The development of hypercoagulability state, as measured by thrombelastography, associated with intraoperative surgical blood loss

Decreased Circulating Red Cell Mass Induced by Intravenous Acepromazine Administration Alters Viscoelastic and Traditional Plasma Coagulation Testing Results in Healthy Horses

Coagulopathy is common in equine critical illness, with its early recognition being crucial for patient management and prognosis. In vitro viscoelastic (VE) hypercoagulability with decreased RCM/PCV has been demonstrated in dogs but not horses. Our objective was to evaluate the effects of acepromazine-induced (0.1 mg/kg IV) decreased RCM on VE and plasma coagulation parameters using a prospective interventional study of eight adult horses. Complete blood count (CBC), fibrinogen, prothrombin time (PT), partial thromboplastin time (PTT), packed cell volume (PCV), total solids (TS), and VCM Vet™ VE testing performed at baseline (T0), 1 h (T1), and 12 h (T2) post acepromazine administration. Splenic volume was determined ultrasonographically. The results were analyzed using one-way repeated measures ANOVA with Tukey's post hoc HSD test to determine the effect of time (sample). PCV decreased 13% points following acepromazine administration from T0 to T1 (p < 0.001), remaining decreased at T2 (p < 0.001). Splenic volume increased from T0 to T1 (p = 0.04) and was not different from baseline at T2. Maximal clot formation (MCF) increased from T0 (p = 0.03). PTT decreased from T0 to T1 and increased at T2 (p = 0.03). No other coagulation parameters were significantly altered. This study demonstrates a non-inflammatory acute model of anemia in horses that impacts VE and plasma-based testing.

Thromboelastography in elective total hip arthroplasty

BACKGROUND

Hypercoagulability plays an important role in predisposing patients to venous thromboembolism (VTE) after total hip arthroplasty (THA). We used thromboelastography (TEG) to examine the coagulation status of patients undergoing THA.

AIM

To examine coagulation as measured by TEG in patients undergoing THA who received standard VTE chemoprophylaxis with enoxaparin.

METHODS

After ethical approval, we performed a retrospective analysis of data collected in patients undergoing primary elective THA. We analyzed TEG data on samples performed before skin incision, intraoperatively and for 5 d postoperatively. Conventional coagulation tests were performed preoperatively and on postoperative day 5.

RESULTS

Twenty patients undergoing general anesthesia and 32 patients undergoing spinal anesthesia (SA) were included. TEG demonstrated a progressively hypercoagulable state postoperatively, characterized by elevated maximum amplitude. TEG also demonstrated transient intraoperative hypercoagulability in patients receiving SA. In contrast, conventional coagulation tests were normal in all patients, pre- and postoperatively, except for an increase in plasma fibrinogen day 5 postoperatively.

CONCLUSION

Despite VTE prophylaxis, patients following total hip replacement remain in a hypercoagulable state as measured by both TEG and conventional tests. This group may benefit from more optimal anticoagulation and/or additional perioperative hemostatic monitoring, via TEG or otherwise.

The Association between Prognostic Nutritional Index (PNI) and Intraoperative Transfusion in Patients Undergoing Hepatectomy for Hepatocellular Carcinoma: A Retrospective Cohort Study

BACKGROUND

PNI is significantly associated with surgical outcomes; however, the association between PNI and intraoperative transfusions is unknown.

METHODS

This study retrospectively analyzed 1065 patients who underwent hepatectomy. We divided patients into two groups according to the PNI (<44 and >44) and compared their transfusion rates and surgical outcomes. We performed multivariate logistic and Cox regression analysis to determine risk factors for transfusion and the 5-year survival. Additionally, we found the net reclassification index (NRI) to validate the discriminatory power of PNI.

RESULTS

The PNI <44 group had higher transfusion rates (adjusted odds ratio [OR]: 2.20, 95%CI: 1.06-4.60, p = 0.035) and poor surgical outcomes, such as post hepatectomy liver failure (adjusted [OR]: 3.02, 95%CI: 1.87-4.87, p < 0.001), and low 5-year survival (adjusted OR: 1.68, 95%CI: 1.17-2.24, p < 0.001). On multivariate analysis, PNI <44, age, hemoglobin, operation time, synthetic colloid use, and laparoscopic surgery were risk factors for intraoperative transfusion. On Cox regression analysis, PNI <44, MELD score, TNM staging, synthetic colloid use, and transfusion were associated with poorer 5-year survival. NRI analysis showed significant improvement in the predictive power of PNI for transfusion (p = 0.002) and 5-year survival (p = 0.004).

CONCLUSIONS

Preoperative PNI <44 was significantly associated with higher transfusion rates and surgical outcomes.

Higher coagulation activity in hip fracture patients: A case-control study using rotational thromboelastometry

INTRODUCTION

Trauma-induced coagulopathy has been extensively investigated in the multitrauma setting, but only sparsely following moderate orthopedic trauma. The purpose of this study was to evaluate changes in the hemostatic profile of patients with hip fractures, using rotational thromboelastometry (ROTEM).

METHODS

198 patients with hip fractures who underwent surgery were included in the study. A matched group of 52 healthy individuals was also enrolled. Demographics, conventional laboratory assays, and ROTEM parameters were recorded and compared between patients and healthy adults. The preoperative and postoperative ROTEM values of fractured patients were also compared.

RESULTS

The conventional coagulation assays were similar for the 2 groups. However, several ROTEM parameters including EXTEM MCF (P < .001), EXTEM alpha angle (P < .001), INTEM MCF (P < .001), INTEM A10 (P < .001), and INTEM alpha angle (P < .001) significantly differed between the 2 groups indicating a higher coagulation potential following hip fractures. Also, fractured patients had significantly lower INTEM and EXTEM CT values (P = .008 and P = .012, respectively) and significantly lower INTEM and EXTEM CFT values (P < .001). Adjusted analysis for confounders further confirmed the direct relationship between hip fracture and higher coagulation activity. Last, INTEM CT and CFT significantly decreased (P = .008 and P < .001, respectively), while INTEM MCF, A10, and alpha angle significantly increased (P < .001) postoperatively, indicating that surgery further increases the coagulation potential.

CONCLUSION

A higher coagulation activity following hip fractures and surgical treatment can be detected by ROTEM shortly after the injury, even when this is undetectable by conventional coagulation assays.

Ability of Thromboelastography to Detect Hypercoagulability: A Systematic Review and Meta-Analysis

OBJECTIVE

To review the current literature on the use of viscoelastic hemolytic assays, such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM), during the perioperative period of patients and determine the ability of TEG and ROTEM to detect hypercoagulability and identify increased risk of the development of venous thromboembolism (VTE).

