Post-operative pain and analgesic use for cardiac surgery with median sternotomy

BACKGROUND Inadequate pain control after median sternotomy leads to reduced mobilization, increased respiratory complications, and longer hospital stays. Typically, post-operative pain is controlled by opioid analgesics that may have significant respiratory and gastrointestinal side effects. Parasternal intercostal neuraxial block (PSB) has emerged as part of a multimodal strategy to control pain after median sternotomy. However, the effect of this intervention on post-op pain and analgesic use has not been fully established. METHODS AND RESULTS We conducted a meta-analysis to assess the effect of PSB on post-op 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: ((post-operative 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: cardiac surgery, median sternotomy, age>18 and parasternal block (continuous and single dose), and exclusion criteria were: non-cardiac surgery, non-parasternal nerve blocks, use of NSAIDS in parasternal infusion. Quality assessment was performed by 3 independent reviewers via the Cochrane risk of bias assessment tool. Of 1165 total citations, 16 were found to be relevant. These were all double blinded RCTs: 7 RCTs with a total of 2223 patients reported post-op pain scores in an extractable format and 11 RCTs (N=2155) reported post-op analgesia use after PSB (Table 1). For post-op analgesia use, morphine equivalent doses were calculated for all studies and post-op 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 24h to 72h post-op. All data analyses were run using a random effects model, using a restricted maximum likelihood estimation, analyzing standardized mean differences with 95% CI's. For studies which only reported median and IQR, standard deviation was estimated by IQR/1.35. Following median sternotomy both post-op pain (SMD -0.49 [-0.92,-0.06]) and post-op morphine equivalent use (SMD -1.68 [-3.11, -0.25]) were significantly less in the PSB group (Fig. 1). CONCLUSION A parasternal nerve block strategy significantly reduces post-op pain and opioid analgesic use. While there was heterogeneity between the RCTs in the amount, type of anesthetic and the use of single vs continuous dosing and the type of control used (Table 1), our analysis suggests that PSB is effective in reducing post-op pain in cardiac surgery patients.