Ultrasound-guided axillary approach for brachial plexus block reduces block onset time compared to midhumeral approach

Aim: Brachial plexus block under ultrasonography guidance is a successful and frequently used anesthesia method for hand, wrist and forearm surgery. Brachial plexus block can be performed with axillary or midhumeral approach technique. In this study, we aimed to compare the intraoperative and postoperative anesthetic and analgesic properties of axillary or midhumeral approach in ultrasonography-guided brachial plexus block. Material and Methods: This randomized, controlled, double-blind, single-center study included 90 ASA I-III risk patients, aged 18-70 years, who underwent hand, wrist and forearm surgery. In Group I, axillary; in Group II, midhumeral approach techniques were performed for brachial plexus block. Cold test was used to evaluate sensory block, and three-point scale was used to evaluate motor block. Postoperative pain was assessed by visual analog scale. Results: There was no statistical difference between age, height, weight, BMI and gender characteristics of the patients included in the study. There was no statistically significant difference between the groups in terms of block onset and regression times on both sensory and motor examination (p> 0.05). The main result was that axillary approach shortens the complete block onset time on both sensory and motor examination (p <0.05). Another important result was that axillary approach provides higher surgeon and patient satisfaction levels significantly comparing to mid-humeral approach (p <0.05). Conclusion: Both approaches can be applied successfully in brachial plexus block and can be used effectively in elective surgeries. In patients who underwent axillary approach technique for brachial plexus block, full block onset time is earlier than in patients undergoing midhumeral approach technique. Therefore, axillary approach technique may be preferred in cases requiring urgent surgical intervention.


Introduction
Brachial plexus blocks are commonly used anesthesia techniques of distal upper extremity, especially for hand, wrist and forearm surgery. As the use of ultrasonography (USG) has become widespread in anesthesia practice, it has been possible to block by visualizing the brachial plexus at different anatomical points throughout the course. USG, furthermore shortened the time to readiness for surgery and decreased the required local anesthetic volume and complications of blocks. [1,2,3] Traditionally, the brachial plexus block is performed in the axillary fossa or in the midhumeral sheath. The characteristics and patient outcomes of the two aforementioned block methods are scarce.
The aim of this study was to compare the axillary and midhumeral brachial plexus block in terms of patient outcomes and to determine which method would be more appropriate in emergency or elective situations.

Material and Methods
This study was planned as a randomized, controlled, doubleblind, single-center study with the approval of local ethics committee numbered E-16-897. Ninety ASA I-III risk patients, aged 18-70 years, undergoing upper extremity distal surgery were included in the study. Patients with concomitant severe cardiac, respiratory, hepatic or renal disorder, mental status disorder, coagulopathy, pregnancy, local analgesic allergy, neurological or neuromuscular disease, infection at the site of application, and patients who did not want to use this method were excluded from the study. After obtaining informed consent, the patients were randomized into two groups. The application site was prepared according to the rules of asepsis-antisepsis. In group I, axillary artery image was detected in axillary fossa by using 6-12 mHz linear ultrasound probe (Logiq e, General Electric, USA). The ulnar, radial and median nerves around the artery were imaged and a 5 cm peripheral nerve block needle was used to block the nerves with the same amount of local anesthetic (5 ml for each nerve).
For each patient, in order to relieve tourniquet pain, 5 ml local anesthetic was applied to musculocutaneous nerve between biceps and coracobrachialis muscles.
In group II, axillary artery image was detected in the humeral canal using 6-12 mHz linear ultrasound probe (Logiq e, General Electric, USA) and each of the musculocutaneous, ulnar, radial and median nerves were blocked with 5 ml local anesthetic. The researcher assessing the block level was blind to the study protocol. Block success was evaluated by sensory and motor block levels. Cold test was used to evaluate sensory block.
The sensation of coldness was evaluated by touching with a cotton pad and ice pack. Evaluation was performed on a scale of 0 = no block, 1 = analgesia (positive sense of touch, negative sense of temperature), 2 = complete sensory block (negative sense of touch), and compared with the opposite arm. A 3-point scale (0 = no block, 1 = partial motor block, 2 = complete motor block) was used to evaluate the motor block.
Loss of movement was evaluated by elbow flexion, thumb abduction, adduction and opposition for musculocutaneous, radial, median and ulnar nerves; respectively. The evaluation was done in every 5 minutes for the first 30 minutes. The total score of sensory and motor block was 12. Surgical anesthesia level and block were accepted as unsuccessful if the total score obtained under block was less than 10. For successful block, total score of sensory blocks should be at least 5 out of 6.
Patients with block failure within 30 minutes were considered to be unsuccessful as a consequence they were excluded from the study and additional anesthesia was applied. Motor and sensory block regression times were considered as the time when the score per nerve decreased from 2 to 1 according to the 3-point scale and cold test, and the time of termination of the block was considered as the moment when the score per nerve was zero. Postoperative pain was evaluated with visual analog scale (VAS). When the VAS value was greater than 4, additional analgesic requirement was considered. Surgical anesthesia duration, patient and surgeon satisfaction were evaluated as very good, good, moderate and bad. Patients were also observed for possible complications by the blinded researcher during the first 24 hours of hospitalization.

Statistical analysis
Data analysis was performed using SPSS 23.0 statistical package program. When evaluating study data descriptive statistical methods (frequency, percentage, mean, standard deviation, median, min-max) were used and qualitative data were compared using Pearson Chi-Square, Fisher or Yates tests.

Results
There were 45 patients in each group. There was no statistically significant difference between the groups in terms of age, height, weight, BMI, gender and ASA characteristics (Table 1).
In the sensory and motor examination (Median-Radial-Ulnar) there was no statistically significant difference between the groups in terms of block onset time (p> 0.05). However there was a statistically significant difference between groups in terms of complete block onset time (p <0.05). In Group II, the duration of complete block onset was significantly longer (p <0.05) (   (Table 3). During the follow-up period, no complications were observed in any of the patients in both group.

Conclusion
In conclusion, both axillary and midhumeral brachial plexus block techniques can be used effectively in anesthesia of hand, wrist and forearm surgeries. According to the results of the study, it can be concluded that axillary approach technique should be the first choice especially in emergency situations because it provides surgical anesthesia level earlier and higher surgeon and patient satisfaction levels than midhumeral approach.