Refinement of analgesia following thoracotomy and experimental myocardial infarction using the Mouse Grimace Scale

Faller, K. M.E., McAndrew, D. J., Schneider, J. E. and Lygate, C. A. (2015) Refinement of analgesia following thoracotomy and experimental myocardial infarction using the Mouse Grimace Scale. Experimental Physiology, 100(2), pp. 164-172. (doi: 10.1113/expphysiol.2014.083139) (PMID:25480160) (PMCID:PMC4340041)

Abstract

New Findings What is the central question of this study? There is an ethical imperative to optimize analgesia protocols for laboratory animals, but this is impeded by our inability to recognize pain reliably. We examined whether the Mouse Grimace Scale (MGS) provides benefits over a standard welfare scoring system for identifying a low level of pain in the frequently used murine surgical model of myocardial infarction. What is the main finding and its importance? Low-level pain, responsive to analgesia, was detected by MGS but not standard methods. In this model, most of the pain is attributable to the thoracotomy, excepted in mice with very large infarcts. This approach represents a model for assessing postsurgical analgesia in rodents. The Mouse Grimace Scale (MGS) was developed for assessing pain severity, but the general applicability to complex postsurgical pain has not been established. We sought to determine whether the MGS provides benefits over and above a standard welfare scoring system for identifying pain in mice following experimental myocardial infarction. Female C57BL/6J mice (n = 60), anaesthetized with isoflurane, were subjected to thoracotomy with ligation of a coronary artery or sham procedure. A single s.c. dose of buprenorphine (1.1 mg kg−1) was given at the time of surgery and pain assessed at 24 h by MGS and a procedure-specific welfare scoring system. In some animals, a second dose of 0.6 mg kg−1 buprenorphine was given and pain assessment repeated after 30 min. The MGS was scored from multiple photographs by two independent blinded observers with good correlation (r = 0.98). Using the average MGS score of both observers, we identified a subset of mice with low scores that were not considered to be in pain by the welfare scoring system or by single observer MGS. These mice showed a significant improvement with additional analgesia, suggesting that this low-level pain is real. Pain attributable to the myocardial injury, as opposed to thoracotomy, persisted at 24 h only in mice with large infarcts >40%. In conclusion, the use of a multi-observer, post hoc version of the MGS is a sensitive tool to assess the efficacy of postsurgical analgesic protocols. Following surgical induction of myocardial infarction, we identified a significant proportion of mice that were in low-level pain at 24 h that were not identified by other assessment methods.

• Item Type: Articles
• Additional Information: This work was supported by the British Heart Foundation (grantnumbers RG/13/8/30266 and FS/07/065 to K.M.E.F.), and theauthors acknowledge support from Wellcome Trust Core Award,Grant 090532/Z/09/Z. J.E.S. is a British Heart Foundation SeniorBasic Science Research Fellow (FS/11/50/29038).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Faller, Ms Kiterie
• Authors: Faller, K. M.E., McAndrew, D. J., Schneider, J. E., and Lygate, C. A.
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: Experimental Physiology
• Publisher: Wiley
• ISSN: 0958-0670
• ISSN (Online): 1469-445X
• Published Online: 14 January 2015
• Copyright Holders: Copyright © 2014 The Authors
• First Published: First published in Experimental Physiology 100(2): 164-172
• Publisher Policy: Reproduced under a Creative Commons License