Stealing Borrowing a couple of pages from both Ambulance Driver and Rogue Medic, I’ve been looking at some of the changes to the CPR and Emergency Cardiac Care Guidelines from the American Heart Association. As is often the the case with changes to the guidelines, big changes are often mentioned in the figurative small print. Here is a a good example,
2010 (New): Once the circulation is restored, monitor arterial oxyhemoglobin saturation. It may be reasonable, when the appropriate equipment is available, to titrate oxygen administration to maintain the arterial oxyhemoglobin saturation ≥94%. Provided appropriate equipment is available, once ROSC is achieved, adjust the FIO2 to the minimum concentration needed to achieve arterial oxyhemoglobin saturation ≥94%, with the goal of avoiding hyperoxia while ensuring adequate oxygen delivery. Because an arterial oxyhemoglobin saturation of 100% may correspond to a PaO2 anywhere between approximately 80 and 500 mm Hg, in general it is appropriate to wean the FIO2 when the saturation is 100%, provided the saturation can be maintained ≥94%.
2005 (Old): Hyperoxia and the risk for reperfusion injury were addressed in the 2005 AHA Guidelines for CPR and ECC in general, but recommendations for titration of inspired oxygen were not as specific.
Why: In effect, if equipment to titrate oxygen is available, titrate oxygen to keep the oxyhemoglobin saturation 94% to 99%. Data suggest that hyperoxemia (ie, a high PaO2) enhances the oxidative injury observed after ischemia-reperfusion such as occurs after resuscitation from cardiac arrest. The risk of oxidative injury may be reduced by titrating the FIO2 to reduce the PaO2 (this is accomplished by monitoring arterial oxyhemoglobin saturation) while ensuring adequate arterial oxygen content. Recent data from an adult study demonstrated worse outcomes with hyperoxia after resuscitation from cardiac arrest.
Now, you may wonder what appropriate equipment is needed for this sophisticated monitoring. The answer is our old friend (and nemesis) the Pulse Oximeter. Every ALS unit should have one, along with End Tidal Carbon Dioxide (ETCO2) monitoring. Since at least 2005, the AHA has been telling us that hypocapnia is bad for patients, especially cardiac arrest patients. As a result, we’ve been using ETCO2 monitoring to make sure that CO2 levels are not too low. Well, it’s a bit more complex than that, but let’s leave that aside for now. Now, the AHA is incorporating the data from a variety of studies showing that hyperoxygenation of living patients is probably just as bad as hypoxygenation. So, they recommend that we monitor both O2 and CO2 levels in post cardiac arrest patients.
Even more surprising, they are recommending titration of Oxygen delivery to patients with Myocardial Infarction and Acute Coronary Syndromes.
2010 (New): Supplementary oxygen is not needed for patients without evidence of respiratory distress if the oxyhemoglobin saturation is ≥94%. Morphine should be given with caution to patients with unstable angina.
2005 (Old): Oxygen was recommended for all patients with overt pulmonary edema or arterial oxyhemoglobin saturation <90%. It was also reasonable to administer oxygen to all patients with ACS for the first 6 hours of therapy. Morphine was the analgesic of choice for pain unresponsive to nitrates, but it was not recommended for use in patients with possible hypovolemia.
Why: Emergency medical services providers administer oxygen during the initial assessment of patients with suspected ACS. However, there is insufficient evidence to support its routine use in uncomplicated ACS. If the patient is dyspneic, is hypoxemic, or has obvious signs of heart failure, providers should titrate oxygen therapy to maintain oxyhemoglobin saturation ≥94%. Morphine is indicated in STEMI when chest discomfort is unresponsive to nitrates. Morphine should be used with caution in unstable angina/non-STEMI, because morphine administration was associated with increased
mortality in a large registry.
I’m not going to discuss the Morphine recommendations for now, but the Oxygen recommendations represent a potentially major change in EMS care. EMTs and paramedics are taught almost from day one that oxygen is one of the most important medications we carry. We give it for just about everything. Most protocols that I’ve seen make placing the patient on O2 one of the first steps in patient care. A good deal of this is based on the 1994 revision to the BLS curriculum that stated that EMTs (and paramedics) were incapable of determining how much Oxygen a patient might require and so a lot should be given. Advances in technology, if not the EMT curriculum, have made this obsolete. As long as a BLS crew has a pulse oximeter and has been taught, not trained what the numbers mean and how to assess a patients respiratory status, they should be able to adjust (titrate) the amount of Oxygen they give to a patient. This holds even more true for advanced level providers who as part of their paramedic training must be able to assess a patients respiratory status.
What will be interesting is to see how much resistance there will be to this change among doctors, nurses, regulators, and EMS providers themselves. I predict that this will be one of the hardest changes to implement, because it destroys one of the oldest, if not the oldest, treatment in EMS. In fact, it predates EMS as even back in the 1960s and before many ambulance crews were able to administer Oxygen to sick or injured people. Some people, especially field providers are going to react as if their mothers were insulted. It will take a while to
get it through their thick skulls convince them that what we’ve been doing since ambulances were pulled by dinosaurs is not only not helpful, but might be harmful to patients.
Sometimes the hardest part of EMS teaching is getting people to unlearn that which is untrue so they can learn what is true.