Factors affecting experimental animal anesthesia

Experimental animal anesthesia is a complex system of work. Correct anesthesia treatment is a powerful guarantee for the success of animal experiments. However, improper treatment of anesthesia will cause errors that are difficult to analyze for experimental results. In order to obtain a good anesthesia effect, in addition to mastering the basic knowledge and technology of experimental animal anesthesia and following scientific anesthesia procedures, you should also understand the various factors that affect experimental animal anesthesia, such as animal factors and environmental factors.

1. Animal factors

1, 1 age and weight

Animal response to drugs varies with age. Some people divided rats and mice into three groups: juvenile, adult, and elderly according to age, and observed the effects of age on acute toxicity such as ethanol, pentane, and dichloroethane. According to the observation of LD50 and anesthesia concentration, the sensitivity showed as infancy> adult> old age. The age difference in response to poisons may be related to toxin enzyme activity. Young animals are very sensitive to poisons due to lack of these enzymes. Newborn rats do not reach the level of adult rats until about 8 weeks after birth. The glucuronide converting enzyme in rats does not reach the level of adult rats until about 30 days after birth. In addition, young animals, especially newly born animals, have not fully developed liver and kidney functions, and the ability to eliminate drugs is low. These factors increase the amount of free drugs and drugs that enter tissues, and are prone to accumulate poisoning.

The basal metabolic rate per unit weight of animals with lower body weight is higher than that of animals. Therefore, the smaller the animal, the greater the dose of anesthetic required per unit body weight. In some chronic experiments, the observation time is longer, and younger animals with smaller body weights can be selected for experiments.

1, 2 Gender

Experiments have shown that animals of different genders have different sensitivities to the same drug and have different responses to various stimuli. The female animal ’s reactivity at different stages of the sexual cycle and during pregnancy and lactation has changed greatly. Therefore, in general In the case, male animals or male and female halves are preferred for experiment. Males have a higher basal metabolic rate than females. During pregnancy, females have increased metabolic rates and are more sensitive to drugs. For example, ergostrine is used in male rats aged 5 to 6 weeks, and analgesic effect can be seen, but for female rats, there is no analgesic effect. 3-month-old lWistar rats ingest and excrete ethanol in terms of unit weight, and there are more females than males.

1, 3 Physiological and health conditions

Lean, muscular animals require a greater amount of anesthetic than fat-rich animals, because the basal metabolic rate is relatively low compared to non-metabolic tissues. Activity can increase the metabolic rate, therefore, the amount of anesthesia required for active animals is large. In animals with poor physical condition, a small amount of anesthetic is required and tolerance is reduced. Prone to poisoning. After the dog has insufficient food intake or weight loss of 10% to 20%, the anesthesia time is significantly prolonged.

1, 4 Animal feeding

Ensuring adequate nutrient supply is an important factor in maintaining animal health, and feed is more closely related to animals. Animal growth, development, reproduction, disease resistance and all life activities depend on nutrient-rich feed. Animals should be put in place one week before anesthesia and given careful feeding and management to keep them in good health. When feeding a balanced diet, the nutrient content should not be too high or too low. For example, dogs with large amounts of meat-eating can increase the basal metabolic rate by 90%; the protein content in mice ’s feed is less than 20%, which is prone to intestinal diseases; vitamins in guinea pig feed Lack of susceptibility to scurvy.

2. Environmental factors

2, 1 temperature

Within a certain range, the temperature changes slowly, and the body can automatically adjust to suit it. However, if the change is too large or too sudden, it will have adverse effects on the body, such as behavior and physiology. Therefore, too high or too low temperature in the experimental environment can cause the body's resistance to decline, the sensitivity to anesthetic drugs increases, and poisoning is prone to occur. Therefore, the effect of anesthesia is affected.

2, 2 Humidity

If the humidity is too high, the microorganisms are prone to multiply, and if it is too low (less than 40%), it will cause dust to fly, which is harmful to the health of animals. The relative humidity of the air is also closely related to the adjustment of animal body temperature. The effect is particularly obvious under high temperature conditions, such as humidity below 40%, rats are prone to bad tail disease, under low humidity conditions, rats or mice lactating female rats are prone to eating children. Humidity directly affects the animal's temperature regulation and health status, and indirectly affects the animal's reactivity to anesthetic drugs. Therefore, the laboratory for animal anesthesia, the relative humidity should be between 40% to 70%, 50% ± 5% is best.

2, 3 Air velocity and cleanliness

Experimental animals generally have larger body surface area per unit weight than humans, so airflow has a greater impact on animals. On the one hand, the air flow rate affects the heat dissipation of the animal's body surface, especially the body temperature of the animal under anesthesia. On the other hand, the proper air flow rate can expel the dirty gas in the laboratory, such as ammonia in time. Experiments have shown that excessive ammonia concentration in the ambient air of the experimental animals can irritate the mucous membrane of the animal and cause tearing, coughing, etc. In severe cases, it can cause mucosal inflammation, pulmonary edema or pneumonia. Therefore, the air in the anesthetized animal laboratory should be kept as fresh as possible. The ammonia concentration is required to be less than 20 mg / L, and the airflow speed is 10-25 cm / s. The number of ventilations is 8-15 times / h. In winter, try to avoid wearing wind.

In summary, animal factors and environmental factors directly or indirectly affect the health of animals, so that the body has different metabolic enzyme systems and clearance capabilities for narcotic drugs, and therefore has different sensitivity to anesthetic drugs. Therefore, the above factors should be fully considered when anesthetizing animals, and the dosage can be increased or decreased as appropriate to obtain a good anesthetic effect.