# Tachycardia = Contraindication for Nitroglycerin?



## halocell (Nov 3, 2019)

Hello, As the title suggests; Is an elevated heart rate considered a contraindication for the administration of Nitroglycerin?

       I ask this because I've been going through NREMT practice exams (Specifically Limmer Creative's EMT PASS) and there reoccurring questions that Involve the idea that a heart rate above 100 is a contra-indiction for Nitro. Prior to these exams I hadn't heard of heart rate playing a factor in administration. Even looking through my textbook and information online I'm finding nothing to support this idea. I'm not claiming that the App is wrong by any means, I just want more information on it since I cant seem to find it anywhere else.


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## Peak (Nov 4, 2019)

Prehospital Nitroglycerin in Tachycardic Chest Pain Patients: A Risk for Hypotension or Not? - PubMed
					

Hypotension following prehospital administration of NTG was infrequent in patients with chest pain. However, while the absolute risk of NTG-induced hypotension was low, patients with pre-NTG tachycardia had a significant increase in the relative risk of hypotension. In addition, hypotension...




					www.ncbi.nlm.nih.gov
				




My thoughts are that if an adult patient is tachycardic it could mean that they are dependent on their heart rate to maintain an adequate CI. If this is the case then they  are probably so hemodynamically fragile that nitro may have increased risk compared to a patient who has a normal heart rate. That being said there are also many other reasons why patients are tachycardic, at the top is anxiety and pain. 

Keep in mind that SL nitro really doesn't provide a lot of benefit in the setting of MI when you look at morbidity or mortality. 

We do give IV nitro to many patients who are tachycardic so it isn't necessarily a 100% contraindication.


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## E tank (Nov 4, 2019)

What do you mean by elevated heart rate? 100? 150?


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## mgr22 (Nov 4, 2019)

ACLS prescribes upper _and lower_ limits on HR for NTG admin. I'm guessing that is to discourage caregivers from jumping to NTG when the presenting problem may be rate-related.


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## RedBlanketRunner (Nov 4, 2019)

@Peak Query. Have you had any experience with nitroprussides? For reasons unknown to me, nitroglycerin is normally not available in most S.E. Asian countries and nitroprussides are used instead. 
Thoughts on this?


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## halocell (Nov 4, 2019)

E tank said:


> What do you mean by elevated heart rate? 100? 150?


According to EMTPASS, a heart rate over 100 is considered elevated


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## Peak (Nov 4, 2019)

RedBlanketRunner said:


> @Peak Query. Have you had any experience with nitroprussides? For reasons unknown to me, nitroglycerin is normally not available in most S.E. Asian countries and nitroprussides are used instead.
> Thoughts on this?



Nitroprusside is a dirty drug with a lot of very undesirable side effects, chief of which being cyanide poisoning and the conversion of hemoglobin to methlyhemoglobin. It should only be used for a few days at most, and that is really pushing it. 

Our patients potentially stay on vasoactive drips for weeks or months so we honestly don't consider it. It also has some similar mechanisms as phosphodiesterase inhibitors and a very large number of our patients are already on sildenafil or tadalifil (+/- bosentan).

When we thing about perfusion we often relate RBCs to the box cars on the train. We need the train to be moving  but we also need the box cars to move oxygen. A lot of our hearts have a goal crit of 50 and we transfuse at 40, so we are really hesitant to give anything that can lower the number of boxcars that can actually do work.

Moving oxygen certaonly isn't the only function of perfusion, so it may have a role for some patients especially if we think that the patient will only need it for a very short period of time. 

Drug choice is often driven by the mechanism we are trying to fight. For drips we mostly give labetalol, metoprolol, nicardipine, and sometimes nitro. We will sometimes give hydralazine but that is for our more long term patients who act up once in a while. If we are maxed out on IV options we may elect to place an NJ and give orals as well, but that is very patient specific and they require good perfusion to the gut.


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## RedBlanketRunner (Nov 4, 2019)

@Peak Not surprising. I'm suppressing a face palm here. Some of the western trained physicians regularly roll their eyes at some common procedures. Care to take a guess why no nitroglycerin?


Peak said:


> Drug choice is often driven by the mechanism we are trying to fight.


Care to elucidate? Do I smell QA violations and insurance carriers?

I tossed the little package with the nitroprusside I was given. A small zip lock bag labelled in Thai so I was only able to go by word of mouth what it was and I was not about to thread my way through border patrols carrying what did not look like a proper medication bottle.
Other typical idiocies: they banned all douche and enema kits here, Thailand, about 10 years ago. Potential to be used as sex toys. Condoms were to be kept concealed out of the public eye in stores and had to be specifically asked for. In the hospital, floor crash carts were kept locked in janitor closets to prevent tampering.
Or a WTF. A nurse removing an IV from my wife, obviously following some very specific procedure. Remove from lock, take bag down, coil tubing a certain way and I stepped in doing a venous tourniquet with my hands, blood all over. HELLO? WAKEY! Clamp, remove from patient, then play with the plumbing. Sharps protocol gone wrong?
Takes a little getting used to the third werld. The nurses here have my sympathy however. The first year on the job they are paid minimum wage. Nepotism and cronyism determines all promotions. Highly attractive nurses are scooped up by the physicians as office decorations.


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## Peak (Nov 5, 2019)

RedBlanketRunner said:


> Care to elucidate? Do I smell QA violations and insurance carriers?



Different drugs have different mechanisms of action. While we may prefer nitroglycerine for hypertension in the setting of a fresh arterial switch or CABG, while instead we would typically prefer nicardipine in the hypertensive crisis patient exhibiting neurological symptoms (although there are a great number of treatment approaches for hypertensive crisis). Often we are balancing multiple pressors, inotropes, and vasodilators/antihypertensives to achieve the desired effect.

The same goes for pressors. Epi is our first line for anaphylactic shock but almost nothing else. Neo is great for sedation related hypotension but definitely isn't our first line in septic shock.


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## RedBlanketRunner (Nov 6, 2019)

@Peak Thanks very much. I'm perforce going to need to crack the books again.
It appears to me that giving out nitroprussides as an alternative to nitroglycerin for basic EMTs to use wholesale is... I'm not going to say dumb, but stands to present all sorts of problems as further treatment progresses. That 72 hour half life is extremely worrisome to my thinking. If nothing else it moves prehospital trauma intervention well into the realm of therapeutic.


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## RedBlanketRunner (Nov 6, 2019)

@Peak I failed to mention an RN rides in the ambulance units.


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## RedBlanketRunner (Nov 6, 2019)

@Peak I'm now getting mixed signals to the exact drug alternative. Isosorbide dinitrate, nicardipine, depending on which authority in which hospital I talk to. So this is all irrelevant. (exasperated sigh)


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