Efficacy of Unilateral Ilioinguinal Transversus Abdominis Plane Block for Alleviation of Catheter-related Bladder Discomfort in Male Patients after Emergence from General Anesthesia: a Prospective, Randomized Controlled Trial


 Background: Urinary catheterization frequently leads to catheter-related bladder discomfort (CRBD) in male patients after general anesthesia. This prospective cohort trial aimed to prove the efficacy of unilateral ilioinguinal transversus abdominis plane block (TAPB) in attenuating CRBD in male patients. Methods: Male patients with a severe CRBD were randomized to receive unilateral ilioinguinal TAPB with 0.375% ropivacaine 10 mL (group T) or intravenous sufentanil 0.15 μg/kg (group C). The primary outcomes were the incidence rates of moderate-to-severe CRBD at 0.5, 1, 2, and 6 hours after treatment, and the other outcomes were postoperative adverse events related to treatments. Results: The incidence rates of moderate-to-severe CRBD were significantly lower in group T than in group C at 0.5 hours (11.5% vs 87.4%, P<0.001), 1 hour (7.6% vs 92.3%, P=0.001), 2 hours (7.6% vs 92.3%, P=0.001), and 6 hours (11.5% vs 100%, P<0.001) after treatment. The postoperative incidences of sedation and respiratory depression were decreased significantly in group T compared to group C (P<0.05). Conclusions: Unilateral ilioinguinal TAPB with ropivacaine can decrease the incidence of moderate-to-severe CRBD and reduce side effects in male patients after general anesthesia compared to intravenous sufentanil administration. Trial registration: This trial was registered with Clinicaltrials.gov as ChiCTR1900022869 on April 29, 2019, http://www.chictr.org.cn/showproj.aspx?proj=38516.


Introduction
Intraoperative urinary catheterization frequently leads to catheter-related bladder discomfort (CRBD) during the postoperative period, especially in male patients receiving general anesthesia. Different types of surgeries cause CRBD, which occurs predominantly in males with an incidence ranging from 47% to 90% 1 . A severe CRBD usually makes the patient agitated, with behavioral responses such as loud complaints, restless extremity movements and attempts to pull out the urinary catheter in the post-anesthesia care unit (PACU) 2 .
CRBD is associated with muscarinic receptors, and anticholinergic agents have been considered as the first line treatment for CRBD 3 . But these medications usually cause dry mouth, facial flushing, and blurred vision. Anesthetics such as sevoflurane, desflurane, tramadol ketamine and dexmedetomidine showed beneficial effects in reducing CRBD as well 4,5,6 . However, administration of these drugs is meanwhile associated with side effects which may cause unpleasant complications and discounted recovery quality. Hence, new and safer techniques or agents are needed in clinical settings.
With the rapid advancement of nerve block in recent years, dorsal penile nerve block and pudendal nerve block have been demonstrated to be effective in decreasing the incidence and severity of CRBD 7,8 . Moreover, efficacy of the transversus abdominis plane (TAP) block has been proven in various types of abdominal surgery 9 but reports that investigate the effects of TAPB in CRBD are unavailable. We hypothesized that TAPB could be employed to reduce CRBD in male patients after general anesthesia with less side effects.

Methods
This prospective, randomized and controlled study was approved by the Research Ethical Committee of the First Affiliated Hospital of Wenzhou Medical University, and written informed consent was obtained from all participants. Before the patients' enrollment, the trial was registered at Chinese Clinical Trial Registry (http://www.chictr.org.cn, ChiCTR1900022869; principal investigator: Xiyue Zhao; date of registration: April 29, 2019).

Patients
Patients with CRBD after various surgeries under general anesthesia between May and September 2019 were enrolled into our study. The severity of CRBD was assessed with a 4-point scale: none (no discomfort when asked); mild (reported by patient only when asked); moderate (reported by patient without being asked and without any behavioral response); or severe (reported by patient independently along with behavioral responses such as flailing limbs, strong vocal response, and attempts to remove the catheter) 5,13,14 . Inclusion criteria were moderate-severe CRBD status, adult male and American Society of Anesthesiologists physical status I-III. Exclusion criteria were histories of urological surgeries, renal insufficiency, prostate hyperplasia, bladder outflow obstruction, neurogenic bladder, over active bladder (>8 times in 24 hours or frequency>3 times in the night), bleeding disorder, and inability to communicate.

Randomization, Concealment, and Blinding
After screening, fifty-two patients were included in our study and randomly divided into intervention group (group T) and control group (group C) by computer. Patients in group T received unilateral TAPB with 0.375% ropivacaine 10mL 10 , and patients in group C received intravenous sufentanil 0.15μg/kg. 11,12 . The investigator who assessed the severity of CRBD was blinded to the group allocation.

Outcomes
The primary outcomes were the severity of CRBD at 0.5, 1, 2, and 6 hours after treatment. All patients were questioned about the symptoms of CRBD by investigators in the PACU and surgical ward. The severity of CRBD was scaled using the methods described above.
Other secondary outcomes were evaluated as follows:

Sample size calculation and randomization
The sample size was planned and calculated according to alleviation of the severity of CRBD in the PACU. The incidence of moderate-to-severe CRBD at 0.5 hour in group T and group C was 11.5% and 84.7%, respectively. Giving α=0.05 and β=0.90, 20 patients in each group were required. Considering a possibility of dropout rate, 26 patients in each group were enrolled.

Statistical analysis
All analyses were conducted using SPSS software (version 17.0). Continuous data were expressed as the mean ± standard deviation (SD), and enumeration data were expressed as a number or ratio. The severity of CRBD was analyzed by the χ2 test. Comparison of continuous data between two groups were performed by t test. A P value of <0.05 was considered significant.

Study Population
Sixty-four patients were assessed for eligibility in this study, and 4 patients were excluded (Figure 1).
After randomization, 4 patients in both groups were excluded because the patients were not compliant with treatment. Therefore, a total of 52 patients were enrolled and analyzed. The patient characteristics were comparable between two groups (Table 1).
There were no differences in deep sedation in PACU between the two groups (P>0.05), but the incidences of PONV and respiratory depression were decreased significantly in group T compared with group C (P<0.05) ( Table 3).

Discussion
This study demonstrated that unilateral ilioinguinal TAPB with ropivacaine can be used as a rescue therapy for moderate or severe CRBD in male patients, it not only reduced the severity of CRBD but also reduced the occurrence of the side effects associated with opioid analgesic drugs for CRBD, including PONV and respiratory depression.
Tramadol, which activates μ-opioid receptors and inhibit M1and M3 muscarinic receptors 16 , is commonly used to decrease the incidence and severity of CRBD There are some limitations to this study. First, the efficacy of TAPB in reducing CRBD was found, but theoretical foundation is still missing. Second, a double-blind could not be achieved due to the completely different route of administration . Third, CRBD predominately occurs in male patients and hence the sample size of female patients who suffered from CRBD was not enough.
In summary, unilateral ilioinguinal TAPB with ropivacaine can decrease the severity of CRBD and reduce the side effects in male patients after general anesthesia as compared to intravenous sufentanil administration.