressure is below 90 mmHg or the diastolic pressure is below 60 mmHg.

While low pressure can be a normal state for very fit people, it can also be a physiological concern. It is often viewed as a physiological state rather than a disease itself. For many, low blood pressure is asymptomatic, meaning it causes no noticeable issues. However, when it drops significantly, it can cause various symptoms. These include dizziness, lightheadedness, confusion, and fatigue. Some people experience blurred vision, nausea, or an irregular heartbeat. In severe cases, hypotension can lead to shock. This is a life-threatening condition where vital organs like the brain are deprived of oxygen and nutrients.

There are several ways the body can experience a drop in pressure. One common cause is hypovolemia, which is a reduction in total blood volume. This can happen due to hemorrhage, or severe dehydration from vomiting and diarrhea. Another cause is excessive vasodilation. This occurs when the blood vessels, specifically the arterioles, widen too much. This can be triggered by the nervous system, certain medications, or even anaphylaxis. Other causes include anemia, vitamin B12 deficiency, or endocrine problems. Heart issues, such as a large heart attack or extremely low heart rate, can also lead to low pressure.

Certain syndromes cause blood pressure to drop in specific patterns. Orthostatic hypotension, or postural hypotension, occurs when a person changes position. This usually happens when moving from a lying or seated position to standing. It represents a delay in the autonomic nervous system's ability to compensate. To diagnose this, doctors perform orthostatic vitals by measuring pressure while lying and standing. A diagnosis is made if systolic pressure drops by more than 20 mmHg. Another condition is vasovagal syncope. This involves an inappropriate drop in pressure due to increased activity in the vagus nerve. This can cause sweating and a sudden loss of consciousness.

Another distinct type is postprandial hypotension. This is a drastic decline in blood pressure that occurs after eating large meals. It typically happens between 30 and 75 minutes after eating. This occurs because a large amount of blood is diverted to the intestines to help with digestion. This process is known as splanchnic blood pooling. For the body to work correctly, it must increase cardiac output to keep the brain perfused. If the autonomic nervous system does not compensate for this shift, blood pressure drops. This is more common in older adults or those with specific disorders.

Medical professionals use several methods to monitor and diagnose these states. They may use a sphygmomanometer for non-invasive measurements. In intensive care settings, they might use an invasive arterial catheter. Doctors also look at the Mean Arterial Pressure, or MAP. The MAP is the average pressure in a patient's arteries during one cardiac cycle. In adults, a MAP below 65 mmHg is considered hypotension. During surgery, maintaining an adequate MAP is vital to prevent kidney injury or stroke. Keeping the MAP above 65 mmHg is a common goal in clinical practice.

Treatment for hypotension is not universal; it depends entirely on the underlying cause. If the cause is dehydration, increasing fluid intake is a common solution. In some cases, doctors may use intravenous fluids to replenish volume quickly. For more serious situations, they may use vasopressors. These are medications designed to narrow blood vessels and raise pressure. Some patients may find relief by adding electrolytes to their diet or using caffeine. Ultimately, the goal of treatment is to ensure that the body's vital systems receive enough oxygen to function properly.