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, 57 (2), 143-156

Bias in Rating of Rodent Distress During Anesthesia Induction for Anesthesia Compared With Euthanasia

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Bias in Rating of Rodent Distress During Anesthesia Induction for Anesthesia Compared With Euthanasia

Brittany A Baker et al. J Am Assoc Lab Anim Sci.

Abstract

Selection of an appropriate method of euthanasia involves balancing the wellbeing of the animal during the procedure with the intended use of the animal after death and the physical and psychologic safety of the observer or operator. The recommended practices for anesthesia as compared with euthanasia are very disparate, despite the fact that all chemical methods of euthanasia are anesthetic overdoses. To explain this disparity, this study sought to determine whether perception bias is inherent in the discussion of euthanasia compared with anesthesia. In this study, participants viewed videorecordings of the anesthesia of either 4 rats or 4 mice, from induction to loss of consciousness. Half of the participants were told that they were observing anesthesia; the other half understood that they were observing euthanasia. Participants were asked to rate the distress of the animals by scoring escape behaviors, fear behaviors, respiratory distress, and other distress markers. For mice, the participants generally rated the distress as high when they were told that the mouse was being euthanized, as compared with the participants who were told that the mouse was being anesthetized. For rats, the effect was not as strong, and the distress was generally rated higher when participants were told they were watching anesthesia. Because the interpretation of distress showed bias in both species-even though the bias differed regarding the procedure that interpreted as distressing-this study demonstrates that laboratory animal professionals must consider the influence of potential perception bias when developing policies for euthanasia and anesthesia.

Figures

Figure 1.
Figure 1.
Methods of anesthesia induction that were recorded for evaluation by the participants.
Figure 2.
Figure 2.
To avoid respondent bias when the recordings were viewed, the anesthesia chamber was set up identically for all anesthesia methods. Carbon dioxide gas was introduced through the diffuser located in the center top of the lid of the chamber. Isoflurane gas was introduced through the hose located at the front left and top of the chamber.
Figure 3.
Figure 3.
Instructions from the questionnaires that were provided to each participant on this study. Note that the bolded words differed depending on the treatment group to which the participant was assigned. These were the only differences between the treatment groups.
Figure 4.
Figure 4.
Survey questions. The demographic questions were asked first, and then questions 5 through 15 were repeated for each of the 4 videos that the participants watched.
Figure 5.
Figure 5.
Distribution of scores for escape behavior by number of respondents observing a mouse anesthetized with the various anesthetic methods. The box indicates responses where the participant reported that the animal exhibited no escape behaviors. (A) Pentobarbital. (B) Isoflurane. (C) 30%/min VDR CO2. (D) 70%/min VDR CO.
Figure 6.
Figure 6.
Distribution of scores for fear behavior by number of respondents observing a mouse anesthetized with the various anesthetic methods. The box indicates responses where the participant reported that the animal exhibited no fear behaviors. (A) Pentobarbital. (B) Isoflurane. (C) 30%/min VDR CO2. (D) 70%/min VDR CO.
Figure 7.
Figure 7.
Distribution of scores for respiratory distress by number of respondents observing a mouse anesthetized with the various anesthetic methods. The box indicates responses where the participant reported that the animal exhibited no respiratory distress. (A) Pentobarbital. (B) Isoflurane. (C) 30%/min VDR CO2. (D) 70%/min VDR CO.
Figure 8.
Figure 8.
Distribution of scores for other distress by number of respondents observing a mouse anesthetized with the various anesthetic methods. The box indicates responses where the participant reported that the animal exhibited no other distress. (A) Pentobarbital. (B) Isoflurane. (C) 30%/min VDR CO2. (D) 70%/min VDR CO.
Figure 9.
Figure 9.
Distribution of scores of appropriateness by number of respondents observing a mouse anesthetized with the various anesthetic methods. The box indicates responses of ‘appropriate.’ (A) Pentobarbital. (B) Isoflurane. (C) 30%/min VDR CO2. (D) 70%/min VDR CO.
Figure 10.
Figure 10.
Distribution of scores for escape behavior by number of respondents observing a rat anesthetized with the various anesthetic methods. The box indicates responses where the participant reported that the animal exhibited no escape behaviors. (A) Pentobarbital. (B) Isoflurane. (C) 30%/min VDR CO2. (D) 70%/min VDR CO.
Figure 11.
Figure 11.
The box indicates responses where the participant reported that the animal exhibited no fear behaviors. (A) Pentobarbital. (B) Isoflurane. (C) 30%/min VDR CO2. (D) 70%/min VDR CO.
Figure 12.
Figure 12.
Distribution of scores for respiratory distress by number of respondents observing a rat anesthetized with the various anesthetic methods. The box indicates responses where the participant reported that the animal exhibited no respiratory distress. (A) Pentobarbital. (B) Isoflurane. (C) 30%/min VDR CO2. (D) 70%/min VDR CO.
Figure 13.
Figure 13.
Distribution of scores for other distress by number of respondents observing a rat anesthetized with the various anesthetic methods. The box indicates responses where the participant reported that the animal exhibited no other distress. (A) Pentobarbital. (B) Isoflurane. (C) 30%/min VDR CO2. (D) 70%/min VDR CO.
Figure 14.
Figure 14.
Distribution of scores of appropriateness by number of respondents observing a rat anesthetized with the various anesthetic methods. The box indicates responses of ‘appropriate.’ (A) Pentobarbital. (B) Isoflurane. (C) 30%/min VDR CO2. (D) 70%/min VDR CO.

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