What is hypertension, or, in lay terms, what is high blood pressure?
Hypertension or high blood pressure refers to a blood pressure reading that is consistently higher than the normal reading of 120/80. But what does this mean? What are we measuring?
Before we can answer that question it is best that we discuss what blood pressure is.
It is best to think of the body’s circulatory system as a pump — the heart — and pipes — the arteries — which moves blood filled with oxygen and nutrients to the body and its organs, and the veins, which bring the blood back to the heart. For this discussion and for simplicity we will exclude the lungs, which are part of this system.
The heart as a pump generates pressure — the blood’s pressure — each time it pumps blood through the arteries and the body. This pressure is therefore depended on a few factors: how hard the heart is pumping, how much blood it is pumping and the resistance to the blood that the piping — the arteries — is providing. All these factors interact with each other and therefore allow us to modify them if the blood pressure is too high.
The two numbers which make up a blood pressure reading, 120/80, indicated the pressure of the blood as it is being pumped. The top number, the systolic number, 120, refers to the pressure as the heart contracts to pump blood. The bottom number, the diastolic, 80, refers to the blood pressure as the heart relaxes after each contraction. Although both numbers are important we are often more focused on the bottom number, since the heart is exposed to this pressure for more time as the heart spends more time in diastole. Hypertension is defined often as having a diastolic number consistently over 90 mmHg.
We can treat high blood pressure in a number of ways. There is always diet and exercise to help lower an elevated blood pressure. If these fail, then medications become the next step. The various medicines available to treat an elevated blood pressure function in three main ways: by decreasing how hard the heart is contracting while pumping blood, by decreasing the amount of blood/fluid the heart has to pump, and by decreasing the amount of pressure that the arteries provide as blood is passed through them.
The medicines which reduce the heart’s pressure are called beta blockers. They work mainly by reducing the pressure and frequency of each contraction. They also work secondarily by decreasing the amount of pressure the arteries provide as blood passes through them.
The medicines that reduces the volume of blood in the circulatory system are called diuretics. They work by having the kidneys reduce the blood volume by extracting fluid from the system. If there is less blood volume then the amount of pressure will be less.
The medicines that work by reducing the amount of pressure the arteries exert on the blood are called calcium channel blockers or ACE inhibitors. Simplistically, they reduce the arteries tone and therefore reduce the pressure that the arteries place on the blood that passes through them.
These medicines can be used independently, but are often combined to achieve the result of lowering the blood pressure. Each of these medicines has side effects that need to monitored. For example, the diurectics can lead to potassium loss from the body. Therefore, a patient on these medicine might often have to have their potassium monitored and take supplements if necessary.
Other anti-hypertensive medications namely the ACE inhibitors, can have a significant side effect called angio-edema, by which the blood vessels become leaky, causing swelling of the soft tissues, including the airways which can make it difficult for the patient to breathe. Patients who are allergic to these medicines should avoid them, since angio-edema can be life threatening.
Hypertension, its causes, treatments and complications, is a complex topic. This first article has merely scratched the surface. We will delve deeper into this very complex topic further with future articles … stay tuned.
Dr. Dwight S. Tyndall, FAAOS, is a minimally invasive spine surgeon practicing in the Region at DrSpine.com. His column, which appears every other week, covers a wide range of health and medical issues.
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