Central nervous system (CNS) depression is a physiological state that can result in a decreased rate of breathing, decreased

heart rate Heart rate (or pulse rate) is the frequency of the heartbeat measured by the number of contractions (beats) of the heart per minute (bpm). The heart rate can vary according to the body's physical needs, including the need to absorb oxygen and excr ...

, and

loss of consciousness Loss may refer to: Arts, entertainment, and media Music * ''Loss'' (Bass Communion album) (2006) * ''Loss'' (Mull Historical Society album) (2001) *"Loss", a song by God Is an Astronaut from their self-titled album (2008) * Losses "(Lil Tjay son ...

possibly leading to

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

. It is the result of inhibited or suppressed

brain activity Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocor ...

Causes

Depression of the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

is generally caused by the use of

depressant A depressant, or central depressant, is a drug that lowers neurotransmission levels, which is to depress or reduce arousal or stimulation, in various areas of the brain. Depressants are also colloquially referred to as downers as they lower the ...

drugs such as

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

opioid Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use ...

barbiturate Barbiturates are a class of depressant drugs that are chemically derived from barbituric acid. They are effective when used medically as anxiolytics, hypnotics, and anticonvulsants, but have physical and psychological addiction potential a ...

benzodiazepine Benzodiazepines (BZD, BDZ, BZs), sometimes called "benzos", are a class of depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed to treat conditions such as anxiety disorders, ...

general anesthetic General anaesthetics (or anesthetics, see spelling differences) are often defined as compounds that induce a loss of consciousness in humans or loss of righting reflex in animals. Clinical definitions are also extended to include an induced com ...

s, and

anticonvulsant Anticonvulsants (also known as antiepileptic drugs or recently as antiseizure drugs) are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of ...

s such as pregabalin used to treat

epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrica ...

Drug overdose A drug overdose (overdose or OD) is the ingestion or application of a drug or other substance in quantities much greater than are recommended.

is 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 as

butanone Butanone, also known as methyl ethyl ketone (MEK), is an organic compound with the formula CH3C(O)CH2CH3. This colourless liquid ketone has a sharp, sweet odor reminiscent of acetone. It is produced industrially on a large scale, but occurs in ...

(contained in plastic cement) or

isopropyl alcohol Isopropyl alcohol (IUPAC name propan-2-ol and also called isopropanol or 2-propanol) is a colorless, flammable organic compound with a pungent alcoholic odor. As an isopropyl group linked to a hydroxyl group ( chemical formula ) it is the s ...

. Other causes of central nervous system depression are metabolic disturbances such as

hypoglycaemia Hypoglycemia, also called low blood sugar, is a fall in blood sugar to levels below normal, typically below 70 mg/dL (3.9 mmol/L). Whipple's triad is used to properly identify hypoglycemic episodes. It is defined as blood glucose bel ...

Comparison

In a study comparing the central nervous depression due to supra-therapeutic doses of triazolam (a benzodiazepine),

pentobarbital Pentobarbital (previously known as pentobarbitone in Britain and Australia) is a short-acting barbiturate typically used as a sedative, a preanesthetic, and to control convulsions in emergencies. It can also be used for short-term treatment of i ...

(a barbiturate) and

gamma-hydroxybutyric acid ''gamma''-Hydroxybutyric acid (or γ-hydroxybutyric acid (GHB), also known as 4-hydroxybutanoic acid) is a naturally occurring neurotransmitter and a depressant drug. It is a precursor to GABA, glutamate, and glycine in certain brain areas ...

(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 of accidental overdose. In the case of accidental overdose of GHB, patients can become drowsy, fall asleep and may enter a

. Although GHB had higher sedative effects at high doses as compared to triazolam and pentobarbital, it had less of an amnestic effect. Arousal of subjects who received GHB sometimes even required a painful stimulus; this was not seen in patients who received triazolam or pentobarbital group. During the heavy sedation with GHB, the subjects maintained normal respiration and

blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure ...

. This is often not the case with opioids as they cause

respiratory depression Hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (''hypo'' meaning "below") to perform needed respiratory gas exchange. By definition it causes an increased concentration of carbon dioxide (hypercapni ...

Treatment

Significant central nervous system depression is treated within a hospital setting by maintaining breathing and circulation. Individuals with reduced breathing may be given supplemental

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

, while individuals who are not breathing can be ventilated with

bag valve mask A bag valve mask (BVM), sometimes known by the proprietary name Ambu bag or generically as a manual resuscitator or "self-inflating bag", is a hand-held device commonly used to provide positive pressure ventilation to patients who are not breathin ...

ventilation or by

mechanical ventilation Mechanical ventilation, assisted ventilation or intermittent mandatory ventilation (IMV), is the medical term for using a machine called a ventilator to fully or partially provide artificial ventilation. Mechanical ventilation helps move a ...

with a

respirator A respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including fumes, vapours, gases and particulate matter such as dusts and airborne pathogens such as viruses. There are two main categories of respi ...

. Sympathomimetic drugs may be used to attempt to stimulate

cardiac output In cardiac physiology, cardiac output (CO), also known as heart output and often denoted by the symbols Q, \dot Q, or \dot Q_ , edited by Catherine E. Williamson, Phillip Bennett is the volumetric flow rate of the heart's pumping output: th ...

in order to maintain circulation. Central nervous system depression caused by certain drugs may respond to treatment with an antidote. There are two antidotes that are frequently used in the hospital setting and these are

naloxone Naloxone, sold under the brand names Narcan (4 mg) and Kloxxado (8 mg) among others, is a medication used to reverse or reduce the effects of opioids. It is commonly used to counter decreased breathing in opioid overdose. Effects begin withi ...

and flumazenil. Naloxone is an opioid antagonist and reverses the central nervous depressive effects seen in opioid overdose. In the setting of a

colonoscopy Colonoscopy () or coloscopy () is the endoscopic examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It can provide a visual diagnosis ('' ...

, 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 to gamma-aminobutyric acid receptors. Similarly to naloxone, flumazenil has 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 of

seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with lo ...

s and 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 use

sedative A sedative or tranquilliser is a substance that induces sedation by reducing irritability or excitement. They are CNS depressants and interact with brain activity causing its deceleration. Various kinds of sedatives can be distinguished, but ...

s but only 0.8% of them result in the administration of one of these

antidotes An antidote is a substance that can counteract a form of poisoning. The term ultimately derives from the Greek term φάρμακον ἀντίδοτον ''(pharmakon) antidoton'', "(medicine) given as a remedy". Antidotes for anticoagulants are s ...

. Even if they are rarely used in colonoscopies they are important in preventing the patient from entering a coma or developing

when sedatives are not properly dosed. Outside of the colonoscopy setting, these agents are used for other procedures and in the case of drug overdose.

References

{{DEFAULTSORT:Central Nervous System Depression Central nervous system Central nervous system disorders