3.9 ESICM Guidelines on Circulatory Shock & Hemodynamic Monitoring

Shock refers to acute circulatory failure caused by various etiologies, with pathophysiological alterations of tissue hypoperfusion leading to oxygen supply–consumption imbalance, often accompanied by elevated lactate and multiple organ dysfunction, with mortality rates reaching 20%–50%. Early identification, precise assessment, and individualized hemodynamic management are keys to rescue. Building on the 2014 guidelines, the European Society of Intensive Care Medicine (ESICM) systematically summarized nearly a decade of evidence-based medicine and released the 2025 Guidelines on Circulatory Shock and Hemodynamic Monitoring (hereinafter 2025 Guidelines), updating key issues such as shock diagnosis, fluid responsiveness assessment, and blood pressure target setting. This section focuses on these hot topics, combining latest evidence and clinical practice for interpretation, providing reference for precise clinical hemodynamic management.

1. Shock Diagnosis: Tissue Perfusion Is More Important

The 2025 Guidelines provide clearer definitions for shock diagnosis, further emphasizing the importance of “tissue hypoperfusion” in the diagnostic system, while updating recommendations for tissue oxygenation monitoring, evolving shock diagnosis from single-indicator to multi-modal diagnostic systems. New diagnostic criteria cover three aspects: tissue hypoperfusion manifestations, hypotension (not mandatory), and lactate > 2 mmol/L. This standard further emphasizes that the essence of shock is “tissue hypoperfusion leading to oxygen supply–consumption imbalance,” with hypotension no longer a mandatory condition.

Clinical practice should focus on tissue hypoperfusion manifestations: (1) skin perfusion abnormalities (cold/clammy skin, mottling, prolonged capillary refill time [CRT]); (2) oliguria (<0.5 ml/kg/h); and (3) altered consciousness (lethargy, coma, agitation). CRT offers advantages of simplicity, non-invasiveness, and rapid bedside implementation; combined with skin temperature and mottling index assessment, it is suitable for early evaluation of all shock types. The ANDROMEDA-SHOCK-2 study showed that in early septic shock, personalized hemodynamic resuscitation targeting CRT outperformed usual care in primary composite endpoints (vasopressor, mechanical ventilation, and RRT duration). Hypotension is typically defined as MAP < 65 mmHg or systolic blood pressure < 90 mmHg, a common but non-mandatory diagnostic condition. Early shock sympathetic activation can maintain blood pressure via vasoconstriction; some patients only manifest tissue hypoperfusion without obvious hypotension. Thus, the guidelines explicitly emphasize avoiding early shock missed diagnosis due to sole reliance on blood pressure values. Lactate > 2 mmol/L is an important laboratory indicator for shock identification, with superior prognostic value over blood pressure. The guidelines recommend lactate > 2 mmol/L as a key diagnostic indicator, combined with lactate clearance rate for dynamic treatment evaluation, excluding non-hypoxic factors (liver dysfunction, drugs, metabolic acidosis). The latest TARTARE-2S study explored a targeted tissue perfusion (TTP) protocol based on CRT, peripheral skin temperature, arterial lactate monitoring, and maintaining MAP at 50–65 mmHg in ICU septic shock patients with lactate > 3 mmol/L. Compared to standard care, it did not increase days of survival with normal lactate and no vasopressors at 30 days, nor reveal additional safety concerns.

Compared to the 2014 guidelines, the 2025 guidelines propose two important updates in tissue oxygenation monitoring:

Pv-aCO₂ and Ca-vO₂ Ratio Monitoring. Pv-aCO₂ reflects tissue blood perfusion status, and Ca-vO₂ reflects oxygen supply–consumption balance; their ratio serves as a marker of anaerobic metabolism, especially suitable for patients with normal SvO₂ but persistent tissue hypoperfusion, complementing single-indicator limitations.

Microcirculation Assessment. The 2014 guidelines did not explicitly emphasize microcirculation assessment; the 2025 guidelines propose “when conditions permit, microcirculation assessment can be used as an auxiliary tool for comprehensive hemodynamic evaluation.” Shock’s essence is tissue hypoperfusion, and macrocirculation improvement (blood pressure, cardiac output) does not equate to microcirculation restoration, especially in distributive shock where microcirculatory dysfunction may persist, causing tissue hypoxia. Sublingual microcirculation visualization technology directly observes microcirculation status, identifying patients with normal macrocirculation but abnormal microcirculation, providing additional intervention basis. This update reflects a “macro–micro combined” multi-modal monitoring concept, aiding comprehensive tissue perfusion assessment.

