Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

Beta vs. Beta Blocker

TOTWTYTR said…

RM has a good head, a good EMS head. Maybe we should just call him that from now on. EMSH.

Emergency Medical S@#$ Head?

Them’s pooping words!

Well, enough bathroom humor. TOTWTYTR presents the case of a patient who is sick

His radial pulse is 150, his BP is 68/P. His 12 lead EKG shows ST elevation in V1-4, with reciprocal changes in II, III, AVF.

He has no significant medical history, takes 81 mg ASA daily, and has no known drug allergies.

IV, EMS aspirin (it isn’t likely to hurt if we give more, but not getting enough aspirin would be a bad thing), oxygen, and some normal saline solution (standard EMS IV fluid).

After 250ml of saline, the patient is still tachycardic, still has chest pain, but his BP is now 88/p.

Here is where it becomes interesting.

Medical control orders Dopamine at 5mcg/kg/min. He also orders Lopressor 5mg IV.

You and your partner are concerned about the effect the Lopressor might have on the BP and try to defer the drug until you are at the hospital. The doctor repeats his orders and tells you that he doesn’t want to delay the patients trip to the cath lab.

So, what do you do now? You are four minutes from the ED door.

There were some creative responses to the situation, even the suggestion of a new name for me. :)

Here is the way I look at this patient. I like to keep things simple. There is very little research to show that EMS is truly beneficial to this patient. There is research that has been done in hospitals, but I don’t know of any studies that looked at the specific combination of medications listed.

The initial BP (Blood Pressure was) 68/palp (palpated).

A palpated systolic pressure is generally a bit lower, maybe 10 points lower, than an auscultated systolic pressure. Palpation of the blood pressure is feeling the pulse, keeping the fingers in the place the pulse can be felt, inflating the BP cuff to the point where the pulse can no longer be felt, letting the cuff deflate slowly until the pulse can be felt again. Auscultation is using a stethoscope to listen for the changes in sounds that are produced when deflating the cuff.

The initial BP of 68/palp is uncomfortably low. The patient presentation does nothing to alter that perception. This patient appears to be having a heart attack. The most important drug is the one he takes every day – aspirin. More is given by EMS. No problem there. Some oxygen is given, how much is not specified, but the AHA (American Heart Association) recommends –

EMS providers may administer oxygen to all patients. If the patient is hypoxemic, providers should titrate therapy based on monitoring of oxyhemoglobin saturation (Class I).[1]

The use of dopamine is mentioned on the label for metoprolol (Lopressor) – as a treatment for metoprolol overdose –

Hypotension: A vasopressor should be administered, e.g., levarterenol or dopamine.[2]

On the dopamine label, there is mention of dopamine and metoprolol drug interaction –

Cardiac effects of dopamine are antagonized by beta-adrenergic blocking agents, such as propranolol and metoprolol.[3]

Maybe Dr. Rumble Fish at medical command was not looking for any cardiac effects from dopamine.

I suppose that it would be interesting to throw them into a patient to watch them fight it out. Not nice. Not civilized. Not ethical. Not humane. Just interesting.

On the other hand, there is a case report that brings up the question of LVOTO (Left Ventricular Outflow Tract Obstruction) in AMI (Acute Myocardial Infarction) with shock.[4] One of the points of this article is that the use of inotropes, such as dopamine, is not to be encouraged if LVOTO is suspected; beta blockers may calm things down and by lowering heart rate, improve BP and patient presentation. I suspect that Dr. Rumble Fish (medical command) was trying to accomplish two tasks, but refusing to acknowledge the problems of trying to combined treatments that antagonize each other.

Some other suggestions for treatment were for the antiarrhythmic drugs – amiodarone and lidocaine.

Amiodarone is not known for being a systolic enhancing drug. Its tendency toward producing hypotension may increase the need for cardioversion of otherwise stable arrhythmia patients. Yes, even VT (Ventricular Tachycardia) can be stable for extended periods.

