What are the common anesthetics for animal experiments? What are the characteristics of each?
动物实验,动物麻醉
z-bo
2020-07-16
2218
What are the common anesthetics for animal experiments? What are the characteristics of each?
Common anesthetics for animal experiments
1. Barbiturates
Various barbiturates have different rates of absorption and metabolism, and their duration of action varies. Barbiturates have a strong inhibitory effect on the respiratory center. When the anesthesia is too deep, respiratory activity can be completely stopped. Therefore, care should be taken to prevent excessive and rapid administration. It also has complex effects on the cardiovascular system, so these drugs are not used for the anesthesia of experimental animals to study cardiovascular function.
(1) Sodium pentobarbital
is most commonly used in experiments. The product is a white powder, usually formulated into a 1% to 3% aqueous solution for intravenous or intraperitoneal administration. The effective duration of one-time anesthesia lasts for 3 to 5 hours, which belongs to the intermediate-effect barbiturates. During intravenous injection, the first 1/3 dose can be injected quickly to quickly pass the excitement period; the second 2/3 dose should be injected slowly, and closely observe the animal's muscle tension, respiratory rate and depth, and corneal reflex. After the animal is anesthetized, it is often due to the effects of anesthetics, muscle relaxation and skin vasodilation, which causes the body temperature to drop slowly, so try to keep warm.
(2) thiopental thiopental (sodillm thiopental)
is a light yellow powder, and its aqueous solution is unstable, so it needs to be temporarily formulated into a 2.5% to 5% solution for intravenous injection before use. -One dose can maintain 0.5 to 1 h. The administration can be repeated when the experiment time is longer, and the maintenance dose is 1/l0～1/5 of the original dose. It is suitable for short-term experiments and belongs to the category of short-acting or ultra-short-acting.
Second, urethane is also known as urethane
has mild action properties, is easily soluble in water, has strong and rapid anesthesia for animals, and has a wide safety range. It can be used in most animal experiments and is more suitable for small animal anesthesia. It can lead to a longer-lasting shallow anesthesia and no obvious effect on breathing. In particular, experiments with greater influence on blood pressure, ECG, and respiration are particularly suitable. The advantages are cheap, easy to use, the administration can be maintained for 4 to 5 hours, and the anesthesia process is relatively stable, the animal has no obvious struggling phenomenon; the disadvantage is slow recovery, the depth of anesthesia and the dosage are difficult to master. Urattan has a strong anesthetic effect on rabbits, and it is a common anesthetic for acute experiments in rabbits. It has a slower effect on cats and dogs. It can induce tumors in rats and rabbits. It is not suitable for long-term survival of chronic experimental anesthesia. This medicine is easily soluble in water, and it is formulated into a 10% to 25% solution when used. If the injection dose is too large, it can cause the blood pressure of the animal to drop, and it also has a great impact on breathing. It is particularly important to keep animals warm during anesthesia with this medicine.
Three, chloral sugar and chloral hydrate
(1) Chloraldehyde, a derivative of chloral hydrate
The drug has low solubility and is usually formulated into a 1% aqueous solution. Before use, it must be heated in a water bath (up to 60 degrees, cannot be boiled) to dissolve it. The drug has a large safety range, can cause long-lasting shallow anesthesia, has no obvious inhibitory effect on the autonomic nerve center, and has little effect on pain, so it is particularly suitable for experiments requiring the retention of physiological reflexes (such as cardiovascular reflexes) or nervous system reactions .
(2) Chloraldehyde hydrate (Trichloroacetaldehyde hydrate)
White crystals, chloral hydrate decompose easily, absorb moisture in the air and deliquesce. Chloraldehyde hydrate can be prepared by yourself or purchased from hospital preparations.
