“She’s a little light-headed and her heart’s going really fast,” the officer says. “She needs you to run a tape on it.”

The woman, sitting on the couch, is pale and looks uncomfortable.

Her pulse is very rapid. Too fast for me to count.

She says this has been going on for twenty minutes. She had an episode that lasted fifteen minutes a few days ago, and just one episode a month before that lasted almost a half an hour. She made it to the doctor’s office. He felt her pulse and discovering it to be very rapid, ordered an ECG. The nurse at the patient’s request brought in a glass of cold water, which the patient drank while she put the electrodes on. When they did the 12-lead her heart was back to normal. Without the printout, the doctor said he couldn’t tell what was wrong.

“Well, let’s not give you a cold glass of water before we record you then,” I say. It is quite likely the cold water triggered the patient’s vagus nerve, which sent a signal to the heart, slowing it down, and giving it a chance to reset in a normal rhythm.


I attach the limb leads, and glance at the monitor.


A PSVT. Paroxysmal Supraventricular Tachycardia. I hit print.

“Consider yourself recorded.”

“You’re going to give me that recording so I can show the doctor?”

“Better than that,” I say, as I attach electrodes to my 12-lead cables. I’m going to take a more detailed picture of your heart, and then I’m going to fix you.”

“Are you going to give me a cold drink of water?”

“Perhaps, but let’s try a couple other things first.”

I instruct her to cough a couple times. No change in the rhythm. I have her bear down like she is going to the bathroom, “but don’t go,” I caution. No change. Both these maneuvers also activate the vagus nerve, which can sometimes slow the heart and help break the rhythm.

We try the cold water.

No change.

“I guess we’ll have to go the medicine route.”

The patient immediately reaches for her medication list to show me what she is already on, but I explain the medicine I am giving her — adenosine — will be IV.

Paramedic Favorite

Years ago I had two patients who were in PSVTs convert before I could give them the adenosine. One self-converted when we were carrying her down the stairs, another when we hit a bump in the road when I was drawing up the medicine. I was a younger medic then and deeply disappointed that I didn’t get to give the drug — a paramedic favorite because of its quick response in the patient condition when it works. Not only did I not give the drug, I failed to record a strip, thinking I had plenty of time. That started me recording a strip as soon as possible and also giving the drug on the spot. That worked well until the day I gave it to a patient sitting at his desk. Five seconds after I pushed the adenosine, the patient then slumped over on the desk in sudden ventricular tachycardia. Opps. A little known, but documented side effect. Now not only do I always get a 12-lead before I try to convert a patient, but I make certain the patient is on the stretcher first. If they are going to go out, I don’t want to have to worry about picking them up.

This woman has nice veins, which is great. Ideally, you want the biggest catheter you can get into the biggest vein you can find closest to the heart. I’m not talking a 12 in the jugular (a neck vein), but if you can put an 18 in the AC — the vein in the crook of the elbow, that is great. IV catheter sizes get bigger as the number gets smaller. Most medics just carry a selection from the tiny 24 to the large bore 14. (Some carry a 12 for needle decompressions.) You want the big vein close to the heart because the drug lasts for such a short time (adenosine’s half life is 10 seconds), you need to get it to the heart before it is deanimated.

I have at times had to settle for hand veins, and a couple times have done it successfully with a 24 in the hand, but ideally the 18 in the AC is what you want. Out in the ambulance, I sink the IV and attach a saline lock. I then draw up the 6 mg (2 cc) dose of Adenosine in a 5 cc syringe (I use a 5 cc in case the drug doesn’t work, then I can use the same syringe for the second dose, which is 12 mg (4 cc) )and 10 cc of normal saline in another syringe. I stick both needles in the saline lock.


I push the adenosine and then rapidly fire the saline a split second later. Think of it as the 10 cc of saline being a rocket booster to hurtle the adenosine payload through the veins up through the vena cava and into the heart where it works its magic. (Be careful when you do this to hold the stopper down after you have fired the first syringe. If you don’t, when you fire the saline it may back up into the first syringe decreasing the pressure of the thrust.)

Uncomfortable Feeling

I still love giving the drug, but for the patient’s sake, I always try the vagal maneuvers first. If the vagal maneuvers don’t work, I hope the patient self-converts. Some people take to adenosine better than others. It can be very uncomfortable. The drug itself only lasts in the body about 15 seconds, but what it does is basically produce asystole -– flat line — until the heart can reset itself. The asystole usually only lasts a few seconds, but it can seem much longer.

“You may feel uncomfortable — it affects everyone differently — but keep in mind it only lasts for a few seconds — ten at most — and then is gone.”

“What do you mean by uncomfortable?” the woman asks.

“Some people feel chest pain, other just anxiety. It is different for everyone.”

