Material and methods
painless, numbness, pain, YiWu, flaccid anal sphincter, NRS
BLIND, LOCAL INFILTRATION, COMPLICATIONS
This single-armed prospective study was approved by the Ethics Committee of the Fourth Affiliated Hospital of Zhejiang University Medical College (YiWu, People’s Republic of China) (No: 202–031). The trial was registered with the Clinical Trial Registry in the 01/02/2021(No: ChiCTR2100042954). The period of enrollment was from March 2021 to February 2022. A total of 80 patients who were scheduled for elective anal fistulectomy or hemorrhoidectomy were selected. The inclusion criteria were (1) age between 18 and 65 years; (2) American Society of Anesthesiologists (ASA) physical status I to II; and (3) body mass index between 18 and 35 kg/mAn 18- or 20-gauge intravenous catheter was inserted into the upper limb in the induction room. During the procedure, noninvasive systemic blood pressure and heart rate were measured using an automatic cycling device (Cardiocap; Mindray). Each block was administered by one experienced anesthetist using an S-Nerve device (SonoSite Inc.). During block placement, no analgesia or sedation was given to the patients.All eligible patients were randomly divided, using a random number table, into one of two groups; group 1 received 20 ml (During the ultrasound-guided CEB, the block performance time (defined as the time from the contact of the ultrasound probe with the patient to the end of the local anesthetic injection) was recorded. In this study, the effectiveness of CEB was assessed through pinprick tests of the perineal area and a lax anal sphincter laxity test was performed after local anesthetics were administered in five-minute intervals for 30 min after. After the local anesthetic was injected, researcher checked the sensations of pinprick test every five minutes in the S3 and T6 dermatome areas at every five minutes for 30 min by a blinded observer. Motor block was evaluated at the end of surgery according to the Bromage scale (0 = full flexion of feet and knees, 1 = just able to move knees, 2 = able to move feet only, and 3 = unable to move feet or knees) performed at 5, 10, 15 min following administration of ropivacaine and at the end of the surgery. In the study, the pinprick test was used to determine the block onset time (defined as the time interval between the end of the local anesthetic injection to less pain in the S3 dermatome areas than T6 dermatome areas) and the block perfect time (defined as the time interval between the end of the local anesthetic injection to a painless pinprick in the S3 dermatome areas and the existence of flaccid anal sphincter) [The block was considered effective if the patient's anal sphincter laxed 30 min after the local anesthetic was injected, and pain-free surgery was achieved without the need for rescue blocks including supplemental opioids, general anesthesia or local infiltration by the surgeon. The block was considered ineffective if there was pain during surgery or the presence of a tight anal sphincter, and the patient received rescue blocks including supplemental opioids, general anesthesia or local infiltration by the surgeon.For postoperative, patients were assessed pain score using the numerical rating scale (NRS; 0 = no pain; 10 = most severe pain imaginable), motor block, numbness, and complications or side effects after operation by an anesthesiologist. Patients were prescribed ketorolac 30 mg intravenously up to 3 times a day if NRS scores were higher than 3. The duration of analgesia, defined as the interval between the block onset time and the initial use of rescue analgesia for surgical site pain.The current study was a double-blind design because the individuals involved in collecting and analyzing data were unaware of the group assignment. The assessment was performed by an independent outcome assessor who was blind to the concentration of local anesthetic that was injected and did not know the result of previously case.