Anesthesia Guidelines: Mice

Find guidelines for mouse anesthesia, including anesthetic drugs and procedures and special considerations for neonatal mouse anesthesia.

Research Animal Resources (RAR) veterinary staff designed these guidelines to be general recommendations, not an inclusive list of all possible drug combinations that can be used in mice. Consequently, guidelines do not reference specific research-associated concerns.

If you have questions about using anesthetics for your particular situation, please work with your area veterinarian to develop the most effective anesthetic plan.

How to use anesthesia

Animals may be anesthetized for surgery, non-surgical procedures that may be painful, or non-painful procedures that require immobilization. Anesthesia causes the loss of feeling in all or part of the body, with or without loss of consciousness.

Steps must be taken before, during, and after anesthesia to ensure animal safety and anesthesia efficacy.  

Anesthetic drugs can be administered parenterally or by inhalation. The choice of anesthetic agent will depend on the procedure to be performed, research aims, and other factors such as animal age; there are special considerations for neonatal mice. Consult your area veterinarian with questions about drug selection.

General guidelines and considerations for mouse anesthesia

Acclimation

A one-week acclimation period is recommended for all animals to prevent stress-induced disease.

Fasting

Pre-anesthetic fasting is usually not necessary for mice due to their inability to vomit. However, if fasting is employed, limit it to no more than two to three hours due to the high metabolic rate of small rodents. Never restrict water.

Eye protection

Mouse eyes remain open under anesthesia. This can lead to corneal drying and trauma. Apply ophthalmic ointment (e.g., Paralube® or Lacrilube®) to eyes if:

• The anesthetic event lasts longer than five minutes.
• Anesthesia is being delivered by facemask. 

Monitoring

Regardless of the anesthetic administered, monitor mice under anesthesia to avoid excessive depression of cardiac and respiratory functions, or insufficient anesthesia. Parameters that can be monitored in an anesthetized mouse without specialized equipment include:

• Anesthetic depth: Toe pinch. 
• Respiratory rate and pattern: The normal undisturbed rate is ~180/minute, a slow rate drop of 50% is acceptable during anesthesia.
• Mucous membrane color: Should be pink, not blue or gray.
• Body temperature: Can be monitored with a rectal thermometer, and should be above 97℉.
• Oxygen saturation and heart rate: Can be monitored using a specialized rodent pulse oximeter, and should be greater than 95% and between 300-800 beats/minute, respectively. 

Heat support

All species are at risk for hypothermia while under anesthesia. Mice are particularly susceptible due to their high body surface area to body mass ratio. Hypothermia induces significant physiological stress on animals that can prolong recovery and potentially be fatal. Guidelines:   

• Provide supplemental heat during all anesthetic events.  Supplemental heat sources include circulating water blankets, electric heating pads, and commercial products that can be warmed in a microwave.  
• Never place the animal directly on the heat source.  

Fluid support

Consider providing warm subcutaneous (SQ) or intraperitoneal (IP) fluids, particularly for prolonged anesthetic events or animals that are ill, aged, or debilitated. 

Recovery

Continue to monitor animals until they are fully recovered. Guidelines:

• Recover animals on paper towels (without bedding) in a clean cage. This minimizes the risk of tracheal obstruction or pneumonia.
• Recover anesthetized animals alone in a cage.
• Continue to provide supplemental heat during recovery.
• When the animal is ambulatory, return it to the home cage with immediate access to food and water.

Contact your area veterinarian with questions or for additional information. 

Anesthetic drugs and procedures