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| ORIGINAL ARTICLE |
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| Year : 2022 | Volume
: 5
| Issue : 4 | Page : 179-184 |
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Outcomes of transversus abdominis plane block in ventral hernia repair: A propensity score matching analysis using a national database
Mazen R Al-Mansour1, Dan Neal1, Cristina Crippen1, Tyler Loftus1, Thomas E Read1, Patrick J Tighe2
1 Department of Surgery, University of Florida, Gainesville, FL, USA
2 Department of Anesthesiology, University of Florida, Gainesville, FL, USA
| Date of Submission | 02-Aug-2022 |
| Date of Decision | 14-Sep-2022 |
| Date of Acceptance | 19-Sep-2022 |
| Date of Web Publication | 24-Dec-2022 |
Correspondence Address:
Mazen R Al-Mansour
University of Florida, PO Box 100109, Gainesville, FL 32610
USA
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/ijawhs.ijawhs_37_22
BACKGROUND: Transversus abdominis plane (TAP) block is often used for post-operative analgesia in ventral hernia repair (VHR). Most studies evaluating TAP in VHR are single-center studies. Our objective was to evaluate the outcomes of TAP in VHR using a national database. MATERIALS AND METHODS: We conducted a retrospective cohort study using Vizient Clinical Database. We included outpatient VHR in adults between 2017 and 2019. Patient, hernia, operative, and hospital characteristics were collected. The patients were divided into two groups depending on whether or not they received TAP. One-to-one propensity score matching (PSM) was used to create balanced groups. Rate of overnight stay, in-hospital opioid prescribing, and costs were compared between both groups. RESULTS: A total of 108,765 patients met the inclusion criteria. After PSM, there were 1,459 patients in each group. There were no statistically significant differences in baseline characteristics between the matched groups. There was no difference in the rates of overnight stay between the two groups (no-TAP=6%, TAP=7%, odds ratio [OR]=1.3, 95% confidence interval [CI] [0.997,1.77]). There were no clinically significant differences in the percentage of patients prescribed opioids (no-TAP=96%, TAP=95%, OR=0.70, 95% CI [0.50, 0.99]) or mean number of opioid doses prescribed (no-TAP=2.7, TAP=2.7, mean pairwise difference [MPD]=0.02, 95% CI [–0.10, 0.13]). The TAP group was associated with higher median direct cost ($4,400 vs. $3,200; MPD=$1,200, 95% CI [$1,000, $1,400]) and total cost ($7,100 vs. $5,200; MPD=$1,900, 95% CI [$1,600, $2,100]) when compared with the no-TAP group. CONCLUSION: We found no evidence that TAP in outpatient VHR was associated with the reduction in the rate of overnight stay or in-hospital opioid prescribing. However, TAP was associated with higher procedural costs. Keywords: Enhanced recovery protocol, multimodal pain control, post-operative opioids, post-operative pain, transversus abdominis plane block, ventral hernia repair
How to cite this article:
Al-Mansour MR, Neal D, Crippen C, Loftus T, Read TE, Tighe PJ. Outcomes of transversus abdominis plane block in ventral hernia repair: A propensity score matching analysis using a national database. Int J Abdom Wall Hernia Surg 2022;5:179-84 |
How to cite this URL:
Al-Mansour MR, Neal D, Crippen C, Loftus T, Read TE, Tighe PJ. Outcomes of transversus abdominis plane block in ventral hernia repair: A propensity score matching analysis using a national database. Int J Abdom Wall Hernia Surg [serial online] 2022 [cited 2023 Mar 20];5:179-84. Available from: http://www.herniasurgeryjournal.org/text.asp?2022/5/4/179/365089 |
| Introduction | |  |
Multimodal pain management of acute post-operative pain has been a hallmark of modern post-operative pain control and enhanced post-operative recovery protocols. The goals of this multimodal approach include reducing post-operative stress and allowing the earlier return to baseline functional status all while reducing opioid consumption. Reducing opioid consumption has been a priority in the last decade due to opioid overdose becoming one of the leading preventable causes of death in North America.[1],[2]
As one of the most common operations performed worldwide, there has been a focus on implementing multimodal pain management approaches to ventral hernia repair (VHR). Transversus abdominis plane (TAP) block has been a key component of this approach. TAP is performed by injecting a long-acting local anesthetic into the plane between the internal oblique and transversus abdominis muscles where the intercostal and lumbar nerves run. Both single injection and continuous infusion catheters have been described with the single injection TAP often providing pain relief for approximately 8–16 h.[3] Multiple studies have evaluated the use of TAP in VHR. These were primarily single center studies with small sample sizes.[4],[5],[6],[7],[8] Moreover, data assessing the cost of these procedures have been limited. Our objective was to assess the outcomes and cost of TAP in outpatient VHR using a national database. We hypothesized that TAP is associated with reduced likelihood of overnight stay, reduced opioid use, and lower overall cost of care in outpatient VHR.
