Assessment of a carbon dioxide laser for the measurement of thermal nociceptive thresholds following intramuscular administration of analgesic drugs in pain-free female cats

Farnworth, M.J. ORCID: 0000-0001-6226-0818, Barrett, L.A., Adams, N.J., Beausoleil, N.J., Weidgraaf, K., Hekman, M., Chambers, J.P., Thomas, D.G., Waran, N.K. and Stafford, K.J., 2015. Assessment of a carbon dioxide laser for the measurement of thermal nociceptive thresholds following intramuscular administration of analgesic drugs in pain-free female cats. Veterinary Anaesthesia and Analgesia, 42 (6), pp. 638-647. ISSN 1467-2987

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Abstract

Objective: To assess the potential for using a thermal carbon dioxide (CO2) laser to 8 assess anti-nociception in pain-free cats.
Animals: Sixty healthy adult female cats with a mean weight (± SD) of 3.3 k g (± 0. 6 11 kg).
Methods: This is a prospective, blinded and randomised study. Cats were systematically allocated to one of six treatments 1) saline 0.2 ml/cat; 2) morphine 0.5 mg/kg; 3) buprenorphine 20 μg/kg; 4) medetomidine 2 μg/kg; 5) tramadol 2mg/kg; 6) ketoprofen 2 mg/kg. Latency to respond to thermal stimulation was assessed prior to intramuscular injection and at 6 time periods following injection (15-30; 30-45; 45- 18 60; 60-75; 90-105; 120-135 min). Thermal thresholds were assessed using time to respond behaviourally to stimulation with a 500 mW CO2 laser with maximum latency to respond set at 60 seconds. Differences in response latency for each treatment across the duration of the experiment were assessed using a Friedman's test. Differences between treatments at any given time were assessed using an independent Kruskal-Wallis test. Where significant effects were identified, pair-wise comparisons were conducted at 30-45, 60-75 and 120-135 min to further explain the direction of the effect.
Results: Cats treated with morphine (χ2 = 12.90; df = 6; P = 0.045) and tramadol (χ2 = 20.28; df = 6; P = 0.002) showed significant increases in latency to respond over the duration of the test period. However, subsequent pairwise comparisons indicated that latencies at specific time points were only significantly different (P < 0.05) for tramadol at 60-75 and 90-105 min after administration. No significant pairwise comparisons were found within the morphine treatment group. Injection of saline, ketoprofen, medetomidine or buprenorphine showed no significant effect on latency to respond.
Conclusions: This project further validates the CO 2 laser technique for use in cats. It can be used for assessment of thermal nociceptive thresholds in pain-free cats after analgesic administration and shows some promise in differentiating amongst analgesic treatments. It may provide a simpler alternative to existing systems although further exploration is required both in terms of its sensitivity and comparative utility (i.e. relative to other thermal threshold systems). Future experiments should seek to quantify the effects of skin temperature and sedation on latency to respond. Given that this technique was found to cause minor skin blistering in individuals that reached the 60 s exposure limit, a cut off time of <45 s is recommended.

Item Type: Journal article
Publication Title: Veterinary Anaesthesia and Analgesia
Creators: Farnworth, M.J., Barrett, L.A., Adams, N.J., Beausoleil, N.J., Weidgraaf, K., Hekman, M., Chambers, J.P., Thomas, D.G., Waran, N.K. and Stafford, K.J.
Publisher: Wiley-Blackwell
Date: November 2015
Volume: 42
Number: 6
ISSN: 1467-2987
Identifiers:
NumberType
10.1111/vaa.12245DOI
S1467298716301441Publisher Item Identifier
Divisions: Schools > School of Animal, Rural and Environmental Sciences
Depositing User: Linda Sullivan
Date Added: 09 Mar 2018 14:17
Last Modified: 09 Mar 2018 14:17
URI: http://irep.ntu.ac.uk/id/eprint/32895

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