Lidocaine and Ketamine Levels in Plasma After Simultaneous Lidocaine/Ketamine Infusions

Lidocaine and ketamine are infused over a period of 30 minutes. The dosage of lidocaine is 4mg/kg is maintained throughout the infusions, and the dosage of ketamine is increased within the first three infusions from 0.15mg/kg at the first, to 0.25mg/kg at the second and 0.5mg/kg at the third infusion. In case patients already experiencing sufficient analgesic effect and/or improvement in quality of life after the 1st or 2nd infusion or if side effects do not allow a further dose increase, no further step up of ketamine dosage is made. As a part of this study, at the end of the first, second and third infusion, side effects will be screened using customized questionnaires (SF - MPQ, BDI-II)