Advances in postoperative pain management

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RA Moore
DSc
Research Director

JE Edwards
DPhil
Senior Researcher
Pain Research and Nuffield Department of Anaesthetics
Oxford Radcliffe Hospitals
Oxford
UK

Pain after operations is a big problem, although part of a wider problem of pain in hospital generally. A decade ago Bruster and colleagues(1) demonstrated that 90% of patients had pain that was moderate or severe at some time, and systematic reviews of pain in hospital confirm similar rates in different places at different times.(2)

It is not just the immediate postoperative period. When patients go home, surveys show that acute pain is poorly treated,(3) and, for French general practitioners, acute pain after surgery was their single biggest clinical problem.(4) And there are even longer-term problems. Another systematic review has examined studies of chronic pain at least one year after surgery.(5) Rates were expectedly high after amputation, but even for relatively simple surgery such as breast surgery or hernia repair as many as one patient in 10 was left with chronic pain. The recent Pain in Europe survey established a prevalence of chronic postsurgical pain in the adult European population of about 0.4%.(6)

An evidence-based approach
In recent years two major themes in postoperative pain management have come together. The first, described above, has been the recognition of postoperative pain as a problem. The second theme concerns the better use and knowledge of evidence in the form of systematic reviews and meta-analyses. Pain, anaesthesia and, increasingly, perioperative medicine have led the way in the rational use of evidence and, indeed, in the creation of the rules that tell us when the evidence is good or bad. In essence, these rules come down to three things:

• Quality: are we sure that we are avoiding bias?
• Size: do we have enough information to be sure of the result?
• Validity: can the trials tell us what we want to know?

Evidence on acute postoperative pain management in the immediate postoperative period comes from a systematic review of 123 papers with a total of just under 20,000 patients.(7) It shows that intermittent intramuscular opioid is far inferior to epidural analgesics or patient-controlled analgesia (PCA) for moderate to severe pain at rest or on movement (see Figure 1). When patients can swallow, we give them oral analgesics. A series of systematic reviews of randomised trials of standard design gives us a “league table” of relative analgesic effectiveness, using the number-needed-to-treat (NNT) for the analgesic compared with placebo and the outcome of patients achieving at least 50% pain relief over six hours(8) (see Figure 2). The lower the NNT, the more efficacious the analgesic.

This sort of information can be really helpful when planning postoperative care. If intermittent intramuscular opioids do not provide good analgesia (probably because nurses and doctors are not available to give them),(1) but does promote postoperative nausea and vomiting, which patients find most distressing and want to avoid,(9) it leads us to change our practice. For oral analgesics other factors might also apply, such as how long the analgesia lasts, with evidence that some of the newer coxibs provide much longer analgesia.(10) Cost-effectiveness arguments also apply, with some excellent evidence emerging that nausea and vomiting are major determinants of cost.(11)

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Future challenges
The most important thing about an evidence-based approach is that it tells us about where there is no evidence, or about where we need more and better evidence. For postoperative pain there are several challenges still to be faced.

One is that we need to examine the use of care pathways. What little evidence we have suggests that organised postoperative care significantly reduces pain, while also reducing overall costs.(12) An extension of the concept of care pathways is that of multimodal strategies to improve surgical outcome, where a systematic review of mostly pilot studies suggests that massive reductions in hospital stay are possible, but only with reorganisation of the perioperative team.(13)

The use of evidence around a whole range of issues relating to perioperative management is essential, as is the generation and incorporation of new evidence. The longer-duration coxibs may have a role to play in reducing postoperative opioid requirement,(14) and hence nausea and vomiting, despite other preoperative interventions having little effect.(15)

What we can say with certainty is that the pace of change has accelerated. It will accelerate further, with perhaps huge changes in postoperative pain management and in perioperative medicine as a whole.

References

1. Bruster S, Jarman B, Bosanquet N, et al. National survey of hospital patients. BMJ 1994;309:1542-6.
2. Visentin M. Verso un ospedale senza dolore. J Headache Pain 2002;3:59-61.
3. Beauregard L, Pomp A, Choinière M. Severity and impact of pain after day-surgery. Can J Anaesth 1998;45:304-11.
4. Robaux S, Bouaziz H, Cornet C, et al. Acute postoperative pain management at home after ambulatory surgery: a French pilot survey of general practitioners’ views. Anesth Analg 2002;95:1258-62.
5. Perkins FM, Kehlet H. Chronic pain as an outcome of surgery. Anesthesiology 2000;93:1123-33.
6. Pain in Europe 2003. Available from URL:www.painineurope.com; accessed 6 November 2003.
7. Dolin SJ, Cashman JN, Bland JM. Effectiveness of acute postoperative pain management: 1. Evidence from published data. Br J Anaesth 2002;89:409-23.
8. Moore A, Edwards J, Barden J, McQuay H. Bandolier’s little book of pain. Oxford: Oxford University Press; 2003.
9. Macario A, Weinger M, Carney S, Kim A. Which clinical anesthesia outcomes are important to avoid? The perspective of patients. Anesth Analg 1999;89:652-8.
10. Barden J, Edwards JE, McQuay HJ, Moore RA. Rofecoxib in acute postoperative pain: quantitative systematic review. BMC Anesthesiol 2002;2:4. Available from URL: http://www.biomedcentral.com/1471-2253/2/4
11. Rainer TH, Jacobs P, Ng YC et al. Cost effectiveness analysis of intravenous ketorolac and morphine for treating pain after limb injury: double blind randomised controlled trial. BMJ 2000;321:1-9.
12. Haynes TK, Evans DEN, Roberts D. Pain relief after day surgery: quality improvement by audit. J One-Day Surg 1995;Summer:12-5.
13. Kehlet H, Wilmore DW. Multimodal strategies to improve surgical outcome. Am J Surg 2002;183:630-41.
14. Sinatra R. Role of COX-2 inhibitors in the evolution of acute pain management. J Pain Symptom Manage 2002;24:S18-S27.
15. Møiniche S, Kehlet H, Dahl JB. A qualitative and quantitative systematic review of preemptive analgesia for postoperative pain relief. Anesthesiology 2002;96:725-41.

Useful websites
Cochrane Collaboration has over 350,000 controlled trials and the Cochrane Library of Systematic Reviews, as well as much more
W:www.update-software.com/clibhome/clib.htm
The evidence-based perioperative
medicine website at the University of Geneva has a list of
systematic reviews in anaesthesia and analgesia.
W:www.hcuge.ch/anesthesie/anglais/evidence/aevbasmed.htm
The Bandolier website contains a lot of information on pain, perioperative medicine, evidence-based medicine, and a list of systematic reviews in pain.
W:www.ebandolier.com

Further reading
Wiffen P. Evidence-based pharmacy.  Abingdon: Radcliffe Medical Press; 2001.
Moore A, Edwards J, Barden J, McQuay H.
Bandolier’s little book of pain. Oxford: Oxford University Press; 2003.