Median sternotomy pain after cardiac surgery: To block, or not? A systematic review and meta-analysis

Background Inadequate pain control after median sternotomy leads to reduced mobilization, increased respiratory complications, and longer hospital stays. Typically, postoperative pain is controlled by opioid analgesics that may have several adverse effects. Parasternal intercostal block (PSB) has emerged as part of a multimodal strategy to control pain after median sternotomy. However, the effectiveness of this intervention on postoperative pain control and analgesic use has not been fully established. Methods and Results We conducted a meta-analysis to assess the effect of PSB on postoperative pain and analgesic use in adult cardiac surgery patients undergoing median sternotomy. PubMed, Embase, Google Scholar, and the Cochrane database were searched with the following search strategy: ([postoperative pain] or [pain relief] OR [analgesics] or [analgesia] or [nerve block] or [regional block] or [local block] or [regional anesthesia] or [local anesthetic] or [parasternal block] and [sternotomy]) and (humans [filter]). Inclusion criteria were: patients who underwent cardiac surgery via median sternotomy, age >18 and parasternal block (continuous and single dose). Exclusion criteria were: noncardiac surgery, nonparasternal nerve blocks, and the use of NSAIDS in parasternal block. Quality assessment was performed by three independent reviewers via the Cochrane risk of bias assessment tool. Of 1165 total citations, 18 were found to be relevant. Of these 18 citations, 7 citations (N = 2223 patients) reported postoperative pain scores in an extractable format and 11 citations (N = 2155 patients) reported postoperative opioid use in an extractable format. For postoperative opioid use, morphine equivalent doses were calculated for all studies and postoperative pain scores were standardized to a 10-point visual analog scale for comparison between studies; both these were reported as total opioid use or cumulative score ranging from 24 to 72 h postoperative. All data analyses were run using a random effects model, using a restricted maximum likelihood estimator, to obtain summary standardized mean differences with 95% confidence interval (CI's). For studies which only reported median and interquatile range (IQR), the median was standard deviation was estimated by IQR/1.35. Following median sternotomy both postoperative pain (SMD [95% CI] -0.49 [-0.92 to -0.06]) and postoperative morphine equivalent use (SMD [95% CI] -1.68 [-3.11 to -0.25]) were significantly less in the PSB group. Conclusion Our meta-analysis suggests that parasternal nerve block significantly reduces postoperative pain and opioid use.