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Ann Thorac Surg 1998;66:2155
© 1998 The Society of Thoracic Surgeons

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Correspondence

Controlled perfusion protects lung grafts during a transient early increase in permeability

^a Cardiothoracic Surgical Unit, Queen Elizabeth Hospital, Birmingham, United Kingdom B15 2TH

To the Editor

We congratulate Bhabra and colleagues [1] on their studies of controlled reperfusion and its effects on lung graft function. However, we have some reservations regarding the conclusions drawn about a transient increase in pulmonary permeability. The methodology used to assess albumin permeability is not a standardized reproducible technique and is open to considerable error. The flux of fluid and solute across the alveolar-capillary membrane is governed by the Starling and Kedem-Katchalsky equations. The Starling equation relates fluid fluxes (J_v) to hydrostatic and oncotic pressure. The different perfusion pressures between the standard and controlled reperfusion groups might well be expected to increase J_v, irrespective of any change in fluid permeability. Solute permeability is described by the Kedem-Katchalsky equation in which J_s = PSC + (1 - _f) · J_v, where J_s is the solute flux, PS is the permeability-surface area product, C is the difference in protein concentration between the plasma and the interstitium, J_v is fluid flux, is the average concentration of protein in the membrane, and _f is the endothelial protein reflection coefficient. Any change in J_v produced by changes in hydrostatic pressure would impact upon J_s and unless the preparation is isogravimetric, permeability changes cannot be derived. Perhaps most importantly, the different reperfusion pressures would be expected to produce marked changes in the surface area of membrane available for solute exchange. We believe that these factors may be sufficient to explain the results of Bhabra and associates’ study without inferring any change in permeability. Further, the extent of exposure of the grafts to recirculated isotope-labeled albumin is another confounding variable. As blood circulates and recirculates through the support animal, there will be a redistribution into the support lungs and other tissues, which will influence the concentration of albumin presented to the endothelium of the graft, producing another source of potential error. Finally, unless the lungs are flushed with isotope-free fluid on completion, blood containing isotope-labeled albumin retained in the pulmonary vasculature (which may be expected to be greater in the high-pressure reperfusion group) will lead to an inappropriately high measure of labeled-albumin within the study lung.

The albumin leak index in this study is thus not a surrogate measure of albumin solute flux or permeability, and at best represents an expression of the total distribution volume of an unknown quantity of labeled-albumin. We again congratulate Bhabra’s group on their very important studies of lung preservation, but the mechanism of protection afforded by controlled reperfusion requires further definition.

References

1. Bhabra M.S., Hopkinson D.N., Shaw T.E., Onwu N., Hooper T.L. Controlled reperfusion protects lung grafts during a transient early increase in permeability. Ann Thorac Surg 1998;65:187-192.[Abstract/Free Full Text]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Stephen J. Rooney Robert S. Bonser Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Rooney, S. J. Articles by Bonser, R. S. Search for Related Content PubMed Articles by Rooney, S. J. Articles by Bonser, R. S. Related Collections Related Article