Ming, for animal experiments, how is anesthesia performed? General or local? What anesthetics are used?

 

In animal research, mouse anesthesia is a critical step for ensuring the smooth progress of experiments. Selecting appropriate anesthetics and methods not only improves efficiency but also minimizes animal distress. Today, let's delve into the details of mouse anesthesia.

 

Mouse Anesthesia
 

Methods
 

Anesthesia is primarily classified into general anesthesia and local anesthesia, with general anesthesia further divided into inhalational and injectable (non-inhalational) types.
 

1. General Anesthesia:  Laboratory animals are generally less cooperative; therefore, general anesthesia is commonly used in experiments.
 

1) Inhalational Anesthesia:  Also known as gas anesthesia. Volatile or gaseous anesthetics are inhaled via the respiratory tract to produce anesthetic effects.

●Characteristics:  Anesthetic depth is easily adjustable, recovery is rapid and smooth, and there is minimal impact on liver and kidney function.

●Common Inhalational Anesthetics:

○Isoflurane:  Induction and recovery are both rapid. It does not significantly affect physiological parameters and is the internationally standard method. Procedure:  First, rapidly anesthetize the mouse in an induction chamber (4% - 5% isoflurane), then reduce to maintenance concentration (1% - 2%). Use a face mask or nose cone to secure the mouse, preventing gas leakage. Experiments should be conducted within a fume hood. Regularly check the weight of the scavenger canister to ensure effective waste gas scavenging. Operators should wear masks.

○Sevoflurane:  Low irritation. Induction and recovery are very rapid, suitable for mice sensitive to respiratory tract irritation.
 

2) Non-Inhalational (Injectable) Anesthesia:  Includes intramuscular, intraperitoneal, and intravenous injections.

●Characteristics:  Simple to perform, requires no special equipment, and is low-cost. However, anesthetic depth and duration are difficult to adjust flexibly. Drugs are metabolized by the liver and excreted by the kidneys, posing a greater impact on liver and kidney function.

●Common Injectable Anesthetics:

○Pentobarbital Sodium:  Suitable for non-survival procedures (e.g., dissection, tissue sampling). Advantages:  Stable anesthetic effect, long duration (30-60 minutes). Disadvantages:  Slow recovery, can cause respiratory depression. High lethality with overdose; requires precise dose control (Typical dose: 40-60 mg/kg, IP).

○Ketamine + Xylazine (K/X Combination):  Suitable for mid- to short-duration procedures requiring sedation and analgesia (e.g., laparotomy, tumor implantation). Advantages:  Relatively safe, highly reversible. Disadvantages:  May suppress body temperature and respiration; requires continuous monitoring. Typical dose: Ketamine 80-100 mg/kg + Xylazine 5-10 mg/kg (IP).
 

2. Local Anesthesia:  Involves using anesthetics to block sensory nerve conduction in a specific body region, while motor nerve conduction remains intact or is partially blocked to varying degrees. Suitable for mid- to short-duration procedures requiring sedation and analgesia (e.g., laparotomy, tumor implantation).

●Advantages:  Relatively safe, highly reversible. Disadvantages:  May suppress body temperature and respiration; requires continuous monitoring.

 

Monitoring Anesthetic Depth

1.Light Anesthesia:  Mild response to toe pinch. Suitable for short, painless procedures.

2.Surgical Anesthesia:  No response to toe pinch, muscle relaxation. Allows for surgeries like thoracotomy or laparotomy.

3.Excessive Anesthesia:  Respiratory rate < 40 breaths/min. Immediately reduce anesthetic concentration or administer an antagonist.

 

Choosing Between Inhalational and Injectable Anesthesia
 

1.Inhalational Anesthesia:

a.Advantages:  Better control over anesthetic depth; rapid induction; rapid, smooth recovery; minimal impact on liver/kidney function.

b.Disadvantages:  Long-term inhalation of volatile anesthetics can harm personnel; equipment cost is higher.

2.Non-Inhalational (Injectable) Anesthesia:

a.Advantages:  Simple operation, no special anesthesia apparatus needed, lower cost.

b.Disadvantages:  Less flexible control over dosage, depth, and duration; drugs impact liver/kidney function more significantly.

 

Anesthesia Precautions
 

1. Pre-Anesthesia Preparation
 

1.Accurately weigh the mouse to calculate the anesthetic dose based on body weight.

2.Check the quality and expiration date of the anesthetic; avoid using expired or degraded agents.

3.Ensure anesthesia equipment (e.g., vaporizer, induction chamber, mask) is functioning properly.
 

2. During Anesthesia
 

1.Strictly adhere to recommended dosages; avoid overdose or underdose.

2.For inhalational anesthesia, ensure accurate gas concentration and prevent leakage.

3.For injectable anesthesia, pay attention to injection site and depth to avoid injuring vital organs.
 

3. Post-Anesthesia Observation
 

1.Closely monitor vital signs: respiration, heart rate, body temperature.

2.Ensure the mouse is in a quiet, warm environment, protected from chilling or injury.

3.If abnormal reactions occur (e.g., rapid breathing, convulsions), take immediate action.

 

Potential Problems and Solutions
 

1.Excessive Anesthesia:  Respiratory rate below 40 breaths/min, excessive muscle relaxation, no response to stimuli.

Solution:  Immediately reduce anesthetic concentration or stop supply; administer an antagonist if necessary.

2.Respiratory Depression:  Slow, shallow breathing, or even apnea.

Solution:  Gently tap the mouse's body or pinch its toe to stimulate breathing. If ineffective, consider a respiratory stimulant.

3.Hypothermia:  Body temperature below normal range, cold limbs.

Solution:  Place the mouse in a warm environment, e.g., on a heating pad (set to ~37°C), avoiding overheating.

4.Delayed Recovery:  Anesthesia lasts longer than expected; mouse fails to regain consciousness.

Solution:  Check vital signs; ensure normal breathing and heartbeat. Slightly increase ambient temperature to promote recovery.

 

References:

[1] Peking University - Laboratory Animal Center

[2] Sun Yat-sen University (Shenzhen) - Laboratory Animal Center

[3]https://mp.weixin.qq.com/s/OTls4T8IILUH0iY-X_X3Fg 

[4]https://mp.weixin.qq.com/s/thrbJ2mVtUzrn6oAnS0HWQ

[5]https://mp.weixin.qq.com/s/-2E4HZZUMVH0B3cmyqZCZQ

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