What I don’t tell her is I have had people who have been treated both by being shocked without sedation and who have received adenosine on the other, and who would prefer I shock them they found the adenosine so unsettling. A patient once told me he they felt like he had died and left his body after I gave him the adenosine, and I have seen patients grab at the chest in sheer terror. I am hoping this one will go easier.

The terror can go both ways. The paramedic has to go through the experience of watching his patient flat line, praying for a beat, and then watching a whole bunch of funky beats and waiting for them to organize into a nice sustained sinus. The years and number of times I have given the drug have somewhat moderated my fear. And I will say it is much less scary for us now that we have the LP 12 monitors. When I started we had LP 5s and 10s which had a much smaller and shorter screen, so you really did see nothing but asystole. Now it is rare because the screen shows several seconds worth of time all at once as opposed to maybe only a second or two, so you never really see just a complete flat line on the screen anymore.

It’ll Pass

“Ready, here goes,” I say, as I fire first the five cc syringe and then the ten.”

I watch the monitor and see the sudden break in the rhythm, and say, “You should be feeling it now.”


“I’m feeling it,” she says.

“It’ll pass, it’ll pass, and you should be feeling better.”

“Let’s hope so.” She looks like it starting to bother her.

“How about now?”


The rhythm is back to sinus.

“I am. That wasn’t too bad.”

“I’m glad for both of us.”


I do a repeat 12-lead, and spend the rest of the ride chatting with the patient. Sometimes I explain in advance what a drug does, but with adenosine, I wait until after to fully explain. I show them the strip and tell them how the drug temporarily stopped their heart.

The heart is very electrical. Each beat originates with an electrical spark in the SA node. The electricity causes the atrium, the top chambers of the heart to contract, pumping blood to the ventricles below. The electricity has to go through a gate called the AV node, where it is delayed temporarily to allow the ventricles to fill with blood, and then the electricity continues down into the ventricles, causing them to contract and pump blood throughout the body. If there wasn’t a delay in the AV node, there ventricles would contract with no blood in them, and that would not be good at all.

In a PSVT, the AV node, instead of acting like a one-way door, suddenly becomes a revolving door. The electricity whirls around causing both chambers of the heart to fire very rapidly — I’ve seen it as high as 240. Because the heart is no longer pumping effectively, this can cause the patient to feel very light-headed and uncomfortable. The body of course cannot tolerate this indefinitely.

Adenosine acts like a stake in the whirling door. Stopping it cold From 170 beats a minute in this woman’s case; it is suddenly not beating at all. The heart then starts back on its own, and after a few funky beats, should resume its regular activity.

The dose of 6 mg, if properly flushed rapidly up to the heart, corrects the rhythm about 60% of the time. I have had several patients who I have had to give 12 mgs to. That I understand is effective a cumulative 92% of the time. If that doesn’t work, you can give a second 12 mg dose. Fail again, and it is time to consider shocking the patient. Adenosine won’t work if the patient has a rapid atrial fibrillation or another problem that originates above the AV node.

I always hope that six works, because if the patient has had a bad experience, I don’t have to try to convince them to let me do it again.

Six is the charm this time. At the hospital I make copies of the 12-leads and conversion strip, leaving one in the patient’s chart and handing her another so she can show it to her cardiologist if the other copy gets lost. The patient says she is not looking forward to spending the night in the hospital, but I tell her while it will be up to the doctor, in many cases, I have observed patients with resolved PSVTs simply be told to follow-up with their cardiologist and sent home. Sometimes they may be put on a beta blocker in the interim.

The next day I get a phone call that the patient stopped by the ambulance headquarters and left a thank you note and an assortment of Christmas cookies for my partner and me.

Here’s some more information on Adenosine


  • Kelsey says:

    Normally I just hook up a bag of NS, clamp the line above the most distal port, push the adenosine in the most distal port, and then squeeze the bag of NS. It goes in pretty fast that way, I think. Don’t you also want the fluids hanging in case of hypotension, or continued SVT?

    What do you think, Peter?

  • medicscribe says:

    Hi Kelsey-

    The method you describe is pretty standard. I’ve seen the ED use that method at times. My unscientific belief is that my way (using a short saline lock and the dual syringe push) provides more force and delivers the drug to the heart quicker and more effectively than saline through gravity, but that is just my guess. I like my way, particuarly for when I can only get an IV in the forearm or hand. I’ve had pretty good luck with it.

    Once I have a lock in place, it is pretty easy to spike a bag and attach it to the lock should I need it. We use locks quite often instead of hanging bags. With permissive hypotension, I even use locks on most of my traumas. Bags can be a hassle to deal with from getting them tangled and yanking the IV out to not noticing a runaway IV when the patient shifts their arm position. I do agree with you that the fluids should be ready if needed, and if you think there is a good possibility you may use them, then you should go ahead and hang them.

