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.

Is limited prehospital resuscitation with plasma more beneficial than using a synthetic colloid? An experimental study in rabbits with parenchymal bleeding

BACKGROUND

Reports of survival benefits of early transfusion of plasma with red blood cells (1:1 ratio) in trauma patients suggest that plasma may be a better fluid to replace Hextend for battlefield resuscitation. We studied possible advantages of prehospital resuscitation with plasma compared with Hextend or albumin in a model of uncontrolled hemorrhage.

METHODS

Male New Zealand white rabbits (3.3 ± 0.1 kg) were anesthetized, instrumented, and subjected to a splenic injury with uncontrolled bleeding. Ten minutes after injury (mean arterial pressure [MAP] < 40 mm Hg), the rabbits received small and equal volumes (15 mL/kg) of rabbit plasma (n = 10), Hextend (n = 10), or 5% human albumin (n = 9) or no fluid. Fluids were administered in two bolus injections (20 minutes apart) and targeted to a MAP of 65 mm Hg. Animals were monitored for 2.5 hours or until death, and their blood losses were measured. Arterial blood samples were collected at different times and analyzed for ABG, CBC, and coagulation tests.

RESULTS

There were no differences in baseline measures among groups. Splenic injury caused similar hemorrhages (9.1 ± 0.4 mL/kg at 10 minutes) and decreased MAP in all subjects. Subsequent resuscitation initiated additional bleeding. At 60 minutes after injury (20 minutes after resuscitation), longer activated partial thromboplastin time and lower fibrinogen concentrations were apparent compared with baseline values with differences among groups. Thrombelastography analysis indicated faster and stronger clot formation with plasma and albumin resuscitation than with Hextend use. Shock indices were increased in all groups, but smaller changes were measured in the albumin group. Total blood loss did not differ among resuscitated rabbits but was higher (p < 0.05) than among nonresuscitated animals. Survival rates were 11% (untreated), 40% (Hextend and plasma), and 89% (albumin, p < 0.05).

CONCLUSION

Resuscitation with plasma or albumin better preserved coagulation function than did Hextend. However, despite these improvements, plasma resuscitation did not reduce blood loss or improve survival, while albumin administration seemed beneficial.

The Effects of Haemodilution with Albumin on Coagulation in Vitro as Assessed by Rotational Thromboelastometry

We investigated the in vitro viscoelastic changes of progressive haemodilution with 4% albumin compared with normal saline (NS) using rotational thromboelastometry (ROTEM®, Pentapharm Co., Munich, Germany). Whole blood samples obtained from 20 healthy volunteers were diluted in vitro with 4% albumin or NS by 10%, 20% and 40%. Fibrinogen concentration and ROTEM® (EXTEM [screening test for the extrinsic haemostasis system], FIBTEM [EXTEM-based assay for the fibrin part of the clot]) variables including coagulation time, clot formation time (CFT), α-angle, maximum clot firmness and lysis index were measured in the undiluted sample and at each degree of haemodilution. There was no significant difference in fibrinogen concentration at equivalent haemodilutions with normal saline and 4% albumin solutions. Forty percent haemodilution with albumin significantly prolonged coagulation time (EXTEM P=0.007, FIBTEM P=0.0001) and significantly decreased lysis index (FIBTEM P=0.009) compared with NS. A significant decrease in maximum clot firmness from undiluted measurements ( P=0.05) was observed at lower haemodilutions with albumin (20% with EXTEM, 10% with FIBTEM) compared with NS (40% with EXTEM and FIBTEM). The adverse effects of large degrees of haemodilution with 4% albumin solution are in excess of what can be explained by haemodilution alone. This study suggests that large degrees of haemodilution with albumin impair fibrinogen activity to a greater extent than equivalent degrees of haemodilution with NS.

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.

Comparisons of lactated Ringer's and Hextend resuscitation on hemodynamics and coagulation following femur injury and severe hemorrhage in pigs

BACKGROUND

This study compared coagulation function after resuscitation with Hextend and lactated Ringer's (LR) solution in pigs with tissue injury and hemorrhagic shock.

