Central Anticholinergic Syndrome
➧ Many of the drugs used in anesthesia and intensive care may cause blockage of the central cholinergic neurotransmission.
➧ Acetylcholine is of significance in the modulation of the interaction among most other central transmitters.
Causes:
1- Overdose of anticholinergic drugs: e.g. Atropine, scopolamine, glycopyrrolate
2- Overdose of drugs that possess an anticholinergic activity:
e.g. Antipsychotics, tricyclic antidepressants, antiparkinsonian drugs
3- It May be induced by opiates, benzodiazepines, phenothiazines, butyrophenones, ketamine, etomidate, propofol, nitrous oxide, and halogenated inhalation anesthetics as well as by H2-blocking agents such as cimetidine.
Clinical Picture:
➧ The clinical picture of the central cholinergic blockade, known as the central anticholinergic syndrome (CAS), is identical to the central symptoms of atropine intoxication.
➧ This behavior consists of agitation including seizures, restlessness, hallucinations, disorientation, or signs of depression such as stupor, coma, and respiratory depression.
Systemic:
➧ Tachycardia: Increased heart rate
➧ Ataxia: loss of coordination
➧ Dry, sore throat, xerostomia, or dry mouth with a possible acceleration of dental caries
➧ Cessation of perspiration → Increased body temperature
➧ Mydriasis: Pupil dilation; consequent sensitivity to bright light (photophobia)
➧ Cycloplegia: Loss of accommodation (loss of focusing ability, blurred vision)
➧ Diplopia: Double-vision
➧ Increased intraocular pressure; dangerous for people with narrow-angle glaucoma
➧ Urinary retention, Diminished bowel movement, and sometimes ileus
➧ Shaking
Central nervous system:
Resemble those associated with delirium, and may include:
➧ Mental confusion (brain fog), Disorientation, Agitation, Irritability, Unusual sensitivity to sudden sounds
➧ Euphoria or dysphoria
➧ Memory problems, Inability to concentrate
➧ Illogical thinking, Wandering thoughts; inability to sustain a train of thought
➧ Incoherent speech
➧ Respiratory depression
➧ Wakeful myoclonic jerking
➧ Photophobia
➧ Visual disturbances: Periodic flashes of light, changes in the visual field, Visual snow, Restricted or "tunnel vision"
➧ Visual, auditory, or other sensory hallucinations:
-Warping or waving of surfaces and edges
-Textured surfaces
-"Dancing" lines; "spiders", insects
-Lifelike objects indistinguishable from reality
-The hallucinated presence of people not actually there
➧ Rarely: seizures, coma, and death
➧ Orthostatic hypotension (sudden dropping of systolic blood pressure when standing up suddenly) and significantly increased risk of falls in the elderly population.
Treatment:
Central anticholinergic syndrome is completely reversible and subsides once all of the causative agents have been excreted.
Physostigmine:
➧ It is one of only a few drugs that can be used as an antidote for anticholinergic poisoning because it crosses BBB.
- Dose: 0.01-0.03 mg/kg IV, repeated after 15-30 min. If necessary.
- Duration of action: about 30-60 min after intravenous IV injection.
- Side effects: nausea and vomiting, abdominal cramps, bradycardia, and hypotension
- Physostigmine was found to increase the risk of cardiac toxicity.
Nicotine:
➧ It counteracts anticholinergics by binding to the nicotinic acetylcholine receptors and activating them.
Caffeine:
➧ It is an adenosine receptor antagonist, that counteracts the anticholinergic symptoms by reducing sedation and increasing acetylcholine activity, thereby causing alertness and arousal.
➧ Caffeine can also inhibit acetylcholinesterase non-competitively.
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