A comparison of intrathecal diamorphine and intravenous morphine for postoperative analgesia in patients undergoing lumbar spinal surgery

INTERVENTION: Intrathecal diamorphine vs intravenous morphine CONDITION: Surgery: Analgesia ; Surgery ; Analgesia PRIMARY OUTCOME: The quality of postoperative analgesia. Patients pain scores will be measured in recovery and on days 1 and 2 postoperatively using a validated pain assessment tool (visual analogue scale 0‐100mm). The assessor will be blinded to the patients treatment group. The amounts of morphine required to achieve adequate analgesia via a PCA system will be recorded in both groups. SECONDARY OUTCOME: Secondary outcome measures include the presence of nausea, vomiting, sedation and pruritis. INCLUSION CRITERIA: All ASA 1,2 and 3 patients between the ages of 18 to 70 years undergoing lumbar spinal surgery via a posterior surgical approach will be invited to participate in the study.