Clinical Research Article

Background: High-dose remifentanil-based anesthesia is associated with opioid-induced hyperalgesia (OIH) and post-anesthetic shivering (PAS). These effects can be prevented by N-methyl-d-aspartate (NMDA) receptor antagonists. This study aimed to investigate correlations between OIH and PAS caused by high-dose remifentanil and the effects of low-dose ketamine on OIH and PAS. Methods: Seventy-five patients scheduled for single-port laparoscopic gynecologic surgery were randomly allocated into three groups, each of which received intraoperative remifentanil: group L at 0.1 μg/kg/min; group H at 0.3 μg/kg/min; and group HK at 0.3 μg/kg/min plus 0.25 mg/kg ketamine just before incision, followed by a continuous infusion of 5 μg/kg/min ketamine until skin closure. Results: PAS, postoperative tactile pain threshold, and the extent of hyperalgesia in group H were significantly different (P < 0.05) than in the other two groups. PAS was significantly correlated with OIH, including mechanically evoked pain such as postoperative tactile pain threshold (r =-0.529, P = 0.01) (r =-0.458, P = 0.021) and the extent of hyperalgesia (r = 0.537, P = 0.002) (r = 0.384, P = 0.031), respectively, in group H and group HK. Notably, both groups were treated with high-dose remifentanil. Tympanic membrane temperature, time to first postoperative analgesic requirement, post-operative pain scores, analgesic consumption, and cumulative patient-controlled analgesia volume containing morphine were comparable in all three groups. Conclusions: OIH, including the enhanced perception of pain, and PAS were both associated with high-dose remifen-tanil, were significantly correlated and were attenuated by a low dose of ketamine. This suggests that a common mecha-nism in part mediated through activation of the central glutamatergic system (e.g., NMDA receptors), underlies the two effects caused by high doses of remifentanil. (Korean J Anesthesiol 2014; 66: 44-51