The effect of target-controlled infusion of low-dose ketamine on heat pain and temporal summation threshold.
We investigated the heat pain threshold (HPT) and temporal summation threshold (TST) before and after target-controlled infusion (TCI) of ketamine with an effect-site concentration (Ce) of 30 and 60 ngml. Healthy young volunteers (n 20) were enrolled. A thermode was applied to the volar side of each volunteers right forearm, and HPT and TST were measured before and after TCI of ketamine. Vital signs and psychedelic effects according to ketamine infusion were also observed before and after TCI of ketamine. Mean HPT after TCI of ketamine with a Ce of 30 and 60 ngml did not increase significantly. However, mean TST after TCI of ketamine with a Ce of 30 and 60 ngml increased significantly, in a dose-dependent fashion, compared with the value before ketamine TCI. Vital signs showed no significant difference before and after ketamine TCI. The visual analog scale score of psychedelic symptoms was higher with a Ce of 60 ngml than with 30 ngml. TCI of ketamine with a Ce of 30 and 60 ngml increased TST but not HPT.