Postoperative pain after cardiac surgery remains a persistent clinical challenge, particularly following procedures that require median sternotomy. This form of surgical access, though essential for procedures like valve replacements and coronary artery bypass grafting (CABG), results in substantial nociceptive input from both the bone and surrounding soft tissues. Effective pain control in the initial 48 hours is vital not only for patient comfort but also for facilitating extubation, respiratory effort, mobilization, and minimizing the risk of complications like atelectasis and pneumonia.

Historically, opioid-based regimens have been the cornerstone of post-cardiac surgery analgesia. While effective, these regimens are associated with significant side effects, including respiratory depression, sedation, nausea, urinary retention, and delayed recovery. As a result, there is increasing interest in regional anesthesia techniques that can reduce opioid requirements and improve recovery profiles.

The serratus anterior plane (SAP) block, a fascial plane block traditionally used for lateral thoracic wall procedures, has gained attention for its potential role in sternotomy analgesia. The study by Bailey et al. explored the use of continuous SAP block catheters in the postoperative cardiovascular ICU setting to determine the feasibility of conducting a larger, definitive trial.

Study objective and methods

The primary aim was to determine the feasibility of a placebo-controlled trial evaluating continuous SAP blocks for post-sternotomy pain in adult cardiac surgery. Secondary aims included comparing postoperative pain, opioid use, and quality of recovery.

• Design: Prospective, double-blind, randomized controlled feasibility trial conducted at a single Canadian academic center.
• Participants: 52 patients undergoing elective or urgent cardiac surgery via median sternotomy were enrolled. Procedures included isolated valve surgeries, CABG, or combined interventions.
• Intervention: All participants had bilateral SAP catheters placed postoperatively in the cardiovascular ICU using ultrasound guidance.
  • Active group: Received 0.2% ropivacaine.
  • Placebo group: Received normal saline.
  • Dosing protocol: Programmed intermittent boluses of 10 mL every 2 hours per side were administered for up to 72 hours via the SAP catheters.
• Feasibility criteria:
  • Minimum recruitment rate of 4 patients/month.
  • Protocol adherence > 90%.
  • Completion rate of the QoR-15 questionnaire > 90%.
  • Combined catheter-related complication rate ≤ 2%.
• Outcomes measured:
  • Pain scores (NRS) at 24, 48, and 72 hours.
  • Total opioid consumption expressed in oral morphine equivalents (OME).
  • Quality of recovery using the QoR-15 at 48 and 72 hours.
  • Long-term pain outcomes at 3 and 6 months using the Brief Pain Inventory.
  • Complication rates including catheter-related events.

Key findings

• Feasibility outcomes:

• • The study failed to meet several key feasibility criteria. The average recruitment rate was only 2.4 patients per month, limiting statistical power and generalizability.
  • Protocol adherence was high but fell short of the 90% target, reaching 88% due to minor deviations.
  • QoR-15 completion rates exceeded expectations at 96%, indicating good participant engagement.
  • Most notably, the incidence of major catheter-related complications was 12%, significantly exceeding the acceptable threshold. Six patients developed pneumothorax, raising safety concerns and precluding trial expansion.

• Analgesic outcomes:

• • Pain scores were low in both groups, with median NRS values ranging from 1.5 to 4.0 at various time points, and no significant differences between groups.
  • Opioid use was modest overall. At 72 hours, total opioid consumption (OME) ranged from 0-32 mg in the ropivacaine group versus 4-40 mg in the placebo group, again with no statistically significant differences.The relatively low opioid requirements may have been influenced by concurrent use of spinal morphine, postoperative sedation protocols, and a standardized multimodal analgesic regimen

• Quality of recovery:

• • QoR-15 scores at both 48 and 72 hours did not differ significantly between groups. This suggests that even with the potential for better anterior thoracic analgesia, SAP blocks did not translate into measurable improvements in overall recovery experience.

• Safety and technical performance:

  • The high rate of pneumothorax was unexpected and may be attributed to the technique or catheter hardware, such as styletted catheters. Although none were advanced forcefully and stylettes were partially withdrawn, the anatomical proximity to pleural structures posed an ongoing risk.
  • Other catheter-related complications included dislodgement and kinking, reported equally across both groups.
  • Placement of SAP catheters was otherwise straightforward, with a median total placement time of 34 minutes for both catheters.

Conclusion

This feasibility study concluded that a large-scale trial evaluating continuous SAP blocks for sternotomy pain is not feasible at the current center due to low recruitment and an unexpectedly high rate of pneumothorax. No significant differences were found in postoperative pain, opioid use, or quality of recovery between the ropivacaine and placebo groups.

Future research

Future trials should focus on alternative regional techniques that may better target the anterior chest wall, such as parasternal intercostal plane (PIP) blocks or combinations of blocks for more comprehensive coverage. Investigating catheter-based PIP techniques and including broader multimodal analgesia protocols may yield improved outcomes. Additionally, multi-center collaboration may help overcome recruitment challenges and provide more robust data on safety and efficacy.

For more detailed information, refer to the full article in BJA.

Bailey JG et al. Continuous serratus anterior block for sternotomy analgesia after cardiac surgery: a single-centre feasibility study. Br J Anaesth. 2025;134:1161-1169.

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