METHODS

Pigs were randomized into control (n = 7 each), LR, and Hextend groups. Femur fracture was induced using the captive bolt stunner at midshaft of the pigs' left legs, followed by hemorrhage of 60% total blood volume and resuscitation with either Hextend (equal to bled volume) or LR to reach the same mean arterial pressure. Pigs in the control group were not bled or resuscitated. Hemodynamics was monitored hourly for 6 hours. Blood samples were taken at baseline (BL), after hemorrhage, 15 minutes, 3 hours, and 6 hours after resuscitation for blood and coagulation measurements.

RESULTS

Mean arterial pressure decreased to 50% of BL by the 60% hemorrhage but returned to near BL within 1 hour after LR or Hextend resuscitation. Heart rate was increased (from 91 ± 4 beats per minute to 214 ± 20 beats per minute) by hemorrhage and decreased after resuscitation but remained elevated above BL in both groups. Resuscitation with Hextend (42 mL/kg) or LR (118 ± 3 mL/kg) reduced hematocrit, total protein, fibrinogen, and platelet counts, with greater decreases shown in the Hextend group. Clot strength was lower but returned to BL by 3 hours in the LR group, whereas it remained reduced for the 6-hour period after Hextend. The overall clotting capacity after LR was decreased after hemorrhage and resuscitation but returned to BL by 3 hours, whereas it remained low after Hextend for the 6-hour experiment period.

CONCLUSION

After traumatic hemorrhage, coagulation function was restored within 6 hours with LR resuscitation but not with Hextend. The lack of recovery after Hextend is likely caused by greater hemodilution and possible effects of starches on coagulation substrates and further documents the need to restrict the use of high-molecular-weight starch in resuscitation fluids for bleeding casualties.

Low-Volume Resuscitation for Severe Intraoperative Hemorrhage: A Step in the Right Direction

The impact on outcomes resulting from crystalloids used with hemostatic close ratio resuscitation (HCRR) in intraoperative hemorrhage (IOH) has not been analyzed. We hypothesize a survival advantage in patients with IOH managed with a low-volume resuscitation (LVR) protocol during HCRR. A 4-year case-control study was conducted to determine the impact on mortality of LVR versus conventional resuscitation efforts (CRE) during HCRR. A total of 45 patients managed with a HCRR + LVR protocol (combination Hextend® and 3% hypertonic saline) and 55 historical cohorts managed with HCRR + CRE (lactated Ringer's) were included. Patient demographics, number of intraoperative units of packed red blood cells (PRBCs) and fresh-frozen plasma (FFP) received, and FFP:PRBC ratio were similar between groups. The mean intraoperative fluid volume was 0.76 L in the HCRR + LVR group versus 4.7 L in the HCRR + CRE group ( P = 0.003). In a linear regression model HCRR + LVR versus HCRR + CRE, mean trauma intensive care unit length of stay was ± versus 11 days ( P = 0.009); 30-day overall mortality was 11.1 versus 32.7 per cent ( P = 0.009); perioperative mortality was 2.2 to 10.9 per cent ( P = 0.13); and intensive care unit mortality 8.8 to 21.8 per cent ( P = 0.07). LVR protocol conveyed a survival benefit to patients undergoing HCRR (odds ratio for mortality, 0.07 [95% confidence interval 0.07–0.54]). This is the first civilian study to analyze the impact of LVR in patients managed with HCRR during IOH. Patients with IOH managed with HCRR and a predefined LVR protocol with Hextend® and 3 per cent hypertonic saline had an overall survival advantage and shorter trauma intensive care unit length of stay. LVR can be an effective alternative to CRE when used in combination with HCRR in patients with IOH.

