Drugs affecting the autonomic nervous system

In the perioperative period anaesthetists use many drugs that affect the sympathetic and/or parasympathetic nervous system. Anaesthetists may use anticholinesterase agents to prevent the breakdown of acetylcholine at the neuromuscular junction in order to reverse competitive neuromuscular blockade. This also preserves acetylcholine and the muscarinic sites in the parasympathetic nervous system. Because this may cause excessive cardiac slowing, a muscarinic antagonist such as atropine may be added. Atropine may also be used to prevent or treat cardiac slowing during surgery. Trimetaphan, a short-acting antagonist at nicotinic receptors in the autonomic ganglia may be occasionally used as an infusion to reduce blood pressure during surgery. Agonists at receptors for norepinephrine may be used to increase blood pressure and antagonists to treat cardiac dysrhythmias. Antagonists at β-adrenoceptors are no longer the first choice of treatment for hypertension.