Nitro/Aspirin in conjunction

[JPINFV]

It absolutely makes more sense to move out right away. I just feel like there was a different process that I was taught...something to do with up to three separate doses, then calling for upgrade...bah nevermind. What the hell was a I taught? <_<

Patients are taught that they should take 3 doses of nitro, and if their chest pain isn't resolved (i.e. it's not stable angina), then call 911. This, for some reason and including the 3 dose nitro treatment, has made it into EMS. The problem is that the 3 dose nitro rule shouldn't apply to medical professionals, and the standard placed on medical professionals, especially those in emergency medicine, are much higher. No one is going to give a chest pain patient nitro in the ED and do nothing else if the pain goes away in 1-3 doses.

 

[Drax]

Patients are taught that they should take 3 doses of nitro, and if their chest pain isn't resolved (i.e. it's not stable angina), then call 911. This, for some reason and including the 3 dose nitro treatment, has made it into EMS. The problem is that the 3 dose nitro rule shouldn't apply to medical professionals, and the standard placed on medical professionals, especially those in emergency medicine, are much higher. No one is going to give a chest pain patient nitro in the ED and do nothing else if the pain goes away in 1-3 doses.

Would you mind going a little into what they would do?

 

[JPINFV]

Would you mind going a little into what they would do?

Chest pain workup?

Chest x-ray, 12 lead ekg, serial troponins. Depending on the presentation, patient's history (TIMI score), and the physician's experience, you're going to see everything from a "delta troponin" (second troponin 2-4 hours after the first, if both are negative, then discharge with PMD followup), to admission with troponins q8 hours x 3 followed by an inpatient stress test (EKG while either on a treadmill or after given a medication to increase the patient's heart rate), or possibly a stress echo (same concept, except with echocardiogram).

Of course if anything is positive, then that's a different situation completely. Additionally, the differential for chest pain is about 3 pages long, hence why every chest pain is going to get a chest x-ray.

 

[rugbyguy]

I apologize, there should be an "n't" at the end of that "would". The last sentence is the most concise question: any experience with a drop in bp associated with ASA which would contraindicate nitro? Any examples of negative interactions at all?

So let's break down the 2 drugs.

Nitro is a vasodilator. As a basic you can only "assist" a pt with their own, which means they have to be prescribed Nitro. First you must check the BP. We check the BP because it is a vasodilator, so we need to make sure the pressure is <90 systolic first as to not knock them out. Nitro is usually prescribed for angina pectoris, which is usually caused by atherosclerosis of the arteries coming off the heart. Nitro dilates the arteries when they wont them self, thus allowing more blood to be pumped into the systemic system, and relieving the patient's pain.

Aspirin is an anti-platelet. This inhibits thromboxin, the chemical that encourages platelets to stick and form clots over cuts in vessels. This way there is less chance of platelets clotting, and then breaking off, forming an embolus, then getting caught in the system later down the line. Also it can make blood less viscous, allowing for easier flow.

These are the main points covered in my EMT class if I remember right on each of these drugs. While they do a lot more, let's focus on these as the others are irrelevant at this time. According to that, why would they not always be given together for chest pain? Nitro for the angina, angina pain means blood is not flowing and properly feeding the heart, so dilate the blood vessels to allow more in, use aspirin to make the blood less viscous and able to move through the body easier.

I knew killing myself the last 3 weeks for my blood and cardiology A&P test would pay off.

 

[Brandon O]

Perhaps the OP has a background in biochem, or just took a good A&P class. Strictly from the pharmocodynamics, it might seem to follow that aspirin could cause vasodilation, given that it's blocking thromboxane A2, a vasoconstrictor. On the other hand, its broader anti-inflammatory effects in blocking the COX-1 pathway might be expected to do the opposite (triad asthma is a cool example of this). Regardless, neither effect has much of a hemodynamic effect in vivo. We use aspirin for the antiplatelet effects.

The idea of nitro being diagnostic for MI is a tricky one. It's probably true that a patient who gets some relief from nitro is more likely to have an ischemic cause (i.e. ACS), but probably LESS likely that it's a total occlusion (i.e. STEMI). Most folks agree now that nitro rarely dilates the actual blocked artery; the body's pretty good about locally regulating bloodflow to manage hypoxia, so odds are that vessel's already fully dilated. (Versus a partial stenosis which does get relief, more like a stable angina.) Nitro's role is more in dilating the peripheral vessels and decreasing cardiac preload, thus reducing work on the heart -- reducing oxygen demand, not increasing supply.

Long story short, it's not much help diagnostically.

There really isn't a place for EMTs to "treat and wait to see a response."

Cardiac arrest.

 

[JPINFV]

Cardiac arrest.

...touche... (even if it isn't ACS being treated at that specific time).

 

[Bearamedic]

Perhaps the OP has a background in biochem, or just took a good A&P class. Strictly from the pharmocodynamics, it might seem to follow that aspirin could cause vasodilation, given that it's blocking thromboxane A2, a vasoconstrictor. On the other hand, its broader anti-inflammatory effects in blocking the COX-1 pathway might be expected to do the opposite (triad asthma is a cool example of this). Regardless, neither effect has much of a hemodynamic effect in vivo. We use aspirin for the antiplatelet effects.

I was medic-taught that asa helps prinzmetal's because it alleviates vasospasm
(txa2, can cause vasospasm?; formation inhibited via asa cox blocking )
Matches up with your initial pharmacodynamics hypothesis.

 

[Brandon O]

I was medic-taught that asa helps prinzmetal's because it alleviates vasospasm

Sounds... duuuubious.

 

[Bearamedic]

Sounds... duuuubious.

Yep, but i dont know enough to say that this definitely isnt the case. I can only rely on what some preceptor said that one time.

 

[Brandon O]

Yeah. I haven't played around with the Prinzmetal's literature enough to know anything for sure, but the choices I've heard recommended include nitro and CCBs. I suppose aspirin could work but that would be rather bizarre compared to its effects elsewhere, and in fact (briefly checking some references now) it looks like it might be deleterious -- due to the aforementioned anti-inflammatory effects.