Nursing Field Notes / Cardiac Pharmacology · Series: Antidysrhythmics 2 of 4

Antidysrhythmics series ← 1 · The 4 classes 2 · ABCDs — atrial 3 · C & D → 4 · LAP →

Antidysrhythmics II 🫀

The ABCDs — atrial rhythm drugs · Atropine · Adenosine · Beta blockers

NG-057 CARDIO PHARM ADHD-friendly visual edition

Page 1 sorted the drugs by channel. This page sorts them by where in the heart they land. ABCD drugs work at the TOP of the heart — the SA node and the AV node — so they fix atrial and nodal rhythms. Two of them are opposites: atropine speeds a slow heart UP, adenosine slams a fast heart DOWN. Learn them as a pair and you can never mix them up.

📄 Simple Nursing original — opens in Drive →

🔤 ABCD = top · LAP = bottomAtropine · Adenosine · Beta blockers · CCBs · Digoxin all aim at the SA/AV node.

🌲 atroPINE = HIGH like a pineHeart rate too LOW with symptoms → atropine pushes it UP toward 60–100.

🦊 adenosine = into the DENSuper Fast = SVT. Give it FAST — IV push over 1–2 seconds, then flush.

💊 -LOL lowers the 2 L'sLow heart rate · Low blood pressure. Bradycardia · Bronchospasm · Blood sugar masking · Bad in HF.

🗺️

THE ABCD MAP

STEP 1 · WHERE THEY LAND

One picture decides everything: is the problem at the top of the heart or the bottom?

🤖 Meet Sparky, your rhythm robot — she only says one thing

🧠 Start at the TOP and walk the alphabet down. A-B-C-D live upstairs at the SA and AV node = atrial and nodal rhythms. L-A-P lives downstairs in the ventricles (page 4) — like something sitting in your lap.

🫀 The heart, cut open — and the two neighborhoods these drugs work in

🧠 “Upstairs is a traffic problem. Downstairs is a house fire.” Upstairs rhythms mostly change the rate — you have time to give a drug. Downstairs rhythms kill the pump — you reach for electricity first.

⭐ Count the rate the way the NCLEX counts it

Answer first: count the R waves in a 6-second strip and multiply by 10. That is the whole trick.

🧠 “Count 8, add a zero.” 8 × 10 = 80. On a bradycardia strip you will only find 4–5 R waves — that is your 40–50.

🧪 The one question that sorts every rhythm on this page

Answer first: before you pick a drug, ask too slow, or too fast?

Too slow (<60) with symptoms → atropine, then pacing
Too fast & narrow & regular (150–250) → vagal, then adenosine
Too fast & irregular (A-fib / A-flutter) → rate control: beta blocker, or a CCB (page 3)
Fast + unstable (low BP, altered, chest pain) → synchronized cardioversion, not a drug

Unstable means the rhythm has stopped perfusing: SBP < 90, altered mental status, chest pain, shortness of breath, cold clammy skin. Electricity beats pharmacology every time.

🧠 “Slow → speed it. Fast → slow it. Crashing → shock it.”

📊 The three drugs on one line

Drug	Given for	What it does to the rate	The #1 thing to watch
Atropine anticholinergic	Symptomatic bradycardia	Rate goes UP ⬆	Tachycardia, urinary retention, dry mouth, confusion in older adults
Adenosine AV nodal blocker	SVT (stable, narrow, regular)	Rate slams DOWN ⬇ — brief pause	Short asystole, flushing, chest tightness, "doom" feeling — expected
Beta blockers -olol	HTN · SVT · sinus tach · rate control in A-fib / A-flutter	Rate eases DOWN ⬇ and stays there	Bradycardia + hypotension, bronchospasm, masked hypoglycemia

🧠 One is the gas pedal, two are the brake. Atropine = gas. Adenosine = the emergency brake (a hard, brief stomp). Beta blocker = the parking brake (gentle and long-lasting).

