Effect of Nefopam on Remifentanil Induced Postoperative Hyperalgesia

Opioids has been reported to cause hyperalgesia. Opioid induced hyperalgesia (OIH) is defined as paradoxically lowering the threshold of pain after the exposure of opioid. Remifentanil is a short acting opioid that is commonly used during anesthesia and surgery. However, OIH was reported to occur after surgery when large amount of remifentanil was administered. On the other hand, nefopam is a centrally acting, non-opioid analgesic. Nefopam has been reported to have analgesic and anti-hyperalgesic effect.

The investigators hypothesized that nefopam administration could prevent OIH or reduce the severity of OIH. Therefore, the objective of the study is to find out the effect of nefopam on remifentanil induced hyperalgesia in patients undergoing laparoscopic abdominal surgery.

Inclusion Criteria:

1. Patients undergoing laparoscopic gastrectomy
2. American Society of Anesthesiologists physical status I or II
3. aged from 20 to 65 years

Exclusion Criteria:

1. Past history of chronic pain
2. Drug or alcohol abuse
3. Psychotic disorder
4. Taking analgesics, anti-epileptics, and anti-depressants.
5. Taking opioids within 24 hrs
6. Renal disease
7. Neuromuscular disease.
8. Moderate to severe cardiovascular disease
9. Pregnant or breast-feeding