Dissociative Drugs: What are they Used For
Dissociative anesthetics are used for anesthesia and sedation. Modern dissociatives are propofol, thiopental, and ketamine. Comparing intravenous dissociatives with inhaled dissociatives, it is necessary to state that intravenous anesthetics are less controlled from the position of the anesthesiologist. The issue of controllability is the ability to control the concentration of anesthetic at all stages of anesthesia. The concentration of intravenous anesthetic can only be measured in an ampoule. When using inhalation anesthetics, the concentration can be measured in the evaporator, while inhaling and exhaling the patient.
It is the result of the work of the early 70s. The first clinical study was conducted by Kay and Rolly and published in 1977 confirmed the effect of this dissociative drug. Propofol quickly begins to act and has a dose-dependent end of action within 10 minutes if administered over 3 hours, and in less than 40 minutes when administered over 8 hours. A unique property of propofol is its antiemetic effect, which manifests itself in concentrations that are significantly less than in other sedatives.
Thiopental is intravenous dissociative that was introduced by Waters and Lundy’s clinical practice in 1934 and became popular due to its rapid onset and short duration of action without stimulating effects. Despite the criticism of the drug, it is still widely used in clinical practice. Thiopental provides a rapid onset of anesthesia, but it quickly accumulates with prolonged use and leads to delayed recovery.
The induction dose of thiopental is 4 mg/kg and is administered within 5–15 s. There is less variability among patients in response to the dose of barbiturates compared to benzodiazepines for anesthesia, but there is still considerable variability in the dosage of thiopental required for anesthesia.
Intravenous dissociative anesthetic Ketamine was synthesized in 1962 by Stevens and was first used in 1965 by Corssen and Domino. Ketamine was released for clinical use in 1970 and is still used in various clinical situations. Ketamine is a derivative of phencyclidine and is fundamentally different from the above hypnotics. It causes dissociative states of hypnosis and analgesia. Ketamine is different from most other drugs used for anesthesia, and there is the presence of a pronounced analgesic effect.
Ketamine does not inhibit the cardiovascular and respiratory systems, but it has adverse psychological effects that occur during the recovery of consciousness after ketamine anesthesia and are defined as awakening reactions. Common signs of these reactions, which vary in severity and manifestations, include vivid dreams, hallucinations, a wrong interpretation of real, and external sensory experience.
The induction dose of ketamine is 2–4 mg/kg intravenously. Ketamine infusion provides analgesia, and it can be used in combination with propofol for total intravenous anesthesia. Preoperative administration of ketamine at a dose of 10–20 mg is used as anticipatory analgesia.