Ultrasound-Guided Peripheral Nerve Blocks Performed by Orthopedic Surgeons: A Retrospective, Multicenter Study in Akita Prefecture, Japan

The shortage of doctors is a societal problem, especially in rural areas such as Akita Prefecture, Japan. Therefore, it is not unusual in Akita for orthopedic surgeons to perform upper and lower limb surgeries under ultrasound-guided peripheral nerve blocks managed by the operators themselves. Multicenter studies of ultrasound-guided peripheral nerve blocks performed by orthopedic surgeons have not been reported. The purpose of this study was to clarify the safety and reliability of ultrasound-guided peripheral nerve blocks performed by orthopedic surgeons in Akita. A total of 1,674 upper extremity surgery cases operated under ultrasound-guided peripheral nerve blocks at 8 hospitals in Akita prefecture from April 2016 to April 2018 were investigated retrospectively. These blocks were performed by a total of 37 orthopedic surgeons, including senior surgeons and residents. In 321 of the 1,674 cases (19%), local anesthetics were added to the surgical field. Two cases with special factors were converted to general anesthesia. There were 2 cases of complications associated with the nerve block, but they were all transient and recovered promptly. The block site and the hospital where the block was performed showed a significant relationship with the addition of local anesthetics to the surgical site (P < 0.001). Surgery time, age at surgery, and surgical site showed no significant relationships with the addition of local anesthetics. The volume of the anesthetic used for the nerve block showed a significant inverse relationship with the addition of local anesthetics (P=0.040). Many orthopedic surgeons in Akita prefecture began to perform ultrasound-guided peripheral nerve blocks, which had a reliable anesthesia effect with no noticeable complications, whether performed by residents or senior orthopedic surgeons, and this is a useful anesthetic technique for orthopedic surgeons.


Introduction
e shortage of doctors is a societal problem, especially in rural areas such as Akita Prefecture, Japan. ere are many hospitals with no full-time anesthesiologists, and the number of operations performed under anesthesiologist management is limited. erefore, it is not unusual that orthopedic surgeons perform upper and lower limb surgeries under ultrasound-guided peripheral nerve blocks managed by the operators themselves in Akita.
e usefulness and complications of ultrasound-guided peripheral nerve blocks performed by anesthesiologists have been reported [1][2][3][4], but no multicenter studies of ultrasound-guided peripheral nerve blocks performed by orthopedic surgeons have been reported. e purpose of this study was to clarify the safety and reliability of ultrasound-guided peripheral nerve blocks performed by orthopedic surgeons in Akita.

