Transition between anesthesia and post-operative analgesia: relevance of intra-operative administration of analgesics.

The rapid awakening without residual analgesic effect seen with the new "fast-in-fast-out" anesthetic agents forces us to anticipate post-operative pain management. More then ever, "balanced analgesia" appears the key for successful transition between anesthesia and post-operative analgesia. This review focuses on practical aspects seeking to answer the following questions: which analgesics should be used?; how should they be given?; at what stage of the anesthetic time should they be injected? In the absence of a loco-regional technique, analgesics must be given before the end of surgery to obtain a quiet awakening. The transition in this delicate period may be facilitated by the intra-operative use of various adjuvant therapies such as ketamine, lidocaine infusion, clonidine, and magnesium, that reduce the needs for opioid and/or post-operative pain severity. All non-opioid analgesics (propacetamol, NSAIDs, tramadol) must be given according to their pharmacokinetic characteristics, indications and contraindications to ensure the required analgesic effect is effective at the time of awakening. If tramadol is not used, an initial dose of a long-acting opioid should be given 20-30 minutes before the end of surgery. Insufficient analgesia must be corrected by titrating an opioid intravenously before allowing the patient to control his/her analgesia using a PCA pump.