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Background and Aims This study aimed to compare the efficacy of single and double injections of ultrasound-guided superficial parasternal intercostal plane blocks (S-PIPB). We hypothesized that double injections would yield superior success rates in achieving sensory blockade compared to the single injection technique.

Methods Seventy cardiac patients undergoing median sternotomy were randomly assigned to receive single or double injections of S-PIPB bilaterally. Each patient received 40 mL of 0.25% bupivacaine with epinephrine 5 μg/mL and dexamethasone 10 mg. Twenty mL/side was injected at the 3rd intercostal level in single-injection group, while 10 mL/injection was administered at the 2nd and 4th intercostal spaces in double-injection group. The primary outcome was successful S-PIPB, defined as sensory loss in the T2-T6 dermatomes at 30 minutes post-block. Secondary outcomes included block-related complications, intraoperative hemodynamics during sternotomy, fentanyl consumption, postoperative pain, and recovery quality.

Results Double injections of S-PIPB achieved greater success rates on both sides of the chest walls (81% vs 51%, P<0.001) and increased the percentage of blockade in dermatomes T1 (83% vs 59%, P<0.003), T7 (67% vs 46%, P<0.017), and T8 (61% vs 39%, P=0.001) compared to single injection. One hematoma occurred in the double-injection group. Intraoperative hemodynamics, postoperative pain, and recovery outcomes were comparable between the two groups.

Conclusions When compared to a single injection, double injections of S-PIPB provided extended coverage of the T2-T6 dermatomes, which are crucial for median sternotomy. However, no differences were observed in intraoperative hemodynamic effects or postoperative pain control after cardiac surgery.