How is microcirculation monitored and managed in sepsis?

Monitoring and Management of Microcirculation in Sepsis

Currently, there is no direct way to monitor microcirculatory changes in sepsis, and management is limited to targeting measurable macrocirculatory endpoints while using indirect markers of microvascular perfusion such as hourly urine output, lactate levels, and biochemical markers of renal function. 1

Current Monitoring Approaches for Microcirculation

Indirect Monitoring Methods

• Hourly urine output: Serves as a surrogate marker of microvascular perfusion (grade E) 1
• Lactate levels: Elevated levels indicate tissue hypoperfusion; lactate clearance (decrease by at least 10-20%) can be used as a resuscitation target 1
• Biochemical markers of renal function: Reflect end-organ perfusion 1
• ScvO2 (central venous oxygen saturation): Target of ≥70% indicates adequate oxygen delivery relative to consumption 1

Emerging Direct Monitoring Technologies

While not yet standard of care, several technologies are being developed to directly visualize and assess microcirculation:

• Videomicroscopic devices:

  • Orthogonal Polarization Spectral (OPS) imaging 2
  • Sidestream Dark Field (SDF) imaging 3
  • Allow direct visualization of microvessels at the bedside
  • Can detect decreased vessel density and increased proportion of nonperfused capillaries in sepsis 2

• Tissue PCO2 measurement:

  • Transcutaneous PCO2 measurement at ear lobe shows promise as an indirect assessment method 3

• Near-infrared spectroscopy (NIRS):

  • Can assess microcirculatory reactivity using vascular occlusion tests 3
  • Provides information about tissue oxygen consumption

Management of Microcirculation in Sepsis

Since direct therapeutic interventions for microcirculation are not yet established, management focuses on optimizing macrocirculatory parameters:

1. Fluid Resuscitation

• Early and aggressive fluid loading is recommended to correct arterial hypotension (grade B) 1
• Improves oxygen delivery to tissues and patient prognosis 1

2. Vasopressors

• If MAP <65 mmHg despite adequate fluid resuscitation, vasopressors should be used (grade B) 1
• Norepinephrine is recommended as first-line vasopressor (grade E) 1
• Early use of vasopressors may reduce organ failure incidence (grade E) 1
• Rescue options for refractory shock:
  • Vasopressin (0.01-0.04 units/min)
  • Terlipressin (boluses of 1-2 mg) 1

3. Inotropic Support

• Not recommended routinely (grade E) 1
• Indicated when low cardiac output is accompanied by ScvO2 <70% despite adequate fluid resuscitation and vasopressor use 1
• Combination of dobutamine and norepinephrine is recommended as first-line treatment 1
• Titrate to targeted responses:
  • Improved ScvO2
  • Improved myocardial function indices
  • Reduced lactate levels 1

4. Blood Transfusion

• Target hemoglobin between 8-9 g/dL in acute anemia 1
• Different targets may be acceptable based on clinical tolerance or ScvO2 levels 1

Clinical Significance and Future Directions

Persistent microcirculatory alterations in sepsis are associated with the development of organ failure and death 2. Research shows that:

• Microcirculatory dysfunction is a pivotal element in sepsis pathogenesis 4
• Improvements in systemic hemodynamics often correlate poorly with microcirculatory improvements 5
• Conventional hemodynamic monitoring fails to detect microcirculatory changes 5

Special Considerations

Pediatric Patients

• Sepsis in children more often characterized by cardiac failure and hypovolemia 1
• Hypotension develops later than in adults 1
• Early aggressive fluid therapy and antibiotics are crucial (grade D) 1
• Norepinephrine is recommended as first-line vasoactive treatment 1
• Phosphodiesterase III inhibitors may be considered for low cardiac output with normal arterial pressure 1

Pitfalls and Caveats

• Relying solely on macrocirculatory parameters may miss ongoing microcirculatory dysfunction
• Despite normalization of global hemodynamic parameters, microcirculatory dysfunction may persist
• Early identification of sepsis is critical for timely intervention and improved outcomes 1
• Performance improvement efforts in sepsis management require multidisciplinary teams and consistent education 1
• While emerging technologies for direct microcirculation monitoring show promise, they are not yet validated for guiding therapy in routine clinical practice 2