CPT code 36566 identifies the insertion of a tunneled central venous access device/catheter whose tip terminates in a central vein or the right atrium. As a commonly used durable vascular access procedure for long-term intravenous therapy, hemodialysis adjuncts, or frequent blood sampling, this code represents significant utilization across inpatient and outpatient procedural settings and is important for facility and physician billing workflows. Key national payers covered in this discussion include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. This publication explains the clinical and billing context for CPT code 36566, including service type, typical sites of service, and common coding considerations. Readers will find concise benchmarks on payer coverage patterns and authorization practices where available, a summary of clinical indications and procedural context, and notes on modifiers and billing scenarios relevant to tunneled central venous catheter insertion. Data not available in the input are identified explicitly. The guidance is intended for coding, billing, and policy audiences seeking a national overview of CPT code 36566 and related administrative considerations.