DATA SOURCES

PubMed, EMBASE, and Cochrane online databases were queried through February 11, 2018, by pairing the terms "thromboelastography," "viscoelastic hemostatic assays," and "rotational thromboelastometry" with "venous thromboembolism," "deep vein thrombosis," "pulmonary embolism," and "hypercoagulability."

STUDY SELECTION

Inclusion and exclusion criteria were established to determine relevance and quality of data, of which 2.54% of initially identified studies met.

DATA EXTRACTION AND SYNTHESIS

Articles and citations were reviewed for relevance by 2 independent individuals following PRISMA guidelines as well as a quality assessment of data as established by Zaza et al. In studies that separated patients postoperatively by VTE development or no VTE development, data were pooled utilizing a modified DerSimmion and Laird random effects model.

RESULTS

One thousand eight hundred ninety-three articles were assessed for eligibility, yielding 370 abstracts. Of the 370 abstracts, 35 studies were included, and of these, only 5 were included in the meta-analysis. Studies included postsurgical patients in a variety of surgical fields, encompassing a total of 8939 patients, with 717 thrombotic events reported. Elevated maximum amplitude (MA) was a statistically significant indicator of hypercoagulability across at least 1 perioperative time point in 17 (50%) of the articles reviewed, consisting of 6348 (72%) patients. The pooled mean MA value for defining hypercoagulability was greater than 66.70 mm. Using a prepublished value for hypercoagulability of 65 mm, the combined effect of MA on the development of VTE in postsurgical patients was determined to be 1.31 (95% confidence, 0.74-2.34, P = 0.175) and was 46% sensitive and 62% specific in predicting a postoperative VTE.

CONCLUSIONS

Only 1 parameter, MA, was consistently used to both define hypercoagulability and be predictive of VTE after traumatic injury and surgical intervention; however, there remains a broad variability in the definition of hypercoagulability as determined by MA and thus limits its predictive ability. In addition, when hypercoagulability was measured throughout the perioperative period, TEG consistently demonstrated hypercoagulability starting on post-op day 1 (POD1).

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Thromboelastographic assessment of the impact of mexiletine on coagulation abnormalities induced by air or normal saline intravenous injections in conscious rats

BACKGROUND

Thromboelastography (TEG) in venous air embolism (VAE) has been poorly studied. We induced coagulation abnormalities by VAE in a rat model, assessed by TEG with and without mexiletine, a lidocaine analogue local anesthetic.

METHODS

Twenty-three Sprague Dawley rats instrumented under isoflurane anesthesia and allowed to recover five days prior to the experiments were randomized into three experimental groups: 1) VAE (n = 6); 2) VAE and mexiletine (n = 9); and 3) normal saline (NS) alone (control group, n = 8). Blood samples were collected at baseline, one hour (h) and 24 h in all groups and analyzed by TEG to record the R, K, angle α and MA parameters.

RESULTS

In Group 1, VAE decreased significantly R at 1 h (31%), K at 1 h (59%) and 24 h (34%); α increased significantly at 1 h (30%) and 24 h (22%). While R returned to baseline values within 24 h, K, MA and α did not. In group-2 (Mexiletine + VAE), K and R decreased at 1 h (48% and 29%, respectively) and at 24 h the changes were non-significant. Angle α increased at 1 h (28%) and remained increased for 24 h (25%). In group 3 (NS), only R was temporarily affected. MA increased significantly at 24 h only in the VAE alone group.

CONCLUSION

As expected, VAE produced a consistent and significant hypercoagulable response diagnosed/confirmed by TEG. Mexiletine prevented the MA elevation seen with VAE and corrected R and K time at 24 h, whereas angle α remained unchanged. Mexiletine seemed to attenuate the hypercoagulability associated with VAE in this experiment. These results may have potential clinical applications and deserve further investigation.

Preoperative Thromboelastography as a Sensitive Tool Predicting Those at Risk of Developing Early Hepatic Artery Thrombosis After Adult Liver Transplantation

BACKGROUND

Whilst causes of hepatic artery thrombosis (HAT) after liver transplantation (LT) are multifactorial, early HAT (E-HAT) remains pertinent complication impacting on graft and patient survival. Currently there is no screening tool that would identify patients with increased risk of developing E-HAT.

METHODS

We analyzed the native procoagulant state of LT recipients, identified through pretransplant thromboelastographic (TEG) data among other known risk factors, to identify risk factors for E-HAT.

RESULTS

The outcomes of 828 adult patients undergoing LT between 2008 and 2013 were analyzed. Overall, 79 (9.5%) patients experienced HAT, E-HAT was diagnosed in 23, and in the remainder this was "late" HAT. The maximum amplitude (MA) on preoperative TEG was significantly higher in patients diagnosed with E-HAT compared with those who did not (71.2 mm vs 57.9 mm; P < 0.0001). Receiver operating characteristic analysis with the cutoff value for MA of 65 mm or greater returned area under the curve of 0.750 (P < 0.001) predicting E-HAT with a sensitivity of 70%. A total of 7% of patients with an MA of 65 mm or greater went on to develop E-HAT (hazard ratio, 5.28; 95% confidence interval, 2.10-12.29; P < 0.001), whereas only 1.2% patients with an MA less than 65 mm experienced E-HAT.

CONCLUSIONS

Preoperative TEG may reliably identify group of recipients at greater risk of developing E-HAT, and intense surveillance and anticoagulation prophylaxis may avoid this serious complication after LT.

Does Hemodilution Enhance or Compromise Blood Coagulation?

The reduction in oxygen-carrying capacity during hemodilution is well tolerated by most patients. However, hemodilution not only decreases O2 transport capacity, but also may influence blood coagulation. Advanced hemodilution with crystalloids does not compromise blood coagulation and, with moderate hemodilution, even augmented blood coagulation may develop. In contrast, blood coagulation is compromised during hemodilution with colloids. The effect of human serum albumin and gelatin is relatively modest, but significantly more than during equivalent hemodilution with crystalloids. Dextran and hydroxyethyl starch compromise blood coagulation more. This results from reduction of factor VIII, a decrease in plasmatic coagulation, and an impairment of platelet function. For hydroxyethyl starch, molecular size and degree of substitution are crucial for the effect on blood coagulation, with hydroxyethyl starch (200,000/0.5) having the least effect. Furthermore, accelerated fibrin formation is observed during hemodilution with Dextran, hydroxyethyl starch, and gelatin with an altered fibrin structure. In vitro clot lysis is also increased with all colloids, but there are no reports on augmented in vivo fibrin degradation products. Besides the effect on intraoperative blood coagulation, the hemodynamic effectiveness, duration thereof, effect on microcirculation and edema formation, and, in particular, the effect on the hypercoagulable state in the postoperative period need to be considered in the choice of the replacement fluid during hemodilution and intraoperative blood loss.

