Propofol is the most commonly used narcotic in general anesthesia and intensive care. It has a sedative, memory– as well as consciousness-suppressing effect and is used in combination with analgesics and muscle relaxants to induce and maintain anesthesia. Its short duration of action makes it very controllable; however, risks and side effects may occur.
What is propofol?
Propofol is a drug and belongs to the group of narcotics. It is a rapid-acting general anesthetic. The lipophilic active ingredient cannot be completely dissolved in water and is therefore produced in the form of a fat emulsion. Soybean oil is usually used for this purpose. New products also use a mixture of triglycerides and long-chain fatty acids instead to enable use in people with soy intolerance. The clear, colorless to pale yellow liquid is administered intravenously. The duration of action is very short, five to ten minutes. Propofol is the world’s most widely used narcotic and is mainly used in general anesthesia and intensive care medicine. It has a memory– and consciousness-suppressing effect and is used in the medical field for the induction and maintenance of anesthesia. Due to its good tolerability, it is also used in sedation. Propofol was first synthesized in 1970, and clinical trials were conducted a few years later. It has been approved for anesthesia as well as intensive care use since 1993.
Pharmacologic effects
Propofol is a hypnotic with sedative or anesthetic, but not analgesic, effects. Its advantage over other anesthetics is more comfortable falling asleep and less nausea after awakening. The way in which propofol induces the sleep-like state during anesthesia is not fully known. It acts on certain receptors in the hippocampus and cerebral cortex. These areas are responsible for memory, short- and long-term memory, and decision-making ability. In addition, it cuts off the conduction of stimuli from the spinal cord to the brain. These effects begin as early as 30 seconds after injection into the vein, when the active ingredient reaches the tissue in the brain with the best blood supply. This is followed by redistribution to the less perfused regions of the brain as well. Propofol has a very short duration of action. To prevent regaining consciousness after five to ten minutes, propofol must be administered at regular intervals. The active ingredient is excreted mainly via the liver and kidneys, and in small amounts is exhaled via the air we breathe. After about two hours, the body has eliminated half of the active ingredient. Propofol cannot be safely combined with all medications without causing interactions. For example, antihypertensive agents are enhanced by propofol; in contrast, other substances such as various analgesics prolong its effects.
Medical application and use
Propofol is used in a variety of medical settings. Its major advantage is its good controllability due to its short duration of action. In laparoscopic minimally invasive procedures such as gastrointestinal endoscopy, it is injected at a lower, sedating dose. In general anesthesia and critical care, it is used to induce and maintain anesthesia. Maintenance of intravenous anesthesia is achieved by a combination of propofol and an analgesic as well as a muscle relaxant, since propofol has neither analgesic nor muscle relaxant effects. For analgesics, opioids are usually used in this case. The aim is to build up a sufficient concentration of the active substance in the blood, which is maintained by a computer-controlled syringe pump. The dosage is calculated taking into account the patient’s age and body weight as well as the planned duration of use. In the course of intensive care, propofol can only be used in adults, not in adolescents under 16 years of age, to prevent life-threatening propofol infusion syndrome. Outside of intensive care, it can be used in children as young as 2 months of age due to its good tolerability. However, due to placental permeability, propofol administration is contraindicated during pregnancy, childbirth, and lactation.
Risks and side effects
Like any medication, propofol can have risks and side effects. Because it is administered intravenously, pain may occur at the injection site due to irritation of the vein wall. Headache, nausea, and vomiting may occur after awakening, although these symptoms are significantly reduced with propofol compared with other anesthetics. Other risks include respiratory depression to respiratory arrest, slowed pulse rate, and hypotension. This occurs mainly in elderly patients with previous cardiac damage. In addition, excitation phenomena such as involuntary movements or muscle twitching, and rarely seizures, may occur. Release of histamine is also possible, to which some individuals exhibit intolerance reactions. If propofol is used for a prolonged period, propofol infusion syndrome may occur in rare cases, often resulting in death. To prevent this, propofol administration should not exceed seven days. Because of its relaxing, euphoric, and even aphrodisiac effects, propofol is often abused. This usually does not lead to physical dependence, but very much to psychological dependence and can become acutely life-threatening.