In summary, although recent tissue perfusion-guided shock treatment protocols have not yet yielded definitive outcomes in shock therapy, the importance of tissue perfusion assessment and treatment is undeniable, requiring further optimization and validation in clinical research. Thus, in clinical practice, when facing suspected shock, physicians should first assess intuitive tissue perfusion indicators (skin perfusion, urine output, consciousness), synchronously test lactate levels; if tissue hypoperfusion manifestations or lactate > 2 mmol/L exist, even without hypotension, shock can be diagnosed. When conditions permit, further monitor Pv-aCO₂, the Pv-aCO₂/Ca-vO₂ ratio, and microcirculation status to comprehensively assess tissue oxygen supply–consumption balance, providing basis for optimizing hemodynamic therapy.

2. Fluid Responsiveness Assessment: Dynamic Indices Are Superior

Fluid resuscitation is the foundation of shock treatment; both fluid deficit and overload lead to poor outcomes in critically ill patients. Accurate fluid responsiveness assessment is a prerequisite for optimizing fluid therapy. Meta-analyses show that for shock patients on high tidal volume ventilation without spontaneous breathing, dynamic indices pulse pressure variation (PPV) and passive leg raising (PLR) achieve AUROC of 0.94, with high predictive value. Static indices like central venous pressure (CVP) are easily influenced by cardiac function, vascular tone, intra-abdominal pressure, etc., with low predictive accuracy. Thus, the 2025 guidelines recommend dynamic indices as first-choice for shock fluid responsiveness assessment, advising matching different dynamic indices to different scenarios based on ventilation status and pathophysiological mechanisms, providing technical support for precise fluid administration.

PLR. Elevating legs 45° returns lower extremity venous blood, simulating approximately 300 ml fluid load hemodynamic effects, with reversibility, avoiding ineffective fluid administration in non-responders. Broad application scope, unaffected by spontaneous breathing or arrhythmias, especially suitable for patients with strong spontaneous breathing unable to cooperate with controlled ventilation. Note: intra-abdominal hypertension may cause false-negative PLR results, requiring exclusion of this interference.

End-expiratory occlusion test (EEOT). Briefly interrupting mechanical ventilation (usually 15–30 s) eliminates alveolar pressure impact on RV preload/afterload, observing cardiac output changes to assess fluid responsiveness. Simple operation, short duration, can serve as PLR alternative, but only applicable to fully controlled ventilation patients. Additionally, EEOT’s cardiac output change threshold for fluid responsiveness (5%) approaches the minimum detectable change of most cardiac output monitoring technologies, requiring high-precision devices (pulse contour analysis, echocardiography).

PPV & stroke volume variation (SVV). Based on cyclical alveolar pressure changes during mechanical ventilation affecting RV preload/afterload and LV afterload, causing cyclical stroke volume and pulse pressure fluctuations; larger fluctuations indicate higher fluid responsiveness. Accuracy depends on stable cardiopulmonary interaction, suitable for mechanically ventilated patients without arrhythmias, no spontaneous breathing, and tidal volume ≥ 8 ml/kg. Vascular tone changes, reduced lung compliance, etc., may also affect results, requiring holistic interpretation.

Inferior vena cava (IVC) diameter variation. Ultrasound measurement of IVC diameter changes during respiratory cycles to assess fluid responsiveness, widely used in critically ill patients. However, a study of 540 acute circulatory failure patients showed overall AUROC of IVC variability is only 0.63, dropping to 0.60 in hypotensive/high lactate patients, with limited predictive value. IVC is easily influenced by spontaneous breathing, intra-abdominal pressure, cardiac function, etc.; guidelines do not recommend using IVC alone to assess fluid responsiveness.

In the authors’ opinion, clinicians applying dynamic indices for fluid responsiveness assessment should consider: (1) strictly match patient ventilation status to avoid misinterpretation in unsuitable scenarios; (2) dynamic indices rely on accurate cardiac output or surrogate measurement, requiring attention to deviations from low-precision devices; and (3) fluid responsiveness is not constant; dynamic assessment during treatment is needed, adjusting fluid therapy strategies via monitoring fluid tolerance.

