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Why do patients with dengue die?

| by Prof. Ranjan Premaratna
Professor in Medicine, faculty of Medicine, University of Kelaniya

( May 11, 2012, Colombo, Sri Lanka Guardian) I should not re-iterate the importance of dengue fever as one of the most dreaded infection in Sri Lanka. As we are well aware, it has become the most widely discussed topic in health sector over the past 2-3 decades. Dengue outbreaks cause panic among both adults and children in most dengue endemic areas in the country and it has become the most important infection that has resulted in direct and indirect economic losses.

At this juncture, therefore it is important to learn about this dreaded infection, more importantly to understand why people die of dengue. Based on what was there in papers and media, I am in the opinion that you are already having a misconception that most of the dengue deaths are due to faults of the medical profession and of the hospitals. This fact was highlighted by several media and the sad part of it was that some of the responsible people in the health sector itself continued to blame the medical profession as the responsible party for these dengue deaths. However, my opinion and understanding is that these blames are quite baseless and are due to their ignorance of this infection.

My attempt with this article is to educate the learned public on why people with dengue die and how we can minimise such deaths.

Death figures vary

First of all, I would like to emphasize the fact that in dengue endemic areas of the world, there is an unpreventable death rate of 0.2-5%. That is 2 out of every 1000 patients with dengue to 5 out of every 100 patients die due to this illness. Therefore, one should understand that this is an infection that is known to cause death around dengue endemic areas of the world. In Sri Lanka these figures varied from 0.5% -0.7%. that is 5-7 out of 1000 people died over the last few years. Although deaths are not expected in any civilised community due to any reason, we have to understand that compared to the death rate by motor traffic accidents, by alcoholism and by other criminal activities of the country dengue causes very lesser number of deaths.

First of all let me explain a little on the disease process of dengue in order to make people understand the reasons of death in dengue.

As you are well aware, dengue causes serious illness by two ways, one is by increase in leakage of fluids (Plasma) out of the small blood vessels and the other is bleeding due to damage to these blood vessels. However, since of late we have found patients who get severe involvement of the heart, liver and the brain resulting in death without bleeding or dengue shock.

Let me explain why this blood vessel damage occur due to dengue:

No drug to prevent dengue

When one is infected with dengue virus after a bite of a dengue mosquito, he develops antibodies against this virus. Unlike in dengue, in most other infections these antibodies prevent occurrence of the infection again in that patient or patient develops immunity against this infection. However in dengue, the scenario is much different to this. That is, dengue has 4 different strains of the virus (D1, D2, D3 and D4). So, if a person is infected by one strain of virus, he is not developing immunity against the other three viruses. Therefore he still can get 3 other dengue infections some time or the other in his life. The risk of such infection is very high among people who live in dengue endemic areas. The problem with such infection is that, if the person gets a second infection by a second dengue virus, the antibodies due to the first infection is going to enhance the growth and the damage caused by the subsequent dengue virus in the body, so the individual is going to develop a more severe infection. He also develops a very high antibody levels and these antibody-antigen complexes cause serious damage to small blood vessels. Although this phenomenon is commoner with the second dengue virus infection, such severe illness may even occur in the first infection. The other problem is, people who get the virus for the first time may not get fever or any illness (asymptomatic dengue), and therefore, he may not be aware that he was down with dengue during the first infection or they may get a mild infection and will be passed as a simple "flu".

The final outcome of the dengue illness will therefore is severe small blood vessel damage that lead either to bleeding or more commonly fluid or plasma leakage out of blood vessels causing blood vessel to dry up and the other organs of the body to suffer without oxygen and other nutrients. If this stage does not improve of its own, then the patient is going to develop very severe dengue that leads to malfunction of most vital organs of the body such as the heart, liver, brain and the kidneys leading to death.

The current problem with dengue is that there is no known drug that can prevent dengue infection or the blood vessel damage. However in more than 90% of patients the resultant blood vessel damage and the subsequent plasma leakage or bleeding is expected to stop within a period of around 48 hours (Figure 2). The only solution therefore, is to closely observe these patients during this vital period for either bleeding or plasma leakage by doing repeated blood pressure monitoring and doing frequent blood counts. Most patients today think that the most important blood test in monitoring dengue is a platelet count. But this is wrong. There is no clear role identified in dengue due to lowering of platelets. But what we do is, we monitor for bleeding and for plasma leakage by continuous monitoring for haemoglobin levels and for another parameter known as packed red cell volume. If there is any change in either the blood pressures, or these blood tests, almost every qualified doctor in the country is very well aware how to identify patients and what treatment should be instituted o them. The problem however is, the only available treatment in dengue for patients who develop these complications is infusion of saline coupled with drinking of fluids, infusion of colloid solutions (dextran) or plasma and if patient develop bleeding is to transfuse them with blood. This is invariably going to work, in patients who spontaneously recover the leakage within the expected 48hour or so, then the chances of death is minimal or I would say it is zero.

