Intrathecal fentanyl : effects on postoperative morphine consumption

الملخص EN

Background Fentanyl is a commonly used adjuvant for spinal anesthesia as it improves the quality and prolongs the duration of analgesia.

However, contradictory data have been reported in the literature on whether the administration of intrathecal fentanyl might lead to acute tolerance to postoperatively administered opioids.

Methods A total of 75 consented male patients undergoing elective unilateral inguinal hernia repair were enrolled into this randomized, double-blind, controlled study.

All patients belonged to ASA grade I–II, were aged between 20 and 55 years, and were taught to use the patient-controlled analgesia and visual analog scale.

After undergoing standard monitoring procedures, the patients were randomly allocated into three groups on the basis of administration of one of three prepared intrathecal injections through a 25-G spinal needle.

Patients in group C received 3.5 ml of hyperbaric bupivacaine (0.5%), patients in group F10 received 10 mg of fentanyl, and patients in group F25 received 25 mg of fentanyl.

The postoperative visual analog scale were measured at 0, 1, 4, 8, 12, 18, and 24 h.

Morphine doses were recorded at 0–4, 4–8, 8–12, and 12–24 h, postoperatively.

Results The pain scores were higher in group C during the first hour of postanesthesia care unit admission compared with group F25.

Morphine consumption was higher in group C (12 mg) compared with groups F10 and F25 (8 and 7 mg, respectively).

Between 4 and 8 h, the consumption was similar in all groups.

Between 8 and 12 h, the consumption increased in group F25.

Between 12 and 24 h, the consumption continued to increase in group F25 (19 mg) when compared with groups C and F10 (14 and 15 mg, respectively).

The mean time to the first morphine bolus was shorter in group C.

Conclusion Intrathecal fentanyl (25 mg) in spinal anesthestics may lead to postoperative opioid tolerance.