Shock is characterized by inadequate tissue oxygenation due to impaired oxygen delivery, increased demand, or inefficient utilization. Assessing fluid responsiveness is crucial to avoid under- or over-resuscitation. The central venous-to-arterial CO₂ difference (Pcv-aCO₂ gap) and left ventricular outflow tract velocity-time integral (LVOT-VTI) are proposed dynamic and biochemical markers for guiding fluid therapy. The study was done to evaluate the predictive value of Pcv-aCO₂ gap and LVOT-VTI for fluid responsiveness in critically ill patients with shock following a mini-fluid challenge