Materials and Methods
A total of 1,674 upper extremity surgery cases operated under ultrasound-guided peripheral nerve blocks at 8 hospitals in Akita prefecture from April 2016 to April 2018 were investigated retrospectively. All patients were preoperatively informed by an attending doctor and agreed to undergo surgery with a peripheral nerve block. e types of operations included distal radius fracture open reduction and internal fixation (ORIF) in 261 cases, finger or hand fracture ORIF in 111 cases, elbow joint fracture ORIF in 35 cases, extensor tendon repair in 59 cases, flexor tendon repair in 14 cases, and nerve repair in 58 cases ( Figure 1). e patients' average age at surgery was 58 years (range: 10-95 years). e average operation time was 67 minutes (range: 2-395 minutes). e type of block to be performed was determined by the visibility of patient's nerves, physical size, and the preference of each practitioner. Using a linear ultrasound probe, the needle was inserted across or parallel to the probe, and the needle was inserted near the nerve under ultrasound guidance. e syringe containing the anesthetics was connected to an extension tube line and 23 gauge sterile standard blunt needle ( Figure 2). e anesthetics were injected little by little about 0.5-2 ml, so as to be diffused the whole circumference of the outside epineurium and never injected intraneurally. Ultrasound-guided peripheral nerve blocks were always performed in the same image with landmark parts visualized. In the interscalene block, the C5-C7 nerves depicted as straight three circular hypoechoic images between the anterior and middle scalene muscles were visualized on the short-axis view, and each nerve was blocked (Figures 3(a) and 3(b)). In the supraclavicular block, the nerve trunks adjacent to the subclavian artery were blocked with the pleura visualized so as not to cause pneumothorax ( Figure 4). In the axillary block, the triangle surrounded by the coracobrachialis and latissimus dorsi muscles was revealed. e median nerve, ulnar nerve, and radial nerve inside the triangle and the musculocutaneous nerve inside the coracobrachialis muscle were blocked (Figures 5(a) and 5(b)). In the forearm block, the median nerve, ulnar nerve, and radial nerve between the muscles were identified, and each nerve was blocked (Figures 6-8).
ere were double-level blocks in some cases (17.1%). In the cases of double-level blocks, the most proximal block was considered the main block. e main blocks were the interscalene block in 86 cases, the supraclavicular block in 786 cases, the axillary block in 761 cases, and the forearm block in 41 cases. ese blocks were performed by a total of 37 orthopedic surgeons, including senior surgeons and residents. In all cases, no intravenous anesthetic was used in combination. ere were no cases using neurostimulators, sterile probe covers, or sterile gloves. e anesthetics used in the block were 0.25% bupivacaine, 0.75% ropivacaine, 1% mepivacaine, and 1% lidocaine, which were used alone or in combination. e volume of anesthetics in the block was 5-40 ml, with the majority of cases (87%) using less than 30 ml, depending on the weight and age of the patient. In all cases, the postoperative condition was examined by operators themselves during hospitalization and outpatient care. e operators examined for complications associated with peripheral nerve blocks. e relationships between the addition of local anesthetics to the surgical field and the main block site, the hospital where the block was performed, and the surgical site were analyzed using the χ 2 test. e relationships between the addition of local anesthetics to the surgical field and operation time, patient's age at surgery, and the amount of anesthetic fluid volume used for nerve blocks were analyzed by logistic regression analysis. All statistical tests were performed using SPSS software (SPSS 16.0J for Windows Base System, SPSS Japan Inc., Tokyo, Japan). Significance was set at P < 0.05.

Results
In 321 of 1,674 cases (19%), local anesthetics were added to the surgical field. Lidocaine and mepivacaine were used, but the additional anesthetic volumes were low (approximately 3-10 ml). Two cases (0.1%) were converted to general anesthesia; one case was a reduction of elbow joint dislocation with severe obesity and poor visualization of the nerves by ultrasound, and the other was a radial fracture ORIF case that was considered unsuitable for surgery under a nerve block because of psychological factors. ere were two cases of complications associated with nerve blocks, namely, nausea in one case and decreased oxygen saturation in another, but both patients recovered promptly. ere were no cases of persistent neuropathy or infection of the nerve block injection sites. e rate of the additional local anesthetic to the surgical field was 35% in the interscalene block, 18% in the supraclavicular block, 20% in the axillary block, and 5% in the forearm block. ere was a significant relationship between the addition of the local anesthetic to the surgical site and the main block site (P < 0.001). e rate of addition of the local anesthetic for each hospital ranged from 6% to 34%; it was significantly different depending on the hospital in which the block was performed (P < 0.001).
Surgery time, age at surgery, and surgical site showed no significant relationships with the addition of the local anesthetic. On the contrary, the volume of anesthetics used for the nerve block showed a significant inverse relationship with the addition of local anesthetics (P � 0.040).

