Interstitial washdown during crystalloid fluid loading in graded hypovolemia -A retrospective analysis in volunteers.

Background: "Interstitial washdown" is an edema-preventing mechanism that implies a greater redistribution of interstitial albumin occurs whenever the capillary filtration is increased.

Objective: To study the effect of interstitial washdown on fluid distribution in normovolemic and hypovolemic volunteers.

Methods: Capillary filtration was increased by infusing 25 mL/kg Ringer's acetate intravenously over 30 min 10 male just after withdrawal of 0, 450, and 900 mL of blood. Population volume kinetic analysis was used to assess the effects of washdown and hemorrhage on fluid distribution, using the difference in plasma dilution based on hemoglobin and albumin as biomarker of washdown.

Results: Blood withdrawal during 10-15 min recruited 100-150 mL of fluid of high albumin content to the plasma, which was probably lymph. The albumin recruitment was temporarily reduced during the fluid loading but increased from 40 min post-infusion and was then greater when preceded by hemorrhage. Simulations suggested that interstitial washdown decreased the extravascular fluid volume by 200 mL over 3 h. The plasma volume and urinary excretion both increased by approximately half this amount.

Conclusions: Blood loss without hypotension probably recruited lymph to the plasma, but interstitial washdown played no major role in determining the distribution of crystalloid fluid after hemorrhage.