Influence of saline infusions on transvascular protein transport

Abstract

Anesthetized rabbits were given an intravenous infusion of saline over a 1-h period to increase transvascular protein transport in skin and skeletal muscle. The infusion rate was adjusted to rapidly decrease the plasma concentration of total protein without increasing mean arterial blood pressure or the venous pressure in the leg. The 1-h clearance for radiolabeled albumin and a set of charge-modified albumins was measured in the heel skin and the gastrocnemius muscle. For both skin and skeletal muscle, the clearance for native albumin during the saline infusion was twice the value for control. The increase in clearance for the most neutral protein was greater than that for native albumin, suggesting that transvascular fluid movement was through a pathway which excludes native albumin. The clearance for cationic albumin increased slightly in skin and did not change in skeletal muscle, indicating that transport of the cationic protein through this pathway is predominantly diffusion. The data were consistent with a two-pore model for transvascular transport of water and proteins and with the increase in water transport through the small pores during the saline infusion.

Volume expansion and plasma protein clearance during intravenous infusion of 5% albumin and autologous plasma

“…Volume expansion with normal saline doubled the clearance of 125 I-labelled albumin in rabbits [14]. Similarly, transcapillary leak was indicated by a progressively larger difference in dilution between Hb and albumin in volunteers receiving Ringer's acetate, dextran 70 and hypertonic saline [15].…”

“…Similarly, transcapillary leak was indicated by a progressively larger difference in dilution between Hb and albumin in volunteers receiving Ringer's acetate, dextran 70 and hypertonic saline [15]. The albumin clearance seems to be is increased by ANP (atrial natriuretic peptide) [10,14], which is released during volume expansion.…”

Colloid osmotic pressure and extravasation of plasma proteins following infusion of Ringer's acetate and hydroxyethyl starch 130/0.4

“…Infusion of albumin 5% greatly increases this capillary leak 1,2 and, in rabbits, volume expansion with isotonic saline doubled the efflux of radio-iodated albumin from the plasma. 3 In healthy volunteers, infusion of both crystalloid fluid and dextran caused a greaterthan-expected dilution of serum albumin, indicating capillary leak. 4 This might have been caused by hypervolaemia, which increases capillary permeability to proteins by stimulating the release of atrial natriuretic peptides.…”

“…4 This might have been caused by hypervolaemia, which increases capillary permeability to proteins by stimulating the release of atrial natriuretic peptides. 3,5 In contrast, albumin became enriched in plasma when Ringer's acetate was infused during thyroid surgery, 6 whereas albumin again leaked from the plasma when volunteers received isotonic saline during experimental isoflurane anaesthesia. 7 Little attention has been paid to the transcapillary flux of proteins other than albumin in connection with the administration of crystalloid and artificial colloid infusion fluids.…”

Microvascular changes and anesthesia

“…Other microvascular events also affect the distribution of fluid. These include an altered post to precapillary resistance ratio and also capillary leak of albumin in response to volume loading (3) or trauma (4).…”