The effect of acute postoperative pain and chronic neuropathic pain on subsequent weight gain in the rat.

Abstract

Acute postoperative pain has demonstrated effects on appetite and weight gain in human studies. This study was designed to test the hypothesis that chronic neuropathic pain has a more significant effect on weight than acute postsurgical pain. One hundred eighteen rats were separated into 3 groups: common sciatic nerve ligation, surgery without ligation, and no surgery. Each group was further divided to undergo testing at 3, 7, and 14 days. On the day of testing, the rats were tested for signs of pressure and heat hyperalgesia and were weighed. The effect on the percentage of change in body weight from the day of surgery to the day of testing was statistically significant for both the condition (F = 15.0, p < 0.0001) and the day of testing (F = 43.3, p < 0.0001). The rats that received no surgery had a change in weight of 2.3% on Day 3, 4.0% on Day 7, and 10.7% on Day 14. In the nonligation surgery group, the change was -3.8% on Day 3, 2.0% on Day 7, and 9.7% on Day 14. In the ligation surgery group, the change was -6.3% on Day 3, -0.7% on Day 7, and 4.9% on Day 14. This group began gaining weight by Day 14 but continued to have less weight gain than the other groups by Day 14. Neuropathic pain inhibits weight gain more than normal, postsurgical pain. Recognizing the difference and initiating effective treatment for neuropathic pain may have an impact on the patient's nutrition.