Microcirculatory effects of intravenous fluids in critical illness: plasma expansion beyond crystalloids and colloids.
OBJECTIVE
Plasma expanders are reviewed to determine their ability to restore microvascular function as a means for extending the transfusion trigger and delaying the use of blood transfusions. This outcome is currently achievable because of the emergence of a new understanding of optimal tissue function that prioritizes maintenance of functional capillary density, which results from the normalization of blood viscosity via the increase in plasma viscosity with new viscogenic colloids.


RESULTS
Use of viscous plasma expanders in experimental models of extreme hemodilution, hemorrhagic shock and endotoxemia shows that the limiting factor in anemia is not oxygen-carrying capacity but the decline of microvascular function due to the lowering of functional capillary density. In support of this hypothesis, we find that viscogenic colloids including high-molecular-weight starches, dextrans, polyvinylpyrrolidone, keratin and polyethylene glycol-conjugated albumin maintain or restore microvascular function in extreme hemodilution, polyethylene glycol-conjugated albumin yielding the best results.


CONCLUSIONS
Preclinical studies show that polyethylene glycol-conjugated albumin at concentrations in the range of 2-4% extends the transfusion trigger, providing the more extended and complete microvascular and systemic recovery from hemorrhagic shock, extreme hemodilution and endotoxemia, postponing the need of reestablish intrinsic blood oxygen-carrying capacity to hemoglobin concentrations lower than those associated with accepted transfusion triggers.
Villela
Nivaldo R
NR
Laboratory for Clinical and Experimental Research in Vascular Biology, Biomedical Center, Universidade do Estado do Rio de Janeiro, Brazil. nivaldovillela@terra.com.br
Salazar Vázquez
Beatriz Y
BY
Vázques
Beatriz Y S
BY
Intaglietta
Marcos
M
D000418:Albumins / Q000627:therapeutic use; D001809:Blood Viscosity / Q000502:physiology; D002196:Capillaries / Q000033:anatomy & histology / Q000502:physiology; D003102:Colloids / Q000627:therapeutic use; D016638:Critical Illness; D019446:Endotoxemia / Q000097:blood / Q000628:therapy; D005440:Fluid Therapy; D006438:Hemodilution; D006801:Humans; D008833:Microcirculation / Q000187:drug effects*; D010952:Plasma Substitutes / Q000737:chemistry / Q000627:therapeutic use*; D010953:Plasma Volume; D011092:Polyethylene Glycols / Q000627:therapeutic use; D012771:Shock, Hemorrhagic / Q000097:blood / Q000628:therapy
D000418:Albumins; D003102:Colloids; D010952:Plasma Substitutes; D011092:Polyethylene Glycols