Thrombelastographic changes in OPCAB surgical patients

The purpose of this study was to determine whether thrombelastography could detect hypercoagulability in the off-pump coronary artery bypass (OPCAB) patient. Seventeen OPCAB and six cardiopulmonary bypass (CPB) patients were studied pre- and postprocedure, as well as on each of the first three postoperative days (POD). In the OPCAB patients, there was a small reduction in the postprocedure coagulation index (CI). This was followed by an increase in the CI on each of the next three POD, reaching a level exceeding the mean preprocedure CI by 2.32 units, indicative of a state of relative hyper- coagulability. The mean CI for the CPB patients decreased significantly in the postprocedure sample. Over the next 72 h, the CI increased to a level that nearly equaled the preprocedure ‘baseline’. We concluded that our study identified a state of relative hypercoagulability in the OPCAB patient 72 h after surgery. The mechanism of this hypercoagulation, as well as the clinical significance of this finding, is yet to be determined.

Heart Transplantation

Although the number of available donor hearts severely limits the epidemiologic impact of heart transplantation on patients with heart failure, patients with end-stage heart failure unresponsive to medical management currently have no other viable alternatives. Destination therapy with a ventricular assist device is the closest toward approaching clinical reality but has been plagued with problems of infection and stroke. The purpose of this review is to summarize recent developments in the field that may broaden the clinical impact of heart transplantation. For example, novel methods of cardiac preservation are being designed to safely evaluate and utilize “extended criteria” donors. Surgical techniques and medical management have reduced the incidence of postoperative right heart failure, and immunosuppressive regimens promise to limit chronic graft vascular disease.

Perioperative blood conservation strategies for major spine surgery

BACKGROUND

Orthopedic surgery, especially spine and spinal deformity surgery, may be associated with high perioperative blood loss. In order to reduce the risk of excessive blood loss and unnecessary blood transfusions, strategies such as Patient Blood Management including goal-directed coagulation management have been developed.

RECENT FINDINGS

Adverse effects of allogeneic blood transfusions have been shown for most surgical fields including orthopedic surgery. Several efforts have been made to increase the preoperative red blood cell (RBC) mass, to reduce the intraoperative blood loss, and to use restrictive transfusion triggers in order to minimize or avoid RBC transfusions. Measures to reduce intraoperative blood loss include new surgical techniques, use of cell salvage where possible, bedside coagulation management with point-of-care devices, substitution of coagulation factors, antifibrinolytic agents, and desmopressin, induced hypotension, and avoidance of hypothermia.

SUMMARY

Blood conservation in spinal surgery is a multidisciplinary approach and the efficacy of most single measures has been shown. Cost-effectiveness and the benefits of long-term patient outcomes are the subjects of current and future research.

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.

Regional citrate anticoagulation for hemorrhage experiments in rats

INTRODUCTION

Hemorrhage alone without concomitant trauma often results in a hypercoagulable state that makes it difficult to prevent clotting within the blood withdrawal catheters. Although systemic administration of heparin can ameliorate this problem, heparin use has many additional actions that may confound interpretation of the hemorrhage experiments. The problem can be resolved by the use of a dual lumen catheter that anticoagulates only the blood within the withdrawal circuit. We describe the design of such a catheter and evaluate its function in studies of hemorrhagic shock in rats.

MATERIALS AND METHODS

Construction directions are provided for the dual lumen catheter along with a commercial source. The catheters were connected to computer controllable infusion syringes. Either citrate or heparin was used for regional extracorporeal anticoagulation. Rats were anesthetized and hemorrhaged to 40mmHg for more than 15min through the use of a computer program written in Labview. Ionized calcium measurements were obtained pre- and posthemorrhage.

RESULTS

The catheters remained patent throughout the experiments. There was no significant difference in the ionized calcium whether citrate or heparin was used for extracorporeal anticoagulation.

CONCLUSION

The dual lumen catheters are suitable for the study of hemorrhagic shock in rats without the need for systemic anticoagulation. The catheters can be used with computer-controlled hemorrhage procedures.

Reducing perioperative blood loss and allogeneic blood transfusion in patients undergoing major spine surgery

At present, individual techniques, including intraoperative acute normovolemic hemodilution, use of tranexamic acid, use of intrathecal morphine, proper positioning, and modification of operative techniques, seem most promising for reducing perioperative blood loss and allogeneic blood transfusion in patients undergoing major spine surgery. Other techniques including preoperative autologous predonation; mandatory discontinuation of use of antiplatelet agents; intraoperative and postoperative red-blood-cell salvage; use of aprotinin, epsilon-aminocaproic acid, recombinant factor VIIa, or desmopressin; induced hypotension; avoidance of hypothermia; and minimally invasive operative techniques require additional studies to either establish their effectiveness or address safety considerations.

The effect of low molecular weight heparin (enoxaparin) on enhanced coagulation induced by crystalloid haemodilution

The purpose of this study was to establish whether a low molecular weight heparin (enoxaparin) attenuated or abolished the enhanced coagulation induced by crystalloid fluid therapy. Twenty young, healthy male volunteers were injected subcutaneously with either enoxaparin 40 mg or saline on two separate occasions one week apart, in a randomised, blinded study. Twelve hours later, a blood sample was taken for thrombelastography analysis and haematocrit. Saline 14 ml.kg⁻¹ was then infused over thirty minutes and thrombelastography and haematocrit measurements repeated. There was a significant post-dilutional difference in the alpha angle (p = 0.002) and k-time (p = 0.001) between the two groups. There was a trend towards reduced shortening of r-time in the enoxaparin group compared to the saline control (p = 0.18). The findings suggest that enoxaparin diminished acceleration of clot formation due to haemodilution.

The effect of ulinastatin on hemostasis in major orthopedic surgery

BACKGROUND

Ulinastatin, a urinary trypsin inhibitor, is widely used to treat acute systemic inflammatory disorders. However, the effects of ulinastatin, especially on the potential for hemostasis, have not been fully elucidated. This study examined whether ulinastatin had any beneficial effects on blood loss and blood transfusion requirements in patients undergoing major orthopedic surgery.

METHODS

Eighty patients, aged 18 to 75 years, scheduled for major orthopedic surgery were enrolled in this study and were divided into the ulinastatin (n = 40) and control (n = 40) groups. Following the induction of general anesthesia, and immediately before the surgical incision, the patients in the ulinastatin group were given 5,000 units/kg of ulinastatin, which were mixed in 100 ml normal saline intravenously over 30 min, while those in the control group received the same volume of normal saline. The amounts of blood loss, infused fluid, and transfused blood products were measured throughout the study period. Blood samples for coagulation parameters were obtained before inducing anesthesia (T1), at the end of surgery (T2), and 12 h after surgery (T3).