Albumin limits mesenteric endothelial dysfunction and inflammatory response in cardiopulmonary bypass

The aim of this study was to investigate the potential anti-inflammatory and endothelial protective properties of albumin during cardiopulmonary bypass (CPB) in an experimental porcine model. Two groups underwent CPB for 90 min (n = 7 in each group), and a baseline (BL) control group did not undergo CPB (n = 7). Priming consisted of a gelatin solution (4% gelofusine, CPBG group) or colloid solution (5% albumin, CPBA group). Mesenteric arterial segments were isolated and exposed in vitro to phenylephrine (with or without nitric oxide synthase inhibition) to assess contractility, and exposed to acetylcholine and sodium nitroprusside to assess relaxation. Plasma tumor necrosis factor (TNF)-α levels, intestinal and pulmonary TNF-α and heme oxygenase (HO)-1 mRNA expression, and organ injury were studied. Upon sacrifice, TNF-α levels were significantly higher in the CPBG group than in the CPBA and BL groups. The contractile response was significantly higher in the CPBG group, whereas the response to acetylcholine was significantly lower in the CPBG group than in the other groups. HO-1 mRNA expression was significantly higher in intestine samples in the CPBA group than in the CPBG and BL groups. HO-1 mRNA expression was significantly higher in lung samples in the CPBA group than in the CPBG group. Leukocyte infiltration was significantly higher in intestine and lung samples in the CPBG group than in the CPBA and BL groups. Albumin priming reduced CPB-induced mesenteric vascular dysfunction and prevented the development of a systemic inflammatory response by modeling HO-1 expression in target organs.

First report on safety and efficacy of hetastarch solution for initial fluid resuscitation at a level 1 trauma center

BACKGROUND

For logistics, the US Army recommends Hextend (Hospira; 6% hetastarch in buffered electrolyte, HET) for battlefield resuscitation. To support this practice, there are laboratory data, but none in humans. To test the hypothesis that HET is safe and effective in trauma, we reviewed our first 6 months of use at a civilian level 1 trauma center.

STUDY DESIGN

From June 2008 to December 2008, trauma patients received standard of care (SOC) +/- 500 to 1,000 mL of HET within 2 hours of admission at surgeon discretion. Each case was reviewed, with waiver of consent.

RESULTS

There were 1,714 admissions; 805 received HET and 909 did not. With HET versus SOC, overall mortality was 5.2% versus 8.9% (p = 0.0035) by univariate analysis. Results were similar after penetrating injury only (p = 0.0016) and in those with severe injury, defined by Glasgow Coma Scale <9 (p = 0.0013) or Injury Severity Score >26 (p = 0.0142). After HET, more patients required ICU admission (40.9% vs. 34.5%; p = 0.0334) and transfusions of blood (34.4% vs. 20.2%; p = 0.0014) or plasma (20.7% vs. 12.2%; p = 0.0251), but there were no treatment-related differences in prothrombin time or partial thromboplastin time. The 24-hour urine outputs and requirements for blood, plasma, and other fluids were similar. However, increased early deaths with SOC implicate possible selection bias. If that factor was controlled for with multivariate analysis, the same trends were present, but the apparent treatment effects of HET were no longer statistically significant.

CONCLUSIONS

In the first trial to date in hemodynamically unstable trauma patients, and the largest trial to date in any population of surgical patients, initial resuscitation with HET was associated with reduced mortality and no obvious coagulopathy. A randomized blinded trial is necessary before these results can be accepted with confidence.

Influence of fluid therapy on the haemostatic system of intensive care patients

Haemostatic alterations associated with the use of fluids are related to non-specific dilutional effects and colloid-specific effects, such as acquired von Willebrand syndrome, inhibition of platelet function and fibrin polymerization. Judging by currently available evidence, dextran, hetastarch and pentastarch have a more pronounced impact than tetrastarch, gelatin and albumin. In patients with hypocoagulability, tetrastarch appears to be a suitable volume expander due to its high safety index and volume efficacy. Gelatins have lower inhibitory effects on clot strength compared with tetrastarch, but their volume efficacy is also lower. Dextrans are potent anticoagulants with a high risk for adverse reactions. Albumin has negligible effects on haemostasis, but low volume efficacy and costs limit the use of a blood product as a routine volume replacement fluid. To avoid potential acidosis-induced changes in haemostasis, plasma-adapted carrier solutions may be used instead of saline-based solutions.

