Which position is the most ideal for performing ultrasound- guided cervical plexus block?

Introduction and Purpose: With the widespread use of ultrasonography (USG) technology and the increase in USG training programs, peripheral nerve blocks have become more preferred. Cervical plexus block, one of these techniques, reduces the need for analgesics by providing effective analgesia during and after surgery. Cervical plexus block is used in neck surgeries and produces anesthesia in the occipital, shoulder and upper pectoral areas. The aim of this study was to determine the closest distance of the reference points to the skin according to the measurements made by giving different positions to the patient under ultrasonography guidance, to determine the most comfortable position that provides the clearest image for the practitioner, to evaluate the most appropriate posture that increases patient satisfaction and to determine the ideal position for cervical plexus block. Method: This study was conducted prospectively at Harran University Faculty of Medicine, Department of Anesthesiology and Reanimation. Harran University Faculty of Medicine Clinical Research Ethics Committee (09.09.2024 Date and Session No. 13 Session No. 30 Decision No. 30) approval decision was taken for this study. This study included healthy volunteers between the ages of 18 and 65 years with a body mass index (BMI) <35, without mobility restriction in the neck region, without trauma, surgical procedure, burn scar and active infection in the study area, and patients who agreed to participate in the study. The study was conducted between September-December 2024 at Harran University Faculty of Medicine Hospital with a total of 100 patients, 47% (n=47) female and 53% (n=53) male. The age, gender, BMI (body mass index) of the patients were recorded and the measurements were evaluated by the same person and the same ultrasound device. The neck area was examined with the linear probe of the ultrasound. The patient was measured in supine position and with the head 45° up with two different positions of the head. The first measurements were made when the head was turned 180° to the right and the second measurements were made when the head was in the midline. After the linear probe of the ultrasound was placed on the neck facing the measurer, the interscalene nerves were brought to the far right on the screen and the image was standardized. The distance of 3 different reference points to the skin was measured in the image. Firstly, the distance of the uppermost interscalene nerve to the skin was measured, secondly, the distance of the upper midpoint of the middle scalene muscle to the skin was measured. And thirdly, the distance of the point where the sternocleidomastoid (SCM) muscle ends was measured. The clarity of the image from the measured areas was recorded as (very poor: 1, poor: 2, fair: 3, good: 4). Thus, these different measurements were compared among themselves. Findings: When we evaluated our image quality according to BMI groups, we determined that the quality did not show statistical significance (p>0.05) according to BMI value in the 45 O, 45 SL, S O and S SL GRNT groups. However, although the 45 SL GRNT group did not show statistical significance in quality according to BMI, it is seen that there is a difference (approximately 2 values) between the BMI values of patients with good and bad images. When the image qualities of 4 different imaging groups were analyzed; it was determined that the group with the best image quality was 45 SL GRNT (48%). In the S SL GRNT group, 55 patients had mediocre image quality. The groups with the best image quality were 45 SL GRNT (48%), S SL GRNT (24%), 45 O GRNT (17%) and S O GRNT (11%). When the image quality was ranked according to mediocre image quality; S SL GRNT (55%), 45 O GRNT (47%), 45 SL GRNT (43%) and SO GRNT (40%). When the groups with poor image quality were ranked; 45 O GRNT (36%) and S O GRNT (36%), S SL GRNT (21%), 45 SL GRNT (9%). In the S O GRNT only group, imaging quality was very poor in 13 patients. According to the quality of the imaging modality, the distance values were on average the same or very close to each other. Although the minimum and maximum values of the qualities in the measurement and the number of people were different, no statistically significant difference was observed between any image method and qualities. Conclusion: We determined that the group with the best image quality was 45 SL GRNT. Poor image quality was more common in the 45 O GRNT and S O GRNT positions. The worst image quality was seen only in the S O GRNT position.45 SL GRNT We found a weak relationship in which image quality was negatively affected as BMI increased. We did not find a direct significant relationship between the distance of the reference points to the skin and image quality between the image groups. As a result, the best image was obtained in the 45 SL GRNT position in the patient. Keywords: cervical block, superficial cervical block, peripheral nerve block, cervical surgery