⬆️

AATROPINE

STEP 2 · SPEED IT UP

Puts the heart rate really HIGH — like sitting on top of a PINE tree. atroPINE.

⚡ How it works — it cuts the brake cable, it does not press the gas

🧠 “Atropine doesn't push the gas — it cuts the brake cable.” That is why every atropine side effect is just “the parasympathetic system switched off” somewhere else in the body.

🚨 Give it for SYMPTOMATIC bradycardia — not just a low number

Answer first: a rate under 60 is only a problem when the client shows signs of poor perfusion.

🧠 Mental status changes — confusion, agitation, "just not acting right", dizziness
💙 Pale, dusky, cyanotic or cool clammy skin
📉 Hypotension — the classic stem reads 88/65
😮‍💨 Chest pain, dyspnea, syncope or near-syncope

A sleeping marathon runner with a heart rate of 48 and a clear head does not get atropine. An athlete's resting bradycardia is normal for them.

🧠 “Treat the client, not the number.” The word symptomatic is doing all the work in that question stem — circle it.

✅ How it's given — and the goal

IV push, on a continuous ECG monitor. Standard adult ACLS dosing is 1 mg IV every 3–5 minutes to a maximum of 3 mg — always confirm your facility's protocol.
Goal: get back to normal sinus rhythm, 60–100, evenly spaced, with a P wave before every QRS — and the symptoms gone.
If atropine fails: transcutaneous pacing, and/or a dopamine or epinephrine infusion. Have the pacer pads on the client before you need them.

Push it fast. A slow atropine push can paradoxically worsen bradycardia. Give it as a rapid bolus, not a slow drip.

🧠 “A-PINE grows tall.” The rate should climb after each dose. If it doesn't, you're going to pacing.

⭐ TOP MISSED TEST QUESTION — “which strip shows the medication worked?”

A client has a heart rate of 38, a BP of 88/65, and reports confusion and dizziness. Atropine is given. Which ECG strip shows the medication was effective?

▼ after atropine ▼

The correct answer is the strip with 8 R waves in 6 seconds (rate 80), evenly spaced, P before every QRS. Not the fastest strip, not the most "active-looking" strip — the normal one.

❌ A strip at 140 is not success — that's overshoot into tachycardia.
❌ A chaotic strip with no P waves is not success — that's a new dysrhythmia.
✅ Success = rate 60–100 · regular · P before every QRS · symptoms resolved.

🧠 “Effective = boring.” When the exam asks whether a rhythm drug worked, the right strip is always the most ordinary-looking one on the page.

⚠️ Side effects — everything dries up, slows down, or blurs

Answer first: block the parasympathetic system everywhere and you get the classic anticholinergic picture.

👁️Can't SEEblurred vision, dilated pupils, photophobia

🚽Can't PEEurinary retention

👄Can't SPITdry mouth

💩Can't POOPconstipation, ↓ bowel sounds

🥵Can't SWEAThot, flushed, dry skin — overheating risk

🧠Confusionespecially in older adults

Use caution in: narrow-angle glaucoma, BPH / urinary retention, and myasthenia gravis.

🧠 “Blind as a bat, dry as a bone, red as a beet, mad as a hatter, hot as a hare.” The oldest mnemonic in pharmacology, and it is still the whole side-effect list.

❌ When atropine will NOT work

Answer first: atropine works at the AV node. If the block is below the node, there is nothing for it to unblock.

Mobitz II second-degree block and third-degree (complete) heart block with a wide QRS — atropine is unlikely to help and pacing is the answer.
Hypoxia-driven bradycardia — fix the airway and oxygen first. A bradycardic hypoxic client needs oxygen, not a rate drug.
Bradycardia in a child is almost always hypoxia until proven otherwise — oxygenate and ventilate before you reach for any drug.

🧠 “Wide and blocked = pace it.” A wide QRS in a slow rhythm means the signal is coming from far downstream — atropine can't reach that far.

