“Cool Knees” as a Measure of Systemic Vascular Resistance in Cardiac Patients

Introduction: Clinical assessment of cardiac output (CO) and systemic vascular resistance (SVR) in cardiac patients is often inaccurate. Since the genicular arteries form a watershed zone accessible to physical examination, we hypothesized that “cool knees” would reflect abnormalities in central hemodynamics. Methods: Nineteen patients with cardiac diagnoses, but without distributive shock, had a measurement of skin temperature over the thigh, knee, and foot in parallel with central hemodynamics derived from invasive monitoring. Results: The temperature gradient from thigh to knee (DTK) reflected increased SVR, and was significantly correlated with SVR, cardiac index (CI), and CO. Cool feet (DTF) were significantly correlated only with systemic hypotension, but not central hemodynamics. Conclusion: Cool knees reflect increased SVR in cardiac patients and may be an important physical exam finding in their assessment and management.