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On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.55 no.1 Campinas Jan./Feb. 2005
Preemptive analgesia, a controversial subject
Experimental studies published in 1992 and 1993 on peripheral sensitization, central sensitization and preemptive analgesia 1-3 have created major expectations around the clinical application of these concepts to control postoperative pain.
Preventing the development of central sensitization would be even better than treating established pain, and this is the concept of preemptive analgesia. In addition to treatment timing, new drugs acting specifically on central sensitization could also be developed 4.
Since that time, several clinical studies were conducted aiming at clinically confirming preemptive analgesia efficacy, however with controversial results.
Early studies were not adequately designed and many have concluded for the existence of preemptive analgesia by comparing analgesic administration before noxious stimulation to no analgesic administration. It is clear that administering analgesics is better than not administering, but the real question is comparing analgesic administration before and after noxious stimulation, and proving that administration before stimulation would improve postoperative pain evolution, be it in intensity or duration.
When an adequate study model was adopted and major surgeries were included, preemptive effect became a chimera. Studies have evaluated opioids, non-steroid anti-inflammatory drugs, local anesthetics alone or in association, by different routes, without sound evidences of preemptive effects 5.
However, the attractive idea that it is possible to prevent central sensitization with a single dose of a single drug is still alive in anesthesiologists' imagination and many of them, in their daily chats, state that they practice preemptive analgesia.
The importance of preemptive analgesia is unquestionable, the need for evidences on its effectiveness or impossibility is mandatory, and investigators in our country and abroad are working toward this direction. This edition of the Brazilian Journal of Anesthesiology publishes one more clinical study on the subject, enriching research line of authors, who have already conducted other major studies on preemptive analgesia 6. The preemptive analgesic effect of S(+)ketamine, N-Methyl-d-aspartate receptor antagonist, has been evaluated in patients submitted abdominal hysterectomy.
I invite readers to carefully comply with the adequate model to evaluate preemptive analgesia, encouraging new groups to do so.
Who wouldn't like to spare patients from postoperative pain with measures preventing central sensitization? But to be qualified to indicate methods or drugs with this aim, we have to review evidences of their effectiveness, which is still waiting for confirmation.
It is important to consider that questions about preemptive analgesia tactics do not threat in any way the importance of treating and controlling postoperative pain by acting before pain is referred. These measures, however, should not be indiscriminately called preemptive analgesia.
Key words: ANALGESIA: postoperative, preemptive
Judymara Lauzi Gozzani, TSA, M.D.
Editor in Chief, Brazilian Journal of Anesthesiology
01. Treede RD, Meyer RA, Raja SN et al - Peripheral and central mechanisms of cutaneous hyperalgesia. Prog Neurobiol, 1992;38:397-421.
02. Davis KD, Meyer RA, Campbell JN - Chemosensitivity and sensitization of nociceptive afferents that innervate the hairy skin of monkey. J Neurophysiol, 1993;69:1071-1081.
03. Woolf CJ, Chong MS - Prremptive analgesia: treating postoperative pain by preventing the establishment of central sensitization. Anesth Analg, 1993;77:1-18.
04. Woolf CJ - A new strategy for the treatment of inflammatory pain. Drugs, 1994;47:1-9.
05. Moiniche S, Kehlet H, Dahl JB - A qualitative and quantitative systematic review of preemptive analgesia for postoperative pain relief. Anesthesiology, 2002;96:725-741.
06. Garcia JBS, Issy AM, Salomão R et al - Preemptive analgesia with epidural bupivacaine plus fentanyl in gynaecological surgery - effects on serum interleukin-6 concentrations. Acute Pain, 2002;4:25-28.