Lidocaine is just plain ineffective. A placebo would probably be as effective. With a narrow complex, lidocaine is not indicated. With a wide complex, you need to avoid bi-fascicular blocks, which are not common, but they tend to develop into a much more stable rhythm. Asystole.

Eventually, I will complete at least one of my antiarrhythmic posts.

Back to our unstable patient. If the BP goes from 68/p to 88/p with 250 ml, why are we not happy with the progress?

Why are we throwing different drugs at the patient? Possibly very dangerous drugs.

Are the lungs still clear? 250 ml might be enough – with this patient – to cause problems.

Another 250 ml is not exactly going to land you a spot on the next Medics Gone Wild video.

The beta blocker is supposed to slow the heart rate, rather than vasodilate. By slowing the heart rate, the blood pressure is expected to drop. On the other hand, it is possible that the patient’s blood pressure is so low because of the heart rate. If you look at the calculation for maximum heart rate (220 – age = maximum heart rate), you will see that this patient is breaking the law. What does that mean?

This is a formula for predicting what the maximum heart rate of the average person will be. It is based on a complex set of variables that include all of the following: Age.

OK, the formula is not at all complex and does not take any variables into effect, except for age. There is at least one ED physician on the lecture circuit, who teaches management of tachyarrhythmias and uses this formula to demonstrate where the dividing line between ST (Sinus Tachycardia) and SVT (SupraVentricular Tachycardia) resides for narrow complex tachycardias.

This may work for Dick and Jane Call 911 and Watch Adults Treat a Tachycardia. As long as Dick and Jane are just calling 911, this is probably not dangerous. It is when you progress beyond Dick and Jane Don’t Do Diddly to a higher level, such as EMT, that you need to recognize how flawed this bi-polar approach is. Tachycardia is not a word that belongs in a Dick and Jane book. Likewise, those limited to monosyllabic expression should not be treating tachycardias. Duh!

For the young man described by TOTWTYTR, the age is 80 years. Using this formula, we can see that his heart rate is greater than his calculated maximum heart rate. 220 – 80 = 140. His rhythm is narrow complex. The rate is 150. Therefore, according to the Formula for Oversimplification and Execution, he has an SVT (possibly a rapid Atrial Fibrillation or VT).

If you approach this patient as having any of those conditions, you would be justified in zapping his heart to a standstill. This is because the arrhythmias listed can be improved with cardioversion. The problem with this patient, although I cannot see the rhythm to identify it, is probably not one of these arrhythmias. Mr. Geezer appears to be having a heart attack. This is something that may cause significant stress. His heart is racing. Perhaps trying to get as many beats in before retirement.

Another example of the folly of this simplistic rule of maximum calculated heart rate is a bit more personal for me. While working out, I often get my heart rate well above my calculated maximum heart rate for extended periods. And yet, I manage to cool down afterward without adenosine, without amiodarone, without cardioversion. It is almost as if I were not violating rules of nature. :)

What are the options?

Antiarrhythmic drug/cardioversion – bad ideas in my opinion.

Beta agonist (dopamine) – bad idea in my opinion.

Beta blocker (Lopressor) – if you have strong reasons for suspecting LVOTO, this may be a good idea. If you believe that the heart rate is the primary problem and fluid is not a problem, ditto.

Fluid – BP of 68/palp (which might translate to an auscultated BP of 78/?) appears to have brought the pressure up to 88/palp (which might translate to an auscultated BP of 98/?).

Mr. Geezer has had aspirin. He is receiving oxygen. He received fluid and now his pressure is probably above 90 systolic.

Why would dopamine be a good idea?

Dopamine is for people who do not improve with fluids.

Is there a more basic understanding of the use of dopamine than that? True, dopamine is used when fluids are contraindicated, but that does not mean that dopamine comes before fluids in other cases.

Dopamine should be used only with reluctance for patients experiencing a heart attack. Dopamine can be a very dangerous drug for a patient having a heart attack. Mr. Geezer appears to be having a heart attack. He appears to be improving with fluids. He does not appear to be someone who would benefit from dopamine – unless things change.

