Evaluation of Supraclavicular Brachial Plexus Blocks at Various Volumes: Impact on Optic Nerve Sheath Diameter

Regional anesthesia involves temporarily blocking nerve transmission and pain sensation in specific areas of the body without causing loss of consciousness. Regional anesthesia techniques include peripheral nerve blocks (PNB), topical anesthesia, infiltration anesthesia, regional intravenous anesthesia (RIVA), and neuroaxial blocks (spinal and epidural anesthesia). Brachial plexus blocks are among the most commonly used regional anesthesia methods within peripheral nerve block applications. Peripheral nerve blocks of the upper extremity can be used either alone for surgical anesthesia or added to general anesthesia for postoperative pain control. Brachial plexus blocks can be performed using various approaches including interscalene, supraclavicular, infraclavicular, and axillary approaches. The supraclavicular block aims to effectively control pain through a procedure targeting the shoulder and upper extremity nerves known as the brachial plexus. Complications of supraclavicular blocks may include pneumothorax secondary to lung trauma, hoarseness due to ipsilateral recurrent laryngeal nerve blockade, Horner syndrome due to stellate ganglion blockade, and hemidiaphragmatic paralysis due to phrenic nerve blockade. The incidence and severity of these complications are reduced with the use of ultrasound (USG) guidance and low-volume techniques. Intracranial pressure (ICP) refers to the pressure formed by the brain and spinal fluid, tissues, and blood surrounding the brain and spinal cord. Normally ranging between 5-15 mmHg, this pressure is critical for brain function and circulation. Abnormal increases in intracranial pressure can lead to intracranial hypertension, with main causes including brain tumors, edema, head trauma, brain aneurysms, intracranial hemorrhage, and issues related to the production and drainage of cerebrospinal fluid. External ventricular drainage (EVD) catheterization is the gold standard method for evaluating increased intracranial pressure. Measurement of optic nerve sheath diameter (ONSD) has been described as a valuable diagnostic method in clinical applications for evaluating intracranial pressure. Observational studies have shown that in cervical sympathetic blocks and interscalene blocks, indirect increases in intracranial pressure can be demonstrated through ultrasound (USG) measurements of optic nerve sheath diameter. It has been shown that hemidiaphragmatic paralysis due to ipsilateral phrenic nerve involvement, which is frequently seen in interscalene brachial plexus blocks, also occurs in supraclavicular brachial plexus blocks in a volume-dependent manner. There are studies in the literature on supraclavicular block applications with different volumes and doses. However, the investigators have not come across a study evaluating the clinical outcomes of optic nerve sheath diameter measurement along with anesthesia quality, side effects, and complications in ultrasound-guided supraclavicular blocks at different volumes. In this study, the investigators aimed to evaluate the anesthesia adequacy, side effects, and complication rates, as well as the postoperative analgesic efficacy of supraclavicular brachial plexus blocks performed at different volumes in our clinical practice under ultrasound guidance. Additionally, the investigators aimed to measure optic nerve sheath diameters with ultrasound and establish their relationship with intracranial pressure according to these different volumes.