What is it?
- Pulmonary thrombosis is a condition in which one or more arteries in the lungs become blocked by a blood clot. This impairs blood supply and gas exchange leading to respiratory failure.
Why in the news?
- Though it is clear that the cause of death in almost all COVID-19 patients is respiratory failure, it is found that pulmonary thrombosis leads to respiratory failure in COVID-19 patients unlike pneumonia being the cause of death in most influenza outbreaks.
Evidences supporting the finding
- Elevated levels of d-dimer, a general marker of thrombosis in blood vessels in high proportions of patients with COVID-19 infection
- Autopsy studies from different countries have shown extensive blood clots in the small vessels of the lung (microvascular thrombosis – MVT) with only little evidence of the pneumonia suggesting that it is the blood clots which cause poor oxygenation and respiratory failure.
- Manifestation of ‘silent pneumonia’ or ‘silent hypoxia’ where relatively well-looking people have low blood oxygen and then suddenly collapse, most likely due to extending pulmonary thrombosis.
|About hypoxia and silent hypoxia:
Hypoxia is a condition characterised by an absence of enough oxygen in the tissues to sustain bodily functions. Hypoxia can either be generalised, affecting the whole body, or local, affecting a region of the body.
‘Silent’ or ‘happy’ hypoxia is a condition in which patients have extremely low blood oxygen levels, yet do not show signs of breathlessness. Despite having oxygen levels below 80 per cent, patients look fairly at ease and alert.
- Early recognition and intervention with blood thinners (anti-coagulants) is needed the most. This can be easily implemented in all hospitals based on some simple assessments:
- Rate of breathing at rest above ~20/minute
- lowered level of oxygen in the finger even when they look relatively well.
- d-dimer levels more than 2-3 fold above normal
- Blood thinners such as heparin or low molecular weight heparin (LMWH) in therapeutic doses should be given immediately till the symptoms resolve.
- In those with higher risks of complications, preventive doses of LMWH have been advised soon after diagnosis under proper medical supervision.
- Public as well as health care professionals should be aware of this problem of blood clots in the lung whose severity is unique to COVID -9.
- However much study is needed to determine the right doses at the right stages of the disease for indicated persons.