Hydroxyethyl starch enhances fibrinolysis in human plasma by diminishing α2-antiplasmin–plasmin interactions

Hydroxyethyl starch (HES) solutions are effective volume expanders but are also associated with poorly understood coagulopathy. Enhanced fibrinolysis following dilution with HES has been demonstrated. This investigation sought to identify the interactions of HES with critical fibrinolytic/antifibrinolytic enzymes. Normal plasma or plasmas deficient in factor XIII, thrombin activatable fibrinolysis inhibitor or alpha2-antiplasmin were either not diluted or were diluted 20% with 0.9% NaCl, 5% human albumin, high-molecular-weight HES (HES 450) or low-molecular-weight HES (HES 130). Plasma was activated with celite and exposed to 75 IU/ml tissue-type plasminogen activator. Coagulation growth/disintegration kinetics were determined with thrombelastography. Compared with undiluted plasma, diluted plasma had a significant decrease in the clot lysis time and the time to maximum rate of lysis in all plasma types except in alpha2-antiplasmin-deficient plasma. The hierarchy of the decrease in clot lysis time and time to maximum rate of lysis was HES 450 = HES 130 > 5% human albumin = 0.9% NaCl. In conclusion, HES dilution enhances fibrinolysis by diminishing alpha2-antiplasmin-plasmin interactions. Further laboratory and clinical investigation is warranted to better define the mechanisms by which HES enhances clot disintegration and to find new therapeutic roles for HES to either prevent or treat thrombosis.

The Coagulation Changes Induced by Rapid In Vivo Crystalloid Infusion Are Attenuated When Magnesium Is Kept at the Upper Limit of Normal

BACKGROUND

Rapid crystalloid infusion enhances coagulation, regardless of electrolytes, pH or osmolality, an effect thought to be related to deep vein thrombosis and other clot formations. Altered serum magnesium may play a role in the balance of coagulation. In this in vivo study we investigated the coagulation response to rapid hemodilution when serum magnesium is maintained or partially increased.

METHODS

Twenty-five healthy volunteers were investigated on three occasions, randomly receiving normal saline, Balsol (magnesium 1.5 g/L), and Balsol plus additional magnesium (magnesium 3.0 g/L). Investigators were blinded to the solution's identity. Baseline blood samples were taken measuring hematocrit, serum magnesium, and thrombelastography (TEG), whereafter 14 mL/kg (20% blood volume) was infused over 30 min, followed by a second blood sample. All results were compared to their own baseline values using ANOVA with LSD post hoc significance testing.

RESULTS

All groups had a similar postdilutional hematocrit decrease, with significant magnesium reduction in the saline group (0.81 +/- 0.07 to 0.74 +/- 0.07 (approximately -8.6%) (P < 0.003)), no change in the Balsol group and significant increase in the Balsol + magnesium group (0.84 +/- 0.07 to 0.99 +/- 0.06 (approximately 17.9%) (P < 0.001)). Postdilutional TEG results reflected no significant change from control in the Balsol + magnesium group. Both of the other two groups had statistically significant increased clot formation (reaction time to onset of clotting and clotting time shortened; alpha-angle increased).

CONCLUSIONS

Rapid hemodilution-induced coagulation may be partially due to decreased magnesium, and the effect is attenuated by maintaining magnesium at the upper limit of normal. Crystalloid resuscitation fluids should possibly contain higher magnesium levels, around 3 mmol/L.

Comparative study of isovolemic hemodilution with 3% albumin, dextran-40, and prophylactic enoxaparin (LMWH) on thrombus formation at venous microanastomosis in rats

