Efficacy of combined ultrasound guided anterior and posterior rectus sheath block for postoperative analgesia following umbilical hernia repair: Randomized, controlled trial

Background
Anatomical variations in the thoracic nerves T7 to T11was found in up to 30% of the population as the anterior cutaneous branch of the nerves are formed before the rectus sheath and so do not penetrate the posterior wall of the rectus sheath. Posterior rectus sheath block was found to be effective for perioperative analgesia. We tested the efficacy of addition of anterior rectus sheath block to capture the anterior cutaneous branch of intercostal nerves as they emerge from the rectus muscle in anterior rectus sheath.
Method
Sixty-three ASA I/II adult patients listed for elective umbilical hernia repair were randomly allocated in one of three groups: Bupivacaine hydrochloride 0.25% was injected by ultrasound guided bilateral posterior rectus sheath in Group I (PRSB) and bilateral anterior and posterior rectus sheath in Group II (APRSB). Group III received bilateral anterior and posterior rectus sheath block using isotonic saline. Twenty-four hours postopetrative morphine consumption, Intraoperative rescue fentanyl dose, equivalent morphine dose in the recovery unit and first morphine dose were recorded. The quality of analgesia is assessed by Visual Analogue Scale for 24 h.
Results
Mean intraoperative rescue fentanyl dose was 19.23 ± 4.96 μg, 15.28 ± 2.75 μg and 12.85 ± 3.65 μg in control, PRSB and APRSB groups respectively (P < 0.001). The mean opioid consumptions in PACU was PRSB 3.47 ± 0.13 mg, APRSB 2.91 ± 0.15 mg and control 4.04 ± 0.56 mg respectively (P < 0.001). Significant difference in intraoperative rescue fentanyl was found between PRSB and APRSB group (P = 0.020). Also statistically significant difference was found between PRSB and APRSB groups in 24 h morphine consumption (P = 0.034).
Conclusion
Addition of ultrasound anterior rectus sheath block together with posterior rectus sheath block added more significant analgesia than if we perform posterior rectus sheath alone. This was evidenced by decrease in Intraoperative rescue fentanyl, PACU morphine analgesia, 24 h morphine and pain assessment score.