Chronic pain after surgery

Surgery is supposed to hurt. Well maybe not ‘supposed’ to, but most people expect some pain after surgery – as one doctor said to me, it’s really ‘planned trauma’. The problem for some people is that the pain doesn’t settle afterwards – and up to 50% of people undergoing surgery can fail to recover fully, and continue to have pain that disrupts life and contributes to misery.

There have been many studies looking at risk factors for chronic pain and as usual, although the model of pain is biopsychosocial, most have examined biomedical factors such as type of surgery, type of anaesthetic, preoperative pain intensity, postoperative pain intensity. Examining psychosocial factors has trailed behind somewhat. This paper by Hinrichs-Rocker, Schulz, Järvinen et al (2009) reviews 50 papers in which psychosocial predictors for and correlates to CPSP were identified. Although this is not a meta-analysis, nor a Cochrane review using the levels of evidence accepted by Cochrane, it is a systematic review and the paper details the processes used to review the literature.

After looking through the major databases, and excluding those studies that did not meet the inclusion criteria (which is specified in the paper), only 36 studies fully met the inclusion criteria, with a further 14 included from the reference lists of these papers. That’s not a lot out of the original more than 800 papers!

What did they find?
After rating each paper in terms of the level of evidence, three tables were developed – Table 1 includes those having a likely association with chronic post-operative pain; Table 2 those with an unclear result, and Table 3, those with factors deemed as unlikely to be associated with chronic post-operative pain.

The psychosocial factors they identified as having a likely association include some very expected factors –

• depression,
• psychological vulnerability (as defined by the authors of the study),
• chronic stress pre-operatively,
• distress pre-operatively, and
• distress at follow-up, and the final factor –
• delayed return to work.

Curiously, pre-operative and peri-operative anxiety was not clearly identified at this point – I found this quite surprising given some of the studies examining pre-operative anxiety in bowel surgery, but there you have it.

Some of the other factors not clearly associated with poorer outcomes include age, social support, psychological aspects of work, income, litigation and higher pain relief expectations, to mention a few. Now simply because they didn’t meet the levels required for this study doesn’t mean they’re not important – each one of these factors has been implicated in some way with post-operative chronic pain – it just means that the jury is out. Not enough evidence has been found yet – so again it’s a case of ‘more research needed’.

The factors clearly not associated with a risk of chronic post-operative pain identified in this study were

• neuroticism,
• female gender,
• employment status,
• education and
• ethnicity

– and I’ll bet the surgeons felt relieved, neither was the surgeon!

For the record, psychological vulnerability was defined as ‘a reaction readiness defined by a low threshold for being influenced and a risk of inexpedient reactions in social interaction and health-related behaviour‘. Hmmmm!  Even reading this several times I’m not sure what it means.

What does this mean?
That up to 50% of people can experience persistent pain after surgery is a worry – especially given the propensity for some people to look for and be offered a ‘quick fix’ surgical approach for some painful conditions. It suggests that surgeons and those looking to offer surgery might need to pay attention to some of these psychosocial factors – maybe delaying surgery so some of the factors can be attended to prior to embarking on a procedure, or maybe ensuring that follow-up includes effective psychosocial input rather than simply following a physical rehabilitation route.

The authors made some good recommendations for people conducting studies of psychosocial factors associated with surgery: ‘studies must be performed prospectively with sufficient numbers of test subjects and completion rates at follow up. The sample size should correspond to the number of factors investigated. In cases of multiple predictor variables, statistical analysis should be multivariate to reduce confounding effects. Standardised instruments should be used such as VAS, NRS, Beck Depression Inventory, STAI.’

Because of methodological shortcomings, this study couldn’t be a meta-analysis, and it’s clear also that many studies simply had to be excluded because of poor sample size, inadequate recording of follow-up dropouts, being retrospective studies, or using poor statistical analysis.

So, it’s important not to draw too strong a conclusion from this single study – but instead, start to look at these factors as well as biomedical ones.

I’d like to see a couple of standardised questionnaires administered before elective surgery, and again at follow-up up to 6 months or more later. It’s not a difficult job, although the lack of administrative support in our DHB might limit it actually being done. But given the cost in terms of frustration, distress – and more importantly, ongoing health care use – even leading to revision of some surgeries to ‘find the cause of the pain’ – maybe it’s something that health care administrators prioritised.

And clinicians? Well, if occupational therapists looked at psychosocial factors before and after surgery along with ADL gadgets, and maybe if physiotherapists looked at confidence as well as walking ability, and if nurses had more training in recognising and managing distress instead of prioritising blood pressure and bowels – even though I admit these are really important things and shouldn’t be forgotten – perhaps some of the issues that people face some months or years down the track when they still have persistent pain that ‘shouldn’t be there because we operated and removed the cause of the pain’ – maybe those issues wouldn’t be quite so complex.

Hinrichs-Rocker, A., Schulz, K., Järvinen, I., Lefering, R., Simanski, C., & Neugebauer, E. (2009). Psychosocial predictors and correlates for chronic post-surgical pain (CPSP) – A systematic review European Journal of Pain, 13 (7), 719-730 DOI: 10.1016/j.ejpain.2008.07.015