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Microcirculatory dysfunction during cardiac surgery remains heterogeneous and inconclusive in current clinical evidenceMicrocirculation in Cardiac Surgery: What We Know and What Remains Unclear

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Key Takeaway
Note that clinical evidence for microcirculatory dysfunction in cardiac surgery remains heterogeneous and inconclusive.

This narrative review addresses microcirculatory dysfunction in patients undergoing cardiac surgery with cardiopulmonary bypass. The scope includes secondary outcomes such as endothelial dysfunction, inflammation, oxidative stress, and organ dysfunction. The authors highlight that clinical evidence remains heterogeneous and inconclusive across these domains.

The review notes that clinical use remains limited by technical challenges and a lack of standardized endpoints. Frequently, the evidence relies on indirect evidence of organ dysfunction rather than direct measures of microvascular perfusion. Important gaps remain in translating findings from experimental models to patients, which affects the certainty of conclusions drawn from preclinical studies that often support biologic plausibility but lack clinical confirmation.

The authors suggest that greater integration of bedside imaging and biomarkers with biophysiological principles may help establish microcirculation as both a mechanistic endpoint and a therapeutic target in cardiac surgery. However, the review does not report specific adverse events, sample sizes, or pooled effect sizes for interventions like volatile anesthetics or statins. The overall certainty is low due to the heterogeneous nature of the available clinical data.

This narrative review examines how cardiopulmonary bypass affects patients undergoing cardiac surgery. The authors looked at various outcomes like inflammation, oxidative stress, and organ dysfunction. Because the study is a review, it does not report new patient data or a specific sample size. Instead, it synthesizes existing information about these complex biological processes.

The evidence remains heterogeneous and inconclusive. Many findings come from preclinical models or rely on indirect measures rather than direct observation of microvascular perfusion in humans. Technical challenges and a lack of standardized endpoints make it difficult to draw firm conclusions about what works best for patients.

Readers should understand that while lab studies suggest certain mechanisms, translating these findings to clinical practice is still difficult. Important gaps remain in moving from experimental models to real-world patient care. Greater integration of bedside imaging and biomarkers may help clarify these issues in the future, but current clinical evidence is not yet definitive.

What this means for you:
Current clinical evidence on microcirculation in cardiac surgery is mixed and relies on indirect measures.

Study Details

Study typeSystematic review
EvidenceLevel 1
PublishedJun 2026
View Original Abstract ↓
Cardiopulmonary bypass (CPB) is a crucial component of cardiac surgery, yet postoperative organ dysfunction remains common despite apparently adequate systemic hemodynamics. This mismatch underscores the importance of the microcirculation, where oxygen delivery and extraction ultimately occur. Increasing evidence suggests that CPB disrupts capillary perfusion through endothelial dysfunction, glycocalyx shedding, inflammation, oxidative stress, hemodilution, functional shunting, and microthromboemboli, thereby causing tissue hypoxia despite normal macro-hemodynamic stability. This review summarizes the physiology of microcirculation and examines the mechanisms by which CPB impairs microvascular function. We also review current tools for microcirculatory assessment, including orthogonal polarization spectral, sidestream dark field, and incident dark field imaging, near-infrared spectroscopy, and circulating biomarkers of endothelial and glycocalyx injury. Although these approaches have improved mechanistic insight, their clinical use remains limited by technical challenges and the lack of standardized endpoints. We further evaluate cardioprotective strategies aimed at preserving microcirculatory function during CPB. These include perfusion and mechanical approaches, ischemic preconditioning, glycocalyx-preserving therapies, and various pharmacologic interventions such as volatile anesthetics, nitric oxide, statins, antioxidants, and antithrombotic agents. Across these domains, preclinical studies often support biologic plausibility, whereas clinical evidence remains heterogeneous and inconclusive and frequently relies on indirect evidence of organ dysfunction rather than direct measures of microvascular perfusion. Important gaps remain in translating findings from experimental models to patients, and greater integration of bedside imaging and biomarkers with biophysiological principles may help establish microcirculation as both a mechanistic endpoint and a therapeutic target in cardiac surgery.
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