Abstract ID: A12

Abstract Title: Use of Methadone as an Adjuvant to Spinal Bupivacaine for Vaginal Hysterectomy. Implications of the Quality of Anesthesia and Analgesia.

Authors: Perez J¹, Mercadal J², Plaza A³, De Santos P⁴
Hospital Clinic Barcelona Barcelona Spain
Poster Type: Poster

ABSTRACT BODY

Introduction.
Methadone is a long acting lipophilic opioid with similar agonism for mu opioid receptors as morphine but with less rostral migration when administered spinally.
The use of low doses of spinal methadone as an adjuvant to bupivacaine for spinal anesthesia has not yet been reported.
Objectives
To study the quality of anesthetic block and post-operative analgesia provided by spinal bupivacaine alone or in combination with fentanyl or methadone, in women scheduled for vaginal hysterectomy.
Patients and Methods
Double blind, controlled study including women scheduled for vaginal hysterectomy under spinal anesthesia. Patients were divided into three equal groups, randomized to receive either 13 mg of 0.5% plain bupivacaine with 0.3 ml of saline (group B0), 13 mg of bupivacaine plus 15 mcg of fentanyl (group BF) or 13 mg of bupivacaine plus 3 mg of preservative-free methadone (group BM). Study variables included: latency and extension of sensory blockade, quality of anesthesia, secondary effects, duration of motor and sensory blockade and time until requisition of the first analgesia at the recovery room.
Results
69 patients were included and divided into the three study groups (n=23).
Demographic data or surgical details (time of surgery, intraoperative bleeding) were not different between groups. Onset of anesthesia, extension of sensory blockade, quality of anesthesia, hemodynamic repercussions, presence of secondary effects and the rate of failed block were similar among groups. Duration of motor blockade was significantly shorter in group BM (129.3ą5.9 minutes) compared to groups B0 (163.8ą9.9minutes) or BF (181.3ą9.3 minutes).
Similarly, the duration of sensory block was statistically shorter in group BM (142.5ą7.2 minutes) than in groups B0 (186.7ą9.5 minutes) or BF (196.2ą10. 9 minutes).
Time until requisition of the first post-operative analgesics was significantly longer in women in group BF (198.4 ą11.8 minutes), compared to those in group B0 (148.3 ą7.3 minutes). Furthermore, patients allocated to group BM showed a significantly longer duration of analgesia compared to the other two groups (306.5ą46.2 minutes, see figure).
Secondary effects related with the use of spinal opioids (nausea, vomiting and pruritus) were similar among women receiving fentanyl or methadone.
Conclusion
The addition of low doses of spinal methadone to bupivacaine created a paradoxical effect on the regional anesthesia. Instead of prolonging the block, as fentanyl does, it attenuated motor and sensory blockade. The physico-chemical properties of combined bupivacaine/methadone are yet to be studied, although we believe that methadone may inhibit the nerve action of bupivacaine. In contrast, postoperative analgesia was significantly enhanced when bupivacaine/methadone was administered spinally, compared to fentanyl or plain bupivacaine alone. This could be explained by the more robust effects methadone has on spinal mu opioid receptors.

ATTACHED FILES

A12_Abstract ASRA fall meeting 2005_J.Perez_Figure 1.doc

Reg Anesth Pain Med 2005; 30(3):A12