Although ambulatory gynecological laparoscopy is considered to be a minimally invasive procedure, only 60% of patients undergoing this procedure are satisfied with postoperative pain control.1 Acute postoperative pain can also delay functional recovery of patients who have undergone outpatient procedures, leading to hospital readmissions.2 Adequate postsurgical analgesia is a major contributing factor for a safe and rapid discharge after ambulatory surgery.3 Multimodal analgesia strategies have been recognized as a potential method to improve postoperative pain management while minimizing opioid-related side effects.4 Improved analgesia without increased analgesic-related side effects is a critical component of the anesthetic plan for ambulatory surgical procedures.
The transversus abdominis plane (TAP) block has demonstrated effectiveness in reducing postoperative pain when used as part of a multimodal analgesic regimen.5 However, recent evidence suggests that the frequently used ropivacaine dose (3 mg/kg) for TAP block may result in maximal plasma concentration levels of ropivacaine that may potentially lead to central nervous system toxicity.6 More importantly, it has not been determined whether the analgesic properties of the TAP block can be translated to a better functional recovery for patients after ambulatory surgery.
The primary objective of this study was to assess the effect of the TAP block on the postoperative quality of recovery using the Quality of Recovery 40 (QoR-40) questionnaire for patients undergoing outpatient gynecological laparoscopy. A secondary objective was to evaluate dose dependency effects of the TAP block on postoperative analgesia, side effects, and time to discharge readiness and the relationship of these factors with quality of recovery.
This study was a prospective, randomized, double-blind, placebo-controlled trial. Clinical trial registration for this study can be found at ClinicalTrials.gov (NCT 01075074). Study approval was obtained from the Northwestern University IRB, and written informed consent was obtained from all the study participants. Eligible subjects were healthy women undergoing outpatient gynecological laparoscopy. Patients with a history of allergy to local anesthetics, chronic use of an opioid analgesic or corticosteroid, and/or pregnant subjects were not enrolled. The reason for exclusion from the study after study drug administration was conversion from a laparoscopic to an open incision. Subjects were randomized using a computer-generated table of random numbers into 3 groups to receive a bilateral ultrasound-guided TAP block using one of the following: saline, ropivacaine 0.25%, or ropivacaine 0.5% (Naropin, APP Pharmaceuticals, Schaumburg, IL). Group assignments were sealed in sequentially numbered, opaque envelopes that were opened by a research nurse not involved with patient care or data collection after the subject provided written informed consent. The same nurse prepared syringes labeled with study drug to blind the investigator performing the TAP block to group assignment. Study subjects and other anesthesia care providers were also blinded to group allocation.
All subjects were premedicated with 0.04 mg/kg IV midazolam. Propofol 1 to 2 mg/kg was administered for anesthesia induction, a remifentanil 0.1 μg/kg/min IV infusion was begun, and rocuronium 0.6 mg/kg IV was administered to induce muscle paralysis. Tracheal intubation was initially attempted by an anesthesia resident physician or a certified registered nurse anesthetist under supervision of an attending anesthesiologist. Anesthesia maintenance was achieved using remifentanil, titrated to maintain the mean arterial blood pressure within 20% of baseline, sevoflurane titrated to a Bispectral Index (Aspect Medical Systems, Inc., Norwood, MA) between 40 and 60, and rocuronium.
After anesthesia induction, a bilateral TAP block was performed in all subjects using ultrasound guidance with a portable ultrasound device (SonoSite, Bothell, WA) and a linear 6- to 13-MHz ultrasound transducer. The technique used to perform the TAP blocks was the posterior approach as previously described by Hebbard et al.7 Once the external oblique abdominal, the internal oblique abdominal, and the transversus abdominal muscles were visualized using the ultrasound probe at the level of the anterior axillary line between the 12th rib and the iliac crest, the puncture area was prepared in a sterile manner. Injection of the study drug was performed using a 21-gauge 90-mm StimuQuik needle (Arrow International, Reading, PA) by a single investigator (GSD). Once the tip of the needle was placed in the space between the internal oblique abdominal muscle and the transversus abdominal muscle, and after negative aspiration of blood, 15 mL of the study drug was administered and distribution of the solution in the TAP was confirmed using ultrasonography observation. A contralateral block was performed in the same manner. At the end of the procedure at removal of the laparoscopic instruments, the remifentanil infusion was discontinued and the subjects received IV ketorolac 30 mg and ondansetron 4 mg.
