Drugs used for general anesthesia are divided into:

1 Inhalation anesthetic: Inhalation anesthetic is volatile liquid or gas, and the former is ether, halothane, isoflurane, enflurane, etc. The latter is nitrous oxide (nitrous oxide).

It is believed that inhalation anesthetics dissolve in the lipid layer of cell membrane, which makes the arrangement of lipid molecules disordered, changes the conformation and function of membrane proteins and sodium and potassium channels, and inhibits the depolarization of nerve cells, thus widely inhibiting the transmission of nerve impulses and leading to general anesthesia.

Anesthetic ether is a colorless, clear and volatile liquid, which has peculiar smell, is flammable and explosive, and is easily oxidized to produce peroxide and acetaldehyde, thus increasing its toxicity. Ether with anesthetic concentration has little effect on respiratory function and blood pressure, and has little toxicity to heart, liver and kidney. Ether also has the effect of curare, so it has a strong muscle relaxation effect. However, this drug has a long induction period and recovery period, which is prone to accidents. Now it is rarely used.

Halothane is a colorless and transparent liquid with a boiling point of 50.2℃, which is non-flammable and non-explosive, but its chemical properties are unstable. The MAC of halothane is only 0.75%, which has strong anesthetic effect and small blood gas distribution coefficient, so the induction period is short and the recovery is fast, but the muscle relaxation and analgesia of halothane are weak. Dilate cerebral vessels and increase intracranial pressure; Increase the sensitivity of myocardium to catecholamine and induce arrhythmia. Repeated use may cause hepatitis or liver necrosis, so be vigilant. Relaxation of uterine muscles often leads to postpartum hemorrhage, which is forbidden for patients with dystocia or caesarean section.

Enflurane and isoflurane are isomers. Compared with halothane, enflurane has a slightly larger MAC, stable, rapid and comfortable anesthesia induction, good muscle relaxation and no increase in myocardial sensitivity to catecholamine. Repeated use has no obvious side effects and occasional nausea and vomiting. It is a commonly used inhalation anesthetic at present.

Nitroxy, also known as nitrous oxide, is a colorless, odorless and non-irritating liquid gas, which is stable, nonflammable and non-explosive. When used in anesthesia, patients feel comfortable and pleasant, have strong analgesic effect, wake up quickly after stopping taking drugs, and have no adverse effects on respiratory, liver and kidney functions. But it has a slight inhibitory effect on myocardium. The MAC value of nitrous oxide is above 100, and the anesthesia efficiency is very low. It needs to be compatible with other anesthetics to achieve satisfactory anesthetic effect. The blood/gas partition coefficient is low and the induction period is short. Mainly used for inducing anesthesia or compatibility with other general anesthetics.

2 intravenous anesthetics

Commonly used intravenous anesthetics are thiopental sodium and chloramine copper.

Thiopental sodium is a barbiturate with ultrashort action. With high fat solubility, it can enter the brain tissue in a few seconds after intravenous injection, with rapid anesthesia and no exciting period. However, due to the rapid redistribution of this drug in the body, it is transported from brain tissue to muscle, fat and other tissues, so the duration of action is short, and t 1/2 is only 5 minutes in the brain. The analgesic effect of thiopental sodium is poor and the muscle relaxation is incomplete. It is mainly used for induction anesthesia, basic anesthesia, abscess incision and drainage, closed reduction of fracture and dislocation and other short-term operations.

Sodium thiopental has obvious inhibitory effect on respiratory center, and newborns and infants are easily inhibited, so it is forbidden. It is also easy to induce laryngeal and bronchial spasm, so bronchial asthma is prohibited.

Ketamine can block the conduction of pain impulses to thalamus and neocortex, and can excite brain stem and limbic system at the same time. It causes confusion of consciousness and transient memory loss, and the analgesic effect is satisfactory, but the consciousness does not completely disappear, and there are often many phenomena such as dreaminess, increased muscle tension and elevated blood pressure. This state is also called dissociative anesthesia.

Ketamine anesthesia has obvious analgesic effect on body surface and poor analgesic effect on viscera, but it can induce quickly. It has a slight effect on respiration and an obvious exciting effect on cardiovascular system. Used for short-term micro-body surface surgery, such as burn debridement, escharectomy, skin grafting, etc.

3 compound anesthesia

Compound anesthesia refers to the simultaneous or sequential application of two or more anesthetic drugs or other auxiliary drugs to achieve perfect intraoperative and postoperative analgesia and satisfactory surgical conditions. At present, the application of various general anesthetics alone is not ideal. In order to overcome its shortcomings, combined drugs or other drugs are often used, which is called compound anesthesia.

In addition, muscle relaxants have N-like effects on the body, which is not a condition for becoming a general anesthetic.

Classification of muscle relaxants: according to the characteristics of their modes of action, they can be divided into depolarization type and non-depolarization type.

Depolarizing muscle relaxant succinylcholine

Features: A. There is a short period of muscle bundle tremor before muscle relaxation, which is fast, short in duration and easy to control. B. continuous medication can produce rapid tolerance. C. The combination of anticholinesterase drugs can not only antagonize the muscle relaxation effect of these drugs, but also strengthen it, so don't use neostigmine excessively for rescue. D clinical dose has no ganglion blocking effect and histamine release promoting effect.

Non-depolarized muscle relaxant cartridge curcumin

Features: A. No muscle tremor before muscle relaxation. B. Inhaled general anesthetics and aminoglycoside antibiotics can strengthen and prolong the muscle relaxation effect of these drugs. C. It has antagonism with anticholinesterase drugs. In case of overdose, a proper amount of neostigmine can be used for detoxification. D. There is additive effect between similar blocking drugs.