Rectus sheath catheters (RSC) are used for postoperative analgesia following midline laparotomies. Local anesthetics are applied to the posterior rectus sheath via the RSC. The target structures are the anterior cutaneous branches of the spinal nerves Th7-Th12. RSC can be used in particular if thoracic epidurals are contraindicated (compromised coagulation), technically unfeasible or refused by the patient.

The study investigates placebo-controlled weather RSC have a significant additional analgesic effect in a multimodal analgesic concept. Primary outcome parameters are the maximum pain score, the Quality-of-Recovery-15-Score (QoR-15GE) and the opioid consumption (morphine equivalents) in the first 72h postoperatively.

Recruitment Patients are recruited during the anesthesiology consultation. Patients who provided written informed consent. fulfill all inclusion and no exclusion criteria will be included in the study.

Allocation of study medication After inclusion in the study, each patient receives a patient number, which is noted on the Case Report Form (CRF). The randomization list was generated via www.random.org (Randomness and Integrity Services Ltd., Dublin, Ireland). Random assignment to groups 1 (verum) and 2 (placebo) was performed on the day of surgery using the sealed envelope technique. The sealed envelope is opened by a doctor not involved in the study immediately before bilateral placement of the rectus catheters catheters. This colleague prepares the study medication (verum or placebo, unlabeled, blinded to the observer and patient).

Anesthesia and perioperative monitoring After a peripheral or central venous line is inserted, a balanced electrolyte solution is connected and the following parameters are monitored until complete postoperative recovery: blood pressure (plethsymographic or via arterial line), electrocardiogram, pulse oximetry.

The surgical procedures are performed under general anesthesia (sevoflurane 0.7-1.0 MAC). Sufentanil (0.2-0.4 microg/kg), propofol (1.5-2 mg/kg) and cisatracurium (0.1-0.15 mg/kg) are administered to induce anesthesia The multimodal analgesia concept includes the intraoperative administration of 4 mg dexamethasone (antiemetic, coanalgesic) and two non-opioids: 1 g metamizole (40 mg parecoxib if contraindications exist) and 1 g paracetamol.

Study intervention Bilateral RSC are placed intraoperatively after closure of the median laparotomy under aseptic conditions, before the wound dressing is applied. For imaging, we use an ultrasound device (FUJIFILM Sonosite, Bothel, WA, USA) with a linear transducer (38mm, 6-13MHz), which is placed obliquely on the upper edge of the median laparotomy. The puncture (puncture direction from medial-cranial to lateral-caudal) is initially performed with an ultrasound-optimized single-shot cannula (SonoPlex 22G50mm to 21G100mm, Pajunk, Geisingen, Germany) in order to reliably identify the compartment of the posterior rectus sheath. After verification of the correct spread of the local anesthetic, the catheter (SonoLong Echo 19G 50-100mm, 20G 50cm catheter, Pajunk, Geisingen, Germany) is placed at the lateral edge of the posterior rectus sheath and again the correct spread of the local anesthetic in the target compartment is verified by ultrasound.

Group 1 Verum (ropivacaine 0.2%) Dosage 2x30ml ropivacaine 0.2% every 8h (120mg every 8h) Daily dose 360mg

Group 2 Placebo (saline 0.9%) Dosage 2x30ml saline 0.9% every 8h

Postoperative care Postoperatively, patients are cared for in the recovery room or intensive care unit. As soon as their condition allows, they are transferred to a peripheral ward. Non-opioid analgesics are continued. An additional opioid-based on-demand medication is prescribed (7.5 mg piritramid), the dose of which is documented as morphine equivalents (5 mg).

Inclusion Criteria:

• Median laparotomy
• Age over 18 years
• Informed consent has been obtained

Exclusion Criteria:

• Local signs of inflammation
• known allergy to local anesthetics used
• chronic pain syndrome
• drug addiction
• post-operative ventilation that cannot be completed on the day of surgery
• lack of consent or cooperation
• pregnancy
• participation in another medical study
• sepsis

all collected IPD

up to 6 months after publication

on request to the principal investigator