Determination of the efficacy and side-effect profile of lower doses of intrathecal morphine in patients undergoing total knee arthroplasty

doi:10.1186/1471-2253-8-5

BMC Anesthesiology

Volume 8

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Laffey JG

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Research article

Determination of the efficacy and side-effect profile of lower doses of intrathecal morphine in patients undergoing total knee arthroplasty

Patrick Hassett¹^,2 , Bilal Ansari¹ , Pachaimuthu Gnanamoorthy¹ , Brian Kinirons¹^,2 and John G Laffey¹^,2

¹Department of Anaesthesia, Galway University Hospitals and National University of Ireland, Galway, Ireland

²Centre for Pain Research, National University of Ireland, Galway, Ireland

author email corresponding author email

BMC Anesthesiology 2008, 8:5doi:10.1186/1471-2253-8-5


Published:	24 September 2008

Abstract

Background

Intrathecal (IT) morphine provides excellent post-operative analgesia, but causes multiple side effects including nausea and vomiting (PONV), pruritus and respiratory depression, particularly at higher doses. The lowest effective dose of spinal morphine in patients undergoing total knee arthroplasty is not known.

Methods

We evaluated the analgesic efficacy and side effect profile of 100 – 300 μg IT morphine in patients undergoing elective total knee replacement in this prospective, randomized, controlled, double-blind study. Sixty patients over the age of 60 undergoing elective knee arthroplasty were enrolled. Patients were randomized to receive spinal anaesthesia with 15 mg Bupivacaine and IT morphine in three groups: (i) 100 μg; (ii) 200 μg; and (iii) 300 μg.

Results

Both 200 μg and 300 μg IT morphine provided comparable levels of postoperative analgesia. However, patients that received 100 μg had greater pain postoperatively, with higher pain scores and a greater requirement for supplemental morphine. There were no differences between groups with regard to PONV, pruritus, sedation, respiratory depression or urinary retention.

Conclusion

Both 200 μg and 300 μg provided comparable postoperative analgesia, which was superior to that provided by 100 μg IT morphine in patients undergoing total knee arthroplasty. Based on these findings, we recommend that 200 μg IT morphine be used in these patients.

Trial registration

ClinicalTrials.gov Identifier NCT00695045