    Thanks for the comment.

  • totwtytr says:

    I’m with Kelsey, I’ll hang a line most of the time. The potential problems you note can be avoided by paying close attention to details like where the IV is and how the drip rate is set.

    Here’s another question. I know a lot of people do it, but what’s the rationale for getting a 12 lead before giving Adenosine? Or Dilitiazem if you think it’s A Fib or A Flutter? I’d certainly get on afterward, if the rhythm broke, but I don’t see a lot of advantage to getting one before hand. If the 12 lead shows ischemia when the rate is rapid, chances are it’s rate related.

    If there is chest pain, it’s also likely rate related. This is a case where you have to fix the rhythm then do the 12 lead. Some medics want to give NTG to these patients to treat the pain, but they seem to have a poor understanding of the relationship between the SVT and the chest pain. If you slow the heart rate down to a sustainable rate, chances are you are going to relieve the pain.

    Just a few random thoughts.

    Maybe it’s just me.

    • medicscribe says:

      Thanks for the comments totwtytr,

      Our protocols request that we get a 12-lead before and after any conversion if feasible. The 12-lead doesn’t really change my care unless I am uncertain what the rhythm is (example, in the case of a wide complex tachycardia, is it an SVT with abberancy or VT). My guess it the 12 leads are useful to the patient’s cardiologist for followup treatment and care. They provide so much more information than any one lead. They confim the precise rhythm, shed light on where the problem lies and may save the patient a trip to the electrophysiology lab.

      I agree with you the problems I sighted can be avoided, but they still happen to me occasionally, so in most cases, unless I am going to run the fluid, I keep it on the shelf or on the bench ready to grab.

  • HwyMedic says:

    Is there documentation supporting this delivery method (2 syringe technique)? A colleague of mine claims the need for this is an EMS myth and we are just diluting the Adenosine. I’ve only been taught/seen your method or similar variations in my training and practice, my colleague is stubborn though and will only believe me if I provide him with documentation not from an EMS source.

    I like to do a 12-lead before converting, I’ve had what appeared to be SVT in leads I,II,III but clearly v-tach in the chest leads (V1-V6).

  • T says:

    Our protocols state that I can’t even THINK about treating an SVT/PSVT unless the patient has “evidence of serious signs and symptoms” which include hypotension, crushing chest pain, severe difficulty breathing, etc.

    I’m not even exaggerating. I wish I was.

    If they’re slightly lightheaded, have a 2/10 chest pain, and have a light shortness of breath, I CANNOT GIVE ADENOCARD.

  • Bob Buckley EMT-P(ret) says:

    I’m also with Kelsey, mostly because I’m an old dog and thats how I was taught. The use of NTG is a hand-me-down, cause we used to be under some impression that, treat the pain…the strip will follow,but at any rate, this is how we learn. Networking opinions, what works…what dosnt.

  • jayne says:

    I have a trick for a vagal maneuver that works so well. I take a O2 tubing and cut a piece out of the tubing about the lenght of a drinking straw. I pinch the far end and tell the patient to blow as hard as they can into the tubing. This works wonders and is easy for the patient to do. It converts allot of my PSVTs!

  • medicscribe says:

    Thanks for all the comments.

    Hyway Medic- There is no evidence for my way. It is how I was taught years ago and I have had success with it. It makes sense to me, but as so often happens in what we do can later be proved to be wrong. We medics like our special tricks of the trade. It would be a shame to find out it isn’t the best way. I’ll have to do a literature search and see if anyone has investigated this. I don’t see the dilution angle though. From that aspect it is no different than following the push by opening up a bag of fluid to run a bolus.

    T- Your serious signs and symptoms sound like our indications for shocking as opposed to a trial of medicine. I sat in on a VT lecture recently where the end point of the discussion was what is stable and unstable and what is a serious sign and symptom and when to wait, when to give a drug, or when to shock are all so variable with each call that it is best left up to the medic to make their choice based on everything they know and everything they see on that call, which I think can be applied to PSVTs or VTs. I am generally fairly liberal about medicine and extremely conservative about electricity. I am just recently opting for more vagal manuevers than I used to, which I do think is best for the patients. I should note that the 2005 AHA Guidelines seem to move backward toward your medical director’s angle by advising “expert consultation” in less dire cases, meaning call medical control or wait till the hospital. No fun for us.

    Jayne- I am anxious to try your method. I can see how that would effective and lessindelicate than telling someone to bear down like they are going to the bathroom.