The objective of the present investigation was to compare the effect of isovolemic hemodilution with 3% albumin, dextran-40, and enoxaparin on the prevention of thrombosis in femoral vein microanastomosis using an experimental model in rats. Forty male Wistar rats were allocated into four groups: group 1, control, thrombogenic model without previous treatment; group 2, hemodiluted, thrombogenic model with previous hemodilution; group 3, dextran-40, thrombogenic model with dextran infusion (10 ml/kg), and group 4, enoxaparin, thrombogenic model with administration of enoxaparin (0.5 mg/kg/day). Hemostatic parameters, hematologic examinations, patency of anastomosis, and histopathological examination were evaluated. The hemostatic parameters were similar in the four groups studied. Group hemodiluted, dextran-40, and enoxaparin showed significantly reduced number of red blood cells and platelets as compared with the control group. The hemodilution significantly increased the patency rates of the vein at 20 min and 48 h. Dextran-40 and enoxaparin improved the patency of the vein only at 20 min, but failed to show a significant increase in the final patency at 48 h. After 48 h, the rate of venous thrombosis, as evaluated microscopically, was significantly decreased in hemodiluted animals (1/8) as compared with controls (10/10); in rats treated with dextran-40 (7/10) and enoxaparin (5/10) the rate of venous thrombosis was significantly higher as compared with rats of the group hemodiluted. Based on these observations, it can be concluded that hemodilution with albumin 3% was a safe and more adequate procedure than the use of the schemes of administration of dextran-40 and enoxaparin used in this study to prevent thrombus formation at femoral vein microanastomosis in rats. Since hemodilution promotes reduction in blood viscosity and in erythrocyte and platelet aggregation as well as dilution of the coagulation factors themselves, its use could provide better microcirculatory blood perfusion, decreasing the risk of thrombosis, and making possible safer microsurgical procedures.

Effects of Hextend Hemodilution on Plasma Coagulation Kinetics in the Rabbit: Role of Factor XIII-Mediated Fibrin Polymer Crosslinking

BACKGROUND

Hydroxyethyl starch administration has been associated with decreases in hemostasis and has recently been demonstrated to decrease fibrinogen (FI)-thrombin-(FIIa)-Factor XIII (FXIII) interactions in vitro in human plasma. Thus, the purpose of the present study was to determine the effect of in vivo hemodilution with Hextend (6% hydroxyethyl starch, mean molecular weight 450 kDa) on plasma coagulation kinetics.

MATERIALS AND METHODS

Eight male, New Zealand White rabbits were intravenously administered with 20 ml/kg of Hextend. Citrated plasma was obtained before, 1 min after, and 1 h after hemodilution. Thrombelastographic analyses were performed, with clot initiation (R, sec), clot propagation (alpha, degrees), and clot strength (shear elastic modulus, G, dynes/cm(2)) determined over 20 min. Samples were celite-activated and had either with addition or without additions of FI, FIIa or activated FXIII (FXIIIa) to restore protein content to prediluted values.

RESULTS

There was no significant difference in R values observed before (229 +/- 30), 1 min after (241 +/- 54), and 1 h after (214 +/- 42) hemodilution. Prediluted alpha values (75.2 +/- 1.9) were significantly decreased 1 min (53.3 +/- 5.9) and 1 h after hemodilution (56.1 +/- 10.2). Prediluted G values (1,992 +/- 434) were significantly reduced 1 min (532 +/- 195) and 1 h after (630 +/- 297) hemodilution. FI, FIIa, and FXIIIa addition significantly decreased R values after hemodilution. alpha and G values were significantly improved by FI and FXIIIa after hemodilution. FIIa addition did not significantly affect alpha or G.

CONCLUSIONS

Hextend hemodilution in rabbits maintains clot initiation by diminishing both FIIa-FI and FXIIIa-fibrin interactions, whereas clot propagation and strength were reduced by diminished FXIIIa-fibrin interactions.

Gelatin and Hydroxyethyl Starch, but Not Albumin, Impair Hemostasis After Cardiac Surgery

We investigated the effect of postoperative administration of colloids on hemostasis in 45 patients after cardiac surgery. Patients were randomized to receive 15 mL kg(-1) of either 4% albumin, 4% succinylated gelatin, or 6% hydroxyethyl starch (molecular weight of 200 kDa/degree of substitution 0.5) as a short-term infusion. There was a comparable decrease in maximum clot firmness of thromboelastometry tracings in gelatin and hydroxyethyl starch groups immediately after completion of the infusion, whereas these values remained unchanged in the albumin group. The impairment in clot strength persisted up to 2 h, although the values partly recovered. Postoperative bleeding correlated inversely with the clot strength in pooled data of the artificial colloids. Fibrin formation (clot formation time, alpha-angle) and fibrinogen-dependent clot strength (maximum clot firmness and shear elastic modulus) were more disturbed in the hydroxyethyl starch group than in the gelatin group. We conclude that after cardiopulmonary bypass surgery, both gelatin and hydroxyethyl starch impair clot strength and fibrin buildup, which may predispose patients to increased blood loss. The greatest impairment in hemostasis was seen after hydroxyethyl starch administration, whereas albumin appeared to have the least effect on hemostatic variables.

