Baxter India's oXiris gets approval for treatment of COVID-19 patients: Here's how blood purification therapy could help with symptoms
The oXiris filter is designed to remove three different things from blood -- cytokines, endotoxins and uremic toxins.
On 7 July 7, Baxter India, a subsidiary of the American Healthcare company Baxter International, announced that the Central Drugs Standard Control Organisation (CDSCO), India has given approval to its blood purification filter oXiris for the treatment of COVID-19 patients.
CDSCO is the National Regulatory authority for drugs and medical devices in India. As per the authorisation, the filter will only be used for severe COVID-19 patients in the country. It will help to clear out extra inflammatory mediators in their blood. Excess inflammation, and the resulting cytokine storm, is suggested to be one of the reasons for mortality in COVID-19 patients.
The US Food and Drug Administration (FDA) had already given emergency use authorization to oXiris in April. As per the FDA, the filter can be used for any patient above the age of 18 who has been admitted in the ICU for COVID-19, those who are at risk of respiratory failure and those who are in need of blood purification, including those on continuous renal replacement therapy (24-hour dialysis).
Blood purification therapy
Blood purification therapy involves the extracorporeal (out of the body) treatment of blood to remove harmful pathogens and toxins from the blood. In this procedure, blood from a patient’s body is passed through a biomembrane, which helps remove the harmful substances from it by using various methods. These methods include:
- Diffusion: The solutes (substances dissolved in a solution) travel across a semipermeable membrane (a membrane that only allows particles of a certain size to pass) across a concentration gradient as soon as they come in contact with the membrane. So say solute A is present in high amounts in the blood. Once inside the blood filter, it will quickly pass out of the blood and through the semipermeable membrane into the dialysis solution. This process depends on the molecular size of the solutes.
- Convection: In this process, the solutes travel across a semipermeable membrane along with water (a process called ultrafiltration), as long as they fit in the pore of the membrane. This process depends on the pressure gradient between the two membranes and is less dependent on the molecular size of the solutes.
- Adsorption: In this method, the blood or plasma is passed through certain sorbents (activated charcoal for example). These sorbents attract and attach to themselves various solutes present in the blood. The affinity of a solute towards a sorbent would hence be one of the driving factors for this type of blood purification therapy.
Once the blood is cleaned, it is sent back into the patient’s body. Hemodialysis is one of the most common forms of blood purification therapies that are currently used for the management of kidney failure.
Blood purification therapy in COVID-19
Since we don’t have a treatment or vaccine for COVID-19, experts have been trying almost every possible therapy for the symptomatic management of the condition. Apart from medications like remdesivir, some healthcare providers have suggested the use of blood purification therapy for reducing inflammatory cytokines in the patient’s body. Removal of excess cytokines is suggested to be one of the ways to reduce the severity of the disease and hospitalisation of COVID-19 patients. It may also help reduce the risk of death in such patients.
However, for the therapy to be effective, the patient should be properly monitored both before and after the therapy -- for their need to get blood filtration therapy and the right time to discontinue the therapy. Proper adjustment of various parameters during the process is also needed.
An article published in the journal Clinical Immunology mentioned three cases of severe COVID-19 patients who got blood filtration therapy in Wuhan, China. Two of them — a 69-year-old man and a 56-year-old man with no past history of health conditions or an underlying disease — benefitted from the therapy. A 65-year-old hypertensive man who got the therapy also showed some improvement but died of complications. The 56-year-old and the hypertensive patients had been treated with Oxiris hemofilter.
The oXiris filter is designed to remove three different things from the blood -- cytokines, endotoxins (toxins produced by some kinds of bacteria) and uremic toxins (toxins that stay in the body due to improperly functioning kidneys). It is so designed to be able to help both sepsis patients and those in need of continuous renal replacement therapy.
The oXiris filter has a three-layer membrane structure and uses adsorption to filter blood.
One of the membranes in the oXiris filter has a heparin (a blood thinner) graft that reduces the chances of blood clot formation. Blood filtering membranes usually activate clotting when they come in contact with blood. These clots can interrupt the blood filtration process when they form within the filters. Those on hemodialysis are often given heparin to prevent blood clot formation.
Contraindications for oXiris
As per the US FDA, oXiris therapy is not given to:
- Patients who are allergic to heparin or any other component of the oXiris set.
- Those with low blood platelet count (thrombocytopenia). Platelets are tiny cells that help the blood to clot.
- If the patient is on a drug that cannot be used with this filter as per the instructions on the filter.
Additionally, oXiris therapy can only be given after a doctor has recommended it.
For more information, read our article on Cytokine storm.
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