Anesthesia is paid on a formula no other specialty uses, and small errors in any part of it repeat on every case. If you want to understand exactly why two practices doing the same surgeries can collect very different amounts — or you're evaluating an anesthesia billing company in Texas — start with how the math actually works.
The Anesthesia Payment Formula
Every anesthesia claim comes down to one equation:
Four variables, each with its own rules. Get any one wrong and the error compounds across your entire case volume. Here's how each works.
Base Units
Each anesthesia CPT code (00100–01999) carries a fixed base-unit value from the American Society of Anesthesiologists' Relative Value Guide, reflecting the complexity of the procedure. Anesthesia for open-heart surgery carries far more base units than a peripheral procedure. The base value is set — the skill is mapping the surgical procedure to the correct anesthesia code and base value, every time.
Time Units
Time units capture the duration of care. Anesthesia time starts when the provider begins preparing the patient and ends when they are no longer in personal attendance. Most payers convert time at one unit per 15 minutes, but some use 10- or 12-minute increments or actual minutes — and the rounding method materially changes the payment. Reported time must reconcile with the anesthesia record; missing or implausible time is one of the most common denials, as covered in our Texas anesthesia denials guide.
Modifying Units
Modifying units come from the patient's physical status (P3 +1, P4 +2, P5 +3) and qualifying circumstances such as emergency conditions (99140, +2) or extreme age (99100, +1). The catch: Medicare does not pay for these units, but many commercial payers do. Applying them uniformly across payers either leaves money uncollected or triggers denials — they have to be handled payer by payer, with documentation.
The Conversion Factor (2026)
The conversion factor is the dollar value multiplied by total units. For calendar year 2026, the national Medicare anesthesia conversion factor is approximately $20.50 (about $20.4976), a slight increase over 2025. Texas localities are published by Novitas, the state's Medicare contractor, and commercial conversion factors typically run higher than Medicare. Out-of-network is a different world entirely — there's no contracted factor, which is where negotiation creates the biggest upside.
| Payer type | Conversion factor basis (2026) | Notes |
|---|---|---|
| Medicare (Texas) | ~$20.50 national; locality-adjusted by Novitas | No P-status / qualifying-circumstance units paid |
| Commercial (BCBS TX, UHC, Aetna, Cigna) | Negotiated; typically above Medicare | Rounding & modifier rules vary by payer |
| Out-of-network | No set factor — benchmarked & negotiated | Up to 6× Medicare with active negotiation / IDR |
Conversion factors change annually and by locality; confirm the current figure for your Medicare locality and each commercial contract.
How to Collect More Per Case
Higher anesthesia reimbursement rarely comes from one big change — it comes from getting every variable right, consistently. The practices that collect the most do these things:
| Lever | What it does |
|---|---|
| Reconcile & round time per payer | Captures every legitimate time unit; stops silent underbilling |
| Match modifiers to staffing | Protects full vs. split unit value; avoids audits |
| Apply P-status / QC where paid | Recovers commercial units Medicare won't pay |
| Keep clean-claim rate at 98%+ | Faster payment, fewer reworks; ~20% fewer denials |
| Audit claims monthly | Catches modifier and time patterns before they compound |
| Negotiate out-of-network | The single largest upside — up to 6× Medicare per claim |
The biggest lever for most Texas groups is out-of-network reimbursement, because anesthesiologists are so frequently non-contracted. How Texas handles that — SB 1264 versus the federal No Surprises Act — is its own topic, covered in our guide to out-of-network anesthesia in Texas. For the full coding mechanics, see our anesthesia medical billing page.
Sources & references: Centers for Medicare & Medicaid Services (CY 2026 Physician Fee Schedule / anesthesia conversion factor); American Society of Anesthesiologists (Relative Value Guide & Medicare conversion factors); Novitas Solutions (Texas anesthesia conversion factors). Figures are approximate and change annually; confirm current values for your locality and payers. General information, not coding or legal advice. Last reviewed June 2026.