Adenosine

• Stable narrow-complex SVT in pregnancy
• Diagnostic unmasking of AF/flutter

Transient A1 activation hyperpolarises AV node → block re-entrant SVT circuits; half-life <10 s.

• 6 mg → 12 mg → 12 mg via large-bore proximal cannula
• Warn patient of chest tightness, doom feeling
• Halve dose on dipyridamole or heart transplant

First dose

6 mg IV rapid push + 20 mL saline flush

Second/third

12 mg if no response

• Absolute2°/3° AV block without pacemaker
• AbsoluteSevere asthma (bronchospasm)
• AbsoluteLong QT / decompensated HF

• Chest tightness, flushing, dyspnoea (seconds)
• Transient asystole
• Bronchospasm (asthma)
• Sinus pause

• • Half-life <10 s → negligible placental transfer
• • Safe every trimester

• Dipyridamole

  Avoid

  Potentiates — halve dose

• Theophylline / caffeine

  Caution

  Antagonise — may need higher dose

• 💡 Do vagal manoeuvres first (Valsalva, modified REVERT)
• 💡 Have defibrillator and airway ready