General anaesthetics 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 coma that causes lack of awareness to painful stimuli,sufficient to facilitate surgical applications in clinical and veterinary practice. General anaesthetics do not act as analgesics and should also not be confused with sedatives. General anaesthetics are a structurally diverse group of compounds whose mechanisms encompasses multiple biological targets involved in the control of neuronal pathways. The precise workings are the subject of some debate and ongoing research.
Ketamine is a dissociative anesthetic used medically for induction and maintenance of anesthesia. It is also used as a treatment for depression,a pain management tool,and as a recreational drug. Ketamine is a novel compound that was derived from phencyclidine in 1962,in pursuit of a safer anesthetic with fewer hallucinogenic effects.
Sodium thiopental,also known as Sodium Pentothal,thiopental,thiopentone,or Trapanal,is a rapid-onset short-acting barbiturate general anesthetic. It is the thiobarbiturate analog of pentobarbital,and an analog of thiobarbital. Sodium thiopental was a core medicine in the World Health Organization's List of Essential Medicines,but was supplanted by propofol. Despite this,thiopental is listed as an acceptable alternative to propofol,depending on local availability and cost of these agents. It was previously the first of three drugs administered during most lethal injections in the United States,but the US manufacturer Hospira stopped manufacturing the drug in 2011 and the European Union banned the export of the drug for this purpose. Although thiopental abuse carries a dependency risk,its recreational use is rare.
General anaesthesia (UK) or general anesthesia (US) is a method of medically inducing loss of consciousness that renders a patient unarousable even with painful stimuli. This effect is achieved by administering either intravenous or inhalational general anaesthetic medications,which often act in combination with an analgesic and neuromuscular blocking agent. Spontaneous ventilation is often inadequate during the procedure and intervention is often necessary to protect the airway. General anaesthesia is generally performed in an operating theater to allow surgical procedures that would otherwise be intolerably painful for a patient,or in an intensive care unit or emergency department to facilitate endotracheal intubation and mechanical ventilation in critically ill patients.
Propofol,marketed as Diprivan,among other names,also known as 2,6-Diisopropylphenol,is a short-acting medication that results in a decreased level of consciousness and a lack of memory for events. Its uses include the induction and maintenance of general anesthesia,sedation for mechanically ventilated adults,and procedural sedation. It is also used for status epilepticus if other medications have not worked. It is given by injection into a vein,and the maximum effect takes about two minutes to occur and typically lasts five to ten minutes. Propofol is also used for euthanasia in Canada.
Desflurane (1,2,2,2-tetrafluoroethyl difluoromethyl ether) is a highly fluorinated methyl ethyl ether used for maintenance of general anesthesia. Like halothane,enflurane,and isoflurane,it is a racemic mixture of (R) and (S) optical isomers (enantiomers). Together with sevoflurane,it is gradually replacing isoflurane for human use,except in economically undeveloped areas,where its high cost precludes its use. It has the most rapid onset and offset of the volatile anesthetic drugs used for general anesthesia due to its low solubility in blood.
Postoperative nausea and vomiting (PONV) is the phenomenon of nausea,vomiting,or retching experienced by a patient in the postanesthesia care unit (PACU) or within 24 hours following a surgical procedure. PONV affects about 10% of the population undergoing general anaesthesia each year. PONV can be unpleasant and lead to a delay in mobilization and food,fluid,and medication intake following surgery.
Remifentanil,marketed under the brand name Ultiva is a potent,short-acting synthetic opioid analgesic drug. It is given to patients during surgery to relieve pain and as an adjunct to an anaesthetic. Remifentanil is used for sedation as well as combined with other medications for use in general anesthesia. The use of remifentanil has made possible the use of high-dose opioid and low-dose hypnotic anesthesia,due to synergism between remifentanil and various hypnotic drugs and volatile anesthetics.
Cisatracurium besilate is a bisbenzyltetrahydroisoquinolinium that has effect as a neuromuscular-blocking drug non-depolarizing neuromuscular-blocking drugs,used adjunctively in anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation. It shows intermediate duration of action. Cisatracurium is one of the ten isomers of the parent molecule,atracurium. Moreover,cisatracurium represents approximately 15% of the atracurium mixture.