Albumin induced hypercoagulability does not reduce blood loss in patients undergoing total hip arthroplasty

BACKGROUND AND AIMS

Albumin may enhance and hydroxyethyl starch (HES) may impair haemostasis. While the effects are also dependent on haemodilution we minimized it by early structured transfusion therapy, and compared albumin and HES regarding blood loss and coagulation parameters in hip arthroplasty patients.

MATERIAL AND METHODS

101 patients undergoing primary hip arthroplasty received in random order 4% albumin (n = 48) or HES (average Mw 120 kDa/molar substitution ratio 0.7, n = 53). The administration of colloid, red blood cell (RBC), fresh frozen plasma and platetet concentrates begun after a 6-8%, 12-16%, 60% and 100% blood loss of the patient's calculated blood volume respectively. Explanatory risk factors for blood loss were modelled by regression analysis.

RESULTS AND CONCLUSIONS

Administration of albumin or HES 1200 ml (500-2000 and 500-1800) [median (range) respectively] did not affect blood loss. The vWF antigen was higher in the albumin group (p = 0.04) postoperatively. Haematocrit value, platelet count, bleeding time, prothrombin time value, activated thromboplastin time, FV activity and fibrinogen concentration were comparable between the groups. Long operation time was associated with great blood loss (p < 0.001). In hip arthroplasty patients with near normal levels of haematocrit albumin enhanced coagulation without altering blood loss.

The Effect of Dilution on Plasma Coagulation Kinetics Determined by Thrombelastography Is Dependent on Antithrombin Activity and Mode of Activation

Hemodilution-associated hypercoagulability has been the focus of several investigations because significant morbidity and mortality have been associated with perioperative thrombophilia. Because most investigations implicate imbalances in procoagulant/anticoagulant activity as the etiology of hemodilution-associated hypercoagulability, we determined the effects of dilution on coagulation kinetics and clot strength with thrombelastography (TEG(R)). Control plasma (+/-celite activation) and antithrombin (AT)-deficient (<10% activity) plasma were diluted 0%, 10%, 20%, and 30% with saline. TEG(R) variables measured included time to clot initiation (reaction time, R), speed of clot propagation (angle, alpha), and clot strength (amplitude, A; or shear elastic modulus, G). Dilution of control plasma (10%-30%) resulted in a significant (P < 0.05) 16% decrease in R values, no change in alpha values, and decrease in A and G values. AT-deficient plasma had significantly smaller R values compared with control, and dilution did not change R values in AT-deficient plasma. Celite activation eliminated dilution-associated changes in R values in control plasma but resulted in linear decreases (R(2) = 0.88-0.96, P < 0.0001) in alpha, A, and G in response to dilution. Thus, our data indirectly support the concept that decreases in AT activity cause dilution-mediated hypercoagulability in plasma. Finally, celite activation permits quantification of dilution with TEG.

Fluid administration during abdominal surgery influences on coagulation in the postoperative period

OBJECTIVE

Postoperative coagulopathy is an important concern for patients after major surgery. Our objective was to define the factors that correlate with postoperative deterioration in coagulation.

DESIGN

Retrospective clinical case study.

SETTING

University hospital.

PARTICIPANTS

Adult patients (n = 150), who underwent major abdominal surgery, were randomly chosen to participate in the study. For each patient, demographic and medical data, anesthetic information, type and duration of surgery, hemodynamic variables, fluid administration, as well as preoperative and postoperative prothrombin time and partial thromboplastin time were collected. Statistical analysis was used to determine which factors correlated with deterioration of coagulation tests.

RESULTS

We found statistically significant correlation between deteriorating coagulation functions and administration of more than 3 l of crystalloids during abdominal surgery. There was also correlation between administration of more than 500 ml of colloid administration and elongation of protrombin time. The remainder of the above studied factors did not correlate with deteriorating coagulation.

CONCLUSIONS

Administration of more than 3-l crystalloids or 500-ml colloids during abdominal surgery correlates with postoperative coagulopathy.