Discussion
In a peripheral nerve block, high success rates have been reported even with conventional methods such as the transarterial technique [5] and the paresthesia technique [6], but they have the disadvantages of directly puncturing arteries and nerves. Although nerve puncture and intraneural injection were reported to, sometimes, produce temporary sensory disturbances, they did not lead to permanent neuropathy [7], whereas it was reported that neuropathy occurred in 2.8% of cases with the seeking paresthesia technique [8]. Nerve puncture and intraneural injection should be avoided as much as possible to prevent neuropathy. In a report on multiple-injection technique comparing ultrasound guidance with nerve stimulation guidance, although ultrasound guidance showed shorter time to onset of the sensory block and fewer needle insertions than nerve stimulation guidance, success rates and complication rates were similar [1]. However, there were individual variations in the locations of the nerves, and it seems easier to perform peripheral nerve blocks by identifying nerves with ultrasound [9][10][11]. In fact, it has been reported that the ultrasound-guided technique had less vessel puncture [12], a significantly higher success rate [13,14], and fewer complications than the nerve stimulation-guided technique [15,16]. However, it is necessary to be careful because there are reports that pneumothorax and nerve palsy have occurred even under ultrasound guidance [17,18], but in the present study, despite being performed by many orthopedic surgeons, complications were only transient and mild, affecting only 0.1% of cases. Ultrasound-guided peripheral nerve blocks were performed mainly by interscalene, supraclavicular, and axillary approaches. e rate of additional local anesthetic to the surgical field was higher with the interscalene block than with other blocks, and it was thought that it was difficult to block the C8 and 1 nerves even under ultrasound guidance. Although the number of cases of forearm blocks was small, the rate of additional local anesthetic was the lowest. Soberón et al. reported that forearm blocks might be used as the primary anesthetic in patients undergoing hand surgery [19]. In the future, the use of forearm blocks may increase in hand and finger surgeries. e volume of the anesthetic used for the blocks in the present study was mostly 30 ml or less depending on the patient's weight and age, which was substantially less than the maximum dose. A study of the Australian and New Zealand Registry of Regional Anaesthesia reported that ultrasound guidance reduced the incidence of local anesthetic toxicity [2]. It was reported that a higher dose and concentration of the anesthetic, but not a higher volume, were associated with longer block duration [20]. On the contrary, a higher volume of the anesthetic showed a lower rate of requiring additional local anesthetic to the surgical field in the present study. It was thought that the higher volume of the anesthetic used for the nerve block could be injected more easily all around the nerve. However, it was reported that 45% of the patients who underwent an ultrasound-guided interscalene block with only 5 ml of ropivacaine developed diaphragmatic paralysis [21]; thus, it is necessary to be careful when increasing the volume of the anesthetic, especially in interscalene blocks.
e Akita Hand Surgery Group has continued to hold skill practice workshops on ultrasound-guided peripheral nerve blocks free of charge for orthopedic surgeons in cooperation with the Akita University Department of

Advances in Orthopedics
Orthopedic Surgery. As a result, ultrasound-guided peripheral nerve blocks, which were previously performed in only a few hospitals, are now performed in many hospitals throughout Akita. However, the block site and the hospital where the block was performed showed a significant relationship with the addition of the local anesthetic to the surgical site. It may be due to the difference in the skills of the practitioners who performed the nerve block and the difference in the performance of the ultrasonic equipment used in each hospital. erefore, in order to further improve the anesthesia success rate, it may be necessary to improve the workshop to be more accurate and comprehensible by teaching the tips and tricks for ultrasound-guided peripheral nerve blocks.

Advances in Orthopedics
As of March 1, 2020, the total population of Akita prefecture was 960,271 and that of Akita city was 304,943; 2/ 3 of the population is outside of Akita city, but full-time anesthesiologists are concentrated in Akita city. Outside of Akita city, there are few emergency hospitals that have fulltime anesthesiologists, and these hospitals provide surgical treatment with part-time anesthesiologists and have a manpower shortage. Under such circumstances, the number of operations that an anesthesiologist can manage for orthopedic surgery is not at all adequate. erefore, it is not unusual that orthopedic surgeons perform upper limb and lower limb surgeries under ultrasound-guided peripheral nerve blocks performed by the operators themselves. Until now, it is unclear whether ultrasound-guided peripheral nerve blocks in Akita prefecture were performed reliably and safely.
e present study showed that cases of transition to general anesthesia were very rare, there were no noticeable complications, and the anesthesia success rate was acceptable in all hospitals.  Advances in Orthopedics 5

Conclusion
As a result of continuing dissemination activities through skill practice workshops, many orthopedic surgeons in Akita prefecture began performing ultrasound-guided peripheral nerve blocks, which had a reliable anesthesia effect with no noticeable complications, whether performed by residents or senior orthopedic surgeons. is is a useful anesthetic technique for orthopedic surgeons to use.

Data Availability
e data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest
e authors declare no conflicts of interest regarding the publication of this paper.