Lack of evidence on COVID-19 treatment a point of tension for haematologists

Haematologists are caught between a rock and a hard place as the COVID-19 pandemic forces clinicians to return to “old fashioned” observational medicine instead of relying on a strong evidence base, the International Society on Thrombosis and Haemostasis (ISTH) virtual conference has heard.

Speaking at the virtual conference held this week, Professor Beverley Hunt, a professor of thrombosis and haemostasis at King’s College London, said there was a tension between the two ways of practising medicine.

“There’s no doubt that every doctor wants the very best for their patient and they interpret that in different ways… in many hospitals there is pressure from the intensivists saying, ‘I’ve got hundreds of ventilated patients, you’ve got to do more, I’ve got to give something more to my patients they’re having thrombosis [despite treatment] all the lines are clogging up, what are you going to do?” she said.

There were also questions about the use of full-dose low molecular weight heparin (LMWH) and whether D dimer readings should be used to make decisions on therapy or not.

“Then we have had pressures also from peers saying we must resist this, we must stick to current guidance until we have got some new evidence and it has been a real tension for some of us to manage this very difficult situation,” she said.

She added that the problem had been compounded by the realisation that they were dealing with two types of thrombosis in the lungs of COVID-19 patients.

As well as the Virchow’s triad of immobile patients with an inflammatory state, prothrombotic changes and epithelial activation there also appears to be a local immunothrombotic effect within the lungs, she said.

And guidance on treatment of VTE in hospitalised COVID-19 patients has taken slightly different stances. According to ISTH guidance, co-authored by Prof. Hunt, all COVID-19 patients should be given thromboprophylaxis. It also states that intermediate dose LMWH should be considered as well as extended duration treatment for patients with high-risk criteria.

Whereas recommendations from an expert panel published in the journal Chest did not change from pre-COVID guidance on how to manage COVID-19 patients in critical care and advised against extended prophylaxis unless data emerges from clinical trials.

Professor Hunt said at the peak of COVID-19, Kings College Hospital had 190 patients on ventilators which meant general physicians were caring for critically ill patients so the guidance had to be very clear.

But she added that even now there are so many more questions than answers.

“It’s not clear how much more risk there is for COVID-19 patients in critical care over the standard patient. We have this tantalising problem of immunothrombosis and the RECOVERY study has shown that dexamethasone should improve outcome… and I suspect by reducing the inflammatory response we will see less immunothrombosis.”

She added there was a desperate need for more studies to guide decisions over LMWH dose, extended prophylaxis and more.

And the clinicians’ role should be to “put our patients into clinical trials as much as we can” so we can gather evidence as fast as possible, she said.

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