Changes in intracranial pressure, coagulation, and neurologic outcome after resuscitation from experimental traumatic brain injury with hetastarch

BACKGROUND

In a model of traumatic brain injury (TBI), 2 protocols compared changes in intracranial pressure (ICP), coagulation, and neurologic outcome after intravenous fluid (IVF) resuscitation with either Hextend (HEX, 6% hetastarch in lactated electrolyte injection) or standard of care, crystalloid plus mannitol (MAN).

METHODS

In the nonsurvivor protocol, swine (n = 28) received a fluid percussion TBI and hemorrhage (27 +/- 3 mL/kg). At 30 minutes, resuscitation began with lactated Ringer's (LR) or HEX. After 60 minutes, MAN (1 g/kg) or placebo was given plus supplemental IVF to maintain cerebral perfusion pressure (CPP) > or = 70 mm Hg for 240 minutes. Swine in the survivor group (n = 15) also underwent TBI and hemorrhage, and resuscitation with HEX was compared to that of normal saline (NS)+MAN. Neurologic outcome and coagulation were evaluated for 72 hours.

RESULTS

In the nonsurvivor protocol, HEX, LR+MAN, and HEX+MAN attenuated the time-related rise of ICP and prevented ICP >20 mm Hg versus LR alone (P < .05). HEX alone maintained CPP (relative to baseline) and decreased total IVF by 50% versus LR +/- MAN (P < .05). MAN had no additive effect with HEX. Coagulation, measured by thromboelastograph reaction time (R), was 11 +/- 1 and 9 +/- 1 minutes at baseline and after TBI (before randomization). At 240 minutes after HEX or LR+MAN, R was 6 +/- 1 or 7 +/- 2 minutes, which indicates a hypercoagulable state, but there was no difference between treatments. In the survivor protocol, ICP and CPP were similar with NS+MAN versus HEX, but IVF requirement was 161 +/- 20 versus 28 +/- 3 mL/kg (P < .05). Motor scores were higher on days 2 and 3 with HEX (P < .05). At 72 hours, R was 28 +/- 14 versus 26 +/- 6 minutes with NS+MAN versus HEX, which indicates a hypocoagulable state, but there was no difference between treatments.

CONCLUSIONS

Hextend as the sole resuscitation fluid after severe TBI reduces fluid requirement, obviates the need for mannitol, improves neurologic outcome, and has no adverse effect on the coagulation profile relative to the crystalloid plus mannitol standard of care.

Hydroxyethyl Starch as a Priming Solution for Cardiopulmonary Bypass Impairs Hemostasis After Cardiac Surgery

We investigated the influence of hydroxyethyl starch (HES) as a priming solution for the cardiopulmonary bypass (CPB) circuit on postoperative hemostasis in 45 patients undergoing elective coronary artery bypass grafting. In a randomized sequence, 20 mL/kg of low-molecular-weight HES (HES 120; molecular weight 120,000 daltons), high-molecular-weight HES (HES 400; molecular weight 400,000 daltons), or 4% human albumin (ALB) was used as the main component of the CPB priming solution. The thromboelastographic values indicating the speed of solid clot formation (alpha-angle) and the strength of the fibrin clot (maximum amplitude and shear elastic modulus) were decreased up to 2 h after CPB in both HES groups. Four hours after the operation, blood loss through the chest tubes had increased in the HES groups: HES 120, mean 804 mL (range, 330-1390 mL); HES 400, mean 1008 mL (range, 505-1955 mL); and ALB, mean 681 mL (range, 295-1500 mL) (P < 0.05 between the HES 400 and ALB groups). We conclude that HES solutions, when given in doses of 20 mL/kg in connection with the CPB prime, compromise hemostasis after cardiac surgery. This effect appears related to formation of a less stable thrombus compared with that formed in the presence of ALB.

IMPLICATIONS

The influence of hydroxyethyl starch (HES) on postoperative hemostasis was investigated in cardiac surgery. The thromboelastographic values indicated that HES solutions, when given in connection with the cardiopulmonary bypass prime, compromise hemostasis after cardiac surgery. This effect seems to occur through the formation of a less stable clot.