Pharmacology and Sedation/Analgesia
Sedation agents and reversal
Moderate sedation in the EP lab commonly combines a benzodiazepine (midazolam) with an opioid (fentanyl). Midazolam is reversed with flumazenil and fentanyl with naloxone; both antidotes are short-acting, so continued monitoring is mandatory because resedation can occur. Monitor level of consciousness, ventilation, oxygenation, and hemodynamics continuously. Airway compromise is the principal risk in a patient lying flat with a drape over the chest.
Antiarrhythmic and procedural drugs
Adenosine transiently blocks the AV node; its half-life is seconds. It is useful for terminating AV nodal–dependent tachycardias, but it can provoke AF and should be used cautiously in severe asthma or bronchospasm. Isoproterenol raises heart rate and can facilitate induction or reveal automaticity; atropine blocks vagal tone. Amiodarone, lidocaine, and ibutilide have distinct roles and proarrhythmic risks (ibutilide causes torsades). Heparin dosing during left-sided ablation is guided by ACT, typically aiming ~250–300 seconds (higher for AF ablation, ~300–350 seconds); check ACT about every 30 minutes and reverse with protamine if needed.
Traps
Do not assume a sedated patient can report symptoms; assess pain and responsiveness. Vasovagal reactions present with bradycardia and hypotension, not tachycardia. A drug that terminates a tachycardia does not necessarily identify the mechanism. Ask about asthma before adenosine, and about renal function before agents cleared renally.
Rule of thumb
For any sedated patient in the EP lab, the fastest way to find the problem when saturations fall is to stop the procedure, call for help, and support the airway - not to reach for another drug.