Britain's Prime Minister Boris Johnson. Photo / AP
Britain's Prime Minister Boris Johnson. Photo / AP
Opinion
COMMENT:
When Boris Johnson went into the hospital a few days ago, it seemed to come as a bit of a surprise to everyone except the doctors who actually manage Covid patients. He had been doing well, in isolation at home for a week.
His symptoms were mild, and hefelt confident. He was working. But then his symptoms worsened and he was admitted to hospital and placed on oxygen. A day later he was moved from the ward into the ICU, in case his condition were to deteriorate and he required intubation and mechanical ventilation.
While this course of events would be unique for influenza, or a host of other viral respiratory infections, it is common with Covid.
Doctors from across the globe have been telling their colleagues of the precipitous decline that some patients show at days 7 to 9.
Their fever is long gone, their severe shortness of breath resolving when they suddenly get worse. Some are in the hospital when it happens, others at home. But when the decline happens, they all end up in ED.
Unable to breathe, their oxygen saturations drop to frighteningly low levels. With hypoxia comes confusion. Doctors increase the oxygen via nasal prongs and face masks, using high flows and sometimes high pressure devices, to get the oxygen levels high enough to sustain the essential organs.
Eventually some patients will require intubation. Recent evidence suggests 80 per cent of those that get intubated for Covid do not survive.
What's happening in these patients isn't clear to us. We do know that T-cells take about a week to ramp up. This could account for the one week lag, as well as the 'cytokine storm' these Covid patients experience.
T-cells are a special cell of the immune system that roams the circulation looking for infections. Cells infected with viruses like Covid present bits of the virus on their outer surfaces, flagging themselves.
T-cells spot the infected cells, and deploy their weapons: enzymes to punch holes in their cell membranes, toxic granules that get spilled into the infected cells, digesting them, cytokines released into the surrounding tissues to tell nearby cells that there is an invasion in progress.
In the body, clinically, this process results in the spaces around the air sacs thickening with inflammatory fluid. Oxygen is not able to diffuse through these swollen walls into the bloodstream. The tissues and organs suffer.
While we can support a patient with oxygen, first with nasal cannulae, then with increasingly invasive forms of assisted ventilation, the level of inflammation can often prove insurmountable. The lungs become stiff. If you were to try to bag ventilate a patient like this, you'd have to use two hands and a fair bit of your strength to get the air in.
All that pressure takes its toll on the lungs and damages them further. There is no alternative though, because if the oxygen levels drop too far there will be damage to the brain.
There is no cure for Covid, no proven treatment, and no quick fix. Some patients can survive the storm, others succumb.
Dr Gary Payinda.
We still don't know much about the recovery from critical illness with Covid. Many require prolonged mechanical ventilation, sometimes for weeks. Some show early signs of lung fibrosis, or scarring. Some don't, and recover fully. We don't know why.
There may be genetic differences in things like Ace-2 enzymes and receptors, the preferred binding site of SARS-CoV-2 virus, that influence an individual's susceptibility and chance of survival. We don't yet know.
It also may be that medications which tamp down the inflammatory response will have a role in treating critical Covid infections. Again, it is too early to tell. Hope in medications at this point is premature.
The 'miracle cure' is, as always, prevention of spread: handwashing, social distancing, and case isolation. And so far, New Zealand, it appears to be working, when compared to our peers, or even when compared to countries that are far richer or more authoritarian than us.
• Dr. Gary Payinda works as an emergency doctor in Northland. He thinks New Zealand's society-wide response to Covid has been nothing short of world-class, and thanks the public who are making this possible.
