Summary & Overview

HCPCS G9771: Peri-Anesthesia Temperature Measurement

HCPCS Level II code G9771 documents a peri-anesthesia temperature measurement meeting a specified threshold: at least one reading ≥35.5°C (95.9°F) within the 30 minutes before or 15 minutes after anesthesia end time. Nationally, perioperative temperature monitoring is an important safety and quality metric because peri-anesthetic hypothermia is associated with adverse outcomes including surgical site infection, coagulopathy, and prolonged recovery. Clear documentation that temperature criteria are met supports quality reporting and care continuity.

This analysis covers major national payers including Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise primer on the code’s clinical intent, the service setting typically involved, and what to expect in billing and reporting contexts. The report summarizes how the code is used for perioperative monitoring, highlights common modifiers and typical service lines (Data not available in the input for specific taxonomies and diagnoses), and outlines benchmarks and policy considerations relevant at the national level. The content is aimed at coding and billing professionals, perioperative clinicians, and policy stakeholders seeking a clear, practical overview of HCPCS Level II code G9771 and its role in peri-anesthesia quality measurement.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicareG9771HCPCS Level IIperi-anesthesiatemperature monitoringperioperative carequality measureanesthesia

Billing Code Overview

HCPCS Level II code G9771 indicates that at least one body temperature measurement of at least 35.5°C (95.9°F) was achieved within the 30 minutes immediately before or 15 minutes immediately after the anesthesia end time. This measure documents peri-anesthetic temperature status surrounding the end of anesthesia care.

Service type: Peri-anesthesia monitoring / Measurement of core body temperature related to anesthesia care

Typical site of service: Operating room, procedure suite, or other anesthesia-provided perioperative settings where intraoperative and immediate post-anesthesia vital signs are recorded

Clinical & Coding Specifications

Clinical Context

A 68-year-old male undergoes an elective total knee arthroplasty under general anesthesia with peripheral nerve block. Near the end of the procedure the anesthesia team performs routine perioperative temperature monitoring. A core temperature measurement of 36.0°C (96.8°F) is recorded 10 minutes before anesthesia end time using an esophageal or bladder probe. This measurement meets the criterion for billing because at least one body temperature ≥ 35.5°C (95.9°F) was achieved within the 30 minutes immediately before or 15 minutes immediately after anesthesia end time. The typical workflow includes continuous intraoperative temperature monitoring by the anesthesia provider, documentation in the anesthesia record of time-stamped temperature values, correlation with anesthesia end time, and attaching the appropriate HCPCS Level II code G9771 on the anesthesia claim when documentation supports the timing and value requirements. Typical site of service is an inpatient or ambulatory surgical center where procedures under monitored anesthesia care or general/regional anesthesia are performed.

Coding Specifications

Modifier	Description	When to Use
`22`	Increased procedural services	Use when unusually complex anesthesia-related temperature management significantly increases the work of the anesthesia team and documentation supports increased complexity.
`23`	Unusual anesthesia	Use when general anesthesia is administered for procedures that normally do not require it, affecting perioperative monitoring including temperature management.
`52`	Reduced services	Use when the anesthesia service or monitoring was partially reduced but documentation supports partial performance relative to usual care.
`53`	Discontinued procedure	Use when anesthesia was discontinued due to extenuating circumstances before completion of planned services, with temperature measurement documented per timing rules.
`54`	Surgical care only	Use when the billing provider is the surgeon for the operative period and anesthesia services are billed separately; modifier rarely applied to anesthesia claims but listed for completeness.
`55`	Postoperative management only	Use when the billing provider performed only postoperative anesthesia services; temperature measurement timing must still meet `G9771` criteria.
`56`	Preoperative management only	Use when only preoperative anesthesia management was provided and temperature documentation falls within the required time window.
`62`	Two surgeons	Use when two surgeons are required and anesthesia documentation including temperature is associated with the case where two surgeons participated.
`AS`	Medically directed anesthesia service	Use when the anesthesiologist medically directs the anesthesia team and documents relevant monitoring including temperature.
`CQ`	Service furnished under an AD separately payable under Part B (CRNA service)	Use when certified registered nurse anesthetist (CRNA) furnishes the service under Medicare Part B billing rules and temperature monitoring is provided.
`QK`	Medical direction of two or more CRNAs by an anesthesiologist	Use when an anesthesiologist medically directs multiple CRNAs and documents monitoring responsibilities including temperature.
`QX`	CRNA service with medical direction by a physician	Use when a CRNA furnishes the anesthesia service under direction and documents temperature monitoring.
`QY`	Medical direction of one CRNA by an anesthesiologist	Use when an anesthesiologist medically directs one CRNA and documents monitoring including temperature.

Taxonomy Code	Specialty	Notes
207L00000X	Anesthesiology	Primary specialty responsible for intraoperative monitoring and documentation of core temperature.
208800000X	Surgery	Surgeons rely on anesthesia monitoring; relevant when coordinating perioperative care and claims.
363A00000X	Critical Care Medicine	In higher-acuity cases where anesthesiology and critical care overlap for temperature management postoperatively.
363LP0800X	Pain Management	Regional anesthesia practitioners who may perform blocks and monitor perioperative vitals including temperature.
207LP2900X	Nurse Anesthetist	CRNAs who frequently provide intraoperative monitoring and documentation required for `G9771`.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
Data not available in the input.	Data not available in the input.	Data not available in the input.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`00530`	Anesthesia for procedures on knee joint; total knee arthroplasty (TKA)	Common primary anesthesia procedure code billed for the case in which perioperative temperature measurement qualifying for `G9771` is obtained.
`01482`	Anesthesia for patient of extreme age, younger than 1 year; not applicable in this adult example but relevant in pediatrics where temperature monitoring is critical	Temperature monitoring documentation and timing rules apply across age extremes when billing `G9771`.
`01936`	Anesthesia for open or surgical arthroscopic procedures on knee; may be billed for complex knee surgeries	Often billed alongside intraoperative monitoring codes; temperature documentation supports `G9771`.
`99100`	Anesthesia for patient of extreme age, 5 years or younger, or older than 70 years, complicated by comorbidities or performed under special circumstances	Older patients often require closer temperature monitoring; used in cases that may justify heightened documentation for `G9771`.
`01990`	Anesthesia for diagnostic or therapeutic nerve blocks and injections (not otherwise specified)	Regional techniques that accompany general anesthesia or sedation and where perioperative temperature monitoring is recorded and relevant to `G9771`.