Audio Summary Transcript

Hello, my name is Shannen Schultz and I'm a small animal general practitioner in Adelaide, South Australia. Throughout my time at vet school and my career, I developed a special interest in aquatic animal health, and optimising the welfare and clinical outcomes of fish patients.

This Knowledge Summary asks the question: do opioids provide adequate perioperative analgesia for teleost fish undergoing surgical coeliotomy? Four studies, all laboratory-based randomised control trials, were critically appraised to attempt to answer this question. The species of fish assessed were the koi carp, rainbow trout, and Nile tilapia, with the population varying between studies. The clinical bottom line is that there are contradicting results regarding the analgesic efficacy of opioids perioperatively in these species, with some evidence of pain alleviation seen when assessing some behavioural parameters, but not when assessing clinical pathology or cardioventilatory data.

All four studies involved assessment of behavioural or physiological parameters in the postsurgical period. Activity level, respiratory rate, food consumption, and hiding behaviour or location in the water were parameters that were assessed by three of four studies, while the fourth assessed only quantifiable cardioventilatory data to measure heart rate, ventilation rate, and heart rate variability.

There are concerns about the applicability of the behavioural indicators of pain, which are commonly used for zebra fish, to other less commonly used species, such as those in the appraised studies. There are currently no standardised measures of pain in these used species, and further research should be done to create similar guidelines for other species, so that there can be uniformity in outcome selection between studies.

Two studies concluded that butorphanol was effective in minimising changes in postsurgical behaviours, compared with the presurgical period. However, the remaining two studies suggested that the outcomes were actually affected not by the alleviation of pain from opioids, but by the sedative effects and cardiorespiratory depression that are caused by opioids.

Within the appraised studies, there is a great deal of variation in species used, opioid intervention administered, and outcomes assessed. Further research needs to be undertaken with a consistent approach to measuring opioid efficacy, and focusing on appropriate dosages required to provide surgical analgesia. This should be done by focusing on determining the physiologic impact of opioids on teleost fish, so that their analgesic effects can be more accurately assessed, as well as development of more uniform measures of pain in these species. Though the authors of the appraised studies disagree regarding the true analgesic efficacy of opioids for teleosts undergoing surgery, and their possible adverse effects, the results of the trials indicate that there is room for opioid analgesia in the anaesthetic protocols for these animals.