A patient shows signs of delirium after anesthesia with specific preoperative medications. What is the likely cause?

The situation described involves a patient showing signs of delirium following anesthesia and the administration of specific preoperative medications. The correct answer indicates that the likely cause of delirium is excessive antagonism at cholinergic receptors due to high doses of anticholinergics like Physostigmine.

Anticholinergics are medications that block the action of acetylcholine (ACh) at muscarinic receptors in the body. When anticholinergics are administered in high doses, they can hinder normal cholinergic signaling, leading to symptoms such as confusion or delirium, particularly in susceptible patients, such as the elderly or those with pre-existing cognitive impairment.

Physostigmine is a reversible inhibitor of acetylcholinesterase, which breaks down acetylcholine. When used in appropriate doses, it can sometimes counteract the effects of excessive anticholinergics by increasing the levels of ACh at the synapses. However, if an individual is exposed to high doses of anticholinergics, excessive blockade of cholinergic receptors can still result in cognitive disturbances, such as delirium, regardless of the presence of Physostigmine.

Thus, the combination of excessive antagonism at cholinergic receptors due to