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Adrenaline (Epinephrine) - Complete Easy Guide

What Is It?

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Mechanism of Action (How It Works)

The Two Key Pathways (from textbook diagrams):

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Dose-Dependent Effects (Very Important!)

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Indications (When to Use)

1. Anaphylaxis (FIRST-LINE, most important!)

• Treats bronchospasm (via β2)
• Reverses hypotension (via α1)
• Reduces mucosal edema

2. Cardiac Arrest (ACLS Protocol)

• Used in asystole, pulseless electrical activity (PEA), and pulseless VT/VF
• Works mainly via α1: raises coronary perfusion pressure and cerebral perfusion pressure during CPR
• Early use is especially important in non-shockable rhythms (asystole/PEA)

3. Bronchospasm / Severe Asthma

• Racemic epinephrine via nebulizer for croup (laryngeal edema)
• Reduces airway mucosal swelling

4. As a Vasoconstrictor (Adjunct to Local Anesthetics)

• Added to lidocaine for dental, ENT, plastic surgery, and orthopedic procedures
• Slows local anesthetic absorption → prolongs duration, reduces systemic toxicity, reduces bleeding

5. Symptomatic Bradycardia

• Used when unresponsive to atropine or pacing

6. Septic Shock / Cardiogenic Shock

• As a vasopressor/inotrope infusion

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Doses at a Glance

Remember the 1:1,000 vs 1:10,000 rule:

• 1:1,000 = 1 mg/mL → used for IM injection (anaphylaxis)
• 1:10,000 = 0.1 mg/mL → used for IV bolus (cardiac arrest)

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Contraindications

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Key Side Effects to Watch For

• Arrhythmias (most feared)
• Myocardial ischemia
• Hypertension / Stroke
• Pulmonary hypertension (increases pulmonary arterial pressure)
• Renal ischemia (intense renal vasoconstriction at high doses)
• Anxiety, tremor, headache

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Quick Memory Summary

"ABCS" of Adrenaline:

• Anaphylaxis (IM, first-line)
• Bradycardia / Bronchospasm
• Cardiac arrest (IV, 1 mg every 3-5 min)
• Shock (vasopressor infusion)

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💉 Adrenaline (Epinephrine) - Complete Easy Guide

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🔬 What Is It?

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⚙️ Mechanism of Action (How It Works)

Two Key Pathways:

Dose-Dependent Effect (KEY CONCEPT):

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💊 Indications (When to Use)

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📐 Doses + HOW TO DILUTE (Practical Guide)

Understanding the Concentrations First:

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🔴 ANAPHYLAXIS

• Route: IM into the outer thigh (anterolateral)
• Dose: 0.3-0.5 mg in adults | 0.01 mg/kg in children (max 0.5 mg)
• Dilution: Use 1:1,000 solution (1 mg/mL) - NO dilution needed for IM
• Draw up 0.3-0.5 mL from the 1 mg/mL vial → inject directly IM
• Can repeat every 5-15 minutes if needed

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🔴 CARDIAC ARREST (IV Bolus)

• Dose: 1 mg IV every 3-5 minutes
• How to dilute from 1:1,000 vial:
  • Take 1 mL of 1:1,000 (= 1 mg)
  • Add 9 mL of Normal Saline (0.9% NaCl)
  • = 10 mL of 1:10,000 solution (0.1 mg/mL)
  • Give the entire 10 mL as the IV bolus
• If you already have a 1:10,000 pre-filled syringe, give 10 mL directly

Memory trick: 1 + 9 = 10 → 1 mg in 10 mL = 1:10,000

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🟠 IV INFUSION (Shock / ICU)

• Dose: 0.01 to 0.2 mcg/kg/min (titrate to effect)
• How to prepare (standard mix):

• Always use an infusion pump - never free-flow
• Use a central line ideally (peripheral OK short-term for emergencies)

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🟠 CROUP (Nebulized)

• Dose: 0.5 mL/kg of 1:1,000 solution (max 5 mL)
• How to give: Add to nebulizer cup with 2-3 mL Normal Saline
• Use the 1:1,000 vial directly - no further dilution needed before adding to nebulizer

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🟡 WITH LOCAL ANESTHETICS (Surgery/Dental)

• Standard concentration: 1:100,000 (1 mcg per 0.1 mL)
• How to dilute from 1:1,000 vial:
  • Take 0.1 mL of 1:1,000 (= 0.1 mg = 100 mcg)
  • Add to 10 mL of local anesthetic (e.g., lidocaine)
  • = 1:100,000 final concentration
• For dental: pre-mixed 1:100,000 or 1:80,000 cartridges are standard

