ATROPINE

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Atropine is a competitive antagonist of muscarinic acetylcholine receptors. As an anticholinergic drug, it exerts various effects on the body, including increased heart rate, bronchodilation, decreased secretions, and reduced gastrointestinal motility. Atropine plays several important roles in anesthesia:

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1. Treatment of bradycardia: One of the most crucial uses of atropine in anesthesia is the treatment of bradycardia (slow heart rate). This can occur due to various reasons, such as vagal stimulation during intubation or surgery, drug side effects, or reflex bradycardia. Atropine is often used as a first-line treatment to counteract these episodes, ensuring adequate perfusion and maintaining hemodynamic stability. 

2. Reduction of secretions: Atropine's anticholinergic effects help reduce airway secretions, which can be beneficial during airway management and endotracheal intubation, improving visualization and reducing the risk of aspiration.

3. Reversal of cholinesterase inhibitors: In certain situations, atropine may be used to reverse the effects of cholinesterase inhibitors, such as neostigmine, which are administered to reverse neuromuscular blockade. Atropine can be co-administered with these drugs to counteract their muscarinic side effects, such as bradycardia, increased secretions, and bronchoconstriction.

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The main effects of atropine include:

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• Heart: Atropine blocks the M2 muscarinic receptors in the sinoatrial (SA) and atrioventricular (AV) nodes, leading to increased heart rate (tachycardia) and increased conduction velocity through the AV node.

• Eyes: Atropine antagonizes M3 muscarinic receptors in the iris and ciliary muscles, resulting in mydriasis (pupil dilation) and cycloplegia (paralysis of the ciliary muscle, causing loss of accommodation).

• Respiratory system: Atropine inhibits M3 muscarinic receptors in the bronchial smooth muscle and glands, causing bronchodilation and decreased bronchial secretions.

• Gastrointestinal tract: Atropine blocks M3 muscarinic receptors in the smooth muscles and glands of the gastrointestinal tract, reducing motility, secretions, and sphincter tone.

• Urinary bladder: Atropine antagonizes M3 muscarinic receptors in the detrusor muscle and bladder sphincter, leading to decreased bladder contraction and increased sphincter tone, which may cause urinary retention.

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                                                                                         Key points about Atropine

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• Atropine is a tertiary amine and can rapidly cross the blood-brain barrier.

 

• Indications include antisialogue, anti-vagal effect, organophosphate/muscarinic poisoning, and bradycardia.

 

• It is an antimuscarinic that works by competitive inhibition of postganglionic acetylcholine receptors.

 

• It has direct vagolytic action, which leads to parasympathetic inhibition of the acetylcholine receptors in smooth muscle.

 

• Atropine has been associated with mild postoperative memory deficits and excitatory reactions.

 

• Atropine should be used with caution in patients with coronary artery disease, narrow-angle glaucoma, prostatic hypertrophy, and bladder-neck obstruction.

 

• Adverse effects include xerostomia (dry mouth), blurred vision, photophobia, tachycardia, flushing, and hot skin.

 

• Constipation, difficulty with urination, and anhidrosis can occur.

 

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