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Critically low blood pressure without treatment can cause death – Cardiologist


Consultant cardiologist at the Department of Medicine, Bayero University and Aminu Kano Teaching Hospital, Kano, Prof Kamilu Karaye, tells EMMANUEL OJO, the risks and complications associated with low blood pressure, also called hypotension

What is hypotension?

Hypotension is the exact opposite of hypertension which is high blood pressure. So, hypotension simply means low blood pressure. Blood pressure is basically the force with which blood passes through arteries, that is blood vessels, after being pumped by the heart. So, when the force with which the blood passes through the artery is low, that is when we say that there is hypotension and it is measured by a sphygmomanometer. It is a small piece of equipment we use to check blood pressure in the hospital.

So, many people actually have their definition and classification of what hypotension is but most people don’t worry much about it unless there are complaints. So, technically and normally, when the upper blood pressure (systolic) is measured, it is usually more than 100 mmHg (millimeters of mercury). When it is below that, then we say it is low. Usually, we don’t worry until it is less than 90 mmHg. The lower one, which is the diastolic blood pressure, should also be between 60 and 89mmHg but when it is less than that, we say that it is low but the most important as far as hypotension is concerned is systolic (the higher one), that is low systolic blood pressure.

What causes hypotension?

There are many causes. First of all, to understand the causes, let us consider factors that generate the blood pressure itself. Blood pressure is a function of how wide or how narrow the arteries are and the heart rate, that is the frequency with which the heart beats every minute and the volume of blood that the heart pumps every minute. That will disrupt or reduce the heart rate or widen the arteries. Making them wider will lead to lower blood pressure.

If you look at it from the point of view of peripheral resistance, many drugs that we use to treat high blood pressure, if one is not careful, maybe the patient takes an excessive dose or the medical practitioner gives a dosage that is too high, it can lead to hypotension and it is a very common experience in my practice as a cardiologist. Also, a very high fever for a long time can lead to that. A severe form of infection like what is called sepsis can even lead to excessively low blood pressure. Another important one is anything that reduces blood volume. So, dehydration from diarrhoea, and vomiting, if frequent and severe, can easily cause low blood pressure or blood loss. Also, in a case of an accident where the victim bled so much, it can lead to low blood pressure. Heart disease that does not allow the heart to pump blood adequately can as well lead to very low blood pressure sometimes.

Low blood pressure or hypotension does not feature prominently as much as high blood pressure. Is it because it is less severe?

Well, the thing is many people have ‘lowish’ blood pressure but when it is critically low, it’s as deadly as hypertension. I used the word ‘lowish’ not ‘low.’ ‘Lowish’ means that it is a bit lower than usual but not critically low or very low. When it is very low, particularly when it causes a compromise of vital organs, it is very deadly. It results in what is called shock. Once it’s low enough that it can lead to adequate perfusion of vital organs like the brain or the kidneys, it can lead to death. It’s a major cause of death. So, it depends on how severe it is, just like hypertension but in general, ‘lowish’ blood pressure is actually healthy. People with ‘lowish’ blood pressure tend to live longer but when it is critically low, that is another issue. Nobody wants extremes. Extremes are dangerous.

Is hypotension as common as hypertension?

As you’ve pointed out, it’s not something that is well studied (in Nigeria) but in societies where it’s been studied, it’s said to be about five per cent of those below the age of 50. Prevalence increases with age. For those above the age of 70, it affects about 30 per cent of them. Those above the age of 70 are fairly common but you see, most of the time, it doesn’t cause much problem, except when it gets critically low to the extent that the person begins to feel sick and that is when it becomes dangerous and the person needs to get it treated. The patient needs to present it to the doctor.

Are there early symptoms that suggest hypotension in a patient?

Once there is impairment of perfusion of important organs like the brain, at that time, the person begins to feel light-headed. Some can even faint if it’s severe enough. So, when it gets to that level, then, it’s really dangerous. Other symptoms include fast heartbeats because the heart will make an attempt to increase its rate and its cardiac output. You remember that it’s a function of some of the heart’s functions and also the peripheral resistance. So, some of the symptoms present themselves because the body is trying to compensate, so, there could also be sweating, the person will feel very weak, maybe reverse in urine output if it’s on for a while and generally, the person will know that something is wrong. There will be dry mouth, especially if it’s because of dehydration. Severe dehydration can also cause that. There are many symptoms and it depends on how it presents but the early ones are the central nervous system functions, that is those that affect the brain functions because the brain doesn’t compromise its blood supply, oxygen and nutrients, it doesn’t tolerate it. Those that have to do with brain function will manifest fast, earlier than the others.

It’s said that the blood pressure in pregnant women is usually lower than it is when they are not pregnant. Does that suggest that pregnant women are prone to having a low blood pressure condition?