| Materials and Methods | | |
We conducted a retrospective cross-sectional study using the Vizient Clinical Database. Our Institutional Review Board approval was obtained. Due to the deidentified nature of the data received, the requirement for informed consent was waived.
Data source
The Vizient Clinical Database (Vizient Inc., Irving, TX, USA), formerly known as University Health Consortium (UHC), is a healthcare analytics platform designed for performance improvement. It contains patient outcomes and financial data from greater than 750 academic, teaching, and community hospitals in the United States.[9]
Inclusion and exclusion criteria
The Vizient Clinical Database was queried for patients meeting the inclusion and exclusion criteria from January 2017 to December 2019. We included all elective outpatient VHRs in adult patients. VHRs were identified using the following current procedural terminology (CPT) codes 49560, 49561, 49565, 49566, 49570, 49572, 49580, 49582, 49585, 49587, 49590, 49652, 49653, 49654, 49655, 49656, and 49657. According to Vizient, outpatient VHR includes all VHRs that did not have an inpatient admission order, regardless of the actual length of stay. We excluded cases with concurrent procedures and those with length of stay greater than 2 days. Inpatient procedures were not included because unlike outpatient procedures, TAP is not coded separately from the primary hernia procedure.
Variables
Data collected included demographics, comorbidities, and hernia and hospital characteristics. The primary outcome was the rate of overnight stay with secondary outcomes being opioid prescribing, direct cost, and total cost. The rate of overnight stay was chosen as the primary outcome as we felt that TAP may facilitate same day discharge and therefore reduce the utilization of hospital beds. Total cost equals the sum of direct cost and indirect cost and these data are captured and reported by Vizient. The cohort was divided into two groups (no-TAP and TAP) using the single injection TAP CPT codes 64486 and 64488. Continuous infusion TAP was not included because of our focus on outpatient VHR where continuous infusion TAP is not frequently used. Opioid prescribing was reported in the Vizient Clinical Database using the concept of defined daily dose. Defined daily dose, according to the World Health Organization, is the assumed average maintenance dose per day for a drug used for its primary indication in adults. The methods of extracting opioid utilization from the Vizient Clinical Database have been previously reported.[10]
Sample size analysis
The primary outcome of our study was the rate of overnight stay. We estimated the rate of overnight stay in outpatient VHR to be 10%. We determined that a reduction of the rate of overnight stay to 5% in the TAP group would constitute a clinically meaningful difference. We also estimated that 10% of outpatient VHRs will receive TAP. Based on this, sample size analysis determined that a sample of size of 2,562 in the no-TAP group and 282 in the TAP group is needed to detect the aforementioned clinically meaningful reduction of the rate of overnight stay with a power of 80% at a significant level of 0.05.
Statistical analysis
Baseline characteristics and outcomes were compared between the two groups. Continuous variables were reported as mean (standard deviations) or median (interquartile range) as appropriate, and categorical variables were reported as counts and percentages. To create balanced groups, logistic regression, with no-TAP vs. TAP, as outcome and all variables in [Table 1] as covariates were used to assign each procedure a likelihood (propensity score) of receiving TAP. Nearest-neighbor propensity score matching (PSM) was then used to pair patients who received TAP with those who did not. Pairs whose scores were within 0.2 standard deviations of all propensity scores were considered candidates for matching. If there were no no-TAP patients within 0.2 standard deviations of a given TAP patient, that TAP patient was not matched and dropped from the analysis. About 2,197 observations missing data on race (2.0% of the total cohort) were imputed with “White” before matching. A total of 12,715 observations missing data on hospital bed size (11.7%) were classified as “Unknown” and included in the matching process. Observations were 100% complete on all other variables used for matching, which was performed using the R package “MatchIt.” Fisher’s exact tests and Mann–Whitney tests were used to assess balance between groups before and after matching. | Table 1: Patient, hernia, and hospital characteristics prior to and after propensity score matching
Click here to view |
For dichotomous outcomes, logistic regression was used to compare the matched no-TAP and TAP groups and comparison was reported as odds ratio (OR) and 95% confidence intervals (CIs). Cluster-robust standard errors, with matched pair as the clustering variable, were used to derive CIs for the estimated effects of TAP. For continuous outcomes, pairwise differences (TAP minus no-TAP) were calculated for each matched pair, and t-tests were used to assess whether these differences were significantly different from 0. All analyses were performed using the R statistical software package (V.4.1.1).
