Evaluation of prophylatic effect of gabapentin on intrathecal fentanyl induced pruritus in patients under orthopedic surgery

Spinal anesthesia is one of the regional anesthesia techniques and the base is the insertions of a special needle at the sterile condition to intrathecal space at a level lower the end of the medulla and injection of local anesthetic alone or in combination with other additives such as opioids, vasoconstrictors to improve quality and duration of the block. One of the most common side effects of intratechal opioids is pruritus. Many drugs are recommended for the prevention of this side effect Gabapentin; an anticonvulsant drug is one of them. The aim of the present study was the evaluation of the prophylactic effect of Gabapentin on intratechal fentanyl-induced pruritus in orthopedic surgeries of lower limbs under spinal anesthesia

80 ASA I-II patients aged between 20 and 50 scheduled for elective lower limb orthopedic surgery were allocated in a double-blind placebo-controlled clinical trial. Patients were randomized to two Gabapentin and placebo groups with equal numbers of patients. Randomization was done using random allocation software. After obtaining written consent, the patients were allocated to Gabapentin (G group) and placebo (P groups). The G group patients received 600 mg of Gabapentin orally two hours before induction of spinal anesthesia and the P group patients received placebo. After IV line, placement and standard monitoring attachment including noninvasive blood pressure, EKG and pulse oximetry, and five cc/Kg Ringer solution were infused into each of the patients. Spinal anesthesia was done Using a 25-gauge Quincke spinal needle, and insertion at L4-L5 or L3-L4 intervertebral space. 12 mg of hyperbaric 0.5% bupivacaine and 30-microgram fentanyl in a sterile condition were injected intrathecally. The patients were positioned supine and the anesthesia level was adjusted to T10 dermatome. 0.015 mg/kg midazolam was used intravenously for sedation. The patients were evaluated at 1,6,12 and 24 hours after spinal anesthesia for pruritus.

Patients of both groups did not differ preoperatively significantly in their basic characteristics and predisposing factors associated pruritus. There was no statistical difference regarding severity, onset time and incidence between two groups.

The use of single 600 milligram Gabapentin 2 hours before spinal anesthesia has no prophylactic effect on intrathecal fentanyl-induced pruritus. The severity, locations, and duration of pruritus between intervention and placebo groups were comparable and there were no statistically significant differences between the two groups.