Efficacy and Safety of Adding Dexmedetomidine to Levobupivacaine in Rectus Sheath Block Compared to Quadratus Lumborum Block in Patients Undergoing Lower Abdominal Cancer Surgery: a Randomized Clinical Trial

Surgical trauma activates numerous receptors leading to severe postoperative pain. Seventy to seventy-five percent of the pain is somatic, originating from the anterior abdominal wall, and it often persists for 72 hours after open surgery. The objective of this study is to compare the efficacy and safety of adding dexmedetomidine to Levobupivacaine in rectus sheath block with quadrates lumborum block in patients undergoing lower abdominal cancer surgeries.

Postoperative pain may cause tachycardia, hypertension, increased cardiac work, nausea, vomiting and ileus. Also, if it is inadequately managed it may lead to hazardous cardiovascular effects, pulmonary dysfunction, immune system, neuro-endocrine and metabolic effects, gastrointestinal- urinary- and cognitive dysfunction and also have psychological, economic and social adverse effects. Therefore, effective pain management is a priority of care and a patient's right.

The American Society of Anesthesiologists recommends use of multimodal pain regimens to minimize opioid use and improve pain control . Opioids are still the go-to medication for treating visceral pain, but they are ineffective against somatic discomfort. An effective Multimodal pain management protocol uses combinations of opioid prescriptions, nonopioid prescription, regional and local anesthesia, and nonpharmacological therapy . To mitigate the adverse consequences of opioid overconsumption, peripheral and regional anesthetic blocks were implemented. The Quadratus lumborum block is one of the perioperative pain management procedures that is administered to patients of all ages who are undergoing abdominal surgery . Nevertheless, there is persistent disagreement regarding the optimal method of administering the block due to the ambiguous mechanisms that are responsible for its effects.

We sought an alternative, such as the Rectus sheath block, to prevent postoperative somatic pain, due to the potential complications of the QLB technique, including retroperitoneal hemorrhage, abscess, and pleural injury . The block was not frequently applied, or insufficient blocks could not be achieved primarily with a single injection method prior to taking advantage of ultrasonography. This was due to the proximity of medicated zones and vital organs, as well as the coherent and thin muscle layers. Currently, this approach is being implemented with catheter placement in the rectus sheath, ultrasonography guidance, and a single injection .

At present, several adjuvants have been added to local anesthetics used in peripheral and regional blocks to decrease the dosage of local anesthetic and enhance its effectiveness . Dexmedetomidine is an adjuvant that acts as a selective alpha two adrenoreceptor stimulating agent. This medication induces drowsiness, analgesia, sympatholysis, and anxiolysis in a dose-dependent manner, without causing significant respiratory depression.

Eligibility Criteria:
Inclusion Criteria:

1. Patients subjected to major lower abdominal cancer surgeries.
2. The enrolled age will be from 18 years to 70 years
3. ASA I-III and NYHA I-III.

Exclusion Criteria:

1. ASA physical status \>III and NYHA\>III
2. Patient refusal
3. Body mass index \>40 kg/m2
4. Preoperative opioid consumption
5. Infection at the incision site
6. A history of hematological disorders or coagulation abnormality
7. Previous abdominal surgeries, severe hepatic or renal impairment
8. Pregnant women

10- Hypersensitivity to any of used drugs