Atropine blocks the action of acetylcholine at muscarinic receptors in the parasympathetic nervous system (PNS). Parasympa-
thetic stimulation via the vagus nerve slows the heart. Blocking this in the sinoatrial (SA) node increases automaticity and therefore heart rate. Blocking parasympathetic activity in the atrioventricular (AV) node facilitates conduction through the node.
• Atropine is given to increase heart rate.
• In symptomatic bradycardia, the dose is 500 mg repeated as necessary to a maximum dosage of 3mg, the dose generally accepted to cause full parasympathetic blockade (Mader et al. 2000).
• A 3mg dose via the IV route is recommended in asystole and pulseless electrical activity (PEA) of a rate below 60bpm. This dose should only be given once.
• The evidence base for the use of atropine in cardiac arrest is sparse.
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