RESULTS

The amounts of blood loss and infused fluid during surgery were not significantly different between the two groups. However, 12 h postoperative blood loss was significantly less in the ulinastatin group than in the control group (255.0 +/- 133.2 ml VS. 395.4 +/- 338.4 ml, P < 0.05).

CONCLUSIONS

Our data suggest that a single infusion of ulinastatin in major orthopedic surgery is associated with decreased blood loss in the early postoperative period.

Critically ill cancer patients are not consistently hypercoagulable after craniotomy

INTRODUCTION

Recent reports using thrombelastography have suggested that neurosurgical patients develop a hypercoagulable state in the postoperative period. Since venous thromboembolism is a potentially life threatening complication in these patients, we studied a similar population in our institution.

METHODS

We conducted a prospective pilot study to evaluate postoperative coagulation changes in critically ill cancer patients after craniotomy. Data collected included demographics, diagnoses, severity of illness, all hematological information (coagulation tests included conventional and TEG), therapies, and complications. Analysis included descriptive statistics, and multivariate regression analysis.

RESULTS

Eleven patients were included in the study. Mean age was 52 +/- 17 years, BMI 28 +/- 6.5, APACHE II and SOFA scores were 11.18 +/- 5.0 and 3.82 +/- 1.6 respectively. The Coagulation Index (CI), which is derived from the measured values of R, K, MA, and alpha angle was 1.22 +/- 3.5, R 4.2 +/- 1.6, K 2.0 +/- 2.1, MA 60.78 +/- 5.97, and alpha angle 66.88 +/- 14.9; while the Thrombodynamic Potential Index (TPI), which is derived from the measured values of K and MA only was 32.48 +/- 21. The CI correlated significantly with R, K, alpha angle, MA, TMA, TPI, PMA, E, A30 and A60 but not with the PTT, INR, or SOFA and APACHE II scores. One patient was hypocoagulable by CI and TPI values; in contrast, nine patients were hypercoagulable by TPI but only one by CI. There were no cases of VTE.

CONCLUSIONS

Hypercoagulability as defined by the CI was not a common finding in this study. Although the TPI indicated hypercoagulability in a large number of patients, we do not believe it is a good tool to assess the patient's clotting status or predictor of thrombosis because in contrast to the CI, it does not take into account the enzymatic portions of the clotting cascade. A larger TEG study is warranted to determine the clinical significance of these changes in this and other populations.

High-molecular-weight hydroxyethyl starch accelerates kallikrein-dependent clot initiation

BACKGROUND

A decrease in reaction time (R; seconds) has been considered a thrombelastographic hallmark of hypercoagulability. However, the cause of changes in R has been influenced by the method of activation (e.g., celite) and the clinical/laboratory setting (e.g., hemodilution). Although antithrombin deficiency has been implicated as a cause of decreased R in unactivated samples after crystalloid dilution, dilution with hydroxyethyl starch (HES) solutions such as Hextend (6% HES solution; average molecular weight 450 kDa) or Voluven (6% HES solution; average molecular weight 130 kDa) has decreased R values in celite-activated samples in vitro and in vivo, with modulation of these R values observed after aprotinin exposure. Thus, this study proposed to define whether HES affects kallikrein-dependent clot initiation.

METHODS

Citrated human plasma was subjected to 0% or 30% dilution with 0.9% NaCl, Hextend, or Voluven, in the absence or presence of aprotinin (200 KIU/mL final concentration). Prekallikrein-deficient (<1% activity) plasma was similarly diluted. After recalcification and celite activation, thrombelastography was performed for determination of R.

RESULTS AND CONCLUSIONS

R in samples without aprotinin diluted with Hextend (mean +/- SD, 132 +/- 6 seconds) was significantly smaller than that in samples with 0% dilution (155 +/- 5 seconds) and 30% dilution with 0.9% NaCl (162 +/- 9 seconds), but was not less than that in Voluven-diluted samples (149 +/- 14 seconds). R significantly increased (28%-68%) in all conditions with aprotinin compared to samples without aprotinin, and Hextend had significantly smaller R compared with that in the other fluids. Lastly, R was not different in experiments with prekallikrein-deficient plasma. These data indicate that Hextend accelerates kallikrein-dependent clot initiation compared with 0.9% NaCl or Voluven.

The haemodilution enhanced onset of coagulation as measured by the thrombelastogram is transient

BACKGROUND AND OBJECTIVE

Crystalloid haemodilution has been widely found to enhance coagulation onset, but the duration of this effect has never been documented.

METHODS

Twelve healthy, consenting volunteers had a rapid infusion of 14 mL kg-1 of normal (0.9%) saline. Blood samples were taken, prior to (control), and immediately after (30 min) the rapid saline infusion was completed (30 min). They were then repeated at regular intervals up to 120 min. Haematocrit/platelet counts were taken to determine the degree of dilution and thrombelastograms, with and without platelet antagonists (ReoPro, Abciximab), were measured in all samples. Antithrombin levels were selectively measured.

RESULTS

The haematocrit and platelet count showed a rapid dilutional decrease at 30 min (mean of -12.2% and -14.4%, respectively), with values returning towards baseline within 15 min after finishing the infusion. There was a significantly faster onset of coagulation (decrease in r-time) in the post-infusion sample (30 min) compared to control (P<0.05), again returning towards normal as the dilution effect was reversed. Similar thrombelastograms findings were evident in the plasma factor only group (platelets inhibited by ReoPro). Antithrombin levels changed in keeping with the haemodilution effect (P<0.0001). There was a linear relationship between antithrombin and thrombelastograms r-time (P=0.012).

CONCLUSION

The faster onset of coagulation brought on by haemodilution return towards normal as the dilutional effect is reversed. This effect is mediated through plasma clotting factors. Of interest is the significant inverse correlation of the onset of coagulation increasing as the antithrombin levels decreased with dilution.

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.

Antithrombin efficiency is maintained in vitro in human plasma following dilution with hydroxyethyl starches

Hemodilution has been associated with changes in hemostasis secondary to modulation of procoagulant activity. However, direct effects of specific fluids on anticoagulants, such as antithrombin (AT), remained undefined. Thus, the purpose of this investigation was to determine whether hemodilution with hydroxyethyl starches (HES) directly diminishes plasma AT activity, which would be manifested by decreases in clot initiation time (reaction time, R) with thrombelastography greater than that seen with 0.9% NaCl (NS). Normal plasma and AT-deficient (<1% activity) plasma were diluted 0 or 30% with NS, Hextend (6% HES; average molecular weight, 450 kDa), PentaLyte (6% HES; average molecular weight, 220 kDa), or Voluven (6% HES; average molecular weight, 130 kDa) (n=6-7 experiments per condition). Undiluted, normal plasma had an R value of 796+/-65 s, which was significantly (P<0.05) greater than R values following NS (690+/-50 s) or Voluven (675+/-68 s) dilution. R values of normal plasma diluted with Hextend (831+/-51 s) or PentaLyte (801+/-72 s) were not different from undiluted plasma but were significantly (P<0.05) greater than those observed following NS or Voluven dilution. There were no significant differences between the conditions when AT-deficient plasma was utilized (R range, 404-440 s). Rather than interfere with AT activity, HES with an average molecular weight of 220-450 kDa maintain AT efficiency.

