Ultrasound-guided axillary brachial plexus block combined with axillary nerve block and ultrasound-guided supraclavicular brachial plexus block provided similar surgical anaesthesia quality and outcomes. Moreover, anaesthesia failure did not occur with either technique: both provided adequate anaesthesia throughout the entire orthopaedic operation. Traditionally, the anaesthesia effect is generally evaluated using the visual analogue score for pain (7)reported during surgery or is based on the surgeon’s or anaesthesiologist’s evaluation of the quality of anaesthesia(8)and at the end of surgery. However, these studies fail to consider the patient’s subjective feelings and postoperative analgesia requirements and do not provide a full assessment. At present, there is no available tool for evaluating the quality and effect of
perioperative anaesthesia. Almasi et al.(9)suggested that the subjective feelings of the patient during surgery and the duration of effective postoperative analgesia are key components that reflect the quality of anaesthesia. Using these measures, they reported that the anaesthesia success rate was significantly higher for ultrasound-guided nerve block than for traditional anaesthesia.
The safety and effectiveness of ultrasound-guided supraclavicular brachial plexus block for upper limb orthopaedic surgery has previously been demonstrated(10). This technique is associated with a shorter onset time, smaller local anaesthesia dose, and lower risk of pneumothorax(11). Pneumothorax did not occur in any of our study patients. The risk of phrenic nerve palsy with this technique presents owing to the anatomy of the nerve itself. Marhofer et al.(12) reported that the incidence of phrenic nerve palsy after supraclavicular brachial plexus block ranges between 36% and 67%. We found a similar rate of 30% in our study. Furthermore, as suggested by Kessler et al.(13), the diffusion direction, drug volume, and concentration of local anaesthesia might explain diaphragmatic paralysis. In addition, phrenic nerve palsy has been associated with the injection site(5). Drug injection via the “corner pocket” might reduce the incidence of phrenic nerve palsy. Accordingly, in our study, the drugs were injected separately for ultrasound-guided supraclavicular brachial plexus block. Nonetheless, phrenic nerve block still occurred.
The brachial plexus forms terminal branches in the axilla, where the musculocutaneous and axillary nerves separate from the lateral and posterior bundles. Injection of local anaesthesia around the brachial plexus through the traditional axillary approach is below the location where these two nerves leave the axillary sheath(14). In general, the axillary brachial plexus block is effective for surgical anaesthesia at and below the elbow(15). Therefore, both the musculocutaneous and axillary nerves should be blocked simultaneously when performing upper limb surgery. Otherwise, the block may be incomplete or fail. In 1974, Winnie et al.(16)injected local anaesthesia with contrast agent in different volumes into different sites of the axillary sheath. They reported that when the injection is performed as high as possible using the axillary approach, the drug can diffuse to both the proximal and distal ends of the sheath. Furthermore, the diffusion was more significant proximally than distally. The drug reached the plane of the coracoid process and musculocutaneous nerve through the axillary sheath. Distal spread was not affected by the humeral head.
Considering the distribution characteristics of the axillary nerve, axillary nerve block(17) is needed during upper limb surgery. This block is generally performed using the posterior approach with ultrasound guidance, which assists in locating the teres minor, deltoid, triceps brachii, and humeral trunk to identify the PCHA. Local anaesthetics are injected based on the position of the PCHA. However, the origin and location of the PCHA can vary between individuals. Therefore, block failure may occur when the injection is based on the PCHA
position. Dhir et al.(18)thought that the failure rate of axillary nerve block would be as high as 41.4%. However, Feigl et al.(19) reported that 99% of axillary nerves pass through the QS, demonstrating anatomic evidence for the anterior axillary approach. In 2017, Chang et al.(20)examined the feasibility of ultrasound-guided anterior axillary nerve block. In this study, the QS was identified by ultrasound, and 5 mL of 0.4% ropivacaine was injected into it. Within 30 minutes of injection, axillary nerve pain disappeared completely in 46.7% of patients; the block was weak in the remaining patients. A small dose of supplementary sufentanil was needed to reduce subjective discomfort. When performing axillary nerve block, the blocking effect can be improved by increasing the concentration or volume of the local anaesthetic.
Previous research(21) has revealed that intravenous Dex provides sedation and prolongs the duration of brachial plexus block analgesia in patients undergoing upper limb orthopaedic surgery. Our study showed similar pain and motor block recovery times in both groups. In addition, the proportion of patients who needed remedial intravenous analgesia was similar. However, because Dex can cause transient bradycardia and hypotension when used as a brachial plexus block adjuvant, its safety needs further study(22).
Our study also has several methodological limitations. First, the clinical efficacy of ultrasound-guided axillary brachial plexus block combined with axillary nerve block regimens with different concentrations and volumes of local anaesthetics has not been further explored. Second, there may be some differences in the accuracy of the injection site without the dual guidance operation of the neurostimulator, resulting in differences in the onset of anaesthesia time and anaesthesia effect in different patients. Third, it lacked an assessment of neurological dysfunction and long-term follow-up.
In conclusion, ultrasound-guided supraclavicular brachial plexus block is associated with the risk of phrenic nerve block. Ultrasound-guided axillary brachial plexus block combined with axillary nerve block can achieve similar surgical anaesthesia quality and outcomes and is not associated with a higher incidence of intraoperative sufentanil use, greater patient discomfort, pneumothorax, or phrenic nerve block.