Microvascular thrombosis seen in ‘early phase’ of respiratory failure in COVID-19

Patients with COVID-19 in the early phase of respiratory failure are presenting with problems with the vasculature of the lungs and microvascular thrombosis, say UK doctors.

A summary of the experience of those on the front line published by the Intensive Care Society said there seems to be several phases in patients presenting to critical care with acute respiratory distress syndrome (ARDS) coming later in progression of the disease.

In a teleconference set up to share learning on what treatments seemed to work, intensive care specialists said the effect on the vasculature in the lungs at this stage meant that early aggressive ventilation may not be the best option.

An accompanying short report from the Intensive Care Society, UCL Partners and the National Institute for Health Research, said in the early phase proning seemed to be key and should be considered to “support the vasculature”.

The report, which is based on the experience from hospitals who have treated the most patients so far in the UK, added that pulmonary vasodilatation may provide some benefit.

Those taking part in the teleconference held in early April heard that doctors were seeing lots of thromboembolic disease but the potential use of routine anti-coagulation was as yet unclear.

The report authors stressed that their goal was to share emerging information but that the situation was changing rapidly and these were observations rather than peer reviewed evidence.

“COVID-19 appears to have several phases,” the short report said. “Management should be guided by timing of the onset of symptoms to understand where in the trajectory of the disease the patient is.”

It continued: “Early phase of respiratory failure primarily affects the vasculature. Pro-coagulation leading to micro-vascular pulmonary thrombosis has been observed.”

Later phases of respiratory failure can involve ARDS, it said.

In a summary of the teleconference shared on social media Dr Daniel Martin, Intensive Care Lead at the Royal Free Hospital, London said: “Early high PEEP is probably not the right strategy and may be harmful. This is not ARDS in the early phase of the illness.

“There is clear microvascular thrombosis happening in the pulmonary circulation, which leads to an increased dead space.

“Thromboembolic disease is prevalent, look for it. No one is sure about whether we should anti-coagulate everyone, this is probably too risky.”

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