Cytokine Storm - The Aftermath of COVID-19 Infection
Also known as hypercytokinemia, a cytokine storm is a physiological reaction in which the immune system causes the uncontrolled and excessive release of pro-inflammatory signaling molecules throughout the body. These pro-inflammatory signaling molecules are medically known as cytokines. While cytokines are a normal part of the immune response of the body to infection, their sudden release in large quantities can lead to multisystem organ failure and, eventually, to death. Recent studies found that infection with the novel coronavirus can also cause a cytokine storm in certain patients, which is the reason why numerous otherwise healthy people lose their lives to infection with this virus. Furthermore, the most severe cases of coronavirus infection usually develop as a consequence of the overactive inflammatory response of the body, which is struggling to fight off the virus. There are many infections, particularly those affecting the respiratory system, that can trigger a cytokine storm, including coronavirus infection. Therefore, inflammation is the key aspect that needs to be taken into consideration when treating patients infected with the new virus.
What Is Inflammation?
The signs of inflammation were first documented in the ancient past when the Roman medical writer Aulus Cornelius Celsus described the four main symptoms of inflammation, which are heat, swelling, pain, and redness. Another important feature of inflammation is the loss of function, which was noted by the Greek medical researcher Galen several years later. If you burn your finger, get a paper cut or contract the coronavirus, your body sends a flood of immune cells to the affected site, whose purpose is to defend your system against bacteria, viruses, dead cells, and debris. White blood cells, known as neutrophils, rush to the area to fight infection, whereas blood-borne cells, known as monocytes, attach themselves to the damaged tissue. There are multiple causes of inflammation, such as:
- the presence of pathogens inside the body, such as bacteria, viruses, or fungi
- external injuries such as scrapes, cuts, burns, or damage through foreign bodies
- the effects of exposure to chemicals or radiation
In other words, inflammation is the defense mechanism of the body against things that should not be in the body. Usually, after the immune cells gobble up foreign invaders and damaged tissue, the inflammatory process recedes and healing begins. However, when a cytokine storm occurs, the body releases too many pro-inflammatory signaling molecules as a consequence of inflammation, which can easily result in serious health complications. In the case of coronavirus infection, a cytokine storm can lead to respiratory failure and, subsequently, to death, if prompt intervention does not occur. For this reason, patients with underlying conditions and diseases, such as diabetes, heart disease, and adrenal insufficiency have a higher risk of experiencing health complications as a consequence of infection with coronavirus, since inflammation is already occurring in their bodies.
Cytokine Storm and Coronavirus Infection
The immune system has the role of a gatekeeper, identifying sources of harm and destroying them before they can cause damage to the body. Nevertheless, when infection with coronavirus occurs, a cytokine storm may soon follow, as the immune response of the body could be overwhelming. Consequently, the runaway inflammation will drive the infection through multiple organ systems. Moreover, the cytokine storm will damage healthy tissue in the body, as the immune cells are released in tremendous amounts, which inevitably leads to the destruction of normally functioning organs, such as the heart. Therefore, inflammation is what ultimately drives infection with coronavirus to affect the entire body. The acute respiratory distress syndrome that some coronavirus patients experience is the result of a cytokine storm and is associated with a high mortality rate. Some of the telltale symptoms of a cytokine storm are:
Additionally, very low blood pressure and increased blood clotting are also signs of a cytokine storm occurring in the body. For this reason, the heart may not be able to pump enough blood as it would normally do, which is why numerous people with coronavirus infection die of heart failure. Nonetheless, a cytokine storm can result in the failure of other organs as well, which is very likely to ultimately lead to death. Interestingly, the largest immune network in the body is found in the gut. Accordingly, the brain and the gut send signals back and forth, flooding a potentially affected area of the body with immune cells to fight off infection. Medical studies revealed that the gut microbiome affects the immune response of both the brain and the gut, thereby affecting brain function, too.
How to Counteract a Cytokine Storm
While medical researchers are still working on a cure for cytokine storms in patients with coronavirus infection, there is now a new drug available for the alleviation of cytokine storms. This medication is called tocilizumab and patients who received it were found to have a 45% lower risk of death from coronavirus infection. Furthermore, patients who were administered tocilizumab intravenously were more likely to leave the hospital and be off a ventilator within a month. Although the drug was originally designed to alleviate rheumatoid arthritis, it proved to be very effective in calming a cytokine storm as well. According to study results, for every 25 patients treated with this drug, a life would be saved. The following are additional study results concerning the use of tocilizumab in coronavirus patients:
- the medication reduced the risk of death: 29% of the patients in the tocilizumab group died within 28 days compared with 33% of the patients in the usual care group
- the drug reduced the likelihood of a patient needing to go on a ventilator or dying from 38% to 33%
Although the use of tocilizumab for patients struggling with coronavirus infection does not guarantee the alleviation of the cytokine storm, the drug holds promising results in certain people who contracted the new virus. Lastly, dexamethasone, a corticosteroid drug, was also found to reduce the intensity of a cytokine storm in coronavirus patients. The results of medical studies showed that patients who received this medication were at a one-third lower risk of dying than those who were not administered the drug.