Ge Qu， Xu-lei Cui， Hong-ju Liu， Zhi-gang Ji，and Yu-guang Huang*

1Department of Anesthesiology，2Department of Urology， Peking Union Medical College Hospital， Chinese Academy of Medical Sciences & Peking Union Medical College， Beijing 100730， China

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Ultrasound-guided Transversus Abdominis Plane Block Improves Postoperative Analgesia and Early Recovery in Patients Undergoing Retroperitoneoscopic Urologic Surgeries： A Randomized Controlled Double-blinded Trial△

Ge Qu1， Xu-lei Cui1， Hong-ju Liu1， Zhi-gang Ji2，and Yu-guang Huang1*

1Department of Anesthesiology，2Department of Urology， Peking Union Medical College Hospital， Chinese Academy of Medical Sciences & Peking Union Medical College， Beijing 100730， China

ultrasound-guided transversus abdominis block； retroperitoneoscopic surgery；postoperative analgesia； postoperative recovery

Objective To evaluate the effects of ultrasound-guided transversus abdominis plane （TAP） block on postoperative analgesia and early recovery in patients undergoing retroperitoneoscopic urologic surgeries.

Methods This was a randomized， controlled， double-blinded trial. Eligible patients scheduled for retroperitoneoscopic urologic surgeries were randomly assigned to two groups. Group TAP received ultrasound-guided TAP block with 0.5% ropivacaine 20 ml at 30 minutes before surgery， and Group C received TAP sham block with normal saline. All patients received retroperitoneoscopic urologic surgeries under general anesthesia. The primary outcome was the severity of pain after surgery. Secondary outcomes included opioids consumption， analgesics， postoperative nausea and vomiting， time to Foley catheter removal and to passage of flatus， length of post-anesthesia care unit stay and hospital stay.

Results Eighty patients completed the study， forty cases in each group. Compared to the Group C， the Group TAP had lower visual analogue scale pain scores within two postoperative days （all P＜0.05）. They also had less consumption of intraoperative fentanyl （2.0±0.5 vs. 3.8±0.7 μg/kg， P＜0.05）， reduced incidence of postoperative rescue analgesic usage （12.5% vs. 45.0%， P＜0.05）， and lower incidence of postoperative nausea and vomiting within postoperative 48 hours （12.5% vs. 25.0%， P＜0.05） when compared to the Group C. In addition，Group TAP had a shortened post-anesthesia care unit stay （25±8 vs. 49±12 minutes， P＜0.05）， and a greaterproportion of patients discharged within postoperative three days （57.5% vs. 35.0%， P＜0.05）.

Conclusion Preoperative ultrasound-guided TAP block is an effective technique to improve postoperative analgesia and early recovery in patients undergoing retroperitoneoscopic urologic surgeries. Chin Med Sci J 2016； 31（3）：137-141

T HE rates of retroperitoneoscopic urologic surgeries have been increasing， for its benefits of less morbidity and mortality over open abdominal surgeries.1Efforts to improve postoperative recovery remains challenging because acute pain acts as a major contributing factor to perioperative stress and delayed recovery.2Ultrasound-guided transversus abdominis plane （TAP） block is a technique to inject local anesthetics between the layers of internal oblique and the transversus abdominis muscles， blocking sensory branches of thoracoabdominal nerves distributed in anterior-lateral abdominal wall. Its efficacy and safety have been shown in laparoscopic hysterectomy3and colorectal surgeries.4However， there are limited data of TAP on the outcomes of retroperitoneoscopic urologic surgeries. The primary objective of this study was to investigate efficacy and safety of ultrasound-guided TAP block on postoperative analgesia and early recovery in patients undergoing retroperitoneoscopic urologic surgeries.

PATIENTS AND METHODS

Patients’ enrollment and grouping

This prospective， randomized， controlled， double-blinded study was conducted at Peking Union Medical College Hospital. The study protocol was approved by the institutional Review Board and is registered at chictr.org.cn（ChiCTR-ICR-15006732）. Written Informed consents were obtained from all participants.

