Central nervous system depression

Central nervous system(CNS)depressionis a physiological state that can result in a decreasedrate of breathing,decreasedheart rate,andloss of consciousness,possibly leading tocomaordeath.

It is the result of inhibited or suppressedbrain activity.

Causes

Depressionof thecentral nervous systemis generally caused by the use ofdepressantdrugs such asethanol,opioids,barbiturates,benzodiazepines,general anesthetics,andanticonvulsantssuch aspregabalinused to treatepilepsy.

Drug overdoseis often caused by combining two or more depressant drugs, although overdose is also possible by consuming a large dose of one depressant drug. Central nervous system depression can also be caused by the accidental or intentional inhalation or ingestion of certain volatile chemicals such asbutanone(contained inplastic cement) orisopropyl alcohol.Other causes of central nervous system depression aremetabolic disturbancessuch ashypoglycemia.

Comparison

In a study comparing the central nervous depression due to supra-therapeutic doses oftriazolam(a benzodiazepine),pentobarbital(a barbiturate) andgamma-hydroxybutyric acid(GHB), it appeared as if GHB had the strongest dose-effect function. Since GHB has a high correlation between its dose and its central nervous system depression, it has a high risk ofaccidental overdose.In the case of accidental overdose of GHB, patients can become drowsy, fall asleep and may enter acoma.Although GHB had higher sedative effects at high doses as compared to triazolam and pentobarbital, it had less of anamnesticeffect. Arousal of subjects who received GHB sometimes even required a painfulstimulus;this was not seen in patients who received triazolam or pentobarbital group. During the heavy sedation with GHB, the subjects maintained normalrespirationandblood pressure.This is often not the case with opioids as they causerespiratory depression.

Treatment

There are twoantidotesthat are frequently used in the hospital setting and these arenaloxoneandflumazenil.Naloxone is anopioid antagonistand reverses the central nervous depressive effects seen inopioid overdose.In the setting of acolonoscopy,naloxone is rarely administered but when it is administered, its half-life is shorter than some common opioid agonists. Therefore, the patient may still exhibit central nervous system depression after the naloxone has been cleared. Naloxone is typically administered in short intervals with relatively small doses in order to prevent the occurrence of withdrawal, pain, and sympathetic nervous system activation. Flumazenil is a benzodiazepine antagonist and blocks the binding of benzodiazepines togamma-aminobutyric acidreceptors. Similarly to naloxone,flumazenilhas a short half-life, and this needs to be taken into account because the patient may exhibit central nervous depression after the antidote has been cleared. Benzodiazepines are used in the treatment ofseizuresand subsequently, the administration of flumazenil may result in seizures. Therefore, slow administration of flumazenil is necessary to prevent the occurrence of a seizure. These agents are rarely used in the setting of a colonoscopy as 98.8% of colonoscopies usesedativesbut only 0.8% of them result in the administration of one of theseantidotes.Even if they are rarely used in colonoscopies they are important in preventing the patient from entering a coma or developingrespiratory depressionwhen sedatives are not properly dosed. Outside of the colonoscopy setting, these agents are used for other procedures and in the case of drug overdose.