One Size Does Not Fit All
Updated: Apr 29, 2020
Sunday 5th April 2020
COVID Figures for 4th April
UK Hospital Deaths 708 / Total 4313
I thought I would update you on the progress of my friend Gary. Gary lives in London and developed coronavirus symptoms a fortnight ago. His fever gradually worsened and he developed breathing difficulties 3 days later. He was admitted to hospital and within 48hrs was transferred to the ICU for intubation and ventilation. He has now been ventilated for 10 days. During this time he has developed two significant complications related to his ICU stay – a pneumothorax and kidney failure requiring dialysis.
A pneumothorax is where the high pressures used during ventilation cause rupture of the alveoli (air sacs) in the lung. The air leaks into the lining of the lung (the pleura) causing a partial lung collapse. The air can also leak through into the cavity containing the heart (the mediastinum) and can make its way up to the skin overlying the chest and neck where it produces swelling and a distinct ‘crackly’ sensation. This is usually cured by insertion of a chest drain into the pleural cavity to allow the air to drain until such time as the air leak has sealed spontaneously.
The kidney failure in Gary’s case was not entirely due to his COVID illness, thankfully, but as a result of dehydration caused by drugs to increase his urine output. This is done because in some lung conditions, inflammation leads to the alveoli filling with fluid (this is called the Acute Respiratory Distress Syndrome – ARDS). Keeping the patient mildly dehydrated may lead to improvement in oxygenation as less of this fluid will then enter the lungs so more alveoli are ‘open’ and are able to take part in the transfer of oxygen into the blood. However, if a patient becomes too dehydrated, then kidney failure can ensue. This normally improves once you rehydrate the patient but in extreme cases of dehydration, dialysis may be needed for a while until the kidneys recover.
The initial recommendations for treating ventilated COVID patients came out of China and Italy. Those recommendations can be summed up by the phrase ‘Keep Dry and Add PEEP’. This phrase was even published in the style of one of those ‘Keep Calm and Carry On’ posters which are all the rage.
PEEP is Positive End Expiratory Pressure and it is the pressure left in the lungs at the end of expiration. Normally, when breathing, you exhale to atmospheric ‘zero’ pressure. This causes closure of some of the alveoli at the bottom of the lung. When you breathe in, some of your effort is required to open these alveoli. This is often best thought of like blowing up a balloon. Let the balloon deflate all the way and it is hard to reinflate it. Let it only partially down and it’s much easier to blow it up. Now imagine that happening millions of times over in your damaged lung; that’s a lot of effort required to breathe in. PEEP can help enormously to keep the lung ‘open’ – this is also how CPAP (Continuous Positive Airways Pressure) works in non-ventilated patients.
So ‘Keep Dry and Add PEEP’ made sense as it is a good summary of a significant part of the strategy for ventilating ARDS patients. However, a lot of the COVID patients that we are seeing do not appear to have ARDS, at least not in the early stages. For these patients, the application of high levels of PEEP when not absolutely necessary will have contributed to lung damage, some of which you can see (e.g. a pneumothorax) and some of which you can’t. This can lead to a prolonged intensive care stay, which is not good for anyone.
The same goes for the kidney failure. Prior to the year 2000, the ventilation strategy for ARDS was causing collateral damage. High pressures were used, causing some of the problems we have already talked about. There was also the realisation that giving patients too much intravenous fluid was, in turn, causing excessive amounts of fluid inside the alveoli. This was worsening the respiratory failure. Keeping patients ‘dry’ improved their chances of survival.
In recent years, however, this has become an ‘overvalued idea’. Patients are now actively being excessively dehydrated in the hope that it will continue to help their respiratory failure. In the past, even on my own unit, I have seen patients dehydrated to the point where they develop kidney failure. This is not good; kidney failure in the ICU is associated with high morbidity and mortality, even if it has been caused by the treatment rather than the disease itself.
Like granny always said: ‘Too much of a good thing is bad for you’
So what can we take away from this?
Everything we do in ICU has the potential to cause harm as well as good.
Keep an open mind. Doubt the effectiveness of everything you do.
One size does not fit all – be wary of protocol-driven treatment strategies. No two patients are the same.
Maybe, just maybe, less is more?