Research: Meningococcal Septicaemia and Intensive Care
* from an article in the BrainWaves by Dr C.J.Best
Meningococcal sepsis is one of the worst infections that children can get. It is caused by Neisseria meningitidis, the same organism that causes ordinary bacterial meningitis. However, instead of causing an inflammation of the linings of the brain which results in the usual meningitis symptoms of headache, stiff neck and fever, for some reason the body does not fight the bug in the same way. The organism overwhelms the patients normal defences and causes enormous damage.
Normally, white blood cells in the body help to fight the infection. These cells release chemicals after exposure to the meningitis bacterium which help other more specialised white blood cells to finally kill the bugs. Usually that is the end of the illness. However this particular infection is so bad that the normal process runs away with itself as the meningitis organism releases a poison, called endotoxin, which sends the whole process into overdrive. More chemicals are produced which affect more white blood cells, providing more fuel to feed the fire. First, the blood stops clotting and the patient begins to have many small haemorrhages or bleeds all over the place. It is this that causes the characteristic purple rash which is in fact blood under the skin. The blood vessel walls start to leak fluid, so water gets into the tissues and the lungs.
Then, these chemicals start affecting organs like the heart. This stops working so well, and cannot push enough blood around the body to cope with the bodies needs. This means that all the other important organs like the liver, kidneys and brain do not get enough oxygen and poisons are not removed fast enough. These organs then stop working. If this process cannot be stopped, death quickly follows.
So what can we do for these patients? The first thing is to get the right antibiotics in as fast as possible to kill the bugs and stop them making any more poison. But, even though the cause of the illness has now been got rid of, the runaway process still continues. They still need a great deal of treatment in our Intensive Care Unit (ICU).
In ICU we first put the patient on a ventilator or breathing machine. They are given drugs to keep them asleep and other medicines to stop them moving. This means that all their energy, even the effort used in the normal person to breathe, can be put towards getting blood and oxygen to the vital organs. We give drugs to help the heart work and blood and other compounds to stop bleeding. In our unit we also have another treatment which we believe can make a big difference.
Haema-diafiltration is a technique which has been used for many years in patients whose kidneys have failed. It is similar in some respects to haemodialysis but easier to do. We used this in several patients who had meningococcal sepsis and noticed that they seemed to get much better a few hours later. So, we decided to start the haema-diafiltration as soon as the patient got to ICU, whether the kidneys had failed or not. Blood is taken out of a large vein, passed through a filter and pumped back in again. The filter has fluid running through it the opposite way to the blood, and this removes toxic compounds. We think that this removes some of the chemicals involved in the continuous white cell activation process mentioned earlier, interrupting it and stopping the damage. The filtration also controls the amount of water in the body, keeps the body temperature down to normal and means that the heart does not have to do so much work.
So far we have successfully used this technique in several patients who have survived when we thought they were going to die. They had no brain or lung damage, but some had to have skin grafts and lost feet. We have not solved these problems.
We are still using these techniques, and are trying to find out why exactly haema-diafiltration should help. A great deal of research is going on in other centres into why some people get this disease and not others, and into the exact nature of the chemicals produced by the white cells and what can be done to influence them. Much more work needs to be done before we have a solution to this awful illness.
Dr C.J. Best
R.H.S.C YorkHill Glasgow