Intravenous medicines for anesthesia
Intravenous (IV) anesthetic medicines are given into a vein. They can be given quickly and are rapidly absorbed into the blood.
IV anesthetics are used to relieve pain (analgesia), to relax (sedate), to induce sleepiness (hypnosis) or forgetfulness (amnesia), or to make you unconscious for general anesthesia. Most IV anesthetics cannot produce all of these effects on their own. An IV anesthetic is often combined with another IV anesthetic or with an inhalant (vaporized liquid) anesthetic.
Intravenous anesthetics include barbiturates, benzodiazepines, propofol, and opioids.
Barbiturates used for anesthesia include methohexital and sodium thiopental. These fast-acting medicines are sometimes used for general anesthesia induction.
Benzodiazepines cause sedation, sleepiness, forgetfulness, and unconsciousness. In higher doses they also produce muscle relaxation. The one most commonly used is midazolam. Benzodiazepines may be used to provide sedation and amnesia during local or regional anesthesia or during procedural sedation, which combines the use of local anesthesia with sedatives to relax you for minor procedures.
These medicines can also be given orally (as a pill) as a premedication before anesthesia to help relieve anxiety.
The first phase of anesthesia, when an anesthetic is first given, is called induction. Propofol (Diprivan) is the most commonly used anesthetic induction agent. It causes rapid and reversible decrease in consciousness with minimal, if any, aftereffects.
Opioids can reduce the sensation of pain and cause deep sleep. Many opioids are used in anesthesia, primarily to relieve pain. They cause some sedation and sleepiness, so they may reduce the need for other sedative-hypnotic medicines during anesthesia. But opioids by themselves are generally not used for anesthesia, because there have been reported cases of awareness during anesthesia when opioids alone were used as anesthetics.
Opioids also may be used for pain relief after surgery.
Opioids commonly used for anesthesia include fentanyl and morphine.
Opioids affect breathing but at usual doses have only minor effects on the cardiovascular system. At higher doses, though, opioids may affect heart rate and blood pressure. Opioids may be associated with nausea and vomiting after surgery. They may also cause constipation, difficulty urinating, and itching of the skin. Allergic reactions are rare.