Preemptive analgesia I: physiological pathways and pharmacological modalities

Abstract

P Pu ur rp po os se e: : This two-part review summarizes the current knowledge of physiological mechanisms, pharmacological modalities and controversial issues surrounding preemptive analgesia.S So ou ur rc ce e: : Articles from 1966 to present were obtained from the MEDLINE databases. Search terms included: analgesia, preemptive; neurotransmitters; pain, postoperative; hyperalgesia; sensitization, central nervous system; pathways, nociception; anesthetic techniques; analgesics, agents.P Pr ri in nc ci ip pa al l f fi in nd di in ng gs s: : The physiological basis of preemptive analgesia is complex and involves modification of the pain pathways. The pharmacological modalities available may modify the physiological responses at various levels. Effective preemptive analgesic techniques require multi-modal interception of nociceptive input, increasing threshold for nociception, and blocking or decreasing nociceptor receptor activation. Although the literature is controversial regarding the effectiveness of preemptive analgesia, some general recommendations can be helpful in guiding clinical care. Regional anesthesia induced prior to surgical trauma and continued well into the postoperative period is effective in attenuating peripheral and central sensitization. Pharmacologic agents such as NSAIDs (non-steroidal anti-inflammatory drugs) opioids, and NMDA (Nmethyl-D-aspartate) -and alpha-2-receptor antagonists, especially when used in combination, act synergistically to decrease postoperative pain.C Co on nc cl lu us si io on n: : The variable patient characteristics and timing of preemptive analgesia in relation to surgical noxious input requires individualization of the technique(s) chosen. Multi-modal analgesic techniques appear most effective.Objectif : La présente revue, en deux parties, résume les connaissances actuelles sur les mécanismes physiologiques et les modalités pharmacologiques de lanalgésie préventive ainsi que sur les questions controversées qui lentourent.Sources : Des articles, de 1966 à aujourdhui, obtenus à partir des bases de données MEDLINE. Les termes de la recherche compren-

Preemptive Analgesia: Is Pain Less Costly When You Pre-Pay For It?

“…3,4 For example, a chronic condition sometimes develops that produces continuous pain long after the original tissue damage from surgery. 4 Peripheral tissue injury, from sunburn to microvascular damage of peripheral nerves in painful diabetic peripheral neuropathy, can sensitize the responsiveness of the nervous system to stimuli at 2 sites, namely, peripheral and central. Peripheral sensitization reduces the threshold for pain in peripheral pain neurons.…”

“…Peripheral sensitization reduces the threshold for pain in peripheral pain neurons. 4 Central sensitization is an activity-dependent increase in the excitability of central neurons in the spinal cord that causes an increase in the response to painful input and a decrease in the pain threshold. 3,4 Thus, pain can beget pain.…”

“…4 Central sensitization is an activity-dependent increase in the excitability of central neurons in the spinal cord that causes an increase in the response to painful input and a decrease in the pain threshold. 3,4 Thus, pain can beget pain. A sensitized nervous system that has experienced pain results in more pain perception than a nonsensitized nervous system.…”

“…For example, circumcised boys experience more pain from subsequent vaccination than boys who are not circumcised or who were circumcised only after application of local anesthetic cream. 4 Acute pain that occurs immediately upon tissue damage sometimes is followed by modified and enduring pain responses that can outlast the tissue damage or even occur in areas without apparent tissue damage. 4 Primary hyperalgesia is enhanced pain perception in the area of original peripheral tissue injury.…”

“…4 Acute pain that occurs immediately upon tissue damage sometimes is followed by modified and enduring pain responses that can outlast the tissue damage or even occur in areas without apparent tissue damage. 4 Primary hyperalgesia is enhanced pain perception in the area of original peripheral tissue injury. 4 Secondary hyperalgesia is enhanced pain perception in undamaged tissue surrounding the area of injury.…”