| Results | | |
Of the entire cohort of 141,776 VHRs captured in the Vizient Clinical Database in the study period, a total of 108,765 (77%) patients met our inclusion and exclusion criteria (no-TAP = 107,296 and TAP = 1,469). The TAP group had a higher proportion of incisional hernias (45% vs. 26%), recurrent incisional hernias (12% vs. 6%), and minimally invasive repairs (48% vs. 31%) compared with the no-TAP group (all P < 0.0001). There were also differences in baselines hospital characteristics between the two groups, which show notably a higher frequency of TAP in teaching hospitals (56% vs. 49%) and a higher frequency of TAP in hospitals in the Midwest census region (56% vs. 39%) (both P < 0.0001) [Table 1].
PSM resulted in 1,459 patients in each of the no-TAP and TAP groups [Figure 1]. The balanced cohort had a mean age of 55 (14) years and 52% were male. Forty-five percent of the ventral hernias were incisional and 38% were umbilical. Fifty-two percent were performed in an open fashion, 41% were laparoscopic, and 7% were robotic. Fifty-five percent were performed at a teaching hospital. The Midwest was the most represented census region at 57%. The matched no-TAP and TAP groups were balanced in terms of demographics, comorbidities, and hernia and hospital characteristics (all P ≥ 0.10). | Figure 1: Flow chart of inclusion/exclusion criteria and propensity score matching. VHR = ventral hernia repair, TAP = transversus abdominis plane block
Click here to view |
Comparing the outcomes of the matched groups, there was no difference in the rate of overnight stay between the no-TAP (6%) and TAP (7%) groups (OR 1.3, 95% CI [0.997, 1.77], P = 0.052). There was a lower proportion of procedures in which opioids were prescribed in the no-TAP (95%) group compared with the TAP (96%) group (OR=0.70, 95% CI [0.50, 0.99], P = 0.045). The mean number of doses of opioids prescribed was similar between the no-TAP (2.7 (1.7) doses) and TAP (2.7 (1.7) doses) groups (mean pairwise difference [MPD]=0.02, 95% CI [-0.10, 0.13] doses, P = 0.793). The TAP group had a higher median (interquartile range) direct cost ($4,400 [$3,000; $6,100]) when compared with the no-TAP group
($3,200 {$1,900; $4,600}) (MPD =$1, 200, 95% CI [$1,000, $1,400], P < 0.0001). Similarly, the TAP group had higher total cost ($7,100 ($4,900; $9,800)) when compared with the no-TAP group ($5,200 [$3,200; $7,300]) (MPD =$1,900, 95% CI [$1,600, $2,100], P < 0.0001) [Table 2]. | Table 2: Outcomes of outpatient ventral hernia repair with and without transversus abdominis plane block
Click here to view |
| Discussion | | |
Our study found no evidence that TAP was associated with a reduction in rate of overnight stay or doses of opioids prescribed in outpatient VHR. The TAP group was associated with a statistically significant (albeit clinically insignificant) lower rate of procedures in which opioids were prescribed (95% vs. 96%) compared with the no-TAP group. TAP was associated with higher direct and total procedural costs. Our study is unique in evaluating TAP in outpatient VHR using a large sample across multiple institutions in the United State of America using a national database. We also contribute to the limited literature assessing the financial cost associated with procedures involving TAP in this setting.
TAP has been shown to reduce post-operative nausea and vomiting, improve pain control, reduce perioperative opioid use, and carry a comparable safety profile when compared with other analgesic interventions in abdominal surgery.[11],[12] Similar observations were seen in a number of studies evaluating VHR. Two randomized controlled trials evaluating TAP in VHR have shown that TAP was associated with reduced post-operative pain and opioid use when compared with standard post-operative opioid-based analgesic regimens.[5],[6] In contrast, our study did not show clinically significant differences in opioid prescribing between patients who received TAP and those who did not. Compared to our study, these randomized controlled trials were single center studies and had small sample sizes (35 and 52 patients in each study received TAP) potentially introducing bias. In contrast, our study only looked at outpatient VHR and only evaluated indicators of in-hospital opioid prescribing, which may not translate to opioid utilization and does not capture out-of-hospital opioid use.
