Which statement is TRUE about injectable anesthetics compared with gaseous anesthetics used with mice?

• A. Gaseous anesthetics cause greater depression
• B. There is no difference in respiratory depression
• C. Injectable agents cause a greater depression of respiration in rodents
• D. Injectable agents avoid respiratory depression entirely

Answer: (C)

When thinking about how anesthesia affects breathing in mice, the depth and control of the anesthetic matter a lot. Injectable regimens, especially when using a combination like ketamine with xylazine, tend to suppress respiration more strongly. Xylazine is an alpha-2 agonist that directly dampens the brain centers that regulate breathing, lowering both the rate and the depth of breaths. Ketamine contributes to anesthesia but, in the presence of sedatives, the overall ventilatory drive can still be markedly reduced. The result is a greater depression of respiration with injectable drugs, particularly with combinations, than you typically see with gaseous anesthetics.

Inhaled anesthetics are delivered as controllable concentrations and can be titrated to maintain lighter planes of anesthesia with less profound respiratory depression. They also allow the addition of supplemental oxygen and often enable faster recovery once the gas is stopped. So, while all anesthesia carries some risk of breathing suppression, injectable regimens used in mice are commonly associated with more significant respiratory depression than gaseous anesthetics, making that statement true.