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Wednesday, September 8, 2010

Oxygen should be used as a drug with side effects

Oxygen is a drug, although often in the hospital setting we use it without thinking much about the consequences. Yet, like all drugs, there may be "side effects" to oxygen that often goes un-thought about.

Neonates are a great example. When a neonate is born and doesn't take a breath right away, it has always been standard practice to ventilate these newborns with positive pressure breaths with 100% oxygen. The theory is that 100% oxygen will help to increase oxygen tension in the lungs, and dilate vessels there. (click here for more reasons not to overoxygenate neonates)

However, newer studies show positive pressure alone will stimulate breathing, and that the 100% oxygen not only is not needed, but can be detrimental. Studies performed in the past 10 years have shown that, even in term infants that are otherwise healthy, a rapid increase in PO2 can increase their risk of developing cancer later in life.

Likewise, as this article notes, scientists have discovered that exposure to 100% oxygen even for as little as three hours can increase free radicals, and these free radicals attack lung cells exposed to 100% oxygen. When free radicals attack lung cells, isofurons are created.

By measuring isofurons, scientists have and will be able to study the effect of oxygen on lung damage, either now or in the future. So while 100% Fio2 exposure may be linked to future consequences, exposure for as little as 3 hours can increase chances of lung damage and risk for disorders such as ARDS

Physicians have known for years higher oxygen levels (FiO2 greater than 60) increased the risk of lung injury if used for extended periods of time. Yet they didn't know that an extended period of time may be considered anything over three hours.

Adult patients are often placed on 100% oxygen for various illnesses, although there have been a few times that we have had an ARDS patient in such a situation, and the patients were eventually cured of the ARDS, went home, only to come back a few years later with terminal cancer.

It just makes me wonder if, perhaps, we medical professionals are way too eager to use oxygen. That, perhaps, we ought to think twice about using it in such high doses. That, perhaps, we ought to try increasing CPAP and PEEP before going over, say, 40% FiO2.

It seems the only time we have doctors unwilling to go over 40% FiO2 at the present time is when the patient is a supposed CO2 retainer who uses the hypoxic drive to breath. Yet recent evidence shows that the hypoxic drive might be a myth that even RT schools are no longer teaching.

And even if a CO2 retainer does use the hypoxic drive to breath, it's a very rare occurrence that only occurs in 10% of COPD patients. Thus, if a patient is an end stage COPD patient (retainer or not) or a terminally ill patient, or otherwise critically ill patient who really needs it, I would say it's fine to use as much oxygen as you need.

Yet if you have a patient who is otherwise young and healthy, and has the prospects of living a normal life if he or she overcomes the present illness, I'd be thinking twice about using higher amounts of oxygen.

Allow me to note here that most patients who are truly CO2 retainers who are using the hypoxic drive only lose their drive to breath when they are in severe distress. If they need oxygen, it should be given. If they lose their drive to breath, that's when the patient should be intubated.

It's ironic that in the hospital setting oxygen is used often when it's not needed or shouldn't be used, and when it 's needed doctors are Leary of it. Yet, we should never lose sight of the fact oxygen is a drug, it has possible side effects, and it should be treated as a drug.

1 comment:

Djanvk said...

A NICU I worked at we used a protocol to keep spo2 between 88-92% and the issues with Retinal Detachments went down by 70%.