The Effect of Quadratus Lumborum (QL) Block on the Incidence of Chronic Neuropathic Pain After Retroperitoneal Laparoscopic Donor Nephrectomy: A Study on Neuroinflammation and Neurophysiology

Primary outcomes

1. Neuropathic Pain Incidence: Neuropathic Pain in 4 Questionnaire

   Time frame: 3 months after intervention

   Pain that develops after a surgical procedure in the area of surgery and its radiation, persists for at least 3 months after surgery, other causes of pain (e.g. infection and history of malignancy) or pre-existing pain have been excluded.

   Total score: 10 Score ≤ 4 = no pain developed Score ≥ 4 = pain developed

2. Neuromodulation Parameter: Degree of functional interference using Behavioral Pain Interference (BPI)

   Time frame: At 3 months after intervention

   The degree of pain that develops after a surgical procedure in the area of surgery and its radiation, persisting for at least 3 months after surgery, other causes of pain (eg infection and history of malignancy) or pre-existing pain have been excluded.

   Behavioral Pain Interference (BPI) questionnaire based on the average of questions 4, 5, and 6

   • Mild (NRS 1-3)
   • Moderate (NRS 4-6)
   • Severe (NRS 7-10)

3. Chronic Pain Severity: Leeds Assesment of neuropathic symptoms and sign (LANSS) scale

   Time frame: At 3 months after intervention

   A measuring tool used to assess neuropathic pain and provides information to differentiate nociceptive pain from neuropathic pain.

   Total score: 24 <12: Not neuropathic >12: Neuropathic pain

4. Neuroinflammation Parameter: Serum Concentration of Toll-like Receptor 4 (TLR4)

   Time frame: At 3 months after intervention

   Transmembrane receptors in the innate immune system. Units: ng/mL

5. Neuroinflammation Parameter: Serum Concentration of Calcitonin gene-related peptide (CGRP)

   Time frame: At 3 months after intervention

   Neuropeptides that play a role in pain transmission and vasodilation Unit: pg/mL

6. Neuroinflammation Parameter: Serum Concentration of Nerve Growth Factor (NGF)

   Time frame: At 3 months after intervention

   Neurotrophic factors that play a role in promoting the growth and survival of sensory neurons Unit: pg/mL

7. Neurophysiology Parameter: Mechanical Detection Threshold (MDt)

   Time frame: At 3 months after intervention

   Measures the minimum force needed for a person to perceive a light mechanical stimulus, tested using von Frey filaments. Skin contact test for 2 seconds using 1 set of von Frey filaments. The examination is performed in m. trapezius.

   Unit: mN Lower result means: higher sensitivity (normal or hypersensitivity) Higher result means: Reduced sensitivity, could indicate hypoesthesia or nerve damage

8. Neurophysiology: Mechanical Pain Threshold (MPt)

   Time frame: At 3 months after intervention

   Accurate measurement of pain threshold. Skin contact test using repeated pinpricks at the same location. Comparative assessment of initial pain scale with pain scale after repeated stimulation. Examination is performed at m. trapezius.

   Unit: Numerical Rating Scale (NRS) from 1 to 10 Lower NRS: higher sensitivity to pain Higher NRS: lower sensitivity to pain

9. Neurophysiology Parameter: Pressure Pain Threshold (PPt)

   Time frame: At 3 months after intervention

   Pain tolerance examination. Pressure assessment in kgf/cm2 units where the patient complains of pain according to the stimulus given. The examination is carried out in m. trapezius Units: kgf/cm2.

   Lower PPT: Increased pain sensitivity Higher PPT: Decreased pain sensitivity

10. Neurophysiology Parameter: Mechanical Temporal Summation of Pain (MTSP)

    Time frame: At 3 months after intervention

    Evaluates central sensitization by applying repeated light mechanical stimuli and rating how pain builds up over time.

    Pressure assessment in kgf/cm2 units where the patient complains of pain according to the stimulus given. The examination is carried out in m. trapezius.

    Units: Verbal Numeric Scale (VNS) from 1 to 10 Higher MTSP score: Indicates central sensitization Lower MTSP score: Normal pain processing

11. Neuromodulation Parameter: Serum Concentration of beta-Endorfin

    Time frame: At 3 months after intervention

    Neuropeptide produced in the anterior pituitary and brain, as an endogenous opioid.

    Units: pg/mL