Neuraxial Spread During Interscalene Block: Volume Considerations

Risk Factors for Neuraxial Spread

Interscalene block performed at higher cervical levels increases the risk of neuraxial spread due to proximity to the neuraxis 1, 2
Traditional approaches using large volumes of local anesthetic increase the risk of spread to the epidural or subarachnoid space 1, 3

The American Society of Anesthesiologists recommends using ultrasound guidance to visualize needle placement and local anesthetic spread, allowing for volume reduction 4, 1
Alternative approaches, such as axillary or infraclavicular approaches, may be safer than high interscalene approaches in patients at risk for neuraxial spread 1

Thorough testing for block success is essential to prevent the need for supplemental blocks or general anesthesia 4
Monitor for signs of high block for at least 30 minutes after block placement 1, 2
Have resuscitation equipment immediately available when performing any interscalene block 4, 3
Calculate safe dose of local anesthetic based on patient weight to prevent local anesthetic systemic toxicity 1

Failure to recognize that an interscalene catheter has migrated into the epidural or intrathecal space can lead to inadvertent administration of excessive local anesthetic doses 1, 2
Patients with anatomical variations or previous neck surgery may be at higher risk for neuraxial spread even with lower volumes 1
Sedation during block placement may mask early symptoms of neuraxial spread, so minimal sedation is recommended 4, 1
Even with ultrasound guidance and reduced volumes, vigilance for signs of neuraxial spread remains essential 4, 3