Anesthesia billing - Supplies and Drugs Modifiers - ZM, ZN

Supplies and Drugs Modifiers

Medi-Cal providers must bill with the following modifiers for supplies and drugs used in performing surgical procedures (CPT-4 codes 10000 – 69999):

Modifier    Definition
    ZM -   Supplies and drugs used in this surgical procedure with other than general anesthesia or no anesthesia.
  ZN  -   Supplies and drugs used in this surgical procedure with general anesthesia.  Supplies and drugs include items such as disposable supplies, anesthetic gases, volatile liquids and all parenteral drugs related to rendering the patient completely unconscious.

Note:    Procedure code-supply modifier combination replaces the use of CPT-4 code 99070 for billing supplies related to surgical procedures.  If CPT-4 code 99070 is used, the claim will be denied.


Billing Requirements

Modifiers ZM and ZN are mutually exclusive; therefore, only one modifier is allowed for each surgical procedure.  To prevent claim denial, select the appropriate modifier based on the preceding description.


Duplicate Billing

Medi-Cal policy limits reimbursement of a surgical procedure with modifier ZM or ZN to one provider, for the same recipient and date of service.  Second and subsequent claims billed for the same procedure with the same modifier ZM or ZN for the same date of service to the same recipient and submitted by the same or different provider(s) will be denied.

    Modifiers ZM or ZN will not conflict with the use of other required modifiers.  For example, modifier AG (primary surgeon) or 80 (assistant surgeon) may be used on separate lines with ZM or
ZN on the same claim form.


Services Performed More Than Once on the Same Day

A surgical procedure with modifier ZM or ZN performed more than once on the same day on the same recipient by the same or different provider(s) requires additional documentation indicating that the service was performed more than once on the same day.  This information may be attached to the claim or entered in the Remarks field (Box 80)/Reserved for Local Use field (Box 19) of the claim.


Anesthesia Injection Codes Not Separately Reimbursable

Local or general anesthesia injections are not separately reimbursable if a claim was previously submitted with a surgical procedure and modifier ZM or ZN.  If a local or general anesthetic is billed separately for the same recipient on the same date of service by the same or different provider, the claim will be reduced by the amount previously paid.  For more information, refer to the Supplies and Drugs section of this manual.