3. Blood Pressure Targets: Emphasizing Individualized Settings

Pathophysiologically, MAP is the determinant of perfusion pressure for all organs except the left ventricle. A retrospective analysis of 77,328 septic shock patients showed the association strength between MAP and ICU mortality is significantly higher than systolic, diastolic, and pulse pressure, further validating the rationality of MAP as the core blood pressure regulation target. The 2025 guidelines recommend initial MAP target of 65–70 mmHg for septic shock patients; studies show MAP < 65 mmHg is significantly associated with increased mortality and organ dysfunction risk (e.g., AKI). However, note that 65–70 mmHg is the “minimum effective resuscitation threshold,” not the ultimate target; if tissue perfusion fails to improve, blood pressure target strategy requires further optimization.

The 2014 guidelines uniformly recommended initial MAP target of at least 65 mmHg for all shock patients. The 2025 guidelines emphasize individualized blood pressure target setting, following “tissue perfusion guidance,” proposing differentiated blood pressure targets for different populations, reflecting the essence of refined shock resuscitation management.

Septic shock with chronic hypertension history. The guidelines suggest higher MAP targets. Chronic hypertension patients’ organ perfusion pressure–blood flow curve shifts rightward; using conventional 65–70 mmHg MAP targets may fail to meet baseline organ perfusion needs, causing occult tissue hypoperfusion. However, the latest OPTPRESS study on blood pressure targets in Japanese elderly septic shock patients showed significantly increased mortality in the high-target MAP group (80–85 mmHg) vs control (65–70 mmHg). In the authors’ opinion, for chronic hypertension septic shock patients, reasonable MAP targets should be individualized and titrated based on tissue perfusion improvement (skin perfusion recovery, clear consciousness, lactate decrease), not fixed values.

Elevated CVP. Effective organ perfusion pressure depends on the MAP–CVP pressure gradient. When CVP is elevated, even if MAP is within conventional target ranges, actual organ perfusion pressure may still decrease, damaging organ function. Thus, the guidelines suggest higher MAP targets. Scenarios like cardiogenic shock and severe pulmonary edema often accompany elevated CVP; besides increasing MAP to maintain sufficient pressure gradient for organ perfusion, reverse fluid resuscitation via diuretics should be used to avoid secondary organ injury from venous congestion; specific MAP targets require clinical adjustment.

Traumatic hemorrhagic shock without traumatic brain injury (TBI) and uncontrolled bleeding. The guidelines recommend initial systolic blood pressure target of 80–90 mmHg (corresponding MAP 50–60 mmHg), i.e., “permissive hypotension” strategy. This strategy balances bleeding control and basic tissue perfusion; excessive blood pressure may cause vessel rupture worsening bleeding, while too low blood pressure may cause vital organ ischemia. Studies show permissive hypotension reduces bleeding volume and mortality in uncontrolled bleeding trauma patients. However, for TBI patients with Glasgow Coma Scale ≤ 8, the guidelines recommend initial MAP target ≥ 80 mmHg, as brain injury requires sufficient cerebral perfusion pressure to avoid exacerbating secondary brain injury from ischemia/hypoxia.

The 2025 guidelines provide clear guidance on shock blood pressure target setting, but issues requiring further exploration remain: specific thresholds for “higher MAP targets” in chronic hypertension patients are unclear, quantitative standards for MAP adjustment threshold matching with CVP in high-CVP patients are lacking, requiring more prospective research. Blood pressure target achievement relies on vasopressors, fluid resuscitation, etc.; clinical practice must balance intervention benefits and risks (e.g., excessive vasopressors may cause over-vasoconstriction worsening tissue ischemia; excessive fluid resuscitation may cause pulmonary edema, intra-abdominal hypertension). Thus, clinical practice must combine MAP targets with tissue perfusion indices and organ function status, implementing multi-modal assessment, avoiding intervention solely guided by blood pressure values.

4. Summary

The 2025 guidelines propose a series of evidence-based recommendations around key issues of shock diagnosis, fluid responsiveness assessment, and blood pressure target setting. Shock diagnosis shifts from single-indicator reliance to multi-indicator combination focusing on tissue perfusion; fluid responsiveness assessment shifts from static to dynamic indices with clear applicable scenarios; blood pressure targets shift from standardized thresholds to individualized regulation, making shock diagnosis and treatment more “precise” and “multi-modal.” The guidelines’ application must still combine clinical reality, avoiding mechanical copying. Current unresolved issues, such as specific MAP thresholds for special populations, interpretation standards for dynamic index “gray zones,” and clinical translation value of microcirculation monitoring, require further clarification through high-quality prospective research. In the future, with the development of precision medicine technologies such as point-of-care testing and artificial intelligence, hemodynamic monitoring and treatment will inevitably become more individualized and intelligent.

(Liu Jingquan, Yang Xianghong; Zhejiang Provincial People’s Hospital)

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