Table 1.
Assessment of microcirculatory disorders in critically ill patients.
| Technique | Principle | Site of measure | Variable | Modifications in sepsis | References |
|---|---|---|---|---|---|
| Microvascular blood flow | |||||
| Laser Doppler | Doppler effect Relative blood flow analysis |
Skin, muscle, digestive mucosa | Blood flow (relative units) | Decreased blood flow Decreased reactivity |
Eun et al. (81) Neviere et al. (82) |
| Pulsatility index | Doppler ultrasonography | Visceral organs (kidney, spleen, liver) | PI= (systolic blood flow velocity-minimum diastolic blood flow velocity)/mean blood flow velocity) | PI is increased in septic shock | Brunauer et al. (83) |
| Videomicroscopy | |||||
| Nailfold videomicroscopy | Transillumination Microscope with reflected light | Finger ungual microcirculation | Vascular density | NA | Freedlander et al. (84) Weinberg et al. (85) |
| OPS and SDF Cytocam incident dark field |
Direct microvascular visualization Absorption of a selected wavelength by hemoglobin | Sublingual microcirculation | Capillary density, perfused capillary density, functional capillary density, microvascular flow index | Decreased capillary density Increased heterogeneity of perfusion |
De Backer et al. (86) Dilken et al. (87) Aykut et al. (88) |
| Tissue oxygenation | |||||
| Near Infrared Spectrometry | Transmitted and reflected light at several wavelengths Different absorption properties of oxy- and deoxyhemoglobin | Muscle Thenar eminence |
Tissue oxygen saturation: StO2 = (HbO2)/(HbO2+Hb) | Decreased StO2 Decreased reactivity |
Mancini et al. (89) Creteur et al. (90) |
| PO2 electrodes | Transcutaneous electrodes that detect oxygen and carbon dioxide | Skin | Tissue PO2 | NA | Vesterager (91) |
| Peripheral tissue perfusion | |||||
| Capillary refill time (CRT) | Return to baseline color of a soft tissue after applying a pressure for 15s | Fingertip or knee | Time (in seconds) to baseline return after releasing the pressure | Increased CRT | Ait-Oufella et al. (92) Lima et al. (93) |
| Mottling | Discoloration of the skin | Knee | Mottling extension | Increased mottling score | Ait-Oufella et al. (94) Ait-Oufella et al. (95) |
| Temperature gradient | Cutaneous probes to evaluate skin temperature | Skin, toe, finger | Central-to-skin temperature gradient Skin-to-room temperature gradient | High central-to-skin temperature gradient Reduced skin-to-room temperature gradient |
Bourcier et al. (96) |
NA, not available; OPS, orthogonal polarization spectral imaging technique; O2, oxygen; PI, Pulsatility index; PO2, Partial oxygen pressure; SDF, sidestream dark field imaging technique; StO2, tissue oxygen saturation.