Pain management in pigs undergoing experimental surgery; a literature review (2012-4)

Failure to provide effective analgesia to animals in noxious studies contravenes the obligation to refine animal experimentation and, by increasing 'noise' in physiological data sets, may decrease the scientific validity of results. Pig models of surgical conditions are becoming increasingly important and used for translational work. This review aimed to determine the extent to which the recent biomedical literature describes pain assessment and alleviation in pigs recovering from experimental surgery. Three databases (Medline, Web of Knowledge, and Google Scholar) were searched to find relevant studies published from January 2012 to March 2014. Information on pain assessment and peri- and postoperative analgesia was extracted. The review identified 233 papers meeting selection criteria. Most articles (193/233, 83%) described use of drugs with analgesic properties, but only 87/233 (37%) described postoperative analgesia. No article provided justification for the analgesic chosen, despite the lack of guidelines for analgesia in porcine surgical models and the lack of formal studies on this subject. Postoperative pain assessment was reported in only 23/233 (10%) articles. It was found that the reporting of postoperative pain management in the studies was remarkably low, reflecting either under-reporting or under-use. Analgesic description, when given, was frequently too limited to enable reproducibility. Development of a pain-scoring system in pigs, together with the mandatory description of pain management in submitted articles, would contribute to improved laboratory pig welfare.