ASRA 2015 Abstract
Comparison of epidural analgesia with bilateral dual transversus abdominis plane infiltration block with liposomal bupivacaine in patients with major open abdominal surgery
Thomas A Nicholas MD, Kosta V Turchaninov MD, PhD,Tyler A Ptacek MD Department of Anesthesiology, University of Nebraska Medical Center, Omaha, NE 68198
Epidural analgesia (EA) has traditionally been regarded as the gold standard for post-operative pain control in major abdominal surgeries. However, this idea has been challenged especially in an era of older and sicker patients requiring increased thromboembolic prophylaxis. Recent studies have questioned whether less invasive regional techniques provide similar pain control with less side effects and risk1-4. This study intends to examine this rational by comparing a lower risk procedure, transversus abdominis plane (TAP) block with liposomal bupivacaine (LB) to EA in major open abdominal surgery.
MATERIALS AND METHODS
Study design. This was an IRB approved prospective randomized study. The epidural or infiltrative TAP block was placed preoperatively by an anesthesiologist trained in both techniques. Thoracic epidurals were placed between the levels of T5-T10. Initially, all patients received a standard epidural solution of 0.05% bupivacaine with hydromorphone 10 mcg/ml. Intraoperative management of the epidural was achieved at the discretion of the primary anesthesiologist. Epidural solution, rate, and bolus dosing were titrated to maximize patient pain control. Epidurals were interrogated to assess level and function in the PACU. Ultrasound-guided bilateral dual (lateral and subcostal approach) TAP blocks were performed based upon Børglum’s technique2. LB 266mg diluted in 40 ml of saline per patient. All TAP patients received post operative I.V. narcotics such as a hydromorphone I.V. PCAs In both groups, the patients underwent general anesthesia in a standard fashion.
Patient selection. Subjects 19 years of age and older undergoing major abdominal surgery at UNMC were included and randomized to either TAP block or EA prior to their abdominal surgery. Exclusion criteria included: chronic opioid use, pregnancy, any existence of contraindication to regional anesthesia, or weight less than 50 kilograms.
Outcome measures. Following surgery, subjects were monitored for up to 96 hours. Pain assessments based on a numeric rating scale were started in the PACU and again at 4, 12, 24, 36, 48, 72 and 96 hours after surgery. Daily intravenous fluids, time to ambulation, hypotension, pruritus, nausea/vomiting, length of hospital stay, any major adverse cardiac or respiratory events, or neurologic complications were recorded during the first 96 hours. Total daily opioid requirements were also recorded for the first 96 hours. All daily patient opioid intake including oral, intravenous, and epidural routes were converted to intravenous morphine equivalents using standard equianalgesic tables. A epidural:intravenous ratio of 1:1 was used prior to table conversion for epidural opoids.
Statistical analysis. Descriptive statistics were used to summarize the distributions of the enrolled patients. Fisher’s exact test was used to compare categorical variables between the two groups. The Mann-Whitney test was used to compare the distribution of continuous variables between the two groups [Note: The Mann-Whitney test compares the medians and is appropriate for data where the sample sizes are very small and not normally distributed]. P<0.05 was considered statistically significant. 47 patients were enrolled (21 EA; 26 TAP). 11 patients were withdrawn. Presented analysis is based on 36 patients (17 EA; 19 TAP).
Our preliminary findings reveal that TAP blocks with LB have statistically significant higher pain scores at the 24 and 48 hour time points. Yet, there was no other time points with statistical significance. The early elevated pain scores may represent the biphasic release of lipospheric bupivacaine. However, one may construe that these elevated pain scores are not clinically significant when considering the raw median pain scores. As well, it is likely that this study is underpowered to accurately identify statistical significance in pain scores. Total narcotic consumption was significantly higher (p-value=0.025) for the TAP group in the first 24 hours. Daily opioid requirements between both groups had no significant differences after 24 hrs. Our determination of epidural opioid equivalence maybe contentious. We did not utilize a epidural:intravenous ratio of 10:1 which has been suggested in literature5,6. If we had utilized this generally accepted but unvalidated ratio then our findings would likely increase the morphine equivalences in the epidural group. Our analysis of morphine equivalence was intended to spur discussion rather than reveal true statistical accuracy especially in these post-operative patients who were receiving a combination of epidural and I.V. analgesia which was not fully restricted by study parameters. We felt this was more reflective of a true post-operative pain protocol which is tailored to the individual patient. One patient did develop an epidural hematoma requiring emergent decompression and resulted in permanent paraplegia. There were no other statistically significant differences found in other categorical variables such as nausea/vomiting, sedation, pruritus, urinary retention, I.V. fluid intake, blood transfusion, or other major complications. In summary, it is our belief that the TAP with LB may provide a viable alternative to patients who have contraindications to thoracic epidural analgesia following major open abdominal surgery. We plan to continue enrollment in order to expand our results
References 1. Rawal N. Epidural technique for postoperative pain: gold standard no more? Reg Anesth Pain Med 2012;37(3):310-7. 2. Børglum J et al. Ultrasound-guided bilateral dual transversus abdominis plane block: a new four-point approach. Acta Anaesthesiol Scand 2011. 3. Niraj, G., et al. "Comparison of analgesic efficacy of subcostal transversus abdominis plane blocks with epidural analgesia following upper abdominal surgery." Anaesthesia 66.6 (2011): 465-471. 4. Rao, Kadam V., et al. "Epidural versus continuous transversus abdominis plane catheter technique for postoperative analgesia after abdominal surgery." Anaesthesia and intensive care 41.4 (2013): 476-481. 5. Krames ES. Practical issues when using neuraxial infusion. Oncology. 1999;13( suppl 2): 37– 44. 6. Du Pen, Stuart L., and Anna R. Williams. The dilemma of conversion from systemic to epidural morphine: a proposed conversion tool for treatment of cancer pain. Pain 56.1 (1994): 113-118.
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