Effects of fluids on microvascular perfusion in patients with severe sepsis.

PURPOSE: To evaluate the effects of fluid administration on microcirculatory alterations in sepsis.
METHODS: With a Sidestream Dark Field device, we evaluated the effects of fluids on the sublingual microcirculation in 60 patients with severe sepsis. These patients were investigated either within 24 h (early, n = 37) or more than 48 h (late, n = 23) after a diagnosis of severe sepsis. Hemodynamic and microcirculatory measurements were obtained before and 30 min after administration of 1,000 ml Ringer's lactate (n = 29) or 400 ml 4% albumin (n = 31) solutions.
RESULTS: Fluid administration increased perfused small vessel density from 3.5 (2.9-4.3) to 4.4 (3.7-4.9) n/mm (p < 0.01), through a combined increase in the proportion of perfused small vessels from 69 (62-76) to 79 (71-83) %, p < 0.01) and in small vessel density from 5.3 (4.4-5.9) to 5.6 (4.8-6.3) n/mm (p < 0.01). Importantly, microvascular perfusion increased in the early but not in the late phase of sepsis: the proportion of perfused small vessels increased from 65 (60-72) to 80 (75-84) % (p < 0.01) in the early phase and from 75 (66-80) to 74 (67-81) (p = ns) in the late phase. These microvascular effects of fluids were not related to changes in cardiac index (R(2) = 0.05, p = ns) or mean arterial pressure (R(2) = 0.04, p = ns).
CONCLUSIONS: In this non-randomized trial, fluid administration improved microvascular perfusion in the early but not late phase of sepsis. This effect is independent of global hemodynamic effects and of the type of solution.