Intraspinal administration of morphine hydrochloride combined with low doses of bupivacaine in hemorrhoidectomy: a clinical randomized trial.

Background: Intrathecal local anesthetics, associated or not to opioids, is commonplace in anorectal surgery, but it is unknown which is the option with the best risk-benefit ratio. The main aim was to assess whether the combination of morphine (50 mcg) with low-dose bupivacaine (3 mg) in an intradural solution has a better analgesic short-term effect than bupivacaine alone at standard doses (5 mg) in hemorrhoidectomy.

Methods: Sixty-six patients of any sex were randomly assigned to two alternative treatments and 63 patients were considered valid for analysis. Hyperbaric bupivacaine 3 mg combined with 50 mcg of intradural morphine hydrochloride (BUP-MOR group) was compared with 5 mg hyperbaric bupivacaine (BUP group). The primary outcome was pain evaluated through a visual analog scale (from 0 to 100 mm) at 24 hours post-surgery. The proportion of patients requiring rescue analgesia, and those presenting with motor blockade and other adverse events was also compared between the two groups.

Results: BUP-MOR group showed a higher efficacy than BUP group in the visual analog scale at 24 hours postsurgery (15±12 vs. 33±22 mm; P<0.001). Also, BUP-MOR group presented a lower percentage of patients who needed rescue analgesia at resuscitation room (6.7% vs. 24.2%; P=0.08) and a lower proportion of patients who had motor blockade (23.3% vs. 51.5%; P=0.02), while they presented a non-significant increased incidence of urinary retention (23.3% vs. 9.0%; P=0.17).

Conclusions: The addition of intradural morphine allows a reduction in the dosage of local anesthetic improves short-term postoperative analgesia and is associated with less motor blockade.