Debra is absolutley correct. Below is an excerpt from "Anesthesia & Pain Coder's Pink Sheet". An example was provided....
Procedure: Left T4, 5, 6, and 7 intercostal nerve blocks #4.
64421 [Injection, anesthetic agent] intercostal nerves, multiple, regional block.
"Even though the pain physician performs four injections, you should only bill the code once, since the CPT definition already accounts for multiple injections. Report this code with ‘1' unit of service"