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.

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.

Decreased factor XIII availability for thrombin and early loss of clot firmness in patients with unexplained intraoperative bleeding

To explore relevant changes in unexplained intraoperative bleeding, we evaluated elements of the final steps of the coagulation cascade in 226 consecutive patients undergoing elective surgery. Patients were stratified for the occurrence of unexplained intraoperative bleeding according to predefined criteria. Twenty patients (8.8%) developed unexplained bleeding. The median intraoperative blood loss was 1350 mL (bleeders) and 400 mL (nonbleeders) (P < 0.001). Fibrinogen and Factor XIII (F. XIII) were more rapidly consumed in bleeders (P < 0.001). Soluble fibrin formation (fibrin monomer) was increased in bleeders throughout surgery (P < or = 0.014). However, F. XIII availability per unit thrombin generated was significantly decreased in bleeders before, during, and after surgery (P < or = 0.051). Computerized thrombelastography showed a parallel, significant reduction in clot firmness. We suggest that mild preexisting coagulopathy is not rare in surgical patients and probably can result in clinically relevant intraoperative bleeding. This hemostatic disorder shows impaired clot firmness, probably secondary to decreased cross-linking (due to a loss of F. XIII, both in absolute measures and per unit thrombin generated). We suggest that the application of F. XIII might be worthwhile to test in a prospective clinical trial to increase clot firmness in patients at risk for this intraoperative coagulopathy.

Changes in thrombelastograph variables associated with aging

Aging is associated with hypercoagulability. To assess thrombelastography (TEG) variables associated with aging, 132 adult patients of various ages undergoing orthopedic surgery for fracture repair had venous blood samples withdrawn for testing of recalcified TEG before the induction of anesthesia. Age was weakly correlated with all TEG variables: r time (R) (r = -0.45, P < 0.001; R = 19.5 - 0.09 x age), k time (K) (r = -0.49, P < 0.001; K = 6.5 - 0.04 x age), maximum amplitude (MA) (r = 0.25, P < 0.01; MA = 53.3 + 0.07 x age), and alpha (r = 0.52, P < 0.001; alpha = 52.8 + 0.2 x age). The correlation was stronger for men than for women. Only R was significantly correlated with age when the women were separately analyzed. Part of the correlation may be attributable to a concurrent decrease in hemoglobin with aging, but age remained an independent predictor of R, K, and alpha on forward stepwise linear multiple regression analysis. Aging was weakly associated with changes in TEG variables, which should be allowed for when interpreting TEG measurements in the elderly.

The effects of perioperatively administered crystalloids and colloids on concentrations of molecular markers of activated coagulation and fibrinolysis

To explore whether intravenous administration of routinely used crystalloid or colloid solutions differently affects the coagulation system, we investigated orthopaedic patients. Since crystalloid solutions might cause hypercoagulability, we here present our results on molecular markers of coagulation and fibrinolysis. Patients undergoing knee replacement surgery randomly received isovolemic amounts of lactated Ringer's solution, 6% hydroxyethyl starch 200/0.5 or 4% modified gelatine. Arterial blood samples for determination of specific molecular markers of activated coagulation (thrombin/antithrombin complex, D-dimer, prothrombin fragment F1 + 2), fibrinolysis (plasmin/alpha 2-antiplasmin complex, tissue plasminogen activator, plasminogen activator inhibitor-1), and concentrations of coagulation factor XIII were obtained at baseline, before tourniquet release, at the end of surgery and 2 h after operation. During the observation period, thrombin/antithrombin complex increased from 4.8 to 54.7 microg/l, D-dimer increased from 0.3 to 6.0 mg/ml, prothrombin fragment F1 + 2 increased from 1.7 to 5.9 nmol/l, tissue plasminogen activator decreased from 7.3 to 6.7 ng/ml, plasminogen activator inhibitor-1 increased from 68.4 to 71.0 ng/ml, plasmin/alpha 2-antiplasmin complex increased from 281.5 to 884 microg/l and factor XIII decreased from 89.0 to 58.5%. All parameters changed significantly but without any detectable difference in the response profile between the groups receiving different intravenous fluids. During knee replacement surgery a pronounced activation of the coagulation/fibrinolytic system was observed, regardless of whether patients received crystalloid or colloid fluids. Thus, these results cannot confirm the hypothesis that crystalloid fluids per se cause hypercoagulability in vivo.

Nicardipine versus nitroprusside for deliberate hypotension during idiopathic scoliosis repair

STUDY OBJECTIVE

To compare coagulation, blood loss, and transfusion requirements between patients receiving nicardipine and nitroprusside for deliberate hypotension during idiopathic scoliosis repair.

DESIGN

Prospective, randomized study.

SETTING

University hospital.

PATIENTS

51 ASA physical status I patients presenting for spine fusion for idiopathic adolescent scoliosis.

INTERVENTIONS

Patients were randomized to two groups to receive nicardipine or nitroprusside to maintain mean arterial pressure (MAP) between 55 and 65 mmHg.

MEASUREMENTS

Blood loss, blood transfusions, and coagulation studies (thromboelastogram and platelet aggregation) before starting vasodilator, 30 minutes and 90 minutes after starting vasodilator, and 30 minutes after stopping vasodilator, were all recorded.

MAIN RESULTS

There was no difference between the groups in blood loss [nicardipine = 1,129 cc (893 to 1,480), nitroprusside = 960 cc (704 to 1,473)] and only one patient required a nonautologous transfusion. There were no differences in prothrombin time (pT, partial thromboplastin time (pTT), platelet count, or platelet aggregation between groups. There were more episodes of severe hypotension (MAP <45 mmHg) in the nitroprusside group (0% vs. 28%, p = 0.0175). On average, patients in the nicardipine group spent 21 minutes less in the recovery room than did the nitroprusside group (p = 0.043).

CONCLUSIONS

Nitroprusside's effect on platelet aggregation produces no increase in blood loss compared with nicardipine. Nicardipine causes less transient severe hypotension than nitroprusside, although both drugs are acceptable choices for obtaining the goals of deliberate hypotension.

