the effect of epidural morphine sponge in postoperative pain control after microdiscectomy

opiates such as morphine are one of the most effective classes of medication prescribed to treat both acute and chronic pain.they act to suppress pain through mu-receptor activation on primary afferent nerve fibers, dorsal horn neurons and supraspinal pain center neorons. when morphine is administered epidurally, it diffuses to the cord substance, producing analgesia [1],the aim of this study was to check the efficacy of this method for controling postoperative lumbar pain after microdiscectomy. in a randomized clinical trial, numbers of 100 patients were included into two equal groups due to low back radicular pain and underwent microdiscectomy. in study group, an absorbable gelatin sponge (gelfoam) is contoured to the epidural space, placed in methylprednisolone acetate (40-80 mg), and then injected with 2 mg/ml morphine and control group received an absorbable gelatin, placed in methylprednisolone acetate (40-80 mg) and were injected with normal saline (5ml) as a placebo. the main outcome to be compared between trial and placebo groups were: patient comfort rate in recovery room and ward, amount of analgesics used, postoperative ambulation time, post operative hospitalization days. the restlessness and agitation during recovery in study group was lower than control group. mean systolic blood pressure increment was lower in morphine group. only 6% of patients in study group compared to 98% in placebo group had either moderate or severe pain six hours after operation. mean morphine dose used for study group was 10.75 mg compared to 21.4 mg among control group patients (p < 0.0001). mean ambulation time was 2 days among study group patients compared to 2.6 days in control group. mean hospitalization length was 4.7 and 7 days in study and control group respectively. by means of the technique assigned to the patient (an epidural morphine sponge) during lumbar microdiscectomy the results were: better controlled postoperative pain, early ambulation of patients and decreased hospitalization length.