**3. Sedation levels**

In recent years, four levels of sedation have been established that extend along a spectrum without clear limits: minimal sedation or anxiolysis, moderate sedation, deep sedation, and general anesthesia [1]. These sedation levels have been characterized by the reaction of a patient to verbal, light contact, or painful stimuli, although they are often associated with physiological changes in vital patient signs.

"Minimal sedation" is also known as anxiolysis and is defined as the lowest drug-induced stage of cognition-impairment. Individuals who are minimally sedated usually respond to simple orders and their breathing/cardiovascular

system is unaffected. Oral benzodiazepines are commonly used to achieve minimal sedatives.

"Moderate Sedation" has traditionally been referred to as "Conscious Sedation". This entitles a deeper depression consciousness level. Individuals who are moderately sedated can still respond to verbal orders, often requiring physical stimulation, and their breathing/cardiovascular function is unaffected. Intravenous benzodiazepines and opioids are examples of drugs used to achieve moderate sedation.

'Deep sedation' leads to major depression of the central nervous system, where patients are no longer conscious and are more difficult to arouse. They will usually respond to painful stimuli but not to verbal or simple tactile stimuli. The respiratory system is stressed and some ventilatory assistance may be required.

Intravenous benzodiazepines, intravenous anesthetics such as propofol, ketamine, etomidate, and dexmedetomidine are examples of medicines used for deep sedation.

'General anesthesia' is the deepest type of sedation in which there is a total lack of consciousness and no response to stimuli. Cardiovascular and respiratory functions are often compromised, therefore, monitoring and assistance, such as ventilatory support, may be needed.

A fifth level/form of sedation, also known as 'Dissociative sedation is a variant of moderate sedation characteristically produced by a medication class known as phencyclidine, such as ketamine, which induces a disconnection between the thalamo-neocortical system and the limbic structures, preventing sensory stimuli from being received by higher centers [2, 3].