Thromboelastogram monitoring in the perioperative period of hepatectomy for adult living liver donation

Living donor liver transplantation (LDLT) is becoming a widespread procedure. However, the risk of surgical and medical complications in healthy donors is still a major concern. Hypercoagulability contributes to thromboembolic complications after surgery, but alterations of hemostasis after liver resection are difficult to predict. This study aims to define the perioperative coagulation profile of living liver donors by the use of both routine tests and thromboelastogram (TEG). Ten subjects undergoing right hepatectomy for LDLT were studied. A complete coagulation screening was performed before operation. The coagulation profile was evaluated by platelet count, prothrombin time-international normalized ratio (PT-INR), activated partial thromboplastin time (aPTT), and TEG at the beginning and at the end of surgery, and on days 1, 3, 5, and 10 after operation, while the donors were under low molecular weight heparin (LMWH) prophylaxis. At preoperative screening, no subject showed evidence of a prothrombotic state. In all cases, TEG was normal at the beginning of surgery. In the postoperative period, despite decreased platelet counts, increased PT-INR, and normal aPTT values, TEG evidenced the progressive development of hypercoagulability in 4 subjects on day 5 and in 6 subjects on day 10. One donor with a definitely hypercoagulable TEG on day 5 experienced deep venous thrombosis (DVT) on day 8, which was resolved with therapeutic doses of LMWH. In conclusion, despite routine tests suggesting hypocoagulability and LMWH prophylaxis, TEG monitoring showed the unexpected occurrence of hypercoagulability in the majority of the subjects after hepatectomy for LDLT. TEG monitoring could be useful in the perioperative management of donors to guide antithrombotic treatment and increase the safety of the procedure.

The effects of a one unit blood donation on auto-haemodilution and coagulation

The effect of haemodilution on coagulation has been extensively investigated. We investigated auto-haemodilution following a 10% blood loss (480 ml) and its effect on coagulation. Ten healthy, unstarved volunteers were enrolled. One unit of blood was taken from each volunteer. Concurrently blood was taken from the opposite arm prior to and immediately after the blood donation, and at 1, 2, 4 and 6 hours. It was tested for thrombelastography, haematocrit and endorphins. There was a significant decrease in r-time from the control sample to the sample taken immediately post blood donation. This value returned to baseline at 1 hour post donation and did not change again. There were no other significant changes in thromboelastographic parameters. Fractional plasma noradrenaline changes were significantly raised at 1 hour post donation (P = 0.048), returning to baseline by 2 hours post donation. The haematocrit showed a rapid (approximately 4%) fall during donation followed by a slow, but progressive decrease over six hours, falling by a mean of 8.3% from pre-donation values. A state of relative hypercoagulability is found immediately after a rapid 10% loss in circulating blood volume. This may be related to the rapid immediate haemodilution. It is unlikely that the sympathetic response to blood loss plays a role. However, after the initial drop, slow restoration of circulating blood volume by autodilution takes six to eight hours, and is not associated with enhanced coagulation. Of interest is that a 10% blood loss in a healthy person does not require volume replacement.

The influence of crystalloid and colloid replacement solutions in acute normovolemic hemodilution: a preliminary survey of hemostatic markers

Acute normovolemic hemodilution (ANH), in which blood for autologous use is collected immediately before the onset of surgical blood loss, is a recommended autologous blood procurement technique for blood conservation. Both crystalloid and colloid replacement fluids have been used to maintain normovolemia during ANH, but few data are available to justify the use of a particular replacement fluid. Therefore, we designed a prospective, randomized study to determine if the replacement fluid choice affects various coagulation variables and perioperative blood loss. Forty adult patients, ASA physical status 1-3, scheduled for ANH during radical prostatectomy were randomly assigned to one of four replacement fluid groups: (a) Ringer's lactate, (b) 5% albumin, (c) 6% dextran 70 (DEX), or (d) 6% hetastarch (HES). After the induction of a standardized general anesthetic, all patients underwent ANH to a final hemoglobin level of 9 g/dL. Complete blood count, prothrombin time, partial thromboplastin time, fibrinogen, factors V and VIII levels, bleeding time, and thromboelastography (TEG measurements were obtained at similar time points in the procedure. When compared with baseline, activated partial thromboplastin time decreased and factor VIII levels increased in the postanesthesia care unit in both the Ringer's lactate and 5% albumin groups. The DEX and HES groups demonstrated a decrease in TEG maximum amplitude between preoperative and postanesthesia care unit measurements and TEG alpha (angle) was decreased from baseline in the DEX group. The changes in factor VIII, activated partial thromboplastin time, and TEG measurements indicate that HES and DEX may attenuate the hypercoagulability related to surgery.

Citrated blood does not reliably reflect fresh whole blood coagulability in trials of in vitro hemodilution

IMPLICATIONS

Citration and storage of whole blood markedly alter the Thrombelastograph effects of hemodilution on coagulation. The results of hemodilution studies in which citrated blood has been used to study coagulation may not be reliable.

The in vitro effects of crystalloids and colloids on coagulation

Classically haemodilution is regarded as causing coagulopathy. However, haemodilution with saline seems to cause a hypercoagulable state both in vivo and in vitro. The aim of the present study was to measure the effect of mild to severe haemodilution using thrombelastography. Blood samples were taken in 12 healthy volunteers and divided into seven aliquots. One aliquot was undiluted and acted as control. The other six were diluted with normal saline, Ringer Acetate, 4% albumin, Dextran 70, 6% and 10% hydroxyethylstarch to 10%, 20%, 40%, 50% and 60% dilution. The dilution was checked by measuring the haemoglobin concentration. Each aliquot was placed in a temperature-controlled thrombelastography channel. Increased coagulation activity, as measured by thrombelastography changes, was detected at low and medium levels of dilution with all the tested solutions. At more than 40% dilution, coagulation returned to normal while in the case of dextran and hydroxyethylstarch coagulopathy developed. For crystalloids and albumin,dilution had to exceed 50% before coagulation was impaired. If these findings can be reproduced in vivo, they may have implications for transfusion practice and prophylaxis against thrombosis.

[Effects of plasma substitutes on hemostasis]

OBJECTIVE

Data synthesis on haemostasis effects of cristalloids and colloids and clinical implications for their use for plasma volume replacement.

DATA SOURCES

Data were searched in the Medline database from 1954 to 2000 using the following key-words: cristalloids, colloids, albumin, gelatin, dextran, hydroxyethyl starch, haemostasis, von Willebrand disease, haemodilution.

DATA EXTRACTION

Publications from 1954 to 1990 were selected depending on the quality of their methodology. Most of articles published after 1990 and all types including case report were accepted.