⬇️

AADENOSINE

STEP 3 · SLAM IT DOWN

DEcreases the heart rate — like sending the fox DEN-wards, Downstairs. Full drug page: NG-094.

🚨 Know how this rhythm looks — Super Fast = SVT

Reading it: narrow QRS (the signal came from above the ventricles) · regular · 150–250 bpm · you cannot find a P wave because it is buried in the previous T wave.

Causes: stimulants (caffeine, energy drinks, decongestants, cocaine), strenuous exercise, hypoxia, fever, anxiety, underlying heart disease.
Feels like: sudden pounding palpitations that start and stop abruptly, chest flutter, lightheadedness, anxiety.

🧠 “SVT = Super Very Turbo.” Super Fast = Supraventricular. Narrow and fast and regular — one look and you know.

✅ The order of operations for stable SVT

Is the client STABLE? Check BP, level of consciousness, chest pain, skin. Unstable → synchronized cardioversion, immediately.

▼

Vagal maneuvers first. Have the client bear down like they're having a bowel movement (Valsalva), or apply ice-cold stimulation to the face. Free, fast, and it works often enough to try.

▼

Adenosine — rapid IV push with an immediate flush. Standard adult dosing is 6 mg rapid IV push, then 12 mg if it does not convert — always confirm your facility's protocol.

▼

Still in SVT → a beta blocker or a calcium channel blocker (page 3), or synchronized cardioversion.

KAPLAN-style trap: a client in SVT with HR 200 · BP 78/40 · RR 30 is unstable. The priority action is synchronized cardioversion — not adenosine, not a vagal maneuver.

🧠 “Vagal · Adenosine · Cardioversion” = V-A-C, in that order — unless the client is crashing, in which case you skip straight to the shock.

⭐ THE two key points — this is what gets tested

🧠 “FAST in, FLUSH after, ARM up.” 1–2 second push · 20 mL saline chaser · elevate. Skip any one of the three and the drug never reaches the AV node.

🚨 Warn the client FIRST — the heart is supposed to stop for a moment

Answer first: a brief pause / asystole on the monitor after the push is expected, not an emergency. It is the AV node rebooting.

😳 Flushing — a hot, red wave over the face and chest
🫁 Chest tightness or pressure, shortness of breath
😨 A "feeling of impending doom" — clients describe it as terrifying
⏱️ It all passes in seconds because the half-life is that short

What you say beforehand: "This medicine works in about ten seconds. You may feel flushed, a heavy squeeze in your chest, and like something is very wrong. That means it's working, and it passes almost immediately. I will be right here."

Cautions: avoid in 2nd-degree (Mobitz II) or 3rd-degree AV block and sick sinus syndrome without a pacemaker. Use caution in asthma / bronchospastic disease. Caffeine and theophylline blunt it (they block the same receptor); dipyridamole and carbamazepine intensify it.

🧠 “Into the DEN.” Adenosine sends the heart into its den for a few seconds — dark, quiet, flatline — and then it comes back out at a normal rate.

🅱️

BBETA BLOCKERS

STEP 4 · THE BRAKES

Names end in -olol. Full drug page: NG-176 · they are Vaughan-Williams Class II (see NG-019).

🎯 Two receptors, two very different consequences

🧠 “β₁ = ONE heart · β₂ = TWO lungs.” Cardioselective drugs (metoprolol, atenolol, esmolol — the ones starting A–M) mostly spare β₂; propranolol hits both. Selectivity is lost at higher doses, so asthma is still a caution.

🚨 The 4 B's — memorize these as the side-effect list

B — Bradycardia (HR below 60) and low BP
B — Bronchospasm — avoid in asthma and COPD
B — Blood glucose masking — the drug hides the tachycardia, tremor and palpitations of hypoglycemia. Diaphoresis is the warning sign that survives.
B — Bad for clients in decompensated / end-stage heart failure (it is negative inotropic; it is started only when the client is compensated and stable)

Plus: orthostatic hypotension — dizziness on standing. Teach slow position changes: lie → sit → dangle the legs → stand.

