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CANADIANJOURNAL OF ANESTHESIA
ticity and postoperative pain.3 5 The antinociceptive treat-
ment should completely block the noxious signals to the
CNS, or else central sensitization may occur in response
to those nociceptive impulses, which break through the
analgesic barrier. Furthermore, total blockade of noci-
ceptive afferent fibres may not be produced by conven-
tional analgesic doses or methods. The aim of treatment
is to minimize patient discomfort, while leaving physio-
logic nociceptive mechanisms intact so that they contin-
ue to function as an early warning system.3 6 An analgesic
plan must include consideration of the best route of
delivering analgesia (oral, iv, epidural, intrathecal or infil-
tration), the potential intensity of the noxious stimuli,
the temporal relationship of nociceptive impulses to the
timing and duration of surgery, the duration of the post-
operative pain state, and the analgesic agents suitable for
administration in each individual case (Table IV).
Different treatment regimes can be used at different
times relative to surgery to maximize the prevention of
pain in response to different levels of sensory input.
The best approach is probably to administer a num-
ber of analgesic agents and techniques in combina-
tion, each of which decreases nociception by working
on a different limb of the pain pathway and at differ-
ent sites. Such an approach will allow synergism
between the different medications while decreasing
the risk of toxicity by limiting the dose of each of the
individual agents. Peripheral nociceptor sensitization
can be attenuated by NSAIDs and local anesthetic
blockade. Opioids are frequently the cornerstone of
postoperative analgesic therapy, and act at a number of
sites (peripheral, spinal and supraspinal) to produce
analgesia and reduce sensitization. Ketamine and
alpha-2 agonists may be combined with opioid thera-
py to enhance analgesia and reduce central sensitiza-
tion. A treatment regimen designed to maximize
postoperative analgesia is outlined in Table V. The
exact clinical role of other agents is, for the most part,
still under investigation, but may provide better
understanding of pain mechanisms and improved peri-
operative care of the surgical patient.
agonists and NMDA receptor antagonists are consid-
ered the main agents in the preemptive analgesic arse-
nal, a variety of other potentially beneficial agents are
under investigation. Until further data are complete,
the presently available analgesics administered correctly
(on time, for the appropriate duration, and in the prop-
er dosage and manner) can improve patient comfort,
decrease postoperative morbidity and have the potential
to effect health care savings.
References
1 Kissin I. Preemptive analgesia. Anesthesiology 2000;
93: 1138–43.
2 Grass JA. Preemptive analgesia. In: Grass JA (Ed.).
Problems in Anesthesia, vol. 10. Philadelphia:
Lippincott-Raven, 1998: 107–21.
3 Kehlet H. Controlling acute pain-role of pre-emptive
analgesia, peripheral treatment, and balanced analgesia,
and effects on outcome. In: Max M (Ed.). Pain 1999 -
An Updated Review. Seattle: IASP Press, 1999:
459–62.
4 Schmid RL, Sandler AN, Katz J. Use and efficacy of
low-dose ketamine in the management of acute post-
operative pain: a review of current techniques and out-
comes. Pain 1999; 82: 111–25.
5 Niv D, Lang E, Devor M. The effect of preemptive
analgesia on subacute postoperative pain (Editorial).
Minerva Anestesiol 1999; 65: 127–40; discussion
140–1.
6 Pasqualucci A. Experimental and clinical studies about
the preemptive analgesia with local anesthetics. Possible
reasons of the failure. Minerva Anestesiol 1998; 64:
445–57.
7 Williams-Russo P, Sharrock NE, Haas SB, et al.
Randomized trial of epidural versus general anesthesia.
Outcomes after primary total knee replacement. Clin
Orthop 1996; 331: 199–208.
8 Møiniche S, Hjortsø N-C, Hansen BL, et al. The effect
of balanced analgesia on early convalescence after
major orthopaedic surgery. Acta Anaesthesiol Scand
1994; 38: 328–35.
9 Ringrose NH, Cross MJ. Femoral nerve block in knee
joint surgery. Am J Sports Med 1984; 12: 398–402.
10 Langer JC, Shandling B, Rosenberg M. Intraoperative
bupivacaine during outpatient hernia repair in children:
a randomized double blind trial. J Pediatr Surg 1987;
22: 267–70.
Conclusion
Preemptive analgesia is not a new concept, but dates to
the early twentieth century. It involves delivery of anal-
gesic therapy that precedes, adequately blocks, and out-
lasts the nociceptive stimuli that accompany tissue
injury. The aim is to prevent the peripheral and central
sensitization that occurs in response to painful stimuli,
while leaving physiological pain responses intact. Such
an effect reduces primary and secondary hyperalgesia,
allodynia and the receptive field changes of dorsal horn
cells. While opioids, NSAIDs, local anesthetics, alpha-2
11 Tverskoy M, Cozacov C, Ayache M, Bradley EL, Kissin I
.
Postoperative pain after inguinal herniorrhaphy with dif-
ferent types of anesthesia. Anesth Analg 1990; 70: 29–35.
12 Bugedo GJ, Cãrcamo CR, Mertens RA, Dagnino JA,
Munoz HR. Preoperative percutaneous ilioinguinal and
iliohypogastric nerve block with 0.5% bupivacaine for