According to the Guide for the Care and Use of Laboratory Animals, the IACUC should carefully consider two types of endpoints during protocol review: the experimental endpoint, which occurs when the scientific aims and objectives have been reached, and the humane endpoint, which occurs when pain or distress in an experimental animal is prevented, terminated or relieved1. In this scenario, Hodges has developed and validated a sophisticated monitoring system for his research study that will allow him to monitor and track changes in a number of physiologic parameters remotely. Most of this monitoring appears to have been designed to assure that his animals can reach the experimental endpoint. However, the monitoring plan described in his protocol does not take advantage of data that could be used to determine early euthanasia criteria, such as the rats' appearance in the images he is collecting. In addition, by indicating that animals with severe hypoglycemia or excessively high or low body temperature would simply be excluded from the study rather than treated or humanely euthanized, Hodges has failed to identify humane endpoints.
The IACUC seems to be asking Hodges to define humane endpoints on the basis of abnormalities in the physiologic data, even if some of these abnormalities do not always indicate pain or distress. For example, bradycardia, tachycardia and cardiac arrhythmia can be benign or clinically insignificant, and mild or moderate hypoglycemia is often subclinical. Taken by themselves, these parameters might not be indicators that an animal requires treatment or has reached a humane endpoint.
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