Eligible participants were patients aged 18-70 years old， undergoing elective retroperitoneoscorpic renal or adrenal surgeries. Inclusion criteria： patients of the American Society of Anesthesiologists （ASA） classification I or II， who underwent a 1-3 hours long surgery， and whose body mass index （BMI） was between 18 and 30 kg/m2. Patients were excluded if they had chronic pain， allergy to local anesthetics， bleeding disorders， liver or kidney insufficiency， or a BMI ＞30 kg/m2.

Patients were randomized to be in two groups： the study group， Group TAP， received ultrasound-guided TAP block with 20 ml of 0.5% ropivacaine at 30 kg/m2minutes before surgery， and the control group， Group C， received ultrasound-guided sham TAP block with normal saline. Random numbers were computer-generated and group assignments were sealed in sequentially numbered，opaque envelopes. An independent researcher who was not involved in patient care or data collection， opened envelopes before each case， and prepared syringes with study drugs （ropivacaine or normal saline）. Patients， TAP block performer， anesthesiologists， surgeons and follow-up investigators were all blinded to group allocation.

Intervention

Patients were routinely monitored， and were premeditated with intravenous midazolam. Thirty minutes before surgery， a TAP block was performed under the guidance of an ultrasound device （Philips CX50） and a linear 5-10 MHz transducer （Philips C12-3）. A posterior approach of TAP block was adopted with patients in a lateral decubitus position. A transducer was placed at the mid-axillary line between the costal margin and iliac crest. The external oblique muscle， internal oblique muscle （IOM）， and transversus abdominal muscle （TAM） were scanned and identified. A block needle （Braun Stimuplex 21G） was advanced near the posterior corner of TAM using an in-plane approach. Once the needle tip was placed in the space between IOM and TAM with a negative aspiration of blood， 20 ml of study drug （ropivacaine or normal saline）was injected. A successful study drug injection was defined as appearance of a hypoechoic ellipsoid with well-defined margins in the ultrasonic imaging. Patients were monitored and observed for detection of complications.

Perioperative management

In the operating room， all patients received general anesthesia. Anesthesia was induced with intravenous propfol，remifentanil， and rocuronium. After endotracheal intubation was performed， ventilation was started with oxygen and air. Anesthesia was maintained with propofol infused at target plasma concentration of 4 μg/ml. Intravenous boluses of fentanyl 50 μg were given repeatedly if needed at the anesthesiologist's judgment. Retroperitoneoscopic renal or adrenal surgeries were performed. Trocars incisions were established at anterior， middle， and posterior axillary lines. At the end of the surgery， patients were allowed to awake， extubated and sent to the post-anesthesia care unit （PACU）.

In the PACU， patients received routine care， and were assessed using the modified Post-Anesthetic Discharge Scoring System.5A score ≥ 9 is considered ready for discharge. Routine postoperative care was conducted when patients were sent back to ward. Postoperative pain intensity was evaluated at PACU， at 9 a.m. on postoperative day 1 （POD1）， POD2， and POD3， respectively. Intramuscular injection of tramadol 100 mg would be administered if the patient reported significant pain anytime at ward［visual analogue scale （VAS） ≥ 30 or pain disrupting sleep］to the decision of physician on call. Patients were followed up during their hospital stay， and were discharged from hospital according to the decision of the attending surgeon.

Outcome variables and definition

The primary outcome variable was VAS pain score on POD1. Secondary outcomes included VAS pain scores in PACU on POD2 and POD3. Data were also collected for intraoperative fentanyl consumption， postoperative rescue analgesic medications； incidence of postoperative nausea and vomiting （PONV） within postoperative 48 hours， time to Foley catheter removal， time to passage of flatus， length of PACU stay and hospital stay. Pain intensity was determined by patients self-assessment on a continuous 100 mm-long VAS， where 0 means no pain and 100 means the most excruciating pain. A PONV event is defined as patient experience vomiting， retching， or drug has to be administered to relieve PONV.

Statistical analysis

Normally distributed continuous variables were expressed as mean±SD， and were compared using two-tailed Student's t-test. Non-normally distributed continuous variables were expressed as median （interquartile range）， and were compared using Mann-Whitney U test. Categorical variables were expressed as numbers （percentage）， and were compared using Chi-square analysis or Fischer's exact test. Statistical analysis was performed using SPSS （version 21.0）. P＜0.05 was considered statistically significant.

