Comparison of efficacy and side effects of intrathecal morphine and Transversus Abdominis Plane block (TAP) for post-cesarean analgesia
Abstract Number: 207
Abstract Type: Original Research
Neuraxial morphine is the standard of care for post-cesarean delivery analgesia in North America. Neuraxial morphine may not be suitable in all patients. A novel alternative is to deposit local anesthetic solution into the transversus abdominis plane (between internal oblique and transversus abdominis) bilaterally, (TAP block). In one study, where patients received spinal anesthesia with bupivacaine and fentanyl, TAP block reduced morphine requirements by 70%(1). A second study compared standard care with standard care plus TAP block; both groups had intrathecal morphine(ITM)(2). There were no significant differences in pain scores or morphine consumption, possibly because ITM works optimally in the first 24 hours postpartum and both groups had ITM. Our hypothesis is that a TAP block will provide equivalent analgesia to ITM.
This is a randomized, double-blinded placebo controlled study. Following power analysis, we intend to enroll seventy subjects. All subjects received 9-12 mg hyperbaric bupivacaine, 10 mcg fentanyl intrathecally for spinal anesthesia and routine postoperative multimodal analgesia (regular acetaminophen & NSAIDs, prn hydromorphone). Subjects in the morphine group had 0.1 mg ITM as part of their spinal. After surgery, all subjects had an ultrasound scan of their abdomen to maintain blinding and subjects in the TAP group had bilateral TAP blocks using 1.5 mg/kg 0.5% ropivacaine (maximum 20 mls). Subjects were assessed post-operatively 2,6,10 and 24 hours for pain at rest and on movement (VAS), PONV, sedation and itch. Analgesics (other than acetaminophen and NSAIDs) were recorded. The primary outcome is morphine equivalents used in the first 24 hours post delivery.
26 subjects have been enrolled thus far with 2 protocol violations excluded (failed spinals); completion expected April 2009. Early results have been analyzed whilst maintaining blinding of treatment group as interim analysis was not included in the initial power calculation.( see table) No patient has required iv PCA.
This is the first study to compare ITM and TAP block for postcesarean analgesia. If equally effective and safe it will offer an alternative to iv PCA morphine for patients having general anesthesia or who have a specific contraindication to morphine.
1. McDonnell JG et al.Anesth Analg 2008;106:186
2. Costello J et al. SOAP abstract A-147 2008