Quantitative systematic review (44 RCTs, n=2,141 participants).
The median Jadad score of the RCTs was 4 out of 5. The funnel plot did not indicate the presence of publication bias.
Results for all surgical groups combined:
Pain scores: The use of continuous wound catheters was associated with a significant decrease in visual analogue scores for pain at rest (weighted mean difference -10mm, 95% CI: -13, -7, p<0.001, n=1,814 patients) and in visual analogue score for pain with activity (weighted mean difference -22mm, 95% CI: -32, -13, p<0.001, n=794 patients) compared to control. Substantial statistical heterogeneity was found (I2=85.3%).
Opioid use: The percentage of patients with need for opioid rescue during the infusion period was significantly reduced in the continuous wound catheter group compared to control (odds ratio 0.15, 95% CI: 0.08, 0.29, p<0.001, n=411 patients). Opioid use per day was also significantly reduced in the continuous wound catheter group compared to control (weighted mean difference -11mg, 95% CI: -14, -7, p<0.001, n=1,637 patients) Substantial statistical heterogeneity was found (I2=99.1%)
Post-operative nausea and vomiting: The percentage of patients that experienced post-operative nausea and vomiting was significantly reduced in the continuous wound catheter group compared to control (odds ratio 0.45, 95% CI: 0.3, 0.68, p<0.001, n=614 patients).
Satisfaction rating: The percentage of patients rating as excellent was significantly greater in the continuous wound catheter group compared to control (odds ratio 7.7, 95% CI: 1.8, 34, p=0.007, n=209 patients).
Length of hospital stay: The number of days of hospital stay was significantly reduced in the continuous wound catheter group compared to control (odds ratio -1 (95% CI: -2, -0.3, p=0.04, n=753 patients).
Further subgroup analyses were reported for the quantitative review.
Qualitative systematic review (51 RCTs, n=2,407 participants).
Cardiothoracic group: In the cardiothoracic group 12 of 14 RCTs reported analgesic efficacy for either pain scores or opioid use which was statistically significant (p<0.05).
General surgery group: In the general surgery group 10 of 12 RCTs reported statistically significant analgesic efficacy as either reduced opioid use or reduced pain scores (p<0.05).
Orthopaedic surgery group: In the orthopaedic surgery group 13 of 16 trials reported a statistically significant reduction in pain or opioid use (p<0.05). Twelve of 16 trials reported a statistically significant reduction in pain scores in the immediate post-operative period (p<0.05). Eleven RCTs reported a reduction in pain scores two to five days postoperatively.
Post-operative nausea and vomiting: Four of six RCTs reported a reduction in post-operative nausea and vomiting but these were not statistically significant.
Satisfaction rating: Three RCTs reported increased patient satisfaction.