Study design and patient enrollment
This prospective observational study was approved by the Nara Medical University Ethics Committee, Kashihara, Nara, Japan (No.2700; registered on July 10, 2020) and registered in the UMIN Clinical Trials Registry (UMIN000041137; registered on July 17, 2020) before enrollment commencement. Written informed consent was obtained from all study participants. All methods were carried out in accordance with Declaration of Helsinki. A total of 10 American Society of Anesthesia (ASA) class I –III adult (18–75 years old) patients scheduled for open radical hysterectomy using a vertical incision or laparotomy using a midline incision from under the xiphoid process to the symphysis pubis (ex. the addition of omentectomy) were enrolled. Exclusion criteria included communication difficulty, allergy to local anesthetic agent, skin disease at puncture site, body mass index >35, body weight less than 42 kg, coagulation disorder (PT-INR >1.25, APTT >35 s, or platelet <100000/µL), and insufficient period of antithrombotic drug withdrawal and chronic opioid use (daily use within 1 month before surgery).
Patients received general anesthesia under standardized monitoring, according to our institutional rules. Anesthesia was maintained by propofol (using target-controlled infusion, according to an electroencephalogram monitor), sevoflurane (1.0–1.5%), or desflurane (4.0–5.0%), based on the discretion of each anesthesiologist and according to the patient’s condition and complications. Remifentanil, fentanyl, and rocuronium were administered by the anesthesiologist in charge, as needed.
Ultrasound-guided M-TAPA was performed using a linear probe (6–13 MHz) of EDGE II (Fujifilm Sonosite, Tokyo, Japan) after anesthesia induction for patients in the supine position. We identified the 10th costal cartilage by the notch between the 9th and 10th costal cartilages and placed a linear probe in the sagittal plane and angled it deeply to view the lower aspect of the chondrium. A 20-gauge Tuohy needle (UNIEVER disposable nerve blockade needle Huber, UNISIS, Tokyo, Japan) was inserted as much as possible via an in-plane technique. However, in patients with protruding thorax, due to emaciation or pectus carinatum, the caudal end of the probe is deeply dug into the patient’s abdomen, leaving no space for needle insertion for the in-plane technique. In these cases, we performed M-TAPA using a ‘hybrid’ technique in which the puncture is started like the out-plane technique, but the needle movement is similar to the in-plane technique (Figure 1). After confirming negative aspiration, we applied 0.25% ropivacaine 30 mL (or 25 mL if the patient weighed less than 50 kg) per side, between the 10th costal cartilage and the transverse abdominis muscle (TAM) at the lower aspect of the chondrium.
All patients were transferred to the ward after their recovery from general anesthesia. An anesthesiologist or a perioperative nurse who belonged to the postoperative care service team, assessed anesthetized dermatomes by pinprick tests at 2 and 24 h after the operation, without the assistance of the anesthesiologist who performed the M-TAPA block. Pinprick tests using 4.0 g Semmes–Weinstein monofilament (SOT-DM06A, SAKAI Medical Co., Ltd., Tokyo, Japan) were performed on the area from Th6 to Th12, based on Keegan and Garrett’s sensory dermatome map, which includes the area 3 cm lateral from the midline incision to avoid wound dressings, to evaluate the anterior cutaneous branch innervation area, and the mid-axillary line to evaluate the lateral cutaneous branch innervation area. The pinprick test was performed in a unified way, from a height of 2.5 cm, lower the monofilament vertically to the examination site for 1.5 s until the filament bends for 1.5 s, and then return the monofilament to its original position for 1.5 s, as per the manufacturing details (0 = loss of pinprick sensation, 1 = decreased pinprick sensation, 2 = normal pinprick sensation). An effective sensory block was defined as a score of 0 or 1.
Intravenous patient-controlled analgesia (IV-PCA) using a mechanical infusion pump (CADD®ฎ-Solis 2110, Smiths Medical Japan Ltd, Tokyo, Japan) was started at the time of wound closure, with a setting of 25 µg/h (25 µg bolus and a lock-out time of 10 min) or 20 µg/h (20 µg bolus and a lock-out time of 10 min). Dosing rate was determined by the anesthesiologist in charge to be approximately 0.5 µg/kg/h per body weight. The decision to discontinue IV-PCA was left to the gynecologist. Moreover, the regimen of postoperative analgesia and antithrombotic therapy was ordered by the gynecologists. Acetaminophen (15 mg/kg) was administered every 6 h, starting immediately after the return of the patient to the ward until the postoperative day (POD) 2. In addition, drip infusion of flurbiprofen was administered when the postoperative pain was uncontrollable. Regular oral administration of celecoxib was initiated in the evening of POD2. Enoxaparin sodium was administered early in the morning of POD1 to prevent VTE.
The primary outcome of this study was the number of anesthetized dermatomes at 2 and 24 h postoperatively. The secondary outcomes were numerical rating scale (NRS) scores (0–10, 0: no pain, 10: worst possible pain), intraoperative and postoperative amount of fentanyl use, occurrence of postoperative nausea and vomiting (PONV) within 48 h postoperatively, the number of additional analgesics used, and the patient satisfaction score (0–10; 0, very unsatisfied; 10, very satisfied).
This study was planned as a pilot study to evaluate the efficacy of M-TAPA in radical hysterectomy. Before the COVID-19 pandemic, we usually recorded 30 cases of radical hysterectomy in our institution yearly ; however, for this study, we chose a sample size of 10 patients in consideration of a possible reduction in the number of operations due to the pandemic and the novelty of M-TAPA.
Cadaveric evaluation was also performed with the cooperation of members of the Department of Anatomy and Cell Biology, Nara Medical University (Kashihara, Japan). Ultrasound-guided M-TAPA was simulated in four sides in two adult male cadavers with the same procedure as clinical study. All cadavers were embalmed using formalin. After the needle tip was confirmed to be in the appropriate space using ultrasound, 25 mL of a water-soluble dye (Sakura Mat Water Colors Multi; Sakura Color Products Corporation, Osaka, Japan) was injected into cadaver 1 and 30 mL of the dye was injected into cadaver 2 (Figure 2). The injections were performed by a single anesthesiologist (N.T.), and approximately 30 min after the injections, an anatomist (C.A.) assessed the spread of the dye.