Effect of Intravenous Magnesium on Postoperative Systemic Inflammatory Response in Patients Undergoing Colorectal Cancer Surgery

The aim of this study is to detect the effect of intraoperative intravenous magnesium sulfate on postoperative systemic inflammatory response by serum inflammatory parameters as CRP, WBCS and neutrophil count. In the anesthesia clinic, an informed written consent will be taken from every patient one day before the surgery. Anesthesia will be provided according to the hospital protocol in respect to preoperative investigations, fasting hours and intra-operative monitoring and drugs. VAS score will be explained to the patient and how to express pain intensity with the use of Visual Analogue Scale (VAS); 10 cm unmarked line in which 0=no pain, 10 cm= the worst imaginable pain. All patients will be clinically assessed and standard preoperative investigations will be done; Complete Blood Count, Coagulation profile, liver function tests, kidney function tests, CRP, chest x-ray and ECG. Intraoperative monitoring items included non-invasive blood pressure (NIBP), heart rate (HR), electrocardiography (ECG), pulse oximetry (Spo2), end-tidal CO2 (EtCo2) and urine output (UOP). Pre-induction hemodynamic parameters (heart rate and mean arterial pressure) will be recorded. General anesthesia will be encouraged with propofol (2 mg/kg) IV followed by atracurium 0.5 mg/kg IV and fentanyl 1 ug/kg. After 3 minutes, intubation will be done. Anesthesia will be maintained with isoflurane 1% MAC in oxygen, air and atracurium 0.1 mg/kg. After the induction of anesthesia, For the patients in group A (study group) (26 patients), a bolus dose of magnesium sulfate (50 mg/Kg over 20 minutes) will be administered then, the maintenance dose of magnesium sulfate (15mg/Kg/hour) will be infused till the end of the surgery. In group B (control group) (26 patients), the patients will receive normal saline with the same volume and the same infusion model. The study drug (MgSO4) and the placebo (normal saline) will be prepared in the hospital pharmacy. Each one will be assigned a code so that the anesthetist will remain blinded to group allocation. Intravenous fentanyl infusion 0.4µg/kg/hr will be administrated during intraoperative period till the end of surgery. At the end of surgery, inhalational anesthetics will be discontinued and muscle relaxant will be reversed by intravenous atropine 10 μg/kg and neostigmine 0.05 mg/kg. In both groups, hemodynamic parameters as heart rate and mean blood pressure (MAP) will be continuously monitored till the end of surgery in addition that urine output (UOP) will be frequently monitored and recorded. If heart rate becomes less than 50 bpm, 0.5 mg IV atropine will be given. 10 mg IV ephedrine will be given if mean arterial pressure becomes less than 60 mmHg. Time of recovery (time period from stopping the anesthetic drug administration and the surgical process has been completed to extubation) will be measured in each group.

Inclusion criteria

• ASA I and ASA II.
• Age (35yrs - 75yrs).
• Patients undergoing open colorectal cancer surgery.
• Sex: Both sexes.

Exclusion criteria

• Renal impairment (Glomerular Filtration Rate < 60 ml\\min).
• Severe cardiac dysfunction (Ejection fraction ≤ 30% or clinical signs and symptoms of reduced left ventricular ejection fraction), preoperative bradycardia (HR < 50 bpm) and atrioventricular block (first, second and third degree).
• Allergy to study drug (MgSO4).
• Patient refusal to precipitate in this study.
• Autoimmune disorders (eg: rheumatoid arthritis, multiple sclerosis and lupus), congenital and acquired immunodeficiency.
• Previous / current immunomodulatory therapy.
• Emergency condition (eg: obstruction or perforation in colorectal cancer).
• Postoperative complications altering inflammatory response (eg: infection, anastomotic leak).
• Duration of operation > 5 hours.
• Cognitive impairment (eg: Dementia) and other psychiatric disorders by history.
• Body mass index less than 18 or greater than 30 kg/m².