Clinical meaning
Critical care medicine manages life-threatening organ dysfunction requiring intensive monitoring and organ support. Shock represents inadequate tissue perfusion classified by etiology: distributive (septic -- most common ICU shock; vasodilatory from cytokine-mediated endothelial dysfunction), cardiogenic (pump failure from MI, cardiomyopathy, valve dysfunction), hypovolemic (hemorrhage, dehydration), and obstructive (PE, tension pneumothorax, cardiac tamponade). ARDS (acute respiratory distress syndrome) involves diffuse alveolar damage from pulmonary or extrapulmonary insults, causing non-cardiogenic pulmonary edema with bilateral infiltrates and refractory hypoxemia. Multi-organ dysfunction syndrome (MODS) is the progressive failure of two or more organ systems, driven by dysregulated inflammatory response, with mortality increasing by 15-20% per organ system involved.
Diagnosis & workup
Diagnostics & workup: - Hemodynamic monitoring: arterial line (continuous BP, ABG access), central venous pressure (CVP via CVC), pulmonary artery catheter (PCWP, CO, SVR -- rarely used now), non-invasive cardiac output monitoring (PiCCO, FloTrac) - Shock differentiation by hemodynamics: Septic (low SVR, high CO, low CVP) → Cardiogenic (high SVR, low CO, high PCWP) → Hypovolemic (high SVR, low CO, low CVP) → Obstructive (variable based on cause) - ARDS Berlin criteria: acute onset (≤1 week), bilateral opacities on CXR not fully explained by effusions/atelectasis, respiratory failure not fully explained by cardiac failure, P/F ratio classification: mild 200-300, moderate 100-200, severe <100 (on PEEP ≥5) - Point-of-care ultrasound (POCUS): cardiac function, IVC collapsibility (volume status), lung ultrasound (B-lines = pulmonary edema, A-lines = normal/pneumothorax), pleural effusion - Lactate: >2 mmol/L indicates tissue hypoperfusion; trend clearance to monitor resuscitation (>10% clearance per 2 hours is favorable) - ScvO2 (central venous oxygen saturation): <70% indicates increased oxygen extraction (inadequate delivery) -- target ≥70% with resuscitation