Challenges of thermal nociceptive threshold testing in the donkey

Nicola J Grint, Helen R Whay, Thierry Beths, Kathy Yvorchuk, Joanna C Murrell

Research output: Contribution to journalArticle (Academic Journal)peer-review

9 Citations (Scopus)

Abstract

OBJECTIVE: To evaluate a thermal nociceptive threshold (TNT) testing device in the donkey, and the influence of potential confounding factors on TNTs.

ANIMALS: Two groups (Group 1 and Group 2) of eight castrated male donkeys aged 4-9 years, weighing 105-170 kg.

METHODS: TNTs were measured by heating a thermal probe on skin until an end-point behaviour (threshold temperature) or a cut-out temperature (51 °C) was reached. The withers and the dorsal aspect of the distal limb were used as sites for TNT testing. The effects on TNT of different confounding factors: the limb tested; rate of heating; and ambient temperature were evaluated. Data were analyzed using general linear models, and Mann-Whitney tests, p < 0.05 was considered significant.

RESULTS: End-point behaviours (skin twitch or donkey looking at test device) when the thermal probe heated the withers were observed in approximately half of tests. TNT was (mean ± SD) 46.8 ± 2.85 °C. Subsequently the limb was evaluated as the test site in Group 1 followed by Group 2 donkeys; end-point behaviour being a foot-lift. In Group 1, 72% of tests ended in an end-point behaviour but the response rate was lower in Group 2 (20%), although TNTs were similar [(47.6 ± 3.3) and (47.3 ± 3.0) °C respectively] for responding animals. Rate of heating, ambient temperature and laterality (right or left) did not affect thresholds, but mean TNT was significantly higher in the forelimb (48.5 ± 2.8 °C) than the hind limb (47.4 ± 2.8 °C) (p = 0.012).

CONCLUSIONS: When a thermal probe cut-out temperature of 51 °C was used in TNT testing in the donkey a high proportion of tests did not produce an identifiable end point behaviour. Higher cut-out temperatures damaged the skin. Under these conditions, thermal nociceptive threshold testing appears not be an appropriate analgesiometry technique in the donkey.

CLINICAL RELEVANCE: TNT testing under these conditions is not suitable form of analgesiometry for donkeys.

Original languageEnglish
Pages (from-to)205-214
Number of pages10
JournalVeterinary Anaesthesia and Analgesia
Volume42
Issue number2
DOIs
Publication statusPublished - Mar 2015

Bibliographical note

© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.

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