The rule
When more than one surgical procedure is done during a single anesthetic, report the anesthesia code with the highest base units and the total anesthesia time for the whole session.
An example
A patient has a knee arthroscopy and a hand procedure in one session. You'd bill the code with the higher base units, with the full time from start to finish.
Bilateral procedures
For procedures on both sides, like both knees, bill the anesthesia code once with the total time. Bilateral modifiers aren't used on anesthesia claims.
Separate sessions
If the patient goes back to the OR later the same day under a new anesthetic, that's a new anesthesia service with its own claim line and time.
Add-on codes
A few anesthesia codes, like the obstetric add-ons, are designed to be billed together. Those follow their own rules. See labor epidural billing.
This article is general information, not billing, legal or tax advice. Payer rules change; always check current guidance.