Comparison of results obtained using clot-fibrinolysis waveform analysis and global fibrinolysis capacity assay with rotational thromboelastography

Global fibrinolysis assays detect the fibrinolysis time of clot dissolution using tissue-type plasminogen activator (tPA). Two such assays, clot-fibrinolysis waveform analysis (CFWA) and global fibrinolysis capacity (GFC) assay, were recently developed. These were compared with rotational thromboelastography (ROTEM). Healthy donor blood samples were divided into four groups based on tPA-spiked concentrations: 0, 100, 500, and 1000 ng/mL. CFWA and GFC fibrinolysis times, including 4.1 µg/mL and 100 ng/mL tPA in the assays, were determined, denoted as CFWA-Lys and GFC-Lys, respectively. Statistical differences were recognized between tPA concentrations of 0 and 500/1000 ng/mL for CFWA-Lys, and 0 and 100/500/1000 ng/mL for GFC-Lys. The correlation coefficients with lysis onset time (LOT) of extrinsic pathway evaluation and intrinsic pathway evaluation in ROTEM were statistically significant at 0.610 and 0.590 for CFWA-Lys, and 0.939 and 0.928 for GFC-Lys, respectively (p-values < 0.0001 for all correlations). Both assays showed significant correlations with ROTEM; however, the GFC assay proved to have better agreement with ROTEM compared with the CFWA assay. These assays have the potential to reflect a hyperfibrinolysis status with high tPA concentrations.

Characterization and Usefulness of Clot-Fibrinolysis Waveform Analysis in Critical Care Patients with Enhanced or Suppressed Fibrinolysis

INTRODUCTION

 Recently, clot-fibrinolysis waveform analysis (CFWA), which is a coagulation and fibrinolysis global assay based on assessing the activated partial thromboplastin time with tissue-type plasminogen activator, was developed. This study aimed to investigate the characteristics of CFWA using plasma samples from patients in the critical care unit.

MATERIALS AND METHODS

 The fibrinolysis times using CFWA were measured in 298 plasma samples. These samples were divided into three groups based on the reference interval (RI) of fibrinolysis time using CFWA: shortened group, less than RI; within group, within RI; prolonged group, more than RI. The coagulation and fibrinolysis markers, including D-dimer, plasmin-α2 plasmin inhibitor complex (PIC), fibrin monomer complex (FMC), plasmin-α2 plasmin inhibitor (α2-PI), plasminogen (Plg), and fibrinogen (Fbg) were analyzed and compared among the three groups.

RESULTS

 The FMC level decreased in the order of shortened, within, and prolonged groups, and the decrease was statistically significant among all three group pairs. The opposite tendency was observed for Fbg and fibrinolysis-related markers of α2-PI and Plg, and significant differences were recognized in all pair comparisons except for between within and prolonged groups in Plg. The mean values of the fibrinolysis markers D-dimer and PIC in all three groups were higher than the cut-off values, and the PIC value differed significantly between the within and prolonged groups.

CONCLUSION

 The fibrinolysis reaction was detected in all three groups, but the status differed. CFWA has the potential to reflect the fibrinolysis status in one global assay.

Sensitivity and specificity of thromboelastography for hyperfibrinolysis: Comparison of TEG 5000 and TEG 6S CK LY30 systems

OBJECTIVES

The sensitivity and specificity of clot lysis at 30 minutes after maximum clot strength (LY30), as measured by thromboelastography (TEG), for clinically significant hyperfibrinolysis have not been compared across the 2 US Food and Drug Administration-approved instruments (the TEG 5000 and TEG 6s [Haemonetics]).

METHODS

We performed a retrospective, single-center analysis of these 2 instruments using the kaolin (CK) reagent.

RESULTS

Local verification studies showed that the TEG 5000 and TEG 6s CK LY30 upper limits of normal (ULNs) were distinct (5.0% and 3.2%, respectively). Retrospective analysis of patient data showed that abnormal LY30 was 6 times more prevalent with the TEG 6s than with the TEG 5000 instrument. LY30 was a significant predictor of mortality with both instruments (TEG 6s: receiver operating characteristic [ROC] area under the curve [AUC] = 0.836, P ≤ .0001; TEG 5000: ROC AUC = 0.779, P = .028). The optimal LY30 cut point was determined based on these mortality data for each instrument. The TEG 6s showed superior mortality prediction than the TEG 5000 at lower LY30 levels (≥10%), with likelihood ratios of 8.22 and 2.62 for the TEG 6s and TEG 5000, respectively. Patients with a TEG 6s CK LY30 of 10% or higher were significantly more likely to die, receive cryoprecipitate, receive transfusions, or receive massive transfusion than patients with a TEG 6s LY30 of 3.3% to 9.9% (all P < .01). Patients with a TEG 5000 LY30 of 17.1% or higher were significantly more likely to die or use cryoprecipitate (P < .05); transfusion and massive transfusion protocol were not significantly different. Whole blood spiking studies showed that 70 ng/mL tissue plasminogen activator (tPA) achieved an average LY30 of approximately 10% for both instruments.

CONCLUSIONS

CK LY30 above the ULN is a sensitive but not specific cutoff for hyperfibrinolysis. At least moderately elevated CK LY30 carries more clinical portent on the TEG 6s instrument than on the TEG 5000. These TEG instruments are not sensitive to low concentrations of tPA.

Therapeutic Fibrinolysis: How Efficacy and Safety Can Be Improved

Therapeutic fibrinolysis has been dominated by the experience with tissue-type plasminogen activator (t-PA), which proved little better than streptokinase in acute myocardial infarction. In contrast, endogenous fibrinolysis, using one-thousandth of the t-PA concentration, is regularly lysing fibrin and induced Thrombolysis In Myocardial Infarction flow grade 3 patency in 15% of patients with acute myocardial infarction. This efficacy is due to the effects of t-PA and urokinase plasminogen activator (uPA). They are complementary in fibrinolysis so that in combination, their effect is synergistic. Lysis of intact fibrin is initiated by t-PA, and uPA activates the remaining plasminogens. Knockout of the uPA gene, but not the t-PA gene, inhibited fibrinolysis. In the clinic, a minibolus of t-PA followed by an infusion of uPA was administered to 101 patients with acute myocardial infarction; superior infarct artery patency, no reocclusions, and 1% mortality resulted. Endogenous fibrinolysis may provide a paradigