Source-backed quick answer
Critical care coding checks for CPT 99291 and 99292
Critical care coding should confirm that the record supports critical illness or injury, total critical care time, physician or qualified professional documentation, CPT 99291 or 99292 use, diagnosis pairing, and separately billable procedure rules.
CMS critical care guidance and the CMS PFS help billing teams check Medicare rules, time thresholds, add-on code logic, and payment status before claim submission.
- 99291 and 99292 time support
- Critical illness documentation
- ICD-10 and procedure pairing
- Unbundling and modifier review
Official sources
Critical Care Diagnosis Coding Principles
Critical care coding requires precise ICD-10 code selection because the diagnosis must justify both the critical care time code and any separately billable procedures. Unlike outpatient E/M where a single diagnosis code often suffices, critical care encounters routinely require three to six diagnosis codes to accurately represent the clinical picture and support the services billed. The primary diagnosis must reflect the critical condition driving the encounter, and secondary codes must support each separately billed procedure.
Sepsis Coding Sequences
Sepsis is the most common critical care diagnosis and has strict coding sequence rules. For sepsis without organ dysfunction: code the underlying infection first (B96.20 for unspecified E. coli, B95.62 for MRSA), then A41.x for the sepsis code (A41.01 sepsis due to MRSA, A41.51 sepsis due to E. coli, A41.9 sepsis unspecified organism). For severe sepsis: add R65.20 (severe sepsis without septic shock) or R65.21 (severe sepsis with septic shock), then code the specific organ dysfunction (N17.9 acute kidney failure, J96.00 acute respiratory failure).
The coding sequence matters for reimbursement. A41.9 as the primary diagnosis with R65.21 and the organ dysfunction codes supports critical care billing and maps to the appropriate DRG for the facility. Reversing the sequence or omitting the R65.2x code understates the severity and can trigger medical necessity denials on the critical care claim.
Respiratory Failure Classifications
Respiratory failure codes drive ventilator management billing and must be specific. J96.00 is acute respiratory failure, unspecified whether with hypoxia or hypercapnia. J96.01 is acute respiratory failure with hypoxia (the most common ICU presentation). J96.02 is acute respiratory failure with hypercapnia (common in COPD exacerbation). J96.20 is acute-on-chronic respiratory failure, used when a patient with chronic lung disease decompensates acutely. The specificity affects payer review: J96.01 with ventilator management (94002) is a clean combination, while J96.00 (unspecified) may trigger a request for additional documentation.
Critical Care CPT and ICD-10 Pairing Rules
The critical care time code (99291) pairs with the primary critical illness diagnosis. Ventilator management (94002/94003) pairs with the respiratory failure code (J96.x). Central line placement (36556) pairs with the condition requiring central access: sepsis requiring vasopressors (A41.x with R65.21), or the need for central medication delivery. Arterial line placement (36620) pairs with the condition requiring continuous hemodynamic monitoring, typically the same critical illness diagnosis. Intubation (31500) pairs with the respiratory failure code or the condition causing airway compromise.
Acute Kidney Injury Coding in the ICU
Acute kidney injury (AKI) is a frequent secondary diagnosis in critical care. Code N17.0 for AKI with tubular necrosis, N17.1 for AKI with acute cortical necrosis, N17.2 for AKI with medullary necrosis, and N17.9 for AKI unspecified. When AKI occurs as part of severe sepsis, it follows the R65.20/R65.21 code in the sequence as the organ dysfunction manifestation. If continuous renal replacement therapy (CRRT) is provided, use 90945 (dialysis procedure with single evaluation) or 90947 (with repeated evaluation), paired with the N17.x code.
Cardiac Arrest and Resuscitation Coding
Cardiac arrest coding uses I46.9 (cardiac arrest, unspecified), I46.2 (cardiac arrest due to underlying condition), or I46.8 (cardiac arrest due to other underlying condition). Resuscitation services are reported under the critical care time code; there is no separate CPT code for CPR by the physician. The time spent performing and directing resuscitation counts toward 99291/99292 total time. Post-cardiac arrest care (targeted temperature management, neurological monitoring) is coded as critical care with I46.x as the primary diagnosis and any resulting organ dysfunction as secondary codes (G93.1 anoxic brain damage, N17.9 AKI).