CPT code 99135 denotes the use of controlled hypotension as an anesthesia add-on service when the anesthesia provider deliberately lowers a patient's blood pressure to facilitate certain surgical procedures. This procedural adjunct matters nationally because it represents a clinically significant modification of anesthetic management that can affect resource use, perioperative risk profiles, and billing complexity. Coverage and payment vary across major national payers and Medicare, which are central to adjudication and clinical documentation expectations. Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will learn the clinical context in which 99135 is reported, typical sites of service where it is used, common billing modifiers associated with anesthesia services, and the implications for claims submission and payer review. The publication summarizes benchmarks and policy nuances relevant to national payers and provides a concise reference for coding staff and anesthesia billing professionals. Data not available in the input for associated taxonomies, ICD-10 diagnosis pairings, and specific payer coverage rules is noted where applicable.