In Response

In Response We thank Forget and Cata1 for their constructive comments in their Letter to the Editor “Multimodal Analgesia for Spine Surgery: Does the Intraoperative Opioid Dose Matter?” and for their interest in our work on ketamine.2,3 We agree that perioperative and postoperative analgesia are the combined results of all analgesic interventions that a given patient has received, and, even more importantly, that the interactions between ketamine and opioids are complicated. It is possible or even likely that all μ-opioids are not similar in their interactions with ketamine, and this should be studied further in a clinical setting (for further discussion for possible differences between morphine and oxycodone interactions with ketamine, we refer to a study by Lilius et al4). Comparisons between different perioperative opioid dose ranges were not included in the protocol of our large Cochrane review but could be considered for the next update. Not just perioperative but probably also preoperative opioid exposure is important for the efficacy of ketamine for postoperative analgesia: it is appealing to think that opioid-tolerant patients would benefit more from intraoperative ketamine infusion than opioid-naive patients. This could be one of the factors that could explain the difference between our spinal surgery patients (who had no preoperative use of strong opioids) and other trials with otherwise similar setting5,6 but much higher average preoperative opioid exposure. Weeks, months, or even years of (high-dose) strong opioid use is probably a more important factor than perioperative opioid administration, but naturally both need to be taken into account. Ars longa, vita brevis! Elina C. V. Brinck, MDDivision of AnesthesiologyDepartment of AnesthesiologyIntensive Care and Pain MedicineTöölö HospitalHelsinki, FinlandUniversity of HelsinkiHelsinki University HospitalyHelsinki, Finland[email protected] Vesa K. Kontinen, DMedSciDivision of AnesthesiologyDepartment of AnesthesiologyIntensive Care and Pain MedicineJorvi HospitalEspoo, FinlandUniversity of HelsinkiHelsinki University HospitalHelsinki, Finland