APLS Workup Components Unaffected by Anticoagulant Therapy
The APACHE II score components that are NOT affected by anticoagulant therapy include: age, admission diagnosis (surgical vs medical), pre-ICU renal status, and the physiologic variables (temperature, heart rate, respiratory rate, oxygenation, arterial pH, serum sodium, serum potassium, serum creatinine, hematocrit, white blood cell count, and Glasgow Coma Scale). 1
Components Affected vs Unaffected by Anticoagulation
Unaffected Components
The APACHE II scoring system includes multiple variables that remain independent of anticoagulant therapy:
- Demographic factors: Age is a fixed variable unaffected by any medication 1
- Admission characteristics: Type of admission (surgical vs medical) and pre-ICU renal status are determined before anticoagulation decisions 1
- Physiologic parameters: The core vital signs and laboratory values (temperature, heart rate, respiratory rate, mean arterial pressure, oxygenation, arterial pH, serum electrolytes, serum creatinine, hematocrit, white blood cell count, and Glasgow Coma Scale) are not directly altered by anticoagulant administration 1
Components That ARE Affected by Anticoagulation
The evidence clearly identifies coagulation parameters as the primary variables influenced by anticoagulant therapy:
- INR (International Normalized Ratio): Directly prolonged by anticoagulants, particularly warfarin and heparin 1
- aPTT (activated Partial Thromboplastin Time): Significantly affected by heparin therapy, with studies showing HR 1.2 (1.1-1.3) for every 10-second increase in bleeding risk 1
- Platelet count: Can be indirectly affected through heparin-induced thrombocytopenia or anticoagulant-related bleeding complications 1
Clinical Context for Risk Assessment
Studies examining bleeding risk in ICU patients identified that while coagulation parameters (INR, aPTT, platelet count) are affected by anticoagulation, the APACHE II score itself—which includes admission diagnosis, age, and pre-ICU renal status—remains a valid predictor of mortality independent of anticoagulation status 1. The risk assessment models that incorporate APACHE II scoring maintain their prognostic value because the majority of scoring components are physiologic and demographic variables unrelated to coagulation 1.
Important Clinical Caveats
Do not confuse coagulation monitoring with APACHE scoring: While coagulation parameters (INR, aPTT) are critical for monitoring anticoagulation therapy and bleeding risk, they are not components of the APACHE II score itself 1. The APACHE II score focuses on acute physiologic derangements and chronic health status, not coagulation status 1.
Anticoagulation affects bleeding risk assessment, not severity scoring: Studies demonstrate that therapeutic heparin increases bleeding risk (HR 3.26,1.72-6.17), but this represents a treatment complication rather than a change in the underlying severity of illness captured by APACHE scoring 2.