Venous dimension of shock: Integrating arterial inflow and venous back-pressure in hemodynamic assessment

Figure 3 Simultaneous arterial-venous perfusion gradient-based bedside assessment of suspected shock or tissue hypoperfusion. After initial stabilization, persistent hypoperfusion should be assessed across three domains: Arterial inflow/forward flow, venous outflow/congestion, and microcirculatory perfusion. Suggested values are pragmatic reassessment triggers, not universal treatment thresholds. The aim is to identify whether ongoing hypoperfusion is driven by reduced arterial inflow, venous congestion, combined inflow-congestion failure, or residual microcirculatory dysfunction. ABC: Airway, breathing, circulation; AVPG: Arterial-venous perfusion gradient; CO: Cardiac output; CI: Cardiac index; CRT: Capillary refill time; CVP: Central venous pressure; IAP: Intra-abdominal pressure; IO: Intraosseus; IV: Intravenous; IVC: Inferior vena cava; LVOT-VTI: Left ventricular outflow tract velocity-time integral; MAP: Mean arterial pressure; PE: Pulmonary embolism; PEEP: Positive end-expiratory pressure; PLR: Passive leg raise; POCUS: Point-of-care ultrasound; Pv-aCO₂: Veno-arterial carbon dioxide tension difference; RV: Right ventricle/right ventricular; ScvO₂: Central venous oxygen saturation; SVI: Stroke volume index; VExUS: Venous excess ultrasound score; TR: Tricuspid regurgitation.