New Study Sheds Light on “Invisible” Animal Pain

Albino Mouse

Over the last several months, Science First has highlighted concerns from the scientific community about the validity of animal experiments. We’ve previously examined widespread reproducibility issues resulting from lack of bias-reducing measures, poorly planned experiments, inappropriate statistical tests and poor reporting on animal attrition (why animals are dropped from studies).

This week’s Science First covers the problems that occur as a result of poor reporting of analgesic (pain reliever) use for painful procedures in lab animals. Scientists that perform procedures on lab animals are tasked with choosing anesthetics for surgery and analgesics for post-operative pain management to control animal suffering. This is a significant decision from an animal welfare perspective that raises interesting scientific challenges, as both pain and the drugs used to manage pain can influence experimental outcomes.

The question must therefore be asked: When researchers publish the results of their studies, are they providing clear and detailed descriptions of their pain relief regimens?

To gain insight to this question, researchers in a recent study examined 400 scientific papers that included major animal survival surgeries as part of their methodology, and scored the level of detail provided on anesthesia and analgesia. The surgeries were quite invasive, and included, among other procedures, craniotomies in macaque monkeys; orthopedic bone, tendon or joint surgeries in dogs; and kidney or liver transplants in rats—all surgeries that were deemed too technically challenging to perform on unanesthetized animals. A laboratory animal veterinarian scored the papers for the completeness of their descriptions of anesthesia and analgesia.

The results revealed a serious deficiency in reporting detailed descriptions of anesthesia and analgesia use. In the authors’ words: “We found animal pain to be largely invisible in published descriptions of animal experiments.”

Among the study’s findings:

  • Of 400 papers, 62 made no mention of anesthesia or analgesia.
  • Only 98 of the remaining 338 papers (29%) mentioned post-surgical analgesia.
  • 240 of the 338 papers (71%) mentioned anesthesia only, but not post-surgical analgesia.
  • 302 out of 400 papers (76%) did not mention whether animals who had undergone major surgery were provided pain medication.

The implications of this under-reporting are many. In particular, scientists referring to the literature as a guide for how to plan their own experiments will not be able to tell if pain treatments were actually withheld or simply edited out of the publication. As a result, the authors conclude that, “Under-reporting encourages under-treatment. It perpetuates itself when research scientists rightly or wrongly believe that analgesics are not used, and cannot be used in their field, and then publish their own work with no mention of pain or pain medicines. The data suffer and the animals suffer.”

Studies such as these—and the issues they uncover—serve to reinforce NAVS’ call for the research community to replace cruel, costly and flawed animal experiments with modern, human-relevant, non-animal approaches. Science can advance without inflicting pain onto animals.

What are your thoughts on this week’s Science First? Send your questions and comments to We look forward to hearing from you.

Pain and Laboratory Animals: Publication Practices for Better Data Reproducibility and Better Animal Welfare
May 2016

We investigated what information on animal pain management a reasonably diligent scientist might find in planning for a successful experiment…We conclude that current scientific literature cannot be trusted to present full detail on use of animal anesthetics and analgesics.

For more information, see PLoS ONE


This entry was posted in News and tagged on September 26, 2016.
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