Well, many hormonal changes in the body can lead to low blood pressure but pregnant women have a sort of distorted hormonal balance within them because of the pregnancy. Pregnancy hormones lead to ‘lowish’ blood pressure. It doesn’t usually get to the level (the critically low level) that the patient is affected. So, as I told you, many people carry ‘lowish’ blood pressure around without having a problem. Sometimes, if some things happen, for instance, if the patient has a fever or goes in the sun for a very long time, such that there is dehydration, diarrhoea, or any other thing, they can easily become symptomatic of ‘lowish’ blood pressure. It’s usually common in pregnant women as you said and it is usually due to hormonal imbalance during pregnancy.

Does it predispose them to any form of risk?

It doesn’t go as low as that to cause symptoms or serious risk. If they have ‘lowish’ or low blood pressure, particularly if the systolic pressure is lower than 90mmHg, then surely, the doctors will look at the kind of drugs she takes or if she has some problems that can lead to lowering the blood pressure. If they don’t find anything and the patient does not complain about anything, it’s just an incidental finding, then the patient can simply be observed. It might not signify anything serious but if something is indicating a disease process going on that is leading to a ‘lowish’ blood pressure, for example, if the heart function is affected, there are other signs and symptoms that will be observed and the patient will be further evaluated to check any possible cause of blood pressure. It’s not usually looked at in isolation, the patient has to be wholly examined in general and find if something else can be found apart from the ‘lowish’ blood pressure which will signify that something is wrong.

What are the other general risk factors that predispose one to hypotension?

Pregnancy is one of them. It’s generally more in females than males, so, gender is also a factor. Inadequate intake of water, especially for those that work in hot environments like Kano, where the weather is hot, moving around in the sun, and not taking adequate fluids can make one develop ‘lowish’ blood pressure. Also, other factors like diarrhoea and vomiting can lead to that too. So, we can call some of the causes risk factors.

Are there health complications?

Yes. If it goes very low, it can lead to poor perfusion of vital organs, what we call ‘shock’. Once it gets to the level of shock, then, the whole scenario changes because, in such a situation, the patient is at high risk of dying. It can lead to kidney failure, collapse, and coma; the patient could lose consciousness, and from there if care is not taken and the patient is not properly treated, they can easily die. Also, depending on the cause, if the cause is, for example, infection and the infection is so severe that it has led to a fall in the blood pressure that vital organs are not well perfused, sometimes, it can lead to shock and because the infection is very severe, something drastic and serious must be done.

So, in itself, low blood pressure may not even be symptomatic but when it gets to a critical level that can affect the vital organs, the whole scenario changes. It depends on how severe it is and for how long it has been going on.

With your experience as a cardiologist, do you think people are well informed about low blood pressure as much as they are about high blood pressure? Or do you think it’s underrated?

Yes, it is true but it is actually less common than high blood pressure, that is hypertension. For example, in Nigeria, hypertension affects about 30 per cent, even sometimes higher in those below 50 years and I was telling you that low blood pressure (hypotension) affects just about five per cent of those less than 50. But as I told you too, it increases with age just like hypertension. Just as it is commonly said that hypertension is a silent killer; even if you don’t have any symptoms, the patient with hypertension can come with a lot of risks and complications. Hypotension doesn’t really cause problems until it reaches a critical level that affects the perfusion of organs, otherwise, it’s not really like hypertension that causes many changes, even when there are symptoms. So, there are important differences between them.

It’s not surprising that many people are not aware of hypotension but if people are aware of hypotension and can fix the problem earlier on, then, it doesn’t deteriorate to the level of perfusion of vital organs, so, it’s a good thing that we are talking about it because whatever is not good is not good.

How is it diagnosed?

Just by simply measuring the blood pressure, just like hypertension. Hypotension is also by measuring blood pressure but it is important for people, especially those taking medicines for hypertension to know that when the blood pressure is too low, it puts them at risk. There should be moderation in the treatment. Treatment should not be overzealous if not, the person becomes hypotensive.

Sometimes, in the treatment of hypertension, if the person is not careful, the person becomes hypotensive. Recently, I diagnosed a patient and I let the patient realise that that was the problem; a new medicine was added to the patient’s blood pressure medication and that was because the doctor felt that the blood pressure was not well controlled. When the dose was too high, the patient started having symptoms up to the extent that he almost fainted, so we diagnosed and discussed it. So, it’s not uncommon for hypertensive patients to end up with hypotension. So, while trying to treat one disease, another problem comes if care is not taken, hence, moderation is important.

How is it managed?

The treatment depends on the cause. The most important thing is to identify what the cause is. Sometimes, we just advise the patient to take more fluids. For example, if the person is dehydrated, it’s just to revitalise the person with some fluids. Sometimes, oral fluid is given and some other times, intravenous fluids have to be given, depending on how severe it is and then, if the cause is heart disease, the doctor will have to look at it and see how to improve the heart’s functions. If it is caused by a drug, it’s just to drop the drug and that alone can just solve the problem. Sometimes, specialised medications have to be used if it is caused by a nervous system disease because some nervous system diseases can also lead to hypotension. So, it depends on the cause.

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