In the postanesthesia care unit (PACU), subjects were asked to rate their pain at rest upon arrival and at regular intervals on a 0 to 10 numeric rating scale (NRS), where 0 means no pain and 10 is the worst pain imaginable. The area under the NRS pain score versus time curve was calculated using the trapezoidal method as an indicator of pain burden during early recovery (GraphPad Prism version 5.03; GraphPad Software, Inc., La Jola, CA). Hydromorphone 0.2 mg IV was administered every 5 minutes to maintain an NRS pain score <4 of 10. In cases of postoperative nausea or vomiting, subjects received 10 mg IV metoclopramide, followed by 5 mg IV prochlorperazine if necessary. Discharge readiness was assessed, using the modified Post-Anesthetic Discharge Scoring System,8 every 15 minutes until subjects met discharge criteria. The Post-Anesthetic Discharge Scoring System assesses 5 criteria: vital signs, activity and mental status, pain nausea and/or vomiting, surgical bleed, and intake and output. Each criterion is scored on a 0 to 2 scale with higher scores representing a more acceptable condition. A score of ≥9 is considered ready for discharge. At discharge, subjects were instructed to take ibuprofen 400 mg orally every 6 hours and a combination of hydrocodone 10 mg plus acetaminophen 325 mg for pain >4 of 10. Postoperative opioid consumption (24 hours) was converted to an equivalent dose of oral morphine.9
Subjects were contacted by telephone 24 hours after the procedure by an investigator unaware of group allocation and were questioned regarding analgesic consumption and pain score, and the QoR-40 questionnaire was administered.10 The questionnaire consists of 40 questions that examine 5 domains of patient recovery using a 5-point Likert scale: none of the time, some of the time, usually, most of the time, and all of the time. The 5 domains include physical comfort, pain, physical independence, psychological support, and emotional state. The individualized items are presented in Table 1. Investigator-administered and patient self-administered QoR-40 scores have been demonstrated to be highly correlated (interclass correlation = 0.86), although differences in validity and reliability between face-to-face and telephone-administered questionnaires have not been assessed.11 Perioperative data collected included subject's age, height, weight, ASA physical status, surgical duration, intraoperative remifentanil use, total IV fluids, and total amount of hydromorphone in the PACU.
The primary outcome was the global QoR-40 score, which ranges from 40 to 200, representing very poor to outstanding quality of recovery, respectively. A sample size of 23 subjects per group was estimated to achieve 80% power to detect a 10-point difference in the aggregated QoR-40 score for the 3 study groups to be compared assuming an overall standard deviation of 12. A 10-point difference represents a clinically relevant improvement in quality of recovery based on previously reported values on the mean and range of the QoR-40 score in patients after anesthesia and surgery.12 The responsiveness of the instrument has been assessed in patients evaluated before and after surgery.13 To account for dropouts, 75 subjects were randomized. The sample size calculation was made using PASS version 8.0.15, release date January 14, 2010 (NCSS, LLC, Kaysville, UT).
The Shapiro-Wilk and Kolmogorov-Smirnov tests were used to test the hypothesis of normal distribution. Normally distributed interval data are reported as mean (SD) and were evaluated with 1-way analysis of variance. Nonnormally distributed interval and ordinal data are reported as median (range or interquartile range) and were compared among groups using the Kruskal-Wallis H test. Post hoc comparisons were made using the Dunn test and corrected for multiple comparisons (n = 6) using the Bonferroni method. The median shift and confidence intervals (CIs) for global QoR-40 scores among groups were determined using the Wilcoxon exact procedure with CIs calculated at 99.17%. Spearman rank correlation was used to assess the association between global QoR-40 scores with 24-hour opioid consumption, area under the pain score × time curve in the PACU, time to discharge readiness, and NRS pain score at 24 hours. CIs for Spearman ρ were calculated at 99.17% using a 10,000 bootstrap sample. Categorical variables were evaluated using a χ2 statistic. Estimates of exact P values were determined for the χ2 and the Kruskal-Wallis test using a Monte Carlo method with 10,000 samples and confidence limits of 99%. All reported P values are 2-tailed. Statistical analysis was performed using NCSS 2007 7.1.21, release date June 1, 2011 (NCSS, LLC) and R version 2.13.0, release date April 13, 2011 (The R Foundation for Statistical Computing).
The details of the conduct of the study are shown in Figure 1. Seventy-five subjects were randomized and 70 completed the study. Patients were enrolled consecutively from April 2010 through February 2011. Patients' baseline characteristics and surgical factors were not different among groups (Table 2).
The median difference (95% CI) in global QoR-40 scores at 24 hours after surgery was 16 (1–30) (P = 0.03) for ropivacaine 0.5% and 17 (2–31) (P = 0.01) for ropivacaine 0.25% compared with saline, respectively. The median difference in global QoR40 scores between the 0.25% ropivacaine and 0.5% groups was 1 (−16 to 12) (P = 1.0). The dimensions of the QoR-40 questionnaire by study groups are shown in Table 3. The ropivacaine groups reported higher median scores in physical independence, pain, and emotional dimensions of the QoR-40 questionnaire compared with saline.
