Section 1.2: Capillary Refill Time-Guided Individualized Resuscitation in Septic Shock

Capillary refill time (CRT) has emerged as a rapid, non-invasive bedside marker of peripheral perfusion and microcirculatory function. In shock states, blood flow is shunted away from cutaneous vessels to prioritize vital organ perfusion. CRT prolongation reflects not only reduced perfusion pressure but also microvascular dysfunction, endothelial activation, and microthrombosis. Rapid CRT normalization after intervention suggests volume responsiveness, whereas persistent prolongation may indicate microcirculatory failure. Consequently, international sepsis guidelines and multiple clinical trials now recommend CRT as a key parameter for guiding hemodynamic resuscitation.

I. Theoretical Basis of CRT in Perfusion Assessment

CRT measures the time required for capillary beds to refill after pressure-induced blanching. Prolonged CRT strongly correlates with inadequate tissue perfusion, particularly in septic shock. Meta-analyses demonstrate a weak but statistically significant inverse correlation between mean arterial pressure (MAP) and CRT (r = –0.158, P < 0.001), indicating that maintaining MAP ≥65 mmHg does not guarantee microcirculatory normalization. A 2025 prospective study confirmed a strong correlation between CRT and skin blood flow (SBF) (r = 0.89, P < 0.0001), independent of infection status or norepinephrine use. While dynamic changes in SBF and CRT remain linked during resuscitation (P < 0.0001), the correlation weakens (r ≈ 0.34), suggesting confounding factors such as environmental temperature, skin pigmentation, sympathetic overdrive, or macro-microcirculatory uncoupling in late-stage shock.

II. CRT in Individualized Septic Shock Resuscitation

Fluid resuscitation remains foundational in septic shock, but excessive fluid administration risks organ edema and dysfunction, while inadequate resuscitation perpetuates hypoperfusion. CRT provides a practical, low-cost endpoint to guide fluid initiation, titration, and cessation.

ANDROMEDA-SHOCK (2019): A multicenter RCT (n=424) compared CRT-guided resuscitation (target ≤3s) versus lactate-guided resuscitation (20% reduction every 2 hours) over 8 hours. Although 28-day mortality showed no statistical difference (34.9% vs. 43.4%, P=0.06), the CRT group received significantly less intravenous fluid, exhibited fewer organ dysfunctions, and demonstrated a Bayesian posterior probability >90% favoring CRT-guided therapy.

ANDROMEDA-SHOCK-2 (2025): A landmark multinational RCT (n=1,501 across 86 ICUs) evaluated the CRT-Guided Personalized Hemodynamic Resuscitation (CRT-PHR) algorithm versus standard care. The 6-hour protocol strictly follows an assess-intervene-reassess loop:

  • Step 1: Hourly CRT assessment. If CRT ≥3s:

    • Pulse pressure <40 mmHg → Assess fluid responsiveness. If positive, administer 500 mL crystalloid/colloid over 30 min (max 1,000 mL), then reassess.

    • Pulse pressure ≥40 mmHg & diastolic BP <50 mmHg → Titrate norepinephrine to raise diastolic BP >50 mmHg (maintaining MAP ≥65 mmHg).

  • Step 2: If CRT remains abnormal after 1h → Bedside echocardiography. If ventricular dysfunction is present, initiate inotropes. If absent or CRT persists, repeat fluid responsiveness testing.

  • Step 3: If targets unmet → Conduct two 1-hour tests:

    • MAP Test: Temporarily increase norepinephrine to maintain MAP 80–85 mmHg (for chronic hypertension). If CRT normalizes, maintain this target.

    • Dobutamine Test: Administer fixed low-dose dobutamine [5 μg/kg/min]. Discontinue if CRT does not normalize.

Results: 65% of patients achieved CRT normalization with Step 1 alone. The intervention group demonstrated a win ratio of 1.16 (95% CI 1.02–1.33, P=0.04) for the composite outcome of mortality, life support duration, and hospital stay, driven primarily by reduced life support duration.

III. Clinical Significance & Limitations

CRT-PHR validates a paradigm shift from fixed-volume protocols to phenotype-directed, microcirculation-targeted resuscitation. It emphasizes early fluid responsiveness testing, avoids blind fluid loading, and relies on accessible tools (pulse pressure, diastolic BP, basic echo) rather than invasive monitors, enhancing scalability.

Limitations: Evaluating CRT-PHR as a bundled protocol obscures the individual contribution of each component. CRT should be interpreted alongside dynamic indices (pulse pressure variation, IVC collapsibility, fluid challenges). Prolonged CRT with poor fluid responsiveness suggests microcirculatory failure or cardiac dysfunction, warranting vasopressor/inotrope optimization rather than additional fluids. Future research must address inter-observer variability, skin pigmentation, ambient temperature, and vascular tone. Importantly, CRT measurement inherently encourages bedside clinical reassessment, a practice that itself improves early septic shock management.

Future Directions: Multimodal perfusion assessment integrating CRT, ScvO₂, lactate, and Pv-aCO₂ gap will refine decision-making. Clinicians should avoid relying on single biomarkers; for example, patients with normal CRT but altered mental status, low ScvO₂, and widened Pv-aCO₂ gap may still require targeted resuscitation.
(Author: Ran Xiao, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology)

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