الفهرس 
? Mechanism of Postoperative Pain and Pre-emptive AnalgesiaOnly 14 pages are availabe for public view
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Abstract
Background: The relief of postoperative pain is a subject, which has been receiving an increasing amount of attention in the past few years. Pre-emptive analgesia aims to decrease acute pain after tissue injury and to inhibit the persistence of post-operative pain and the development of chronic pain. Gabapentin and pregabalin are structural analogues of gamma amino butyric acid that were introduced as antiepileptic drugs and have been extensively used to treat painful neuropathies. Recently, they have been studied as pre-emptive analgesics with a variety of surgical procedures to reduce postoperative pain and analgesic requirements.
Aim of the study: The aim of this study is to compare the effect of pre-emptive single dose of oral gabapentin and oral pregabalin on acute postoperative pain after elective gynecological surgeries performed under spinal anesthesia.
Patients and methods: A total of 75 ASA grade I and II patients scheduled for elective gynecological surgeries were randomized into 3 groups 25 patients each. One hour before surgery the blinded drug selected for the study was given with a sip of water. group A: received identical placebo capsules, group B: received 900 mg of gabapentin capsules and group C: received 300 mg of pregabalin capsules. Spinal anesthesia was instituted at L3-L4 interspace and a volume of 3.5 ml of 0.5% hyperbaric bupivacaine and 25 mcg fentanyl was injected through a 25 gauge spinal needle. Postoperatively, analgesia was administered in the form of paracetamol 1 gm given IV every 8 hours regularly for the first 48 hours, and meperedine 50 mg given IM repeated on demand. Pain scores at the first 24 hours postoperatively, duration of effective analgesia and the total number of doses of rescue analgesia required in the first 24 hours postoperatively were considered as the primary outcome measures. Duration of motor block, sedation scores at the first 24 hours postoperatively, hemodynamics and side effects were considered as the secondary outcome measures.
Results: A significantly longer duration of effective analgesia in pregabalin group (218.80±23.64) and gabapentin group (207.40±23.36) was observed in comparison with the placebo group (177.2±20.37), with the duration being longer in the pregabalin group. The number of meperidine doses required in the first 24 hours postoperatively was significantly reduced in the gabapentin and the pregabalin groups when compared to the placebo group (P-value<0.001). The incidence of hypotension, bradycardia and shivering was equal in the three groups. There was a highly significant reduction in the incidence of PONV in both the gabapentin and the pregabalin groups. However, there was a highly significant incidence of postoperative sedation and dizziness with both the gabapentin and pregabalin groups versus control group.
Conclusion: Preemptive administration of a single dose of gabapentin 900 mg or pregabalin 300 mg in female patients undergoing elective gynecological surgeries under spinal anesthesia was effective in decreasing the intensity of acute postoperative pain and decreased meperidine requirements during the first 24 hours postoperative without serious side effects.