DATA SYNTHESIS

Cristalloids induces a moderate hypercoagulable state with 10 to 30% haemodilution. Hypocoagulation is observed above 50% haemodilution. Albumin does not impair hemostasis except with a 50% or more haemodilution where hypocoagulation is observed. Dextran dramatically impairs haemostasis and fibrinolysis. With increasing dose, a progressive decrease of all von Willebrand multimers, mostly the largest, is observed. Till 50% haemodilution, gelatin has a moderate impact on hemostasis, but platelet aggregation is moderately modified. However this moderate impairment of haemostasis may potentiate the haemostatic effect of other colloids when used in association with gelatin. More than 30% haemodilution with hydroxyethyl starch (HES) has a serious effect in vitro on platelet function and fibrinoformation. In most studies in human, less than 20 ml.kg-1 plasma volume replacement has no clinical impact, but in some evaluations postoperative bleeding is more important with HES, particularly HES 450, in comparison to other colloids. With HES 450 and HES 200 highly substituted (0.6 of degree of substitution) intravascular cumulation of large molecules leads to type I von Willebrand syndrome when doses overtake 80 ml.kg-1. Dextran and HES are prohibited in patients with impaired haemostasis due to congenital disease (haemophilia and von Willebrand disease) or acquired defect (thrombocytopenia). Caution is required in patients with renal failure or receiving antithrombotic or non-steroidal anti-inflammatory agents. Patients without a haemorrhagic diathesis must not received more than 1.5 g.kg-1.j-1 of dextran and restrictive conditions of use must be respected with HES.

CONCLUSION

Except isotonic cristalloids, all colloids induce haemostastic changes particularly for haemodilution over 30%. Effects are more pronounced with HES and dextran.

Effects on coagulation of intravenous crystalloid or colloid in patients undergoing peripheral vascular surgery

BACKGROUND

This study investigated whether haemodilution-enhanced coagulation can be demonstrated under regional anaesthesia, whether this occurs before surgery, and whether the fluid used influences the effect.

METHODS

Patients were randomly allocated to receive either crystalloid or colloid intravenous fluid. An epidural was administered. Samples of venous blood were taken before fluid administration, after completion of the epidural and initial fluid load, during surgery before heparin, and after 24 h. Thrombelastograph analysis was performed, and full blood count, international normalised ratio, activated partial thromboplastin time, D-dimers and thrombin-antithrombin complex were measured.

RESULTS

In the crystalloid group, enhanced coagulation compared with baseline was demonstrated after initial fluid load (mean (SD) r-time 10.1 (4.9) min; P < 0.033; k-time 3.5 (1.7) min; P < 0.01; alpha-angle 54.9 (13.9) degrees; P < 0.01) and before heparin administration (r-time 8.8 (3.9) min; P < 0.01; alpha-angle 54.9 (12.6) degrees; P < 0.02). There was no enhancement of coagulation in the colloid group. There were no changes from baseline after 24 h.

CONCLUSIONS

This study confirms that the enhanced perioperative coagulation mechanism is related to dilution, rather than surgery, and is triggered by rapid crystalloid haemodilution. Consideration should be given to the use of colloid rather than crystalloid solutions for rapid fluid loading in vasculopathic patients undergoing surgery.

A prospective, randomized comparison of thromboelastographic coagulation profile in patients receiving lactated Ringer's solution, 6% hetastarch in a balanced-saline vehicle, or 6% hetastarch in saline during major surgery

OBJECTIVES

To compare the effects of lactated Ringer's solution (LR), 6% hetastarch in a balanced-saline vehicle (HS-BS), and 6% hetastarch in normal saline (HS-NS) on coagulation using thromboelastography.

DESIGN

Prospective, randomized double-blinded evaluation of previously published clinical trial.

SETTING

Tertiary-care medical center.

PARTICIPANTS

Patients undergoing elective noncardiac surgery with an anticipated blood loss >500 mL. A total of 90 patients were enrolled with 30 patients in each group.

INTERVENTIONS

Patients received a standardized anesthetic. LR, HS-BS, and HS-NS were administered intraoperatively based on a fluid administration algorithm. Hemodynamic targets included maintenance of arterial blood pressure, heart rate, and urine output within a predefined range.

MEASUREMENTS AND MAIN RESULTS

Thromboelastography variables for r time, k time, maximum amplitude, and alpha angle (mean +/- SD) were recorded at induction of anesthesia, at the end of surgery, and 24 hours postoperatively. Patients in the LR group showed a state of hypercoagulation at the end of surgery with reductions (p < 0.005) in r time (-3.8 +/- 6.7 mm) and k time (-1.7 +/- 2.5 mm). This state of hypercoagulation continued into the postoperative period. Patients in the HS-NS group showed a state of hypocoagulation with increases (p < 0.05) in r time (+6.2 +/- 8.5 mm) and k time (+1.7 +/- 3.9 mm) and a reduction in maximum amplitude (-8.0 +/- 9.8 mm) at the end of surgery. This state of hypocoagulation was reduced in the postoperative period. Patients in the HS-BS group showed no significant changes in coagulation status at end of surgery, with the smallest changes in r time (-0.3 +/- 4.1 mm), k time (+0.1 +/- 3.1 mm), maximum amplitude (-5.4 +/- 12.3 mm), and alpha angle (0.3 +/- 12.5 degrees ).

CONCLUSION

LR-treated patients exhibited a hypercoagulative profile that persisted into the postoperative period. HS-BS administration was associated with a lesser change in the coagulation profile compared with HS-NS, which was associated with a hypocoagulative state.

In vivo effect of haemodilution with saline on coagulation: a randomized controlled trial

BACKGROUND

Previous studies have shown that 10-30% haemodilution with crystalloid may induce a hypercoagulable state demonstrable by using the Thrombelastograph (TEG). While most are in vitro studies, the few in vivo studies are limited by confounding surgical or 'environmental' factors. We conducted this randomized controlled study to evaluate the coagulation changes associated with in vivo haemodilution.

METHODS

Twenty patients undergoing major hepatobiliary surgery were randomly allocated to one of two study groups. Group H (n = 10) had 30% blood volume withdrawn over 30 min and replaced with saline. Group C (n = 10) did not have any blood withdrawn. Blood samples were taken in both groups at 10, 20 and 30 min. Native TEG, complete blood count, coagulation profile, fibrinogen, antithrombin III, protein C and thrombin-antithrombin complex concentrations were measured.

RESULTS

Compared with Group C, Group H patients had significantly greater shortening of r-time at 30 min (-30% vs +36%), greater shortening of k-time at all time points (-36% vs +17% at 10 min; -37% vs +44% at 20 min; -45% vs +49% at 30 min), and greater widening of alpha at 30 min (+71% vs +4%). The decrease in antithrombin III and other natural procoagulants and anticoagulants closely followed that of haematocrit, with the exception of thrombin-antithrombin complex.

CONCLUSION

In vivo haemodilution of up to 30% with saline can induce a hypercoagulable state. The mechanism remains unclear as disproportionate dilution of natural anticoagulants was not detected. Thrombin-antithrombin complex concentration remained stable despite haemodilution in Group H, which may suggest increased thrombin generation.

