Revised Starling equation and the glycocalyx model of transvascular fluid exchange

An improved paradigm for prescribing intravenous fluid therapy

T. E. Woodcock*, T. M. Woodcock

*Corresponding author for this work

    Research output: Contribution to journalReview article

    322 Citations (Scopus)

    Abstract

    SummaryI.V. fluid therapy does not result in the extracellular volume distribution expected from Starlings original model of semi-permeable capillaries subject to hydrostatic and oncotic pressure gradients within the extracellular fluid. Fluid therapy to support the circulation relies on applying a physiological paradigm that better explains clinical and research observations. The revised Starling equation based on recent research considers the contributions of the endothelial glycocalyx layer (EGL), the endothelial basement membrane, and the extracellular matrix. The characteristics of capillaries in various tissues are reviewed and some clinical corollaries considered. The oncotic pressure difference across the EGL opposes, but does not reverse, the filtration rate (the 'no absorption' rule) and is an important feature of the revised paradigm and highlights the limitations of attempting to prevent or treat oedema by transfusing colloids. Filtered fluid returns to the circulation as lymph. The EGL excludes larger molecules and occupies a substantial volume of the intravascular space and therefore requires a new interpretation of dilution studies of blood volume and the speculation that protection or restoration of the EGL might be an important therapeutic goal. An explanation for the phenomenon of context sensitivity of fluid volume kinetics is offered, and the proposal that crystalloid resuscitation from low capillary pressures is rational. Any potential advantage of plasma or plasma substitutes over crystalloids for volume expansion only manifests itself at higher capillary pressures.

    Original languageEnglish
    Pages (from-to)384-394
    Number of pages11
    JournalBritish Journal of Anaesthesia
    Volume108
    Issue number3
    DOIs
    Publication statusPublished - Mar 2012

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    Keywords

    • fluid therapy
    • intensive care

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