Comparison of Postoperative Analgesic Effect of Intrathecal Magnesium and Fentanyl Added to Bupivacaine in Patients Undergoing Lower Limb Orthopedic Surgery

The Effects of Intrathecal Magnesium and Fentanyl Added to Bupivacaine on Postoperative Analgesic Requirement in Patients Undergoing Lower Limb Orthopedic Surgery

Magnesium has been suggested that NMDA (N-methyl D-aspartate)receptor antagonists induce preemptive analgesia when administrated before tissue injury , thus decreasing the subsequent sensation of pain.

Following Ethics Committee approval and informed patients consent, Ninety patients 20-60 yr old ASA physical status I or II, scheduled for femur surgery under spinal anesthesia, were studied in a prospective, double-blinded, randomized way. The patients were randomly allocated to one of three groups of 30 each. The magnesium group (groupM) received bupivacaine 15mg combined with 0.5ml magnesium 10%,the fentanyl group (group F) received bupivacaine 15mg combined with0.5 ml fentanyl[25microgram] and the placebo group (group P) received bupivacaine 15mg combined with 0.5ml distilled water intrathecally . Time to first requirement of analgesic supplement, Sensory block onset time, maximum sensory level , onset of motor block, duration of blockade, hemodynamics variables, the incidence of hypotension, ephedrine requirements, bradycardia ,hypoxemia [Saturation of peripheral oxygen (SpO2)<90], postoperative analgesic requirements and Adverse events, such as sedation, dizziness , Pruritus and postoperative nausea and vomiting were recorded. Patients were instructed preoperatively in the use of the verbal rating scale (VRS) from 0 to 10 (0no pain, 10maximum imaginable pain) for pain assessment. If the VRS exceeded four and the patient requested a supplement analgesic, methadon5 mg intravenously , was to be given for post-operative pain relief as needed .

Inclusion Criteria:

.patients with American Society of Anesthesiologists(ASA) physical status I and

II, undergoing elective femur surgery

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Exclusion Criteria:

• significant coexisting disease such as hepato-renal and cardiovascular disease
• any contraindication to regional anesthesia such as local infection or ''''bleeding disorders
• allergy to opioids
• long-term opioid use
• history of chronic pain.