Correlation between body weight changes and postoperative pain in rats treated with meloxicam or buprenorphine

Abstract

It is essential to identify objective and efficient methods of evaluating postoperative pain in rodents. The authors investigated whether postoperative changes in rates of body weight gain could serve as a measure of the efficacy of meloxicam or buprenorphine analgesia in growing rats. Young adult male Lewis rats underwent general endotracheal anesthesia and thoracotomy and were treated postoperatively for 3 d with saline (no analgesia), buprenorphine (six doses of 0.1 mg per kg) or meloxicam (three doses of 1 mg per kg). The authors evaluated rats' daily growth rates for 5 d after surgery and compared them with baseline (preoperative) growth rates. To discriminate between the effects of postoperative pain and other concurrent physiologic effects associated with anesthesia, thoracotomy or analgesia, the authors evaluated weight changes in multiple control groups. Treatment with buprenorphine in the absence of any other procedure or with anesthesia alone significantly affected rats' body weight. Notably, growth rate was maintained at near normal levels in rats treated postoperatively with meloxicam. These findings suggest that growth rate might serve as an efficient index of postoperative pain after major surgical procedures in young adult rats treated with meloxicam but not in rats treated with buprenorphine.The clinical assessment and treatment of pain in the laboratory animal present unique challenges for scientific investigators, IACUCs, institutional veterinarians and regulatory agencies. Evaluation of pain in the ubiquitous laboratory rodent is especially challenging. Several studies suggest that clinical parameters such as change in body weight and daily oral fluid intake correlate with postoperative pain in rodents [1][2][3][4] . Although such parameters provide appropriate indications of rodent well-being during routine clinical care and maintenance, these objective measurements fail to account for typical factors operant during the postoperative period, such as the effect of narcotic analgesic medications on volition and the physiologic stress response to surgery. Recently, Flecknell and colleagues pioneered a method of postoperative behavioral monitoring in rats as an objective means to determine pain and analgesic efficacy 3,5,6 . With this scoring method, trained personnel observe rats for 5 -10 min relatively soon after surgery and document behavioral indicators of pain. We sought to investigate whether daily assessment of body weights could be an alternative or adjunct to the proposed behavioral scoring paradigm. Body weight can be accurately measured, and the timing of evaluation is flexible. This method is also objective and efficient, particularly for evaluating pain in group-housed rodents. Furthermore, a standardized, simple evaluation

Paradoxical surrogate markers of dental injury-induced pain in the mouse

“…Short term decreases in total weight and prolonged attenuation of weight gain rates are commonly observed after manipulation of rodents in experimental models of neuropathic and inflammatory pain [5; 8; 65; 68]. Consistent with those findings, we observed that bilateral DPI led to greater deficits in body weight relative to control animals.…”

Immunoneutralization of the aminoprocalcitonin peptide of procalcitonin protects rats from lethal endotoxaemia: neuroendocrine and systemic studies

“…Chronic i.c.v. For presumptive analgesia, meloxicam [1 mg/kg of body weight, s.c. (subcutaneously); Metacam ® ; Boehringer Ingelheim], a non-steroidal anti-inflammatory drug used for post-operative pain in rats [27], was administered immediately after surgery while the rats were still under anaesthesia and recovering on a temperature-regulated heating pad. Rats were anaesthetized with a ketamine cocktail (100 mg/ml ketamine; 5 mg/ml xylazine and 10 mg/ml acepromazine) and were placed in a stereotaxic frame.…”

Optimizing the dosing interval of buprenorphine in a multimodal postoperative analgesic strategy in the rat: minimizing side-effects without affecting weight gain and food intake

“…The dose of meloxicam used in this study is substantially lower than reported in the literature 22 and was based on multimodal pain management experience in our veterinary academic teaching hospital with client-owned rodents. The dosages in the literature are based on unimodal analgesia in experimental pain with maximum effect.…”