Mechanisms of postoperative prolonged plasma volume expansion with low molecular weight hydroxethy starch (HES 200/0.62, 6%).
OBJECTIVE
To define the mechanisms of the stable and prolonged post-operative plasma volume expansion observed with Hydroxyethyl Starches (HES) and to determine whether a partial intravascular hydrolysis of large molecules contribute to reinforce the colloid-osmotic effect.


METHODS
Prospective, pharmacologic study using single dose of drug.


METHODS
University-based, post-anesthesia care unit.


METHODS
The protocol was performed during the post-operative period, in 10 patients after stable recovery from general anesthesia for carotid endarterectomy.


METHODS
HES 200/0.62 (500 ml) was infused over 30 min. Standard hemodynamic and biological variables, HES concentration and colloid osmotic pressure were obtained at each measurement. Plasma volume was calculated using 51Cr-labelled RBCs. Patterns of changes in number average molecular weight (MWn) and weight average MW (MWw) were measured using gel permeation chromatography. Measurements were obtained at control, end of infusion, 1 h, 3 h, 6 h and 24 h after infusion.


RESULTS
Plasma volume increased by 693 ml (+21%) after the infusion of HES and remained constant over 24 h. HES concentration progressively decreased to reach a value of 35% of the peak at 24 h. MWn and MWw, initially decreased when compared with the dose solution and changed little in the 24 h study period. Diuresis significantly decreased at 3 h up to 24 h. Plasma albumin decreased after infusion and then progressively increased to reach a significantly higher value at 24 h than after infusion.


CONCLUSIONS
Initial plasma volume expansion and decrease in HES concentration agree with previously-published data. Maintenance of plasma volume expansion over 24 h was not related to a partial intravascular hydrolysis. Low elimination rate of HES, extravascular mobilization of albumin and post-operative renal adaptations were possibly the 3 main mechanisms to explain a prolonged plasma volume expansion with HES 200/0.62, 6%.
Degrémont
A C
AC
Départment d'Anesthésie-Réanimation, Hôpital Tenon, France.
Ismaïl
M
M
Arthaud
M
M
Oulare
B
B
Mundler
O
O
Paris
M
M
Baron
J F
JF
D000368:Aged; D016903:Drug Monitoring; D016894:Endarterectomy, Carotid; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D006868:Hydrolysis; D007262:Infusions, Intravenous; D008875:Middle Aged; D008970:Molecular Weight; D009997:Osmotic Pressure; D010952:Plasma Substitutes / Q000493:pharmacokinetics / Q000627:therapeutic use*; D010953:Plasma Volume / Q000187:drug effects*; D011108:Polymers / Q000493:pharmacokinetics / Q000627:therapeutic use*; D011182:Postoperative Care; D011446:Prospective Studies; D013213:Starch / Q000493:pharmacokinetics / Q000627:therapeutic use*; D013997:Time Factors
D010952:Plasma Substitutes; D011108:Polymers; C062890:polystarch; D013213:Starch