Cholinergic syndrome: common causes and symptoms

This alteration of the neurochemical balance is usually caused by substance intoxication.

There are many neurotransmitters that have an effect on our organism, regulating our psyche and our behavior. One of the main ones is acetylcholine, which is fundamental in the activity of the brain.which is fundamental in the activity of the cerebral cortex and in the realization of a great number of mental and physical processes. Examples are attention, consciousness, memory and muscle activation.

However, an excess of this substance can be dangerous or even lethal, and can give rise to the set of alterations denominated as cholinergic syndrome..

What is the cholinergic syndrome?

It is denominated cholinergic syndrome to the set of alterations or symptoms generated by the stimulation of the various acetylcholine receptors in the organism by an excess of this substance. in the organism before an excess of this substance. Intoxication occurs, generally as a consequence of exposure or administration of external substances that generate such excess.

Among them the following stand out overdose of certain drugs with cholinergic action, such as pilocarpine such as pilocarpine (glaucoma medication also used for the treatment of dry mouth in various disorders), betanecol (used in megacolon and vesicular problems) or medications that inhibit anticholinesterase such as those used to combat Alzheimer's disease (e.g. rivastigmine), due to their excessive use and in excessive quantity in relation to the time in which they act on the organism.

It can also be produced by intoxications derived from pesticides and insecticides. We can also find cases derived from nicotine excesses or from the consumption of some specific mushrooms and fungi such as amanita muscaria. mushrooms and fungi such as amanita muscaria.

Cholinergic syndrome is life-threatening and requires medical attention. The most common symptoms are exaggerated secretion of fluids (saliva, tears, sweat, mucus and mucous membranes in the respiratory tract...), muscle pain and paralysis (which may include the muscles that allow breathing) and cardiorespiratory disturbances.

Tachycardia tends to appear initially and may evolve into bradycardia (i.e. acceleration of the Heart rate which may become slowing) and respiratory difficulties (including bronchospasm which prevents the passage of air into the lungs) which may end in cardiorespiratory arrest. can lead to cardiorespiratory arrest and death in the absence of assisted respiration.. Vomiting, lethargy and confusion and diarrhea are also common.

Main symptoms depending on the activation of specific receptors.

Acetylcholine has different receptors within the nervous system, among which nicotinic and muscarinic receptors stand out. In this sense, cholinergic syndrome can appear in which only one of the types of receptors is affected, or a process can follow depending on the type of receptors that are activated. Generally, the following sequence usually occurs.

1. Nicotinic cholinergic syndrome

This type of cholinergic syndrome is characterized by the presence of muscular pains, cramps and paralysis, tachycardia and hypertension which may be followed by bradycardia, hyperglycemia and calcium excess. The presence of mydriasis (i.e. pupil dilation) in the first moments of acute intoxication is also very characteristic.

However, this mydriasis is only initial, because with time the sympathetic nervous system is activated to produce miosis (abnormal contraction of the pupil). Muscles are weakened and reflexes are lost.

2. Muscarinic cholinergic syndrome

In this stage of the syndrome the effect is due to the excess of activation of the muscarinic receptors. Miosis or contraction of the pupil, blurred vision, slowing of the heart rate or bradycardia, lacrimation of the eyes and eyesight or bradycardia, lacrimation, sialorrhea (excess salivation), incontinence, nausea and vomiting and respiratory problems that could lead to respiratory arrest. Hypothermia and problems such as hypotension also appear.

3. Central or neurological cholinergic syndrome

It is common that in addition to the above mentioned neurological syndrome appears, consisting of the appearance of headache, irritability, hypothermia, altered consciousnessThe neurological syndrome consists of headache, irritability, hypothermia, alteration of consciousness that can lead to coma, convulsions, cardiorespiratory depression and even death.

Treatment

As we have indicated above, cholinergic syndrome requires immediate medical treatment due to its potential to cause the death of the sufferer.

The first step is to stabilize the patient in terms of keeping his or her heart and respiratory rate under control and, if necessary, to use life support measures and even assisted respiration. Oxygen administration is essential. In severe cases, intubation of the patient and removal of excess secretions by this or other routes may be required.

Subsequently at the pharmacological level the administration of atropine is usually seen as a solution for muscarinic symptoms together with substances that reactivate or potentiate cholinesterases (the natural enzymes that degrade acetylcholine in our body) to alleviate nicotinic symptoms. The use of diazepam or other tranquilizers may be required in cases where seizures appear in order to decrease the level of activation.

Bibliographic references:

• Bargull-Díaz, I.C.; Lozano, N.; Pinto, J.K. & Aristizábal, J.J. (2012).Intermediate syndrome in acute organophosphate poisoning: case report. Medicina U.P.B. 31 (1): 53-58.
• Gervilla, J.; Otal, J.; Torres, M. and Durán, J. (2007). Intoxication by organophosphates. SEMERGEN.; 33: 21-3.
• Moreno, A. (2014). Main toxic syndromes and antidotes. Hospital 12 de octubre.