The Guide for the Care and Use of Laboratory Animals states that selection of appropriate analgesia and anesthesia should be based on veterinary judgment and whether it “...best meets clinical and humane requirements as well as the needs of the research...”1. A common and effective (when done correctly) method of anesthesia in neonatal rodents is hypothermia. Jeffries wishes to use hypothermia for his blunt trauma research in 10-d-old rats, which falls outside of the commonly accepted age limit of 7 d for this technique. As a neonate becomes more mobile, the safety and practicality of hypothermia anesthesia decreases and alternative methods should be explored2.

Although Jeffries' concern about the potential effect of isoflurane on cerebral cortical function is justified, other considerations should accompany this concern. First, the previous traumatic injury studies he found used isoflurane as an anesthetic. Its effects notwithstanding, it may be beneficial for Jeffries to use isoflurane so that his results can be compared to the results obtained in previous studies. Second, isoflurane is the most common inhalant anesthetic used in rodents but is not the only one that can be used. Halothane or sevoflurane might be appropriate alternatives to provide anesthesia without affecting cortical function in the same way as isoflurane. Similarly, injectable anesthetics other than ketamine (e.g., alpha 2 agonists, barbiturates) should also be explored.

These alternative methods of anesthesia bring up the importance of pilot studies. Literature on rodent anesthesia is robust but far from exhaustive. Therefore, it is often advisable that researchers carry out well-designed pilot studies prior to beginning their larger experiments to specifically address the needs of their projects, especially when animal welfare is in question. In Jeffries' case, a pilot project could be used to determine whether the parameters that are of interest to him would be affected by an inhalant or injectable anesthetic. A pilot study could also be used to determine whether 7-d-old rats could be used in place of 10-d-old neonates, which would allow him to use hypothermia anesthesia.

Despite best efforts to minimize variables in research, it is impossible to control for everything. In this scenario, the pain and distress caused by the procedure might be an experimental variable required for the goals of Jeffries' research (is this experiment designed to evaluate physical trauma, psychological trauma or both?). However, Jeffries' concern regarding the effect of anesthesia on the experiment could mostly be alleviated by ensuring that proper control animals are included in the study design to address the effects of strain, age, anesthetic, etc.

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