Before We Start
Four drugs that can restart a heart or reverse a crisis — in seconds
In a cardiac arrest or emergency, a nurse does not have time to look up drug names. The crash cart is open, the team is working, and someone needs to draw up the right medication right now. LEAN gives you the four most critical emergency drugs in one four-letter word that you can recall under pressure.
These four drugs — Lidocaine, Epinephrine, Atropine, and Narcan — cover the four most common emergency scenarios: ventricular arrhythmia, cardiac arrest, bradycardia, and opioid overdose. Learn them cold.
💡 ACLS Context
LEAN comes from ACLS (Advanced Cardiovascular Life Support) training. As a nurse, you may not be the provider directing the code — but you will be the one drawing up medications, pushing drugs, and documenting. Knowing what each drug does, when it is used, and what dose to prepare makes you an effective code team member. In many facilities, nurses also run rapid response calls where these drugs may be the first-line intervention.
The Mnemonic
LEAN — four emergency drugs every nurse knows cold
L — Lidocaine
Ventricular arrhythmias — the heart is beating chaotically
Lidocaine is a Class IB antiarrhythmic — it stabilizes the electrical activity of cardiac cells by blocking sodium channels. When the ventricles are firing in a dangerous, disorganized pattern, lidocaine slows and regulates that firing.
When it's used:
• Ventricular tachycardia (V-tach) — the heart is beating dangerously fast from the ventricles
• Ventricular fibrillation (V-fib) — the heart is quivering randomly, not pumping at all
• Used in the post-defibrillation period to prevent arrhythmia recurrence
Important nursing points:
• Lidocaine is also a local anesthetic (same drug used in your dental office)
• IV administration in emergencies — cardiac monitoring required
• Toxicity signs: SAMS — Slurred speech, Altered CNS, Muscle twitching, Seizures
• Overdose of lidocaine causes the very cardiac arrhythmias it is supposed to treat
💊 "Lido for the lethal rhythms" — Lidocaine is your drug when the ventricles are the problem. V-tach and V-fib kill because the heart stops pumping blood effectively. Lidocaine stabilizes the electrical chaos.
E — Epinephrine
Cardiac arrest — the heart has stopped, and you need to restart it
Epinephrine (adrenaline) is the most important drug in cardiac arrest. It stimulates both alpha and beta adrenergic receptors — causing vasoconstriction, increasing heart rate, and increasing the force of cardiac contractions.
Why epinephrine in arrest: During CPR, blood flow is inadequate. Epinephrine's vasoconstriction increases coronary perfusion pressure — it forces more blood into the coronary arteries so the heart has oxygen to restart. It also increases the likelihood that defibrillation will work.
ACLS dose: 1mg IV/IO every 3–5 minutes during cardiac arrest. Given while CPR continues — you don't stop compressions to give epinephrine.
Other uses of epinephrine:
• Anaphylaxis — 0.3–0.5mg IM into outer thigh (EpiPen)
• Severe bronchospasm
• Septic shock (as a vasopressor)
💊 Epinephrine is always in the code. 1mg IV every 3–5 minutes, alternating with CPR and defibrillation. Know the dose. Know the route. Know the timing. In a code, this is drawn up and ready before it is ordered.
A — Atropine
Bradycardia — the heart is beating too slowly
Atropine is an anticholinergic drug — it blocks the parasympathetic (vagal) signals that slow the heart. By blocking vagal tone, atropine speeds up the heart rate.
When it's used:
• Symptomatic bradycardia — HR below 60 with symptoms (hypotension, dizziness, chest pain, altered LOC)
• Bradycardia with hemodynamic instability
• Organophosphate (pesticide) poisoning — atropine blocks the cholinergic overdrive
ACLS dose for bradycardia: 0.5–1mg IV, may repeat every 3–5 minutes, max 3mg
Remember: Atropine works at the SA node and AV node — it speeds up the node that is firing too slowly. It does NOT work well in second-degree Type II or third-degree (complete) heart block — those patients need a pacemaker, not atropine.
Side effects — think OPPOSITE of the 4 Can'ts: Dry mouth, urinary retention, blurred vision, constipation, tachycardia, confusion (especially in elderly).
💊 "A for Atropine, A for too sloooow" — the heart is beating so slowly that not enough blood is reaching the brain and vital organs. Atropine kicks off the parasympathetic brake. If atropine doesn't work, the next step is transcutaneous pacing.
N — Narcan (Naloxone)
Opioid overdose — the antidote that reverses everything
Naloxone is a pure opioid antagonist — it competitively displaces opioids from receptors and reverses all opioid effects within 1–2 minutes. It has no effect of its own — it only works if opioids are present.
When it's used:
• Opioid overdose (hospital or community) — the opioid triad: pinpoint pupils, respiratory depression, unconsciousness
• Respiratory depression from therapeutic opioid doses in sensitive patients
• Post-operative opioid reversal when needed
Routes and doses:
• IV: 0.4–2mg — fastest, titrate carefully
• IM: 0.4–2mg — reliable when no IV access
• Intranasal: 4mg spray (Narcan nasal spray) — used in community setting
Duration warning: Narcan lasts 30–90 minutes. Most opioids last much longer. Monitor for re-narcotization — the patient can return to respiratory depression after Narcan wears off. Repeat dosing or a continuous infusion may be needed.