However if this patient continues to leak plasma there is no effective treatment to stop it. Then the treatment with fluids needs to be a continuous process in order to maintain an effective blood volume in blood vessels. However the problem is as there is continued leakage of fluid out of leaky blood vessels these patients get all these fluids accumulated in body cavities such as in the chest cavity and in the abdominal cavity (tummy) or even in the tissue spaces. The final outcome of such a patient is filling of the body and the organs with the fluids that is been given to the patient with good intention to prevent death. This invariably leads to fluid overload related organ malfunction. Patient find difficult to breath, heart may not function properly. However due to continued leakage of fluids out of the blood vessels keep them dry and the subsequent outcome is malfunction of vital organs of the body leading to multi organ failure as discussed above. At this stage the chances of patient survival is minimal. On the other hand at some point of this severe illness, patients may develop severe blood vessel damage and together with very low platelets they will developsevere bleeding, either to exterior (vomiting blood) or to the interior of the body. Such patients need immediate blood transfusions. However, if the disease process does not stop of its own, then patient will need lots of blood and it itself is not good to the body.

Can lead to cardiac failure

The other problem we face is, even if the patient reverses of this blood vessel damage after severe illness, the already leaked out fluid is going to get rapidly reabsorbed into the blood vessels leading to overwhelming influx of plasma in the blood vessels and this phenomenon can lead to severe cardiac failure due to inability to cope up with a huge amount of fluids gushing into the heart and the lungs that it self will lead to death of these patients. I hope now you may be having a very clear idea as to how difficult to manage a patient with severe illness with dengue who continue to have plasma leakage out of their damaged blood vessels.

So now you may understand that it is the continuing fluid leakage that is the hallmark of death in patients with severe dengue. Although, such continued fluid leakage occurs in a small minority of patients, most of the time, doctors after much effort manage to treat them successfully. However the patients who are in this severe most end are always at risk of death.

Adequate fluid resuscitation

Therefore, what I re-iterate is that more than 90% patients who develop dengue resolve thins plasma leakage spontaneously and the management is adequate fluid resuscitation. The once who are unfortunate and do not get spontaneous recovery from this blood vessel damage and the resultant fluid/ plasma or blood leakage are at very high risk of death.

Therefore, deathsdue to dengue are truly due to the disease evolution process and is not a fault of attending doctors or physicians. I am yet to hear or see a doctor who has not struggled to prevent a death of patient not only with dengue but due to any other illness.

Early detection important

However, I would like to stress upon some important facts that are needed from the patients side in order to early recognition of severe dengue or to prevent death.

If you are down with fever and you are living in a dengue endemic area, try diagnose dengue by yourself. If you have this sign in your body after pressing your chest, arms, you are likely to have dengue.

In that case or even otherwise, do not exert yourself. Physical rest is mandatory. (We have had deaths of mothers whose children were concurrently ill simply due to forgetting their illness and exerting themselves in order to look after the sick child)

Try to drink adequate amonts of fluids such as jeevani or counjee, and not plain water.

Go to the doctor within the first two days of fever and get a full blood count done and get the blood pressure recorded and keep them written in a paper and do not lose them because this base line is very important to early identify severe illness.

Do not take any pain killer drugs of your own from the pharmacy. What you can take safely is paracetamol. But do not take them also too frequently.

If you are vomiting or having diarrhoea, always seek admission because you may become fluid depleted.

You have to seek advice any time you have any bleeding; don’t forget-coffee colour vomiting or black colour (tar like) stools.

Immediately see a doctor if you have and faintness and un explained sweating and sever weakness.

Do not get admitted at the last stage of illness, try to seeks admission after consulting your family doctor or hospital OPD at lest by the 4th day if you are not feeling well.

More important however, as there is currently no effective treatment against dengue, the main responsibility of you is prevention of dengue. As you are well aware, you are the one who breed these mosquitos. So if you get dengue, its not another’s fault its your own fault. If you find the mosquito given in the picture flying around you in the mornings and evenings, that means, there is a breeding site within 500 meters around you. That is either in your own house or in your garden... check for any breeding sites around.

Do not let children play around during day time with minimal clothing.

Try to use a mosquito repellent whenever children / adults go out even to school.

So until such time, an effective treatment against fluid leakage of dengue or bleeding due to blood vessel damage is found, anyone with dengue is at risk of death. So it is our own responsibility to keep around us free of dengue mosquitoes. Doctors will do their best but if you continue to leak fluids, get other forms of severe dengue such as heart involvement, liver involvement or brain involvement... doctors may be helpless...