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Fluid therapy in ICU patients serves to maintain tissue perfusion and is directed at increasing cardiac stroke volume (SV) through an increase in preload: fluid responsiveness. Although there is increasing evidence that the regional blood flow cannot be predicted from global hemodynamic measurements, the relation between SV and parameters of peripheral perfusion is not clear. The aim of our study was to evaluate the effect of an increase in preload on commonly used parameters of peripheral perfusion.
Hemodynamically unstable patients with clinically suspected fluid responsiveness underwent a passive leg raising (PLR) test, which consisted of 5 minutes of rest in a semirecumbent position of 30°, followed by 5 minutes PLR (lower limbs elevated at 30° and trunk in supine position). SV was measured continuously by pulse contour analysis using PiCCO (Pulsion). Peripheral perfusion was measured continuously with sidestream dark field imaging (sublingual area) and laser Doppler flowmetry (LDF) (finger).
Sixteen patients (age: 63 years (55 to 72), APACHE II: 25 (20 to 28), SOFA: 10 (7 to 13)) were included in our study. Of these 16 patients, six (38%) increased their SV by >10% in response to a PLR. Flow indices (LDF and sublinguale microcirculatory flow) did not change. However, there was a trend in increase of the functional capillary density in the responders (see Figure Figure11).
These data suggest that increasing SV in hemodynamically unstable patients might improve peripheral perfusion, however only in the sublingual area and not in all patients. There was no relation between systemic circulation and peripheral perfusion: it remains to be investigated whether optimizing SV actually results in improved tissue perfusion.