What is a parasympathetic block?

A parasympathetic block is a type of regional anaesthesia that involves the inhibition of the parasympathetic nervous system, which is responsible for the body's "rest and digest" functions. It is often used during surgeries, such as eye surgeries, where it is important to reduce secretions and muscle activity in the area being operated on.

The parasympathetic nervous system controls a variety of functions in the body, including:

* Salivary and tear production

* Heart rate and blood pressure

* Gastrointestinal motility

* Bladder and bowel function

A parasympathetic block temporarily disrupts the communication between the parasympathetic nervous system and the organs it innervates. This can be achieved through the use of local anaesthetics, such as lidocaine or bupivacaine, which block the transmission of nerve impulses. In some cases, a parasympathetic block can also be achieved through the use of anticholinergic drugs, which block the action of acetylcholine, a neurotransmitter that is essential for parasympathetic nerve transmission.

Parasympathetic blocks are typically administered by injection near the nerves or ganglia of the parasympathetic nervous system. The duration of the block depends on the type of anaesthetic used and the dose administered. Parasympathetic blocks are generally safe and well-tolerated, but there are some potential risks and complications, such as:

* Hypotension (low blood pressure)

* Bradycardia (slow heart rate)

* Urinary retention

* Dry mouth

* Blurred vision

* Difficulty swallowing

These risks and complications are usually transient and resolve once the block wears off.