Comparing pain relief with and without magnesium sulfate in a nerve block for patients having chest surgery.

This study will include 60 consecutive patients or the available number of patients meeting the inclusion criteria within a period of 2 years scheduled for elective thoracotomy under general anesthesia, with ASA status I, II, or III. General anesthesia will approximately last 2-3 hours.. Demographic and clinical data will be collected using a standardized form. The exclusion criteria are: age under 18 years, allergy to any of the drugs used, infection at the block site, spinal deformity, existing coagulation disorders, patient refusal to provide informed consent, as well as morbid obesity (body mass index >40). Patients will be randomized into two groups (trial and control) using a random number generator. Both groups will receive general endotracheal anesthesia performed by an experienced anesthesiologist (defined as more than 10 years of clinical experience). All patients will be informed of the risks and benefits of the procedure during the preoperative visit, one day before surgery, and will be asked to sign informed consent. The paravertebral block will be performed in a designated anesthetic induction room adjacent to the operating theatre, equipped with all mandatory monitoring equipment including ECG, non-invasive blood pressure, pulse oximetry, and oxygen delivery systems. Prior to induction of general anesthesia, patients will undergo an ultrasound-guided paravertebral block (PVB) approximately 30 minutes before induction of anesthesia.. Trial group will receive a mixture of 13.5 mL 0.5% bupivacaine and 150 mg (1mL=50mg) magnesium sulfate (total volume 15 mL), while control group will receive 13.5 mL 0.5% bupivacaine and 1.5 mL of 0.9% saline. On the day of surgery, after admission to the preoperative area, intravenous access will be established and blood samples collected for baseline laboratory values. Patients will then be positioned sitting with their back and neck flexed forward for PVB administration. Under ultrasound guidance, the spinous processes of vertebrae Th4, Th5, and Th6, as well as the corresponding ribs and paravertebral spaces, will be identified. A linear ultrasound transducer will be placed longitudinally along the paravertebral spaces, lateral to the midline, oriented cranially. The transducer will be moved medially until rounded ribs and the parietal pleura are visualized. After identifying the desired paravertebral space, a 25G needle will be inserted using the out-of-plane technique under strict aseptic conditions. After confirming negative aspiration for blood or air, a total of 5mL of the LA mixture will be administered in 3 paravertebral spaces between Th4-Th7. Following the PVB, a "pinprick" test will be used to assess the extent of sensory block, and the onset of analgesia will be recorded (defined as a reduction in pinprick and cold sensation (tested with an alcohol-soaked cotton swab) of at least 75%). Before induction of general anesthesia, standard monitoring will be applied (ECG, non-invasive blood pressure, SpO2), and a radial arterial line will be placed on the opposite side of the thoracotomy for continuous blood pressure monitoring. During surgery, participants will be monitored by the anesthesiology attending. Postoperatively, monitoring will be continued in the ICU by the attending anesthesiologist. General anesthesia will be identical in both groups. Induction will be achieved with intravenous propofol (1.5–2.5 mg/kg), sufentanil (0.2 µg/kg), and rocuronium (0.6 mg/kg). Patients will be intubated with a double-lumen endotracheal tube. Maintenance will be with sevoflurane in an oxygen/air mixture. Mechanical ventilation parameters will include tidal volume 6–8 mL/kg, PEEP 5 cm H2O, and end-tidal CO2 maintained between 30–35 mmHg. Throughout the surgery, invasive blood pressure will be monitored continuously, with systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR) recorded every 5 minutes. At the end of anesthesia, prior to extubation, neuromuscular blockade will be reversed with 2.5 mg neostigmine and 1 mg atropine. Postoperative pain will be assessed using the Numerical Pain Rating Scale (NPRS) at rest and during coughing every 2 hours after surgery. Time to first report of pain (defined as NPRS >=1) will be recorded. For NPRS scores of 1–3, patients will receive 1 g IV paracetamol; for scores 4–10 sufentanil will be administered in incremental boluses of 10 mcg until an NPRS <= 3 is achieved. Total analgesic consumption within the first 24 hours will be recorded and converted to morphine equivalent doses. Blood samples for calculating neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and monocyte-to-lymphocyte ratio (MLR) will be collected at three time points: preoperatively, and at 6 and 24 hours postoperatively. These biomarkers will be analyzed for their potential association with postoperative pain intensity and analgesic requirements. Fidelity to the intended procedures will be maintained by following a standardized protocol checklist at each step of patient care, direct supervision of all procedures by experienced anesthesiology attendings, and regular data audits conducted by the study’s research coordinator."