RESULTS

A total number of 86 patients were randomized， and 80 patients completed the study. CONSORT diagram is shown in Figure 1. Demographic characteristics and perioperative data were not different between groups （all P＞0.05， Table 1）.

Postoperative VAS pain scores of the Group TAP were significantly lower than that of the Group C within the first two days after surgery （all P＜0.05， Table 2）. Compared to the Group C， the Group TAP had less consumption of intraoperative fentanyl， lower incidence of postoperative rescue analgesic uses， lower PONV incidence， and a shortened PACU stay； in addition， the percentage of patients who was discharged within postoperative three days in the Group TAP was significantly higher than that in the Group C （57.5% vs. 35.0%， all P＜0.05， Table 3）.

Figure 1. Consort flow study diagram. TAP： transversus abdominis plane.

Table 1. Patients' demographic and clinical characteristics （n=40）

Table 2. Comparisons of postoperative VAS pain scores at the indicated time§（n=40）

Table 3. Comparisons of opioids consumption and recovery variables （n=40）

DISCUSSION

Our study demonstrates that for the patients who receive retroperitoneoscopic urological surgeries， preoperative TAP substantially decreased postoperative pain scores，intraoperative fentanyl consumption， and the incidence of postoperative rescue analgesic use. These findings are particularly important because conflicting data existed in previous studies on this particular type of surgery.6-8Our study adds new evidence to current knowledge of analgesic methods for retroperitoneoscopic urological surgeries.

Another important finding of the current study is the accelerated postoperative recovery of patients in the Group TAP. We discovered that， besides a lower incidence of PONV and shortened PACU stay in the TAP Group， there was also higher percentage of patients who were discharged from hospital in 3 days after surgery in the TAP group than in the control group. These findings are important because no such evidence has ever been reported in previous studies on the effect of TAP block on early recovery in retroperitoneoscopic surgeries.7

We adopted the posterior approach performing TAP block with patients in lateral decubitus position in this study. This approach has several advantages over lower TAP block. Retroperitoneoscopic surgery involves trocar incisions at mid-axillary and post-axillary lines. Studies on cadavers9and volunteers10had demonstrated that TAP block performed near the posterior corner of transversus abdominis muscle covers the anterior-lateral abdominal area as far back as the post-axillary line. Moreover， a lateral decubitus position enhances safety of TAP block， because the contents of the abdominal cavity fall away from the needle trajectory. Patients were awake during and 30 minutes after the block. We did not detect any potential side effects associated with TAP block. In addition， a meta-analysis examining the use of TAP block also did not find any increase of potential harms.11

Other methods have been shown to improve postoperative analgesia after laparoscopic surgeries， such as systematic lidocaine infusion，12application of non-steroidal anti-inflammatory drugs， and port site local anesthetic injections.13TAP block serves as a potent and targeted regional anesthetic technique to improve perioperative analgesia by blocking nociceptive pathways along the peripheral nerves to the central nerve system.14However， as regional anesthesia is time-consuming and requires more equipment and specialized staff， investigations are needed to explore the cost-effectiveness of TAP block comparing to other analgesic methods.

There are limitations to our study. Although the proportion of early discharged patients in the TAP group was higher than the Group C， we did not discover a statistical significant difference in the length of hospital stay between the two groups. This is probably because of a relatively small sample size of our study. In addition， multiple factors are related to patient discharge from hospital， including maintenance of normothermia， early oral nutrition and mobilization， early removal of Foley catheter， and etc.15Data of the above factors were not incorporated into this study.

In summary， preoperative ultrasound-guided TAP block is an effective and safe technique to improve postoperative analgesia and early recovery in patients undergoing retroperitoneoscopic urologic surgeries. As a component of multimodal analgesic strategy in an Enhanced Recovery after Surgery （ERAS） program， TAP block seems promising to improve early and comprehensive outcomes for them. Further investigation of integrating TAP block into an ERAS strategy would be needed to provide evidence for clinical practice.

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for publication March 1， 2016.

*Corresponding authors Fax： 86-10-69152058， E-mail： garybeijing@163.com