Are multiple CT scans dangerous? Why are steroids prescribed for COVID-19 patients?
The story so far: As doctors try out different protocols to manage patients with COVID-19, Dr Randeep Guleria, director of the Institute of Medical Sciences of India (AIIMS) and member of the National COVID-19 Working Group, cautioned against using CT scans. indiscriminately to diagnose the disease, especially in the early stages. This exposes individuals to unnecessary radiation, which could be harmful in the long run, he said. A single scan equals 300 x-rays, warned Dr Guleria, which can increase the risk of cancer later in the lives of young people. Doctors and the World Health Organization (WHO) are also warning against the use of corticosteroids like dexamethasone, a strong anti-inflammatory drug, for patients with non-severe COVID-19. Corticosteroids have been shown to benefit patients with moderate and severe infection.
When is a scanner recommended for a COVID-19 patient?
An RT-PCR test is the standard for diagnosing or confirming COVID-19. The use of computed tomography for the diagnosis of COVID-19 should be limited to that subset of patients who may present with classic symptoms of the disease but whose RT-PCR test result is negative. However, a chest CT scan can be useful to assess patients with moderate or severe disease, to identify complications such as thromboembolism or pneumomediastinum.
There are certain situations involving COVID-19 patients in which a clinician may depend on a CT scan to make treatment decisions. These include scenarios where a patient may have classic symptoms of COVID-19 but their RT-PCR test is negative, or situations where a pulmonary CT angiogram might be in order to rule out pulmonary embolism in a patient who is taking blood thinners and steroids. and shows no signs of recovery. Additionally, in cases where an intensive care unit patient with severe COVID-19 shows no improvement and a chest x-ray shows new lesions, a CT appearance could give a clue to a dangerous superfungal diagnosis associated with COVID. -19 infections such as aspergillosis or mucormycosis. In a fourth scenario, a clinician might order a chest CT scan to rule out spontaneous pneumomediastinum, a potentially fatal complication.
“However, these four scenarios together constitute less than 2% of the situations where a CT chest is ordered in COVID-19 cases. Rather than the results of a CT scan, it is oxygen saturation that is key to treatment decisions. Yet in 95% of cases, a CT scan is a misused tool, often prescribed to rule out pneumonia, even in mild cases of COVID-19. There is no point in ordering a CT scan early in COVID-19, as even patients of mild severity can have frosted glass opacities in the lungs, which do not deserve treatment and will resolve on their own ” , explains R. Aravind, Head of Infectious Diseases, Government Medical College, Thiruvananthapuram.
The consensus statement from the Fleischner Society, an international multidisciplinary association for chest radiology, states that “imaging is not indicated” if COVID-19 infection is suspected with mild clinical features. The statement supports the use of imaging in patients with deteriorating respiratory status as well as in those with moderate to severe clinical features indicative of COVID-19 pneumonia.
Read also | CT scanners can be spreaders if protocols are not followed
In summary, although CT scans have been used to assess the severity of COVID-19 pneumonia, its routine use is not recommended.
Are multiple CT scans dangerous?
When indicated, a chest CT scan should be performed with a low dose single phase protocol using rapid scanning techniques to minimize motion artifacts (patient movement leading to subtle errors).
There is no evidence to support the routine use of multiphase chest computed tomography in patients with COVID-19 pneumonia. Dr Guleria said that according to data from the International Atomic Energy Agency, a CT scan equates to almost 300 to 400 chest x-rays, which puts young people at substantial long-term cancer risk. A study published in the New England Journal of Medicine in 2007, according to data from 1991 to 1996, 0.4% of all cancers in the United States may be attributable to radiation from CT studies and the current estimate could be between 1.5% and 2% .
Apart from all this, the risks of transmission and contamination faced by radiology technicians and personnel whenever a COVID-19 patient undergoes diagnostic imaging, especially in an enclosed, air-conditioned space cannot be ruled out. .
Why are steroids prescribed for COVID-19 patients?
Even though many doctors in India had started treating critically ill COVID-19 patients with corticosteroids like dexamethasone much earlier during the pandemic, the recommendation on their use by international agencies like the WHO did not come. until September 2020, following the UK RECOVERY trial, which found mortality. benefit for patients who have received steroids.
In many patients, death occurs as a result of a hyperimmune response (cytokine storm) to the SARS-CoV-2 virus, which damages the lungs and other organs, leading to multi-organ dysfunction syndrome. Corticosteroids like dexamethasone, as anti-inflammatory agents, work by calming the immune system and preventing the progression of organ damage.
“Steroids are the most powerful weapon we have to fight COVID-19. But the therapeutic window to start steroids has to be right. Determining when, how much and for how long is an art that must be mastered, ”says Dr. Aravind.
One of the main concerns is that we don’t want to start taking steroids too early in the disease when viral replication occurs, as this could interfere with the immune system’s natural ability to fight back. We also don’t want to miss that tipping point where steroids can stop the immune system from triggering the cytokine storm, he says.
WHO guidelines state that steroids can be given to patients with a resting saturation rate less than 94% and a resting respiratory rate greater than 24 per minute. However, steroids may benefit some patients who are not yet on supplemental oxygen, but who show early signs that they could get worse.
The Kerala guidelines therefore speak of recognizing stress desaturation – the drop or depletion of oxygen saturation by more than 3% from baseline oxygen levels, after exercise or after testing. six-minute walk – and treat it at the right time for that interstitial inflammation. can be stopped. The walk test requires individuals to walk for six consecutive minutes, without a break, on a flat surface with an oximeter in their finger. After six minutes, if the oxygen level does not decrease, the individual will be considered healthy. But if the oxygen level drops below 93%, or 3%, or if the individual suffers from shortness of breath, it is advisable to see a doctor.
“We want to take care of patients who are at risk of progressing to hypoxemia at rest. The first characteristic of COVID-19 pneumonia will be interstitial involvement, which leads to a mismatch between oxygen supply and demand. Thus, patients with normal oxygen saturation (> 94%) at rest in ambient air and who are clinically stable are subjected to the six-minute / 40-step walk test. If oxygen levels drop after the walk test, these patients may start taking low-dose steroids after consulting the pulmonologist or doctor to prevent cytokine storm syndrome, ”says Dr. Aravind.
When do steroids become a double edged sword?
That said, steroids can prove to be a double-edged sword if the dosage, timing, or duration of the drug is wrong. Steroids are not required for all patients, and certainly not for mild patients in the early stages of the disease. The trigger for starting steroids should be desaturation on exertion, not on the day of illness.
Dr Guleria had recently pointed out that he was seeing many mild cases of COVID-19 where steroids had stimulated viral replication, causing oxygen levels to drop. There is potential harm associated with long-term steroid use in a serious COVID-19 patient. This includes an increase in blood sugar, which will need to be carefully managed with insulin to prevent secondary bacterial or fungal infections.