General Updates | Acute chest syndrome in sickle cell disease: pathophysiology, management, and prevention

The acute chest syndrome is a very well known complication of sickle cell anemia, sickle cell disease, where there is lack of oxygen transport in the lungs as a result of ongoing sickling within the lung physiology. And it is a life threatening disease. It causes hypoxemia. It causes, both acutely it can cause respiratory failure. It is one of the common reasons why patients are admitted to intensive care and rarely in, you know, in certainly in high income countries now, death from acute chest syndrome is rare because there are good supportive treatments available for for patients with acute chest syndrome. But it happens, you know, it causes death in in patients with sickle cell anemia.

So the pathophysiology of acute chest syndrome is again very varied, and perhaps not everything is known about it. But there is a big role to play or various players are actually implicated in acute chest syndrome. For example, you know, one of the key triggers of acute chest syndrome is infection, be it viral or bacterial. And that can sort of trigger inflammation locally within the lungs and can result in increased lack of oxygen transport within the alveolus, and hypoxia then gives rise to sickling, as we have discussed. So it could be a combination of the alveolum becoming completely inflamed and infected, as well as these hypoxic red cells that are causing further damage and causing even more reduction in gas exchange due to vaso-occlusion.

And it is associated with pain. Often the pain can be both in the lungs as well as in the surrounding ribcage. It can be associated with reduced respiratory physiotherapy for example. So if a patient comes in with abdominal pain or undergoes abdominal surgery because by dint of the fact that they are not really, you know, undergoing good diaphragmatic movement and taking deep breaths, it might result in stasis and acute chest syndrome. And some interventions have been shown that are quite helpful. For example, doing regular chest physiotherapy through incentive spirometry was shown in the 80s in a randomised controlled study to actually reduce the risk of developing acute chest syndrome.

The other thing about acute chest syndrome is that the treatment is completely supportive care. There is nothing specific that you can give to somebody that can be treating acute chest syndrome. So you presume that every patient that comes in with an acute chest syndrome has an infection, so you give them antibiotics. The hypoxemia you give them oxygen. In terms of ventilation, you might give them high flow nasal oxygen, you might give them normal oxygen, or they may, in worst case scenarios, they might end up needing ventilation. 

In terms of the anemia that is associated with the sickling and hemolysis, you certainly would want to be giving them some form of transfusion, either type top-up transfusion or exchange transfusions. We do use, in many scenarios, a small dose of dexamethasone over 2 or 3 days or four days, and then taper and reduce it to avoid rebound pain.

However, prevention of recurrent chest syndrome, it can be done. Preventing chest syndrome can be done, and currently hydroxycarbamide is the treatment that is very well proven through clinical research that reduces the recurrence, reduces the incidence, of chest syndrome in patients with sickle cell. So that is something that, with increased and widespread use of hydroxycarbamide, is something that we would expect. And, as I said to you earlier, there is nothing really other than hydroxycarbamide that is currently available as well as blood transfusions being another. So if a patient has blood transfusion for some other indication, such as, let’s say stroke, it has been proven very clearly that it also reduces the risk of acute chest syndrome. So that is something that you know is regularly used in patients. And of course other forms of curative therapy such as transplants, allogeneic stem cell transplant, and gene therapy will also prevent future occurrence of acute chest syndrome.

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