    Bob-So much of what we learn is handed down to us, and then we play with it and either hand it down or cast it off. I wrote this piece, and have thought of writing similar ones, aimed at new medics. It seems when I am precepting, we do a call, and then I sit my preceptee down and hold court on all the similar calls I have had and the various tricks I use. It is good to hear from other people about the way they do it and what they been taught both by those who came before and their own experience. While I am a firm believer in evidenced based medicine, much of what we do hasn’t been studied. I wish I did more SVTs. I only gave adenosine twice in the last year. While I once gave it twice in a day, I likely won’t give it enough in the future to test out all the ideas I have in my mind now. My results would only be anecdotal. Maybe I can find a service willing to do a project. Start by comparing vagal manuvers, and then if the rhythm persists, comparing the syringe blast with the saline bag wide open.

    Thanks again for all the great comments. I’m always anxious to hear how other medics do the job.

    Happy Holidays,

    Peter C

  • medicscribe says:

    I did some further checking this morning and came up with the following:

    1. From the drug insert:

    Dosage and Administration
    For rapid bolus intravenous use only.
    Adenocard (adenosine injection) should be given as a rapid bolus by the peripheral intravenous route. To be certain the solution reaches the systemic circulation, it should be administered either directly into a vein or, if given into an IV line, it should be given as close to the patient as possible and followed by a rapid saline flush.

    2. This is from the Merck Manual on-line:

    Administration: I.V.
    For rapid bolus I.V. use only; administer I.V. push over 1-2 seconds at a peripheral I.V. site as proximal as possible to trunk (not in lower arm, hand, lower leg, or foot); follow each bolus with a rapid normal saline flush (?5 mL). Use of 2 syringes (one with adenosine dose and the other with NS flush) connected to a T-connector or stopcock is recommended (ACLS, 2005).

    When I looked in my AHA and ACLS texts, I couln’t find the specific mention of the two syringes. Here is what I did find.

    3. AHA

    If reentry SVT does not respond to vagal maneuvers, give 6 mg of IV adenosine as a rapid IV push (Class I). Give adenosine rapidly over 1 to 3 seconds through a large (eg, antecubital) vein followed by a 20-mL saline flush and elevation of the arm.

    The specific note of an amount of the flush (I’ve read variously 5, 10 or 20 and the term “flush” suggests to me they are talking about using a syringe. The elevation of the arm is again something I have heard of but never practiced. I will try to remember to do it next time.

  • Medic4Christ says:

    Very nice commments and discussion. I agree with medicscribe in the way adenosine is administered. I have done it from the NS bag hanging method and syringe flush, and the flush is much more effective and has a much higher successful conversion rate, especially with first 6 mg dose. It does not dilute the dose. It’s like putting a rocket booster on the shuttle to overcome the force of gravity using acceleration. With the short half-life this is a must. I made the mistake the first time I used it of waiting too long to push the syringe bolus and it didn’t convert with the first dose. I always have my second syringe ready but I’ve never used both like this. I like it and will try it. Another suggestion is: I always use a 8″ extension on the end of my IV setup. That way you have a saline lock if you want it or can easily hook up your line. Many of our med’s come with needleless and some with needles to this eliminates further complicates, as our extensions have both. Lastly, you should be treating your patient, not the monitor or one specific sign/symptom. Is the pt symtomatic or asymomatic and then base treatment on this. Some pt’s may not present serious and this is where the term “atypical” presentation comes in. RATE, RHYTHM, BP! Least evasive treatment should be considered first, but situations vary. What is best for your patient is what is to be done!! “To do no Harm!”

  • Medic4Christ says:

    Forgot. Could also be a-fib with aberrancy. So need to slow the rate down enough to see if Cardizem is needed. Sometimes a-fib rate is so fast (with RVR), hard to tell. So if Adenosine doesn’t work, then it’s probably afib or flutter or could even be junctional tach. If irregular and wide, then Amiodarance 150 mg over 10 min. should be used.

  • Magestic0o says:

    I want to quote your post in my blog. It can?
    And you et an account on Twitter?

  • medicscribe says:

    You can quote my post on your blog. I don’t have a twitter account.

    Medic4Christ, thanks for the comments. We use to use 3-way extensions all the time, but we stopped carrying them. Now we just have locks (we are actually called extensions thought they are only about four inches) and bags. You can screw off the end of the lock and screw in the bag if you need to. For awhile we carried prepackaged adenosine, which required me to screw on a needle to the end of the adenosine so I could do my double syringe.

    I did finally find the ACLS reccomendation for the double syringes. It is in the appendix of the 2005 Guidelines pocket handbook.

  • Vanessa says:

    I have PSVT and have been converted twice with Adenosine and it feels horrible, like an elephant sitting on our chest, I once went to the ER after 30 in V-tach, and a doctor said he learned this maneuver that usually works 90% of the time. Have the patient lay down and push down just below the rib cage like a Heimlich maneuver area but just pressure with your hands, continue to push down and it should convert.

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