Hemodilution with albumin, but not Hextend, results in hypercoagulability as assessed by Thrombelastography in rabbits: role of heparin-dependent serpins and factor VIII complex

Anticoagulant action of low, physiologic, and high albumin levels in whole blood

Albumin is the most abundant plasma protein. Critical illness is often associated with altered, predominately decreased, serum albumin levels. This hypoalbuminaemia is usually corrected by administration of exogenous albumin. This study aimed to track the concentration-dependent influence of albumin on blood coagulation in vitro. Whole blood (WB) samples from 25 volunteers were prepared to contain low (19.3 ± 7.7 g/L), physiological (45.2 ± 7.8 g/L), and high (67.5 ± 18.1 g/L) levels of albumin. Haemostatic profiling was performed using a platelet function analyzer (PFA) 200, impedance aggregometry, a Cone and Platelet analyzer (CPA), calibrated automated thrombogram, and thrombelastometry (TEM). Platelet aggregation-associated ATP release was assessed via HPLC analysis. In the low albumin group, when compared to the physiological albumin group, we found: i) shortened PFA 200-derived closure times indicating increased primary haemostasis; ii) increased impedance aggregometry-derived amplitudes, slopes, ATP release, as well as CPA-derived average size indicating improved platelet aggregation; iii) increased TEM-derived maximum clot firmness and alpha angles indicating enhanced clot formation. TEM measurements indicated impaired clot formation in the high albumin group compared with the physiological albumin group. Thus, albumin exerted significant anticoagulant action. Therefore, low albumin levels, often present in cancer or critically ill patients, might contribute to the frequently occurring venous thromboembolism.

Effect of 6% hydroxyethyl starch 130/0.4 as a priming solution on coagulation and inflammation following complex heart surgery

PURPOSE

Prolonged duration of cardiopulmonary bypass aggravates the degree of inflammation and coagulopathy. We investigated the influence of 6% hydroxyethyl starch (HES) 130/0.4 on coagulation and inflammation compared with albumin when used for both cardiopulmonary bypass priming and perioperative fluid therapy in patients undergoing complex valvular heart surgery.

MATERIALS AND METHODS

Fifty four patients were randomly allocated into albumin-HES, albumin-nonHES, and HES-HES groups. The cardiopulmonary bypass circuit was primed with 5% albumin in the albumin-HES and albumin-nonHES group, and with HES in the HES-HES group. As perioperative fluid, only plasmalyte was used in the albumin-nonHES group whereas HES was used up to 20 mL/kg in the albumin-HES and albumin-HES group. Serial assessments of coagulation profiles using the rotational thromboelastometry and inflammatory markers (tissue necrosis factor-α, interleukin-6, and interleukin-8) were performed.

RESULTS

Patients' characteristics and the duration of cardiopulmonary bypass (albumin-HES; 137±34 min, HES-HES; 136±47 min, albumin-nonHES; 132±39 min) were all similar among the groups. Postoperative coagulation profiles demonstrated sporadic increases in clot formation time and coagulation time, without any differences in the actual amount of perioperative bleeding and transfusion requirements among the groups. Also, inflammatory markers showed significant activation after cardiopulmonary bypass without any differences among the groups.

CONCLUSION

Even in the presence of prolonged duration of cardiopulmonary bypass, HES seemed to yield similar influence on the ensuing coagulopathy and inflammatory response when used for priming and perioperative fluid therapy following complex valvular heart surgery compared with conventional fluid regimen including albumin and plasmalyte.

Effects of PentaLyte and Voluven hemodilution on plasma coagulation kinetics in the rabbit: role of thrombin-fibrinogen and factor XIII-fibrin polymer interactions

BACKGROUND

Hydroxyethyl starch (HES) administration has resulted in decreased hemostasis and fibrinogen (FI)-thrombin-(FIIa)-Factor XIII (FXIII) interactions. I proposed to determine the hemostatic effect of hemodilution with PentaLyte (6% HES, mean molecular weight 220 kDa) and Voluven (6% HES, 130 kDa).

METHODS

Rabbits were intravenously administered 20 ml/kg PentaLyte or Voluven (n = 8 per fluid) over 10 min. Plasma was obtained prior to, 1 min and 1 h after hemodilution. Thrombelastography was performed, with clot initiation (R, sec), clot propagation (alpha, degrees), and clot strength (shear elastic modulus, G, dynes/cm2) determined over 20 min. Celite-activated samples had either no additions or addition of FI, FIIa or activated FXIII (FXIIIa) to restore protein content to pre-diluted values.

RESULTS AND CONCLUSIONS

While there were no significant differences between the groups, R significantly decreased 1 h after hemodilution compared with values observed before and 1 min after hemodilution, whereas alpha and G significantly decreased 1 min after hemodilution and then significantly, but only partially, increased 1 h after hemodilution compared with pre-dilution values. Addition of FI, FIIa and FXIIIa significantly decreased R in both groups. alpha and G 1 min after hemodilution were significantly enhanced by FI, FIIa, FXIIIa in both groups; however, 1 h after hemodilution, rabbits administered PentaLyte had alpha and G enhanced only by FI and FXIIIa addition, whereas animals administered Voluven had alpha and G significantly enhanced by FI addition. PentaLyte and Voluven hemodilution initially diminishes FIIa-FI and FXIIIa-fibrin, but within an hour primarily inhibit FXIIIa-fibrin interactions in the rabbit.

