Differences in capillary recruitment between cardiac surgery and septic patients after fluid resuscitation

Background: Clinical evaluation of the effects of fluid therapy remains cumbersome and strategies are based on the assumption that normalization of macrohemodynamic variables will result in parallel improvement in organ perfusion. Recently, we and others suggested the use of direct in-vivo observation of the microcirculation to evaluate the effects of fluid therapy. Methods: A single-centre observational study, using in-vivo microscopy to assess total vessel density (TVD) in two subsets of ICU patients. Results: After fluid resuscitation TVD showed no difference between sepsis patients (N = 47) and cardiac surgery patients (N = 52): 18.4[16.8–20.8] vs 18.7[16.8–20.9] mm/mm2, p = 0.59. In cardiac surgery patients there was a significant correlation between the amount of fluids administered and TVD, with an optimum in the third quartile. However, such correlation was absent in septic patients. Conclusions: TVD after fluid administration is not different between 2 subtypes of intensive care patients. However, only in septic patients we observed a lack of coherence between the amount of fluids administered and TVD. Further research is needed to determine if TVD may serve as potential endpoint for fluid administration.