The postoperative pain after open nephrectomy remains a major concern because some patients still demonstrate acute pain that may develop chronic pain that lasts for months following the surgery.

Epidural analgesia is the gold standard for abdominal surgery including for open nephrectomy, however, it has unfavorable side effects such as paresthesia, hypotension, hematomas, an impaired motor of lower limbs and urinary retention that could delay recovery.

Various techniques have tried to replicate the analgesic efficacy of epidural analgesia. They include transversus abdominis plane analgesia (TAP), rectus sheath analgesia (RS), wound infusion analgesia (WI) and transmuscular quadratus lumborum (TQL) analgesia. However, each of these techniques has specific limitations that prevent them from being the analgesic technique of choice for all open abdominal surgeries.

Up to the investigator's knowledge, there is no study done to compare ESPB versus QLB as pre-emptive analgesia in patients undergoing open nephrectomy.

Open surgery remains basic surgery for patients requiring radical or partial nephrectomy and is associated with a high incidence of intense immediate postoperative pain and chronic pain the months following surgery [1]. The physiopathology of acute pain is explained as it is mediated by inflammatory cell infiltration, activation of the pain pathways in the spinal cord, and also reflexive muscle spasm. All of these three mechanisms of acute pain are typically ameliorated during the postoperative recovery [2].

Regional anesthesia techniques are commonly enhanced for pain management in open nephrectomy as they decrease parenteral opioid requirements and improve patient satisfaction [3].

Erector Spinae Plane block (RSPB), first described by Forero et al.,[4] for analgesia in thoracic neuropathic pain, has also been reported for the management of other causes of acute and postoperative pain [5,6,7]. In this ultrasound-guided (USG) technique, a local anesthetic (LA) is applied between the erector spinae muscle and the transverse process of the thoracic vertebra leading to the spread of LA cephalad, caudally and through the paravertebral space [4,5,8].

Quadratus Lumborum block (QLB) was initially described by R.Blanco as an abstract at the annual European Society of Regional Anaesthesia (ESRA) congress in 2007, where the LA was injected at the anterolateral aspect of the QL muscle (type 1 QLB) [9]. Later, J. Børglum used the posterior transmuscular approach by detecting Shamrock sign and injecting the LA at the anterior aspect of the QL (type 3 QLB) [10]. Recently, R. Blanco described another approach by injecting the LA at the posterior aspect of the QL muscle (type 2 QLB), which may be easier and safer as the LA is injected in a more superficial plane, so the risk of intra-abdominal complications and lumbar plexus injuries is less [11]. Finally, the intramuscular QLB (type 4 QLB) was done by injecting LA directly into the QL muscle [12].

The investigators hypothesize that performing ultrasound-guided ESPB block will be more superior to or equal to QLB in providing postoperative analgesia for patients undergoing open nephrectomy under general anesthesia.

Inclusion Criteria:

• Patient acceptance.
• BMI ≤ 30 kg/m2
• ASA II and III.
• Elective open nephrectomy under general anesthesia

Exclusion Criteria:

• History of allergy to the LA agents used in this study,
• Skin lesion at the needle insertion site,
• Those with bleeding disorders, sepsis, liver disease, and psychiatric disorders

planned after the completion of the study and publication

planned after the completion of the study and publication

principal investigator

Double (Participant, Outcomes Assessor)