Frédéric Caruso, MD

🫀Hemodynamic stability does not necessarily mean adequate tissue perfusion. A patient with septic shock reaches a MAP of 65 mmHg, cardiac output improves, and vasopressor requirements decrease. Yet capillary refill remains prolonged, lactate is elevated, and organ dysfunction persists. Has resuscitation succeeded? Dr. Carlos Sanchez-Escalante and Xavier Monnet propose a fundamental shift: perfusion assessment should focus on physiological coherence rather than normalization of isolated numbers. The central problem is that macrocirculatory recovery does not guarantee microcirculatory recovery. CRT provides a practical starting point. It is inexpensive, rapidly responsive, and supported by clinical evidence. However, temperature, sympathetic activity, edema, and measurement technique influence its interpretation. Lactate remains valuable for risk assessment, but hyperlactatemia does not necessarily indicate persistent tissue hypoxia. Adrenergic stimulation, altered metabolism, and impaired clearance may sustain elevated concentrations after perfusion improves. Treating every persistent lactate elevation with additional fluids or vasopressors risks producing congestion rather than restoring perfusion. Venous oxygen saturation and the venoarterial CO₂ gap offer complementary information. SvO₂ reflects the relationship between oxygen delivery and consumption, but normal values cannot exclude impaired extraction or microcirculatory shunting. The Pv-aCO₂ gap helps assess whether blood flow is sufficient relative to metabolic CO₂ production. Neither measurement directly demonstrates microcirculatory recovery. Peripheral perfusion index, obtained through photoplethysmography, provides continuous information about peripheral circulatory changes. Its interpretation requires attention to temperature, vascular tone, and vasopressor exposure. When uncertainty persists, advanced assessment may incorporate cardiac output, tissue oxygenation, microcirculatory imaging, and venous congestion. An especially relevant concept is effective tissue perfusion pressure. MAP alone does not determine regional blood flow. Critical closing pressure, vascular tone, extravascular compression, and venous outflow influence the pressure gradient available for tissue perfusion. Consequently, increasing arterial pressure may not improve organ perfusion, particularly when vascular resistance or venous congestion is elevated. The authors propose a progressive approach: begin with clinical examination and basic markers, integrate complementary measurements when signals disagree, and escalate monitoring according to unresolved uncertainty and patient risk. The objective of resuscitation is not to normalize every variable. It is to restore effective tissue perfusion without creating additional injury through unnecessary interventions. Reference 📚 Sanchez-Escalante C, Monnet X. 2026. Critical Care Medicine. doi.org/10.1097/CCM.00000000…