Correlation analysis (ρ, 99.2% CI) demonstrated an inverse relationship between 24-hour opioid consumption (−0.61, −0.34 to −0.79), the area under the pain score versus time curve in the PACU (−0.56, −0.28 to −0.76), pain score (0–10 scale) at 24 hours (−0.53, −0.25 to −0.73), and time to discharge readiness (−0.65, −0.42 to −0.81) (Fig. 2). Area under the pain score versus time curve and 24-hour opioid consumption were lower in the ropivacaine TAP groups compared with saline (Table 4). Pain score at 24 hours was less with ropivacaine 0.5% compared with saline, and there was a trend toward decreased pain at 24 hours between saline and ropivacaine 0.25% (P = 0.09). Time to meet discharge criteria (95% CI) from the hospital was decreased by 30 minutes in the ropivacaine TAP groups, and pairwise comparisons demonstrated a trend between ropivacaine 0.25% (P = 0.08) and ropivacaine 0.5% (P = 0.05) with saline, respectively. There was no difference in the number of antiemetic doses administered in the first 24 hours (median 0, range 0–2, P = 1.0) among groups. No adverse effects or complications related to the TAP block were reported in any of the interventional groups.
The important finding of the study was the improved global quality of recovery in patients who received a TAP block with 0.25% or 0.5% ropivacaine compared with saline. The difference was present in the physical independence, pain, and emotional subcomponents of the quality of recovery instrument. Patients in the ropivacaine groups had less pain burden in the recovery room, used less opioids in the first 24 hours after surgery, reported lower pain scores at 24 hours, and there was a trend for these patients to be ready for discharge earlier compared with the saline group. There was an inverse relationship between measures of postoperative pain control and discharge time with quality of recovery, suggesting that the effect of the TAP block on these factors directly translated into improved quality of recovery.
Another finding of this study was the beneficial effect of ropivacaine 0.25% with a median (interquartile range) of 1.1 mg/kg (0.95–1.4 mg/kg) compared with saline on postoperative quality of recovery and analgesia. This has important clinical implications because the more frequently used dose of ropivacaine (3 mg/kg) for TAP block may lead to maximal plasma concentration levels of ropivacaine that can potentially lead to central nervous system toxicity.6 The risk of local anesthetic neurotoxicity may be reduced using lower doses of ropivacaine (0.25%) while maintaining improvement in quality of recovery and postoperative analgesia. In a review of efficacy of the TAP block, it was noted that there is a lack of evaluation of the dose dependency of the analgesic effect.14
Opioid analgesics are frequently used to treat postsurgical pain, but opioid-related side effects can prevent rapid functional recovery. Regional anesthesia techniques have been recognized as a valuable multimodal strategy in ambulatory surgery15; however, there is a lack of evidence suggesting that regional anesthesia methods can decrease surgical ambulatory unit time.16 Our study demonstrated a shorter time to meet discharge criteria in the higher-dose ropivacaine group compared with the saline group, but we were underpowered to demonstrate an improvement in the lower-dose ropivacaine group.
The effect of TAP block on postoperative pain has not been evaluated for outpatient laparoscopic procedures, but has demonstrated consistent beneficial results in laparoscopic procedures performed in the inpatient setting. El-Dawlatly et al.17 demonstrated an intraoperative and postoperative reduction in opioid consumption in patients undergoing laparoscopic cholecystectomy. In a prospective cohort study with patients having laparoscopic colon resections, Conaghan et al.18 showed a reduction in postoperative opioid consumption in patients receiving a TAP block compared with patients who did not receive a TAP block. In the aforementioned studies, the equivalent potency dose of local anesthetic was similar to our ropivacaine 0.5% dose and no placebo blocks were performed. Waisel and Truog19 have suggested that a placebo group should always be included in cases in which the regional intervention poses a minor risk to patients, because regional anesthesia studies are vulnerable to a substantial placebo effect. An additional strength of our findings is that the efficacy of the TAP block was shown to improve analgesia management and quality of recovery compared with a placebo block.
Different techniques have been described in the performance of the TAP block. In the current investigation, we used the ultrasound-guided posterior approach originally described by Hebbard et al.7 This subcostal technique has more spread of the local anesthetic toward the supraumbilical abdomen.20 The needle is inserted close to the xiphoid process and the anesthetic is injected between the transversus and rectus abdominis muscles or between the rectus and posterior rectus sheath. The needle is then aimed inferolaterally to the TAP to block the intercostal nerves. Lee et al.21 concluded in an observational study that the posterior approach (lower cephalad spread) seems to be more suitable for lower abdominal surgery and the subcostal approach (higher cephalad spread) is more suitable for upper abdominal surgery.
