Comparing pain intensity rating scales in acute postoperative pain: boundary values and category disagreements.

Pain intensity assessment scales are important in evaluating postoperative pain and guiding management. Different scales can be used for patients to self-report their pain, but research determining cut points between mild, moderate and severe pain has been limited to studies with < 1500 patients. We examined 13,017 simultaneous acute postoperative pain ratings from 913 patients taken at rest and on activity, between 4 h and 48 h following surgery using both a verbal rating scale (no, mild, moderate or severe pain) and 0-100 mm visual analogue scale. We determined the best cut points on the visual analogue scale between mild and moderate pain as 35 mm, and moderate and severe pain as 80 mm. These remained consistent for pain at rest and on activity, and over time. We also explored the presence of category disagreements, defined as patients verbally describing no or mild pain scored above the mild/moderate cut point on the visual analogue scale, and patients verbally describing moderate or severe pain scored below the mild/moderate cut point on the visual analogue scale. Using 30 and 60 mm cut points, 1533 observations (12%) showed a category disagreement and using 35 and 80 mm cut points, 1632 (13%) showed a category disagreement. Around 1 in 8 simultaneous pain scores implausibly disagreed, possibly resulting in incorrect pain reporting. The reasons are not known but low rates of literacy and numeracy may be contributing factors. Understanding these disagreements between pain scales is important for pain research and medical practice.

Prognostic factors for chronic post-surgical pain after lung and pleural surgery: a systematic review with meta-analysis, meta-regression and trial sequential analysis.

Chronic post-surgical pain is known to be a common complication of thoracic surgery and has been associated with a lower quality of life, increased healthcare utilisation, substantial direct and indirect costs, and increased long-term use of opioids. This systematic review with meta-analysis aimed to identify and summarise the evidence of all prognostic factors for chronic post-surgical pain after lung and pleural surgery. Electronic databases were searched for retrospective and prospective observational studies as well as randomised controlled trials that included patients undergoing lung or pleural surgery and reported on prognostic factors for chronic post-surgical pain. We included 56 studies resulting in 45 identified prognostic factors, of which 16 were pooled with a meta-analysis. Prognostic factors that increased chronic post-surgical pain risk were as follows: higher postoperative pain intensity (day 1, 0-10 score), mean difference (95%CI) 1.29 (0.62-1.95), p < 0.001; pre-operative pain, odds ratio (95%CI) 2.86 (1.94-4.21), p < 0.001; and longer surgery duration (in minutes), mean difference (95%CI) 12.07 (4.99-19.16), p < 0.001. Prognostic factors that decreased chronic post-surgical pain risk were as follows: intercostal nerve block, odds ratio (95%CI) 0.76 (0.61-0.95) p = 0.018 and video-assisted thoracic surgery, 0.54 (0.43-0.66) p < 0.001. Trial sequential analysis was used to adjust for type 1 and type 2 errors of statistical analysis and confirmed adequate power for these prognostic factors. In contrast to other studies, we found that age had no significant effect on chronic post-surgical pain and there was not enough evidence to conclude on sex. Meta-regression did not reveal significant effects of any of the study covariates on the prognostic factors with a significant effect on chronic post-surgical pain. Expressed as grading of recommendations, assessment, development and evaluations criteria, the certainty of evidence was high for pre-operative pain and video-assisted thoracic surgery, moderate for intercostal nerve block and surgery duration and low for postoperative pain intensity. We thus identified actionable factors which can be addressed to attempt to reduce the risk of chronic post-surgical pain after lung surgery.