During anesthesia, which statement about respiratory effects is true?

• A. Gaseous anesthetics cause greater respiratory depression than injectable
• B. Both cause no respiratory depression
• C. Injectable anesthetics can cause greater respiratory depression than gaseous anesthetics
• D. Respiratory depression is not a concern when using anesthesia

Answer: (C)

Respiratory function during anesthesia is strongly influenced by the route of administration. Injectable anesthetics such as propofol or thiopental act quickly on brainstem centers that regulate breathing and can produce apnea and a rapid, marked drop in both tidal volume and respiratory rate, especially when given as a bolus or at higher doses. This means they can depress respiration more profoundly than many gaseous (inhaled) anesthetics when depth of anesthesia is increased.

Inhaled agents like isoflurane or sevoflurane depress ventilation as well, but their effects are more dose-tentative and easier to titrate. Because you can adjust the vaporizer concentration gradually and maintain anesthesia while the animal continues to breathe on its own, the overall respiratory depression is often less severe at equivalent levels of anesthesia compared to a rapid IV dose.

So, the statement that injectable anesthetics can cause greater respiratory depression than gaseous anesthetics is consistent with how these drugs commonly behave, especially during induction. Respiratory depression is indeed a concern with any anesthesia, and no-pertaining option would be incorrect.