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Quick Dilution Cheat Sheet

STARTING VIAL: 1 mg/mL (1:1,000)
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├── IM Anaphylaxis → NO dilution → give 0.3-0.5 mL
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├── IV Cardiac Arrest → + 9 mL NS = 10 mL (1:10,000) → give ALL 10 mL
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├── IV Infusion → + 99 mL NS = 100 mL (10 mcg/mL) → pump
│
└── With local anesthetic → 0.1 mL + 10 mL LA = 1:100,000

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❌ Contraindications

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⚠️ Key Side Effects

• Arrhythmias (most feared)
• Hypertension / Stroke
• Myocardial ischemia
• Pulmonary hypertension
• Renal ischemia (high doses)
• Tremor, anxiety, headache, pallor

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🧠 Easy Memory Summary

"ABCDE" of Adrenaline Uses:

• A - Anaphylaxis (IM, 0.3-0.5 mg, 1:1,000)
• B - Bronchospasm/Bradycardia
• C - Cardiac arrest (IV, 1 mg, every 3-5 min)
• D - Drip for shock (infusion, 0.01-0.2 mcg/kg/min)
• E - Extend local anesthetics (1:100,000)

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💊 Nitroglycerin (GTN) - Complete Easy Guide

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🔬 What Is It?

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⚙️ Mechanism of Action (How It Works)

What Does This Relaxation Actually Do?

Simple analogy: NTG acts like loosening a tight belt (veins) so the heart doesn't have to pump so hard, AND opens up the pipes (coronary arteries) that supply the heart.

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✅ Indications (When to Use)

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❌ Contraindications (When NOT to Use)

Most important to remember: "Have you taken Viagra recently?" ALWAYS ask before giving NTG!

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💉 Routes, Doses, and HOW TO DILUTE

Available Forms:

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🔴 ACUTE ANGINA - Sublingual (Most Common Use)

• Dose: 0.3-0.4 mg sublingual tablet OR 1-2 sprays under tongue
• Repeat: Every 5 minutes, up to 3 doses in 15 minutes
• No dilution needed - ready to use
• If no relief after 3 doses → suspect ACS, start IV NTG

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🔴 IV INFUSION - Acute ACS / Pulmonary Edema / Hypertensive Emergency

• If normotensive: aim for ≤10% reduction in MAP
• If hypertensive: aim for 20-30% reduction in MAP
• Max dose: 200 mcg/min (for hypertension) | up to 400 mcg/min (for acute angina)

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How to Dilute for IV Infusion (Step-by-Step):

To run at 10 mcg/min → set pump to 6 mL/hr To run at 20 mcg/min → set pump to 12 mL/hr Formula: Rate (mL/hr) = Dose (mcg/min) × 60 / Concentration (mcg/mL)

Important: Use glass bottles or polypropylene tubing - NTG adsorbs (sticks) to standard PVC plastic tubing, which reduces the actual dose delivered!

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🟡 TOPICAL OINTMENT (2% Nitro-Bid)

• Dose in inches (1 inch = approximately 15 mg)
• Start: 0.5 to 1 inch applied to skin (chest, upper arm, or back)
• Increase to up to 2 inches if needed
• Apply every 6-8 hours with a 10-12 hour nitrate-free period overnight

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🟡 TRANSDERMAL PATCH (Nitro-Dur)

• Start: 0.2-0.4 mg/hr patch
• Titrate to 0.4-0.8 mg/hr
• Apply for 12 hours, remove for 12 hours (to prevent tolerance)

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🟡 ANGINA PROPHYLAXIS (before exertion)

• Sublingual: 0.3-0.4 mg, 5-10 minutes before activity
• Spray: 1-2 sprays, 5-10 minutes before activity

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⚠️ Side Effects

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🔄 Tolerance - The Nitrate-Free Interval

Exception: Variant angina (Prinzmetal) worsens in the morning - so these patients should have their nitrate-free period in the late afternoon instead.

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⏱️ Onset vs Duration (All Forms)

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🧠 Quick Memory Summary

"NTG = No Tension/pressure in the veins and arteries"

VEINS (preload) > Arteries (afterload) - remember this dominance!

"AVOID if: V-RICH"

• Viagra / Sildenafil (within 24-48 hrs)
• RV infarction
• ICP raised
• Cardiac shock / hypotension
• Hypovolemia

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Quick Dilution Card

NTG VIAL: 5 mg/mL (50 mg in 10 mL)
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├── SUBLINGUAL → NO dilution → 0.4 mg tablet or spray, q5min x 3
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├── IV 100 mcg/mL → 50 mg + 450 mL D5W = 500 mL
│    Start: 5-10 mcg/min → Rate: 3-6 mL/hr
│    Max: 200-400 mcg/min
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└── OINTMENT → Apply 0.5-2 inches to skin, no dilution
     Use POLYETHYLENE/GLASS tubing (NOT PVC!)

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