The effect of TAP on length of stay has not been rigorously studied. Jain et al.[8] compared the outcomes of laparoscopic VHR using intraperitoneal onlay mesh approach in patients who received TAP and those who did not (25 patients in each group). They found that the TAP group was associated with length of stay that was one hour shorter compared with the group that did not receive TAP (23 vs. 24 h, P = 0.03, respectively). In our opinion, this difference, while statistically significant, is clinically unimportant. A more noticeable difference in length of stay was demonstrated in a study by Shao et al.[13] They compared the outcomes of abdominal wall reconstruction before and after implementation of an enhanced recovery after surgery pathway including TAP use (53 patients in each group). The use of TAP was found to be associated with a reduction in the length of stay by an average of one day. A major difference between the population in our study compared with the study by Shao et al. is that we did not evaluate inpatient VHRs and only 5% of the patients in our study underwent component separation.
A key finding in our study is that TAP was associated with an median of $1,200 increase in direct cost and $1,900 increase in total cost. We are not aware of any studies that evaluated TAP costs in VHR. A meta-analysis evaluating TAP in abdominal-based autologous breast reconstruction found no statistically significant difference in cost between patients who received TAP and those who did not.[14] This magnitude of increase in procedural cost with single injection TAP was higher than we would have anticipated. This raises a question if this increase was driven by more expensive local anesthetics (e.g., liposomal bupivacaine) or if there were other factors not captured by the database that increased the cost of the VHR procedure.
Our study results are to be interpreted in light of its limitations. Our study evaluated only outpatient VHR as Vizient Clinical Database does not code TAP separately for inpatient VHR procedures. While this is a significant limitation, the study remains relevant because a significant portion of VHRs are performed as outpatient procedures (>78% in our study). The database does not collect data on post-operative pain levels and therefore we were unable to compare pain control between the two groups. A potential concern is that TAP might be under-coded when performed by the surgeon (as opposed to anesthesiologist) because it is not billed separately from the VHR procedure. Details of the TAP procedure were also unable to be accounted for, including unilateral vs. bilateral, the type of local anesthetic used, use of adjuncts (e.g., dexamethasone), and the technique used (ultrasound-guided vs. direct visualization). Similarly, details of the VHR not captured by the database may influence the evaluated outcomes such as whether the defect was closed, mesh fixation technique (e.g., transfascial sutures), mesh position, and so on. Furthermore, many outcomes anticipated to be influenced by single-injection TAP would be expected within the first twelve hours of block placement; both pain intensity and opioid utilization assessments in this interval were not available using this particular administrative dataset.
As a retrospective study, our analysis is subject to selection bias. We attempted to minimize the effect of confounding variables by using PSM to create balanced groups. However, confounding factors that are not captured by the Vizient Clinical Database might have influenced both TAP use and the outcomes and these could not be addressed statistically. For example, behavioral factors (e.g., anxiety, substance use) and prior prescription opioid use can influence the outcomes that we evaluated but are not captured by the Vizient Clinical Database. Missing data can introduce bias. The database structure was a limitation, as files often recorded only the presence of a variable and not a definitive absence. Therefore, it not known whether the absence of that variable is a true absence or a missing variable. Database research is frequently hampered by under-coding, with some studies demonstrating a majority of hospital admissions missing codes for common comorbidities and medications, potentially introducing bias to our study.[15],[16]
| Conclusion | | |
In patients undergoing outpatient VHR, TAP use was not associated with clinically significant reduction in the rate of overnight stay or in-hospital opioid prescribing but was associated with higher direct and total costs.
Authors’ contribution
MRA: Concept and study design, interpretation of data, drafting the article, and final approval of the version to be published (guarantor);
DN: Analysis of data and drafting the article;
CC: Concept and study design, acquisition, and interpretation of data;
TL: Critical revision of the article;
TER: Critical revision of the article;
PJT: Concept and study design and critical revision of the article.
Financial support and sponsorship
Patrick J. Tighe work is supported by National Institute of Health grants: K07 AG073468-01 and R01 AG121647-04. Tyler Loftus work is supported by the National Institute of Health K23 GM140268 grant and the University of Florida Thomas Maren Junior Investigator Fund.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1]
[Table 1], [Table 2]
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