🧠 “-LOL lowers the two L's” — Low heart rate, Low blood pressure. Then add the 4 B's on top of it.

⭐ COMMON QUESTION — “what drug caused this rhythm?”

5 R waves in 6 seconds × 10 = a rate of 50. Regular, P before every QRS, narrow — this is sinus bradycardia, not a block and not a new dysrhythmia.

Answer: a beta blocker (the classic stem names propranolol). Digoxin and calcium channel blockers can do the same thing — see page 3.

🧠 Slow + regular + P waves present + a drug on the MAR ending in -olol = you found your culprit.

✅ Before you give it, and what you teach

Before EVERY dose:

Apical pulse for a full 60 seconds + blood pressure
Common hold parameters: HR < 60 or SBP < 90 — always follow the provider's written parameters
Hold and notify the provider rather than skipping silently
Listen to lung sounds if the client has any airway history

What the client must hear:

Never stop a beta blocker abruptly — rebound tachycardia, hypertension, angina and even MI
Take your own pulse daily and record it; report a rate under 60
Change position slowly — sit on the edge of the bed before standing
If you have diabetes, check your sugar more often — the racing-heart warning is gone; sweating is still there
Report new wheezing, weight gain, swelling or worsening shortness of breath

🧠 “Pulse, Pressure, Position, Persist.” Check the Pulse and Pressure, teach slow Position changes, and Persist with the drug — never stop it cold.

⚡

QUICK RECALL

SAY IT OUT LOUD

🌲 atroPINE = up a PINESymptomatic bradycardia. Goal = NSR 60–100, evenly spaced, P before every QRS.

🦊 adenosine → the DENSVT. 1–2 second IV push + 20 mL flush + elevate. A pause is expected.

💊 -LOL = the 4 B'sBradycardia · Bronchospasm · Blood sugar masking · Bad in heart failure.

🔢 6-second × 108 R waves = 80. 5 R waves = 50. 4 R waves = 40.

🎯 Cover & check — 7 rapid-fire questions

Q1: What does the ABCD mnemonic tell you about where these drugs work?

They work at the TOP of the heart — the SA node and AV node — so they treat atrial and nodal rhythms: sinus brady, sinus tach, SVT, A-fib and A-flutter. LAP drugs (page 4) work at the bottom, in the ventricles.

Q2: A client has a heart rate of 46 and is asleep, alert when woken, BP 118/72. Does she get atropine?

No. Atropine is for symptomatic bradycardia — hypotension, altered mental status, chest pain, dyspnea, pale/dusky skin. A well-perfused client with a low rate is monitored, not medicated.

Q3: Which strip shows atropine was effective?

The one with a rate of 60–100 (about 6–10 R waves in a 6-second strip), evenly spaced, with a P wave before every QRS — and resolved symptoms. Not a tachycardic strip and not a chaotic one.

Q4: How do you give adenosine, and what do you do immediately after?

Rapid IV push over 1–2 seconds into the largest, most proximal vein (antecubital), immediately followed by a 20 mL normal saline flush, then elevate the arm. Run a continuous ECG strip through the push. Its half-life is under 10 seconds.

Q5: The monitor shows a few seconds of flatline right after the adenosine push. What do you do?

Stay with the client and keep watching — a brief pause/asystole is the expected effect while the AV node resets. Assess the client (responsiveness, pulse), and expect sinus rhythm to return within seconds. The client should have been warned about flushing, chest tightness and a feeling of doom beforehand.

Q6: A client in SVT has HR 200, BP 78/40, RR 30. Priority action?

Synchronized cardioversion. The client is unstable — electricity comes before pharmacology.

Q7: Why is propranolol a problem for a client with asthma, but metoprolol less so?

Propranolol is non-selective — it blocks β₂ receptors in the bronchioles as well as β₁ in the heart, causing bronchoconstriction. Metoprolol is cardioselective (mostly β₁), though selectivity is lost at higher doses, so caution still applies.