💊 Narcan is in LEAN because opioid overdose has become one of the most common emergency presentations nurses encounter — in hospitals, EDs, and in the community. Know the nasal spray route as well as IV. In many states, nurses can administer Narcan without a physician order in an emergency.
🏥 Clinical Scenario — Rapid Response, Room 8
You respond to a rapid response call on a medical floor. The patient, Mr. Torres, 68 years old, is found pulseless and not breathing. CPR has been started by the floor nurse. You arrive as the medication nurse.
L
Rhythm check after 2 minutes CPR: Monitor shows ventricular fibrillation. Shock delivered. Post-shock rhythm: still V-fib with some organized complexes. Team leader calls: "Lidocaine 1–1.5mg/kg IV push." You draw up lidocaine 100mg (for a 70kg patient) and push it IV over 60–90 seconds during CPR. Rationale: stabilize the chaotic ventricular firing to make the next shock more effective.
E
Epinephrine called: "Epi 1mg IV now, repeat every 3–5 minutes." You draw up epinephrine 1mg from a 1:10,000 solution (1mg/10mL) and push IV while CPR continues. No pause in compressions. Team leader notes time — next dose in 3–5 minutes if still in arrest.
A
Rhythm converts: After second shock + lidocaine + epi, rhythm converts to sinus bradycardia — rate 34, BP 78/50, patient not yet conscious. "Atropine 1mg IV." You push atropine. One minute later: rate increases to 58, BP 92/60. Patient beginning to respond. Transcutaneous pacing on standby.
N
Post-resuscitation review: Patient was on a fentanyl patch for chronic pain. Patch found on his back — 100mcg/hr patch, placed yesterday. Team leader asks: "Is this fentanyl-related?" RN notes pinpoint pupils in now-arousable patient. Narcan 0.4mg IV given cautiously — titrated to maintain respirations without reversing all analgesia. Fentanyl patch removed. ICU transfer arranged.
📌 NCLEX Application
LEAN appears on NCLEX in several ways:
Drug selection questions: "Which medication would the nurse prepare for a patient in symptomatic bradycardia with a HR of 38 and BP of 80/50?" → Atropine (A in LEAN).
Cardiac arrest drug questions: "During CPR for a patient in ventricular fibrillation, which medication would the nurse anticipate administering?" → Epinephrine 1mg IV every 3–5 minutes (E in LEAN).
Overdose recognition questions: "A patient is found unresponsive with a respiratory rate of 6 and pinpoint pupils. Which drug does the nurse prepare?" → Naloxone/Narcan (N in LEAN).
Key NCLEX fact: In cardiac arrest, the nurse does NOT stop CPR to give medications. Epinephrine is given IV push WHILE compressions continue. Stopping CPR to give a drug is an incorrect action on NCLEX.
⚠️ The Trap — Atropine in Complete Heart Block
Students learn "atropine for bradycardia" and apply it universally. But atropine does NOT work for all bradycardias — and using it in the wrong type can waste precious time.
Why atropine fails in complete heart block: In third-degree (complete) AV block, the atria and ventricles are beating independently — the electrical signal from the SA node is completely blocked from reaching the ventricles. Atropine speeds up the SA node, but if that signal can't get through the AV node to the ventricles, increasing SA node rate does nothing for the ventricular rate.
What these patients need: Transcutaneous pacing (TCP) — external electrical pacing applied through pads on the chest. This bypasses the damaged conduction system entirely and directly paces the ventricles.
NCLEX application: A patient in third-degree heart block with HR 28 and BP 70/40 — atropine is tried first per ACLS protocol, but if it doesn't work, the next answer is transcutaneous pacing — not more atropine.
✓ Quick Self-Test
Answer before checking:
1. What does LEAN stand for?
2. In cardiac arrest, which LEAN drug is given every 3–5 minutes IV?
3. A patient has a HR of 38 with dizziness and BP of 82/50. Which LEAN drug is indicated?
4. Why must you continue monitoring after giving Narcan?
5. Which type of heart block does NOT respond well to atropine?
Answers:
1. Lidocaine, Epinephrine, Atropine, Narcan (Naloxone).
2. Epinephrine — 1mg IV every 3–5 minutes during cardiac arrest. Given while CPR continues.
3. Atropine — symptomatic bradycardia with hemodynamic instability. Start with 0.5–1mg IV.
4. Narcan lasts 30–90 minutes. The opioid may last longer. Re-narcotization (return of respiratory depression) can occur when Narcan wears off before the opioid clears.
5. Second-degree Type II (Mobitz II) and third-degree (complete) AV block. Atropine speeds up the SA node but cannot overcome a blocked AV node. Transcutaneous pacing is required.