C5 ventral ramus block for clavicle surgery: How low concerning the volume can we go?

Clinical case reports mention 3-5 ml of local anesthetic (LA) at the cervical root 5 (C5) for surgical anesthesia essential for clavicle surgeries with reasonable success. A volume of 5 ml LA has been shown to cause hemidiaphragmatic paresis.

We implement the 3-5 ml LA for awake clavicle surgeries along with a supraclavicular nerve (SCN) block with another 2 ml. To understand the spread of injectate, we conducted anatomic macroscopic dissection on Theil based cadavers. Post ultrasound injection of 3 ml of blue latex in one cadaver and green latex in the other, we dissected one cadaver and the other cadaver underwent a cross-section.

Dissection confirmed a vertical spread of dye more caudad than cephalad. There was no neuraxial spread visualized in the cross-section. The phrenic nerve (PN) was not stained in both cadavers, but a possibility exists depending on its course.

Based on this limited study we recommend a volume of LA of 3 ml at the level of C5 and another 2 ml at the level SCN of LA for clavicle surgeries.