Intraoperative autotransfusion in hip arthroplasty

Two groups of patients having primary or revision total hip replacement were studied during a period of 11 months. The first group of 40 consecutive patients consented to have whole blood collected coincident with acute normovolemic hemodilution. An inventory of autologous red blood cells, plasma, and platelets was prepared in the operating room as a preliminary to surgery. Subsequently, the same supplies and equipment were used for autotransfusion intraoperatively. In a case-control study, another 40 patients having total hip replacements were matched for age, gender, and weight. The second group of patients refused hemodilution and received autotransfusion alone. The perioperative transfusion requirements of the two groups were compared. The total blood product donor exposure rate of the first group was 1/4 of the controls (0.6 and 2.4 donor units per patient, respectively). The average length of stay in the hospital after surgery for the first group was shortened significantly (6.2 versus 8.4 days), possibly from less immunogenic insult associated with increased transfusions of autologous blood products. Hemodilution, followed by autotransfusion, was cost effective in primary and revision total hip replacements, autotransfusion alone was cost effective only in revision arthroplasty.

Are lactated Ringer's solution and normal saline solution equal with regard to coagulation?

Crystalloids represent an attractive strategy to alleviate intravascular volume deficits. Crystalloid hemodilution was associated with hypercoagulability in in vitro and in vivo studies. The influence of different crystalloids on coagulation in the surgical patient is not well studied. In a prospective, randomized study in patients undergoing major abdominal surgery, we used either lactated Ringer's solution (RL) (n = 21) or 0.9% saline solution (SS) (n = 21) exclusively for intravascular volume replacement over 48 h to maintain central venous pressure between 8 and 12 mm Hg. Activated thrombelastography (TEG) using different activators (intrinsic TEG, extrinsic TEG, heparinase TEG, aprotinin TEG) was used to measure coagulation time, clot formation time, and maximum clot firmness. Measurements were performed after induction of anesthesia (T0), immediately after surgery (T1), 5 h after surgery (T2), and on the morning of the first (T3) and second (T4) postoperative days. RL 18,750 +/- 1890 mL and 17,990 +/- 1790 mL of SS were infused during the study period. Acidosis was seen only in the SS-treated group. Blood loss was not different between the groups. Fibrinogen and antithrombin III decreased similarly at T1 and T2 in both groups, most likely because of hemodilution. Differences in TEG data from normal baseline were seen only immediately after surgery and 5 h thereafter, indicating mild hypercoagulability in the intrinsic TEG (RL, from 147 +/- 130 s to 130 +/- 11 s; SS, from 146 +/- 12 s to 131 +/- 12 s). There were no differences in coagulation between RL- and SS-treated patients. We conclude that in major abdominal surgery intravascular volume replacement with crystalloids resulted in only moderate and abbreviated changes in coagulation. No differences in activated TEG and blood loss were seen between an RL- and an SS-based intravascular volume replacement regimen.

IMPLICATIONS

In 42 patients undergoing major abdominal surgery, either lactated Ringer's solution or 0.9% saline solution were exclusively used for volume therapy for 48 h. Activated thrombelastography revealed some mild hypercoagulability after surgery. No differences in coagulation were seen between the two intravascular volume replacement strategies.

Changes in coagulability as measured by thrombelastography following surgery for proximal femoral fracture

The effect of surgery for femoral neck fracture on whole blood coagulation and the relationship of altered coagulation to deep venous thrombosis were investigated in 250 patients. Whole blood coagulation was measured using thrombelastography preoperatively, in the early postoperative period and at 6-week review. Significant hypercoagulability was demonstrated after surgery and persisted to 6-week review. A significant correlation between hypercoagulability and the development of deep venous thrombosis is demonstrated. Hypercoagulability is shown to be a major factor in thrombosis formation following proximal femoral neck fracture surgery.

Resuscitation with Hextend decreases endogenous circulating heparin activity and accelerates clot initiation after hemorrhage in the rabbit

Hemorrhagic shock can result in a hypercoagulable state and has been associated with both hemorrhagic and thrombotic complications in the perioperative period. The author hypothesized that hemorrhage and resuscitation could result in a hypercoagulable state via changes in the heparin-antithrombin III anticoagulant mechanism in rabbits. Rabbits sedated with ketamine underwent sham operation (n = 8) or hemorrhage (25 mL/kg blood shed) for 60 min, followed by resuscitation with an equal volume of 5% human albumin (n = 8) or Hextend (n = 8). Coagulation analysis with the Thrombelastograph analyzer and determination of endogenous heparin and antithrombin III activity were performed on arterial blood samples obtained before hemorrhage and 30 min after resuscitation. The reaction time significantly decreased by 34% after hemorrhage and resuscitation with Hextend, whereas no other significant changes in Thrombelastograph variables were noted. Antithrombin III activity was significantly less in the Albumin (83% +/- 8% of control, mean +/- SD) and Hextend (88% +/- 8%) Resuscitated groups compared with the Sham-Operated animals. Of interest, only the Hextend-Resuscitated animals demonstrated a significant decrease in heparin activity (53.4 +/- 13.6 mU/mL before hemorrhage, 42.3 +/- 5.6 mU/mL after resuscitation). A Hextend)-mediated decrease of both heparin and antithrombin III activity may explain the acceleration of clot initiation compared with albumin administration after hemorrhage in the rabbit.

IMPLICATIONS

Hemorrhage may result in a hypercoagulable state after resuscitation. Decreases in both endogenous heparin and antithrombin III activity after hemorrhage and Hextend resuscitation in rabbits resulted in a significantly decreased time to clot coagulation analysis initiation without a significant change in the rate of clot formation or final clot strength.

Thromboelastography: a reliable test?

The thromboelastograph (TEG), a measure of global haemostasis, is routinely used during cardiac and hepatic surgery to optimize blood product selection and usage. It has recently been suggested that it may also be a useful tool to screen patients with hypercoagulable states. Limited published data on performance characteristics has led to speculation regarding its consistency and, therefore, validity of the results. This study was designed to assess the effect of stability of blood samples prior to testing, repeated sampling, intra- and inter-assay variability using the native, celite, tissue factor (TF) and Reopro-modified TEG. Analysis of native and celite samples after storage over 90 min showed a period of instability up to 30 min. Thereafter, all parameters between 30 and 90 min were stable [P = not significant (NS)]. When the same sample was repeatedly assayed, both native and celite TEG parameters showed a significant change towards hypercoagulability (P < 0.01), whereas the TF and Reopro-modified TEG showed no change. Intra- and inter-assay variability on samples tested after 30 min showed excellent reproducibility for all parameters (P = NS). The data suggest that the TEG is a useful tool in haemostasis but requires a formal standard operating procedure to be adopted that takes into account the initial period of sample instability.