Colloids decrease clot propagation and strength: role of factor XIII-fibrin polymer and thrombin-fibrinogen interactions

Colloid-mediated hypocoagulability is clinically important, but the mechanisms responsible for coagulopathy have been incompletely defined. Thus, my goal was to elucidate how colloids decrease plasma coagulation function. Plasma was diluted 0% or 40% with 0.9% NaCl, three different hydroxyethyl starches (HES, mean molecular weight 450, 220 or 130 kDa), or 5% human albumin. Samples (n=6 per condition) were activated with celite, and diluted samples had either no additions or addition of fibrinogen (FI), thrombin (FIIa) or activated Factor XIII (FXIIIa) to restore protein function to prediluted values. Thrombelastographic variables measured included clot propagation (angle, alpha), and clot strength (amplitude, A; or shear elastic modulus, G). Dilution with 0.9% NaCl significantly decreased alpha, A and G-values compared to undiluted samples. Supplementation with FI, but not FIIa or FXIIIa, resulted in 0.9% NaCl-diluted thrombelastographic variable values not different from those of undiluted samples. FI supplementation of HES 450, HES 220, HES 130 and albumin-diluted samples only partially restored alpha, A and G-values compared to undiluted samples. FIIa addition only improved clot propagation and strength in albumin-diluted samples. FXIIIa supplementation improved propagation in samples diluted with HES 450, HES 220 and albumin, and clot strength improved in HES 450 and albumin-diluted plasma. Considered as a whole, these data support compromise of FIIa-FI and FXIIIa--fibrin polymer interactions as the mechanisms by which colloids compromise plasma coagulation. Investigation to determine if clinical enhancement of FXIII activity and/or FI concentration (e.g. fresh-frozen plasma, cryoprecipitate) can attenuate colloid-mediated decreases in hemostasis is warranted.

Effects of coagulation factor deficiency on plasma coagulation kinetics determined via thrombelastography: critical roles of fibrinogen and factors II, VII, X and XII

BACKGROUND

Thrombelastography (TEG) is used to assess coagulopathy. However, a comprehensive characterization of the effects of specific coagulation factor deficiencies and mode of activation on TEG data does not exist.

METHODS

Thrombelastography was performed for 15 min with control plasma and plasmas deficient (<1% activity) in Factors II, V, VII, VIII, IX, X, XI, XII, or XIII activated with celite (0.28 mg ml(-1)) or tissue factor (TF, 0.1%) (n = 6 per condition). Additional fibrinogen concentration activity (75-345 mg dl(-1)) and Factor II, VII, X and XII activity-response relationships (1%, 6.25%, 12.5%, 25%, 50% and 100% activity) were obtained (n = 8 per condition). Thrombelastography parameters included reaction time (R), angle (alpha), and clot strength (A, amplitude; G, elastic modulus).

RESULTS

Celite activation of FXII-deficient plasma, TF activation of FVII-deficient and FX-deficient plasma, and celite or TF activation of FII-deficient plasma resulted in an almost undetectable clot. Compared to control values, celite activation of plasmas deficient in FXI, FIX and FVIII resulted in prolonged R and decreased alpha values, whereas TF activation resulted in decreased alpha values. Celite and TF activation of FV-deficient plasma resulted in prolonged R and decreased alpha values, whereas FXIII-deficient plasma had decreased alpha, A and G-values compared to control values.

CONCLUSIONS

The fundamental finding of this study is that coagulation factor deficiencies affect TEG parameters in both a factor-dependent and activation-dependent fashion. Utilizing both celite and TF activation improves the diagnostic power of TEG. Based on such TEG data, more targeted administration of blood products could potentially help improve perioperative hemostatic outcomes.

Hemodilution with lactated Ringer's solution causes hypocoagulability in rabbits

Hemodilution (HD) has been associated with hypercoagulability. It was hypothesized that HD with lactated Ringer's solution (LR) would result in hypercoagulability in rabbits. Sedated rabbits (n = 12) underwent HD with LR (40% estimated blood volume replaced with five volumes of LR) via ear vessels. Key procoagulants and anticoagulant activities were assessed prior to and 3 h after HD. Hemostatic function was assessed with the activated coagulation time and platelet-inhibited thrombelastography. Circulating tissue factor activity was much more diluted (-67.2% from baseline) than tissue factor pathway inhibitor (-45.2%) or antithrombin (-9.5%) activities after HD. HD significantly decreased factor VIII complex activity (-31.5%) more than protein C activity (-5.9%), and factor X activity (-29.2%) was more diluted than antithrombin activity. The activated coagulation time and thrombelastography demonstrated a significant decrease in hemostatic function after HD. Hemodilution with LR caused hypocoagulability in the rabbit. A greater decrease in circulating procoagulant activity than anticoagulant activity appears to be the mechanism underlying HD-mediated decreases in hemostasis.