Chest pain? MONA no longer answers the door
By Mike McEvoy
Morphine, oxygen, nitrates, and aspirin — collectively known as MONA — are no longer the preferred door prizes for chest pain patients entering the emergency cardiac care system. The Emergency Cardiac Care (ECC) Guidelines 2010 put the kibosh on the morphine and oxygen piece of MONA after research demonstrated increased mortality from the morphine and no evidence supporting use of oxygen while other data suggested harm, especially with high flow oxygen.
Nitrates and aspirin however, are lifesavers in the setting of suspected acute coronary syndromes. This is great news for BLS providers who are trained and ready to deliver both medications currently recommended for chest pain patients. But are you completely familiar and comfortable with administering nitroglycerine and aspirin? This article will tell you what you need to know.
Of course, morphine and oxygen still have a limited role in acute coronary syndromes. Morphine can be considered for patients whose chest pain continues despite maximal doses on nitroglycerine, something highly unlikely to occur in the prehospital environment or emergency department. Oxygen should still be given for patients with pulse oximetry saturations less than 95% or those in shock, with acute shortness of breath, or signs of heart failure — all relatively uncommon prehospital presentations. That leaves us with nitrates and aspirin.
The most common nitrate is nitroglycerine, available in many different forms, all of which offer the beneficial effects of dilating coronary arteries (particularly in the areas where plaque disruption may be blocking blood flow), and dilating venous blood vessels which reduces resistance to blood flow in the body. Patients with chest pain of suspected cardiac origin should receive up to 3 doses of nitroglycerine given either by sublingual tablets or spray (such as NitroMist), administered at 3 to 5 minute intervals until their pain is relieved, their systolic blood pressure dips below 90 mmHg or systolic blood pressure drops more than 30 mmHg from baseline.
Nitroglycerine is contraindicated in patients with hypotension (SBP < 90 mmHg), significant bradycardia (< 50 BPM), right ventricular (RV) infarction, or those who have recently taken a phosphodiesterase inhibitor such as Viagra, Cialis or Levitra. In practice, how would an EMT recognize a patient with an RV infarct and what happens if your patient fails to tell you they took an erectile dysfunction (ED) drug within the previous 24 hours? Well, truth be told, it’s like pornography: you’ll know it when you see it.
Give nitro to an RV infarct patient or one who has taken an ED drug and you’ll quickly see hypotension. Quickly means once the nitro is absorbed which typically takes three to five minutes (a good time to recheck the blood pressure) and hypotension means pretty low BP (usually less than 80 systolic). Don’t panic, though: despite grave warnings to the contrary, it is incredibly hard to find any documented reports of adverse patient outcomes in either of these situations. Instead of going to pieces, lay your patient down and elevate the legs. Doing so takes advantage of a well known ability to raise blood pressure by autotransfusing blood volume from the legs into the central circulation. Pressure will increase and in three to five minutes the nitro will wear off. Enough of that: don’t give the patient any more nitro.
What else do you need to know about nitroglycerine? Well, for starters, it comes in many different forms. There are 272 different nitro products available on the market. They range from inexpensive sublingual tablets to chewable capsules to patches to sublingual spray to paste to intravenous forms. Nitroglycerine tablets are the least expensive and most commonly prescribed.
Tablets are light sensitive (they degrade when exposed to sunlight or high temperatures) and therefore are packaged in small dark colored glass bottles. Once opened, moisture in the air tends to degrade the tablets over the course of several months, so the bottle should be replaced every six months.
Storing the bottle in a pants pocket increases temperature and will accelerate nitro degradation. Tablets that have lost their potency have a sweet taste; tablets with full potency taste bitter, commonly induce a headache, and (obviously) help to relieve chest pain. Ask your patient about the taste of their sublingual nitro tablets. If they report a sweet taste, consider the tablet's lifespan expired and administer additional doses from another source.
Counsel your patients with nitro prescriptions to not carry their bottle in their pants pockets and to refill the prescription every six months. Note also that plastic containers leach nitroglycerine from tablets and from intravenous preparations. Tablets must be kept in the glass container they are dispensed in. Special non-leaching plastic intravenous bags and tubing must be used when infusing nitroglycerine. Lastly, when assisting with administration of nitro tablets, consider using a straw to strategically place the tablets into the buccal mucosa (under the tongue) to avoid placing your fingers into the mouth. Check first to ensure your patient has saliva in their mouth; without saliva, sublingual meds will never dissolve. Nitro spray requires caution as well; EMS providers who get too close to their patient when spraying sublingual nitro spray have been known to experience dizziness and syncope from inhaling the medication mist.
Early administration of aspirin in the setting of acute myocardial infarction has been demonstrated to significantly reduce mortality — so much so that emergency medical dispatch protocols advise patients without contraindications to take aspirin immediately on contacting 911 when acute coronary syndrome is suspected.
The recommended dose is 160 to 325 milligrams. Chewable aspirin is absorbed more quickly than swallowed aspirin. Most dispatch and prehospital protocols recommend chewing four baby aspirins (81 milligrams each). When baby (chewable) aspirin is not available, an adult (325 milligram) aspirin tablet can be chewed (not very tasty but equally effective). If residual aspirin remains in the mouth or no saliva is present, the patient can drink eight ounces of water to increase absorption.
You may be surprised at all the potential sources of aspirin. Aspirin suppositories can be given if a patient is too nauseous to swallow or chew tablets. Aspirin is also a component of many other medications such as Pepto-Bismol; reading medication labels will surprise you. There is also a new powdered aspirin product on the market contained in a foil envelope (Aspirin to Go) that can be kept in a wallet or pocketbook and used in case of headache, injury or administered as a lifesaver in a chest pain emergency.
Aspirin inhibits the action of platelets, preventing their ability to clump together forming clots. Since the mechanism of acute coronary syndrome is usually ruptured plaque in one of the coronary arteries with clot formation obstructing blood flow. Prompt administration of an antiplatelet agent such as aspirin significantly reduces damage and can be lifesaving, the earlier the better, hence the reason why dispatchers recommend it.
Some responders wonder about aspirin overdoses. Let’s say the 911 dispatcher instructs a patient to chew 324 milligrams of baby aspirin, the first responders do the same, and the emergency department gives yet another dose. Is that too much? Not at all, actually. Some therapeutic regimens call for 5,000 milligrams of aspirin daily, depending on the indication. In the setting of a patient with potential acute coronary syndrome, better safe than sorry.
With MONA no longer meeting chest pain patients at the door, it is nice to know that our first responders and EMTs now have the tools and knowledge to deliver life saving interventions to patients who present with chest pain potentially of acute coronary syndrome origin. Keep your focus on nitroglycerine and aspirin. Meeting patients at the door with these two medications will improve outcomes and help you to help your patients.
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