Do we have enough information to decide about LVOTO? I don’t think so.

The patient appears to be improving enough to take the 4 minute ride to the hospital without further treatment, in my opinion.

Perhaps Dr. Rumble Fish (medical command) should avoid the martial arts orders. This patient has a huge potential to get worse, a short transport time, appears to be improving with treatment, and no good reason to explore experimental therapy.

Footnotes:

^ 1 (Circulation. 2005;112:IV-58 – IV-66.)
© 2005 American Heart Association, Inc.
2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Part 8: Stabilization of the Patient With Acute Coronary Syndromes

^ 2 Lopressor (metoprolol tartrate) injection, solution; DailyMed

^ 3 Dopamine hydrochloride and dextrose (Dopamine Hydrochloride and Dextrose) injection, solution; DailyMed

^ 4 Dynamic Left Ventricular Outflow Tract Obstruction in Acute Myocardial Infarction With Shock: Cause, Effect, and Coincidence
Anand Chockalingam, Lokesh Tejwani, Kul Aggarwal, and Kevin C. Dellsperger
Circulation. 2007;116:e110-e113, doi:10.1161/CIRCULATIONAHA.107.711697
FREE Full Text | FREE PDF – At least they appear to give full access for free.

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Comments

  1. Thank you for including citations in your writing, I appreciate being able to find the referenced articles. I don’t believe I’ve ever commented so I just wanted to say thanks for your thoughtful writing.

  2. Jen,Thank you for the kind words. I try to keep it understandable for everybody reading. If I am not making myself clear, maybe I am the one who is misunderstanding something. Feel free to ask for clarification or to disagree with anything I write.

  3. Interesting case. Correct me if I’m wrong but doesn’t SVT often have ST/TW changes that mimic STE?

  4. Completely agree. The problem is dopamine is a bad idea. Adding a beta blocker to dopamine is an extremely bad idea. This patient has radial pulses before his pressure improves. Why add dopamine when fluids appear to be working? I have never given dopamine to a patient with radial pulses and an improving BP?

  5. John,I don’t know how often SVT presents with ST elevation, but I don’t believe that it is common. At a rate of 150, with narrow QRS complexes, you probably should be able to see P waves.If it were an arrhythmia, then I don’t think that the fluid bolus would have resulted in such an improvement in the blood pressure. Of course, that is assuming that the fluid caused the change in blood pressure, which is far from certain.

  6. first rule of fire,Excellent point about the radial pulses. We should not even be considering dopamine in a patient, who appears to have adequate peripheral perfusion and appears to be improving.Dopamine is to keep the patient from getting worse. It is Epinephrine Light. When it comes to using sledge hammers on insects, this is just switching from a 10 pound sledge to a 5 pound sledge – still the wrong tool for the job.No, the patient is not a happy camper, but he appears to be getting closer to happy. 🙂

  7. Gang, is it time to review pharmacology? Dopamine acts as a beta agonist, but because it’s not terribly selective, it also acts as an alpha agonist. Metoprolol acts as a beta blocker and, because it’s highly selective, has relatively few alpha effects. So we might expect a patient who received appropriate doses of both dopamine and metoprolol to experience no net change in his beta activity. But his alpha activity would increase. Wouldn’t some peripheral vasoconstriction push our patient’s central blood pressure upwards?Dopamine alone probably would have been harmful to TOTWTYTR’s patient. Metoprolol alone might also have been harmful (depending upon the heart’s position on the Starling curve.) But the combination seems potentially useful to me — and well within an emergency physician’s scope of practice to order.Surely TOTWTYTR knows his medical command physician better than we do; perhaps he’s a numbskull, perhaps not. We could second-guess the appropriateness of hanging a drip only 4 minutes from the ED. But on its face, the physician’s order does not seem utterly unreasonable to me.

  8. Anonymous,I could not keep it simple, so I wrote a post in response to your comments. They are good comments. I just think it is getting more than a bit too aggressive with medicines for EMS.

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