Effect of Lidocaine Versus Magnesium on Postoperative Pain in Spine Surgery

This is a double-blinded prospective controlled randomized clinical trial that will be performed in Assiut university hospital.

After obtaining approval from Assiut University Hospital Ethical Committee and informed written consent from patients, this study will be conducted on ASA status I, II and III patients, aged between 18y and 60 y, both male and female, undergoing spinal fusion surgery (single, and double level).

Subjects will be excluded if they met any of the following criteria: Previous spine surgery, morbid obesity (BMI > 40), spine metastatic tumor, allergy to an amide LA, or magnesium sulfate, heart block, renal, or liver dysfunction, substance abuse disorder, chronic opioid use, or electrolyte disturbance , administration of any sedative, preexisting mental illness, psychological or emotional problems.

Randomization will be performed using lidocaine group, magnesium group, combined (lidocaine and magnesium) group and control group registers, which will be placed in sealed envelopes prior to study initiation, and opened prior to anesthesia by a physician who will prepare the IV solution, and identify it with the patient number, according to the envelope drawn. The solution will be handed to another physician, blind to the prepared solutions' content, who will be responsible for the anesthesia. The solution volume will be equal. The responsible investigator will remain blind to the chosen group until the end of the study.

Allocation concealment will be done using serially numbered closed, opaque envelopes. Each patient will be given a serial number from a computer-generated randomization table, and will be placed in the appropriate group after opening the corresponding sealed envelope. Counseling for participation will be conducted before recruitment.

Operative technique: Patients will be monitored with continuous electrocardiography, capnography, pulse oximetry, and intermittent non-invasive blood pressure measurements every 5 minutes.

After establishment of venous access, anesthesia will be induced with propofol 2 mg / kg, fentanyl 1.5 µg / kg and cisatracurium 0.15 mg/kg. Endotracheal tube of appropriate size will be inserted and mechanical ventilation utilizing isoflurane in oxygen/air mixture at sufficient concentration to maintain systolic blood pressure within the limit of 20% baseline value.

All patients will receive 30 mg ketorolac IV infusion after induction of anesthesia, Paracetamol 1g will be given by IV infusion to all patients before extubation. Reversal of residual muscle relaxant will be accomplished using neostigmine, and atropine at the end of the operation guided by train of four.

Intraoperative fluid therapy will be administered in the form of normal saline after calculation of fasting and maintenance fluid requirements.

Patients will be discharged to PACU then to the ward after fulfilling the standard criteria.

No other anesthetics or sedatives will be allowed during the operation. In the first 24 hours postoperative; patients will be given Ketorolac 30 mg slowly IV (diluted to 10 ml) every 12h, and paracetamol 1g injection every 8 hours; starting 8 hours after extubation. Morphine 0.1mg/kg slowly IV will be given as rescue analgesia when numeric rating scale (NRS) is ≥4, or if the patient requested additional analgesia, with a minimum 8 hours interval between the 2 consecutive injections. Total doses of IV morphine will be documented.

After 24 hours post-operation; paracetamol 1 g every 8 hours will be given orally for 5 days. Ketolac 30 mg will be given orally only if needed.

Pain will be assessed during rest and cough in the first 24 h, and during movement after 24h. postoperative.

All patients will be urged to ambulate as early as practically possible. Collected data will include patient's characteristics, and surgical data including age, gender, weight, height, duration of surgery, and duration of hospital stay. Postoperative pain evaluation during rest will be assessed by numeric rating scale (NRS). Patients' satisfaction will be assessed by using 5 points Likert score for satisfaction where 1=strongly dissatisfied; 2=Dissatisfied; 3=neither satisfied nor dissatisfied; 4=Satisfied; 5=strongly satisfied. The two scores will be recorded at the following times: immediately at 1 h; 6 h; 12 h; 24 h; at discharge time; 1 month; 2 months, and 3 months postoperative.

Time to the first request for analgesia and the total dose of rescue analgesia (morphine) in the first 24 hours after surgery will be recorded. The long-term follow-up of postoperative back pain for 3 months will be conducted through the outpatient orthopedic clinic, or by telephone.

Hemodynamics and blood loss will be reported First time to pass flatus, first time to defecate and incidence of complications will also be reported (such as hypotension, bradycardia, anxiety, dizziness, muscle twitching, nervousness, reaction at the site of injection, cardiac arrest, double vision, nausea, seizures, unconsciousness, euphoria, tinnitus, vomiting).

Testing for gross mental and neurologic defects will be performed with the Mini-Mental Status Examination, which has a standard scoring method with a maximum score of 30. The total duration of the testing will not exceed 45 minutes. Interruptions will be allowed at the request of the patient between, but not within, individual tests of the session. The tests will be administered by the same examiner to limit interexaminer variability.

The anxiety and depression status will be evaluated by Self-Rating Anxiety Scale (SAS) and Self-Rating Depression Scale (SDS), and QOL will be measured by Short Form Health Survey 36 (SF-36) in eight sections, including vitality, physical functioning, bodily pain, general health perceptions, mental health, physical, emotional, and social role functioning.

The study portion of the tests will be performed at least 6 hours after the initial intravenous bolus of drugs, while the control portion will be performed at least 24 hours after the studied drugs are discontinued. Tests will be repeated after 1 week and 4 weeks.