Comparison of two different doses of intrathecal fentanyl during knee arthroscopy under spinal anesthesia

الملخص EN

Introduction : The use of intrathecal fentanyl has gained popularity over the last few years; it may augment the analgesia produced by local anesthetic through direct binding with specific spinal receptors.

Fentanyl, a lipophilic opioid has a rapid onset of action, it does not tend to migrate intrathecally to the 4th ventricle in sufficient concentration to cause delayed respiratory depression.

Aim of the work : the aim of the study is to assess and compare the effectiveness and safety of two doses of intrathecal fentanyl (12.5 and 25 µg) added to 0.5% hyperbaric bupivacaine in young adults during knee arthroscopy.

Patients and methods : 75 young adult ASA I physical status scheduled for knee arthroscopy under spinal anesthesia were enrolled in this random blind study to receive intrathecal 2 ml of 0.5% hyperbaric bupivacaine + 1 ml of 0.9 % saline (group I, n = 25) or 2 ml of 0.5% hyperbaric bupivacaine + 12.5µg fentanyl in 1 ml of 0.9 % saline (group II, n = 25) or 2 ml of 0.5% hyperbaric bupivacaine + 25µg fentanyl in 1 ml of 0.9 % saline (group III, n = 25).

Vital signs, sensory level, motor block and side effects were observed intraoperatively and for 12 hours postoperatively.

Postoperative pain free duration and the time of first analgesic requirement were determined.

Results : There were no hemodynamic changes throughout the procedure.

The onset of spinal block was not enhanced in group II and III.

However, the time of sensory regression was significantly prolonged in the fentanyl groups in comparison to group I but there was no significant difference between group II and III and the duration of motor block was not prolonged in the fentanyl groups in comparison to group I.

The postoperative pain free duration and the time of 1st analgesic requirement were significantly longer in group II and III (7.9 ± 0.23, 10.8 ± 0.47 and 8.2 ± 0.34, 11.2 ± 0.25 hrs) in comparison to group I (3.22 ± 0.14, 4.2 ± 0.25 hrs).

However, there was no significant difference between group II and III.

There was no significant difference in the incidence of nausea-vomiting, urinary retention, pruritus, respiratory depression and sedation between the three groups.

Conclusion : The addition of 12.5 µg fentanyl to intrathecal bupivacaine is easy, safe and effective in prolonging postoperative analgesia and the time of 1st analgesic administration after knee arthroscopy.