Objectives: This clinical study tested the hypothesis whether intraoperative high versus low dose of intravenous remifentanil resulted in postoperatively increased pain sensitivity to painful cold or pressure stimulation in eye surgery patients without significant postoperative pain.
Methods: Forty-two minor eye surgery patients were randomized to receive intraoperative high (0.4 microg/kg/min) or low (0.1 microg/kg/min) dose of intravenous remifentanil plus isoflurane over an average period of 70 minutes. Pain assessment at the surgical site, postoperative versus preoperative baseline measurements by the cold as well as the pressor test, sedation score, and withdrawal signs were evaluated 30 and 90 minutes after stop of remifentanil infusion. Patients with pain at the surgical site were excluded.
Results: Pressure pain tolerance thresholds at the palmar carpus of the right hand were significantly decreased in these patients after cessation of intraoperative high but not low dose of IV remifentanil. However, withdrawal latencies to cold stimulation were not significantly altered. Isoflurane concentrations were slightly higher in patients receiving the low dose of remifentanil, however, there were no significant differences in length of anesthesia and postoperative sedation. Signs of withdrawal were not observed.
Discussion: After high dose intravenous remifentanil our results show signs of a reduced tolerance to painful pressure but not cold stimuli distant to the surgical field. Although clinically relevant surgical pain was not reported in these patients, the demonstrated induction of hyperalgesia to painful pressure stimuli suggests a general effect in the central nervous system.