The use of local anesthetics through other local and regional methods has been attempted to decrease postoperative pain in patients undergoing laparoscopic surgery. The infiltration of trocar sites with local anesthetics in patients undergoing laparoscopic gynecological surgery has not been shown to be advantageous in improving postoperative analgesia.22,23 Local anesthetic irrigation of the peritoneum has not shown consistently beneficial results in the management of postoperative pain in patients undergoing laparoscopic gynecological procedures. Goldstein et al.24 showed a reduction in postoperative pain when patients received ropivacaine (but not bupivacaine) compared with saline. More recently, Chou et al.25 were also unable to demonstrate an improvement in postoperative analgesia when patients had the peritoneum instilled with bupivacaine compared with saline.
No previous studies have evaluated the learning curve associated with the time to perform TAP blocks. In our experience, the TAP block has a fast learning curve and requires a short performance time, especially by experienced physicians. We did not encounter difficulty implementing the procedure in our clinical setting; however, it is possible that different providers in different clinical circumstances may find obstacles to the routine implementation of a TAP block as part of a multimodal pain strategy to improve postoperative quality of recovery.
Although we did not observe complications from TAP blocks, the true incidence of complications (systemic toxicity, vascular, or visceral injury) is still unknown. The lack of complications of our tightly controlled study (with a single operator) does not imply that the TAP block is without potential complications. It is conceivable that the use of ultrasound allowing direct needle visualization might reduce the incidence or potential for complications, but studies confirming this statement are lacking.
Other interventions have been examined in the outpatient surgery setting in an attempt to improve postoperative quality of recovery. Peng et al.26 evaluated the use of low-dose pregabalin in patients undergoing laparoscopic cholecystectomy showing no benefit on postoperative quality of recovery. Our group has examined the effect of dexamethasone on postoperative quality of recovery in a similar patient population as the current investigation and we detected a dose-response beneficial effect of preoperative dexamethasone on postoperative quality of recovery.27 Dexamethasone was not used as an antiemetic strategy in the current study. It is possible that the use of higher doses of preoperative dexamethasone (0.1 mg/kg) would have led to different results than those observed with the TAP block. Because both strategies (dexamethasone and TAP block) seem to be effective in improving postoperative quality of recovery, clinicians can decide based on potential risks of each strategy which one is more suitable to their individual patients. In addition, because a ceiling effect was not observed with either intervention examined, it is possible that by using multimodal strategies, a greater beneficial effect on postoperative quality of recovery may be detected.
There are limitations to our study. We were underpowered to detect a difference in the physical comfort dimension of the quality of recovery questionnaire between the ropivacaine groups and the saline group. We did not obtain local anesthetic levels to compare the safety profile regarding the potential for local anesthetic toxicity between the higher 150-mg and lower 75-mg ropivacaine dose. Because all blocks were performed after induction of anesthesia, we were unable to assess and compare the anatomical distribution of analgesia among groups. Our study population was female patients undergoing laparoscopic gynecological procedures and the body mass index range was narrow. We also did not obtain preoperative quality of recovery scores of studied subjects, therefore we could not evaluate whether the effect of the TAP block was altered by a patient's baseline characteristics. However, because we used a random design, it is likely that differences in baseline quality of recovery scores among the study groups were similar. Further studies adequately powered to detect dose-dependent differences in recovery and analgesia from TAP analgesia in other study populations and other surgical procedures are needed.
In conclusion, when used in a multimodal regimen for postoperative pain after outpatient laparoscopy, TAP block not only reduces postoperative pain, but also enhances quality of recovery in patients undergoing ambulatory surgery. Our findings suggest that lower doses of ropivacaine, such as 75 mg, also have beneficial effects on postoperative quality of recovery when compared with saline.
Name: Gildasio S. De Oliveira, Jr., MD.
Contribution: This author participated in the design, conduct of the study, and writing of the manuscript. This author attests the integrity of the original data and the analysis.
Name: Paul C. Fitzgerald, MS, RN.
Contribution: This author participated in the conduct of the study and manuscript preparation.
Name: R-Jay Marcus, MD.
Contribution: This author participated in the conduct of the study and manuscript preparation.
Name: Shireen Ahmad, MD.
Contribution: This author participated in the conduct of the study and manuscript preparation.
Name: Robert J. McCarthy, PharmD.
Contribution: This author participated in the study design, data analysis, and manuscript preparation. This author attests the integrity of the original data and the analysis.
This manuscript was handled by: Spencer S. Liu, MD.
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© 2011 International Anesthesia Research Society
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