Dexmedetomidine,sold under the trade name Precedex among others,is a drug used in humans for sedation. Veterinarians use dexmedetomidine for similar purposes in treating cats,dogs,and horses. It is also used in humans to treat acute agitation associated with schizophrenia or bipolar I or II disorder.
Ro48-6791 is a drug,an imidazobenzodiazepine derivative developed by Hoffman-LaRoche in the 1990s.
Paul Frederick White,FANZCA is a researcher in anesthesiology,research consultant at Cedars-Sinai Medical Center at Los Angeles,retired professor and former holder of the Margaret Milam McDermott Distinguished Chair of Anesthesiology at The University of Texas Southwestern Medical Center at Dallas,and the author and editor of several journals and textbooks on the subject. With over 450 peer-reviewed publications and authorship in 9 anesthesiology textbooks,White has helped shape and revolutionize the field of ambulatory anesthesia and intravenous anesthesia.
Blood–gas partition coefficient,also known as Ostwald coefficient for blood–gas,is a term used in pharmacology to describe the solubility of inhaled general anesthetics in blood. According to Henry's law,the ratio of the concentration in blood to the concentration in gas that is in contact with that blood,when the partial pressure in both compartments is equal,is nearly constant at sufficiently low concentrations. The partition coefficient is defined as this ratio and,therefore,has no units. The concentration of the anesthetic in blood includes the portion that is undissolved in plasma and the portion that is dissolved. The more soluble the inhaled anesthetic is in blood compared to in air,the more it binds to plasma proteins in the blood and the higher the blood–gas partition coefficient.
Steven Shafer is a professor of anesthesiology at Stanford University. In 2011,the International Society of Anaesthetic Pharmacology gave him their lifetime achievement award.
Coinduction in anesthesia is a pharmacological tool whereby a combination of sedative drugs may be used to greater effect than a single agent,achieving a smoother onset of general anesthesia. The use of coinduction allows lower doses of the same anesthetic agents to be used which provides enhanced safety,faster recovery,fewer side-effects,and more predictable pharmacodynamics. Coinduction is used in human medicine and veterinary medicine as standard practice to provide optimum anesthetic induction. The onset or induction phase of anesthesia is a critical period involving the loss of consciousness and reactivity in the patient,and is arguably the most dangerous period of a general anesthetic. A great variety of coinduction combinations are in use and selection is dependent on the patient's age and health,the specific situation,and the indication for anesthesia. As with all forms of anesthesia the resources available in the environment are a key factor.
Target-controlled infusion (TCI) automates the dosing of intravenous drugs during surgery. After the anesthetist sets the desired parameters in a computer and presses the start button,the system controls the infusion pump,while being monitored by the anesthetist. TCI is as safe and effective as manually controlled infusion.
Alex Bekker is a physician,author and academic. He is a professor and chair at the Department of Anesthesiology,Rutgers New Jersey Medical School. He is also professor at the Department of Physiology,Pharmacology &Neurosciences. He serves as the Chief of Anesthesiology Service at the University Hospital in Newark.
Total intravenous anesthesia (TIVA) refers to the intravenous administration of anesthetic agents to induce a temporary loss of sensation or awareness. The first study of TIVA was done in 1872 using chloral hydrate,and the common anesthetic agent propofol was licensed in 1986. TIVA is currently employed in various procedures as an alternative technique of general anesthesia in order to improve post-operative recovery.
Remifentanilic acid is a metabolite of the potent short-acting synthetic opioid analgesic drug remifentanil. It is an analog of fentanyl and remifentanil,but is not active as an opioid in its own right.
Ciprofol is a novel 2,6-disubstituted phenol derivative that is used for the intravenous induction of general anesthesia. A short-acting and highly selective γ-aminobutyric acid agonist,ciprofol is 4–6 times more potent than other phenol derivatives such as propofol or fospropofol.