The pharmacological action and pharmacokinetics of chloral hydrate, [mechanism of action] This product is a hypnotic and anticonvulsant. The hypnotic dose can induce falling asleep within 30 minutes. The hypnotic effect is gentle, does not shorten the REMS sleep time, and has no obvious sequelae. The mechanism of hypnosis may be similar to barbiturates, causing similar physiological sleep, with no obvious aftereffect. After absorption, most of it is distributed in the liver and other tissues, and is quickly reduced to trichloroethanol by alcohol dehydrogenase, which has the central inhibitory effect equivalent to chloral hydrate. Since the half-life of chloral hydrate is very short (only a few minutes), trichloroethanol plays a hypnotic role, it is inactivated by combining with glucuronic acid, and is excreted by the kidneys. The plasma half-life of trichloroethanol is 8 hours.
[Pharmacokinetics] Gastrointestinal or rectal administration can be quickly absorbed, reaching the peak in 1 hour and maintaining for 4-8 hours. It is highly fat-soluble and easily passes through the blood-brain barrier to distribute various tissues throughout the body. The plasma T1/2 is 7 to 10 hours. It is rapidly metabolized in the liver into active trichloroethanol. The protein binding rate of trichloroethanol is 35-40%, and the T1/2 of trichloroethanol is about 4-6 hours. Oral chloral hydrate can fall asleep within 30 minutes, the duration is 4 to 8 hours. Trichloroethanol is further combined with glucuronic acid to be inactivated and excreted by the kidney without hysteresis and accumulation. This medicine can pass through the placenta and secrete into milk
chloral hydrate injection can be prepared by yourself
①Solvent: Normally use normal saline, preferably 5～10% glucose injection or 5% glucose magnesium sulfate injection (5% glucose solution 100ml plus magnesium sulfate 5g), now the laboratory seems to use distilled water to prepare, if used The method of intraperitoneal injection is anesthesia, which requires aseptic treatment, or use sterile saline or add penicillin to maintain sterility.
②Concentration: High concentration is highly irritating and easy to cause hemolysis; low concentration increases the amount of drug solution injected and increases the burden on the heart and lungs. The usual concentration for injection is 10%. The volume required for intraperitoneal injection at a concentration of 10% will be relatively large, so high-concentration reagents can be used, so that the amount of intraperitoneal injection liquid is controlled within 0.5ml, which will be better for animals.
③ Preparation: The chloral hydrate solution after boiling and disinfection can be decomposed into acidic liquid, which can cause acidosis in animals after injection. Sterilize the container during preparation, add the required solvent and boil for 15 minutes. When it is cooled to 60～80℃, add the required chloral hydrate, shake well to fully dissolve the drug, and apply it after sterile filtration.
Caution
① When the drug solution is left for a long time, the potency will be reduced. It needs to be stored in a brown bottle or a glass bottle protected from light. It should be used up within 2 to 3 days and should not be stored for a long time.
② Abdominal anesthesia with chloral hydrate solution is likely to cause adhesion of abdominal organs or irritant ascites. If animals still need to be reared for a period of time after anesthesia and the test items are related to abdominal organs, they should not be used.
③The protective effect of chloral hydrate on the brain tissue is weak. Rats with focal cerebral ischemia and cerebral ischemia reperfusion usually use chloral hydrate anesthesia. Pentobarbital has a strong protective effect on the brain tissue and should not be used.
Four, mixed anesthesia
In the experiment, chloral sugar and urethane are often used together. The chloralose was dissolved in 25% uratan solution by heating method, so that the chloralose concentration was 5%. The intravenous dose of dogs and cats is 1.5～2m1/kg mixed solution, and the dosage of chloralose is 75～100 mg/kg. Rabbits can also use this dose for intravenous injection. Compared with diethyl ether, the advantages of non-volatile anesthetics such as barbiturates, chloraldose, and uratan are: easy to use, one-time administration (except thiopental) can maintain anesthesia for a longer period of time, surgery and experiments There is no need for someone to manage anesthesia during the process, and the anesthesia process is relatively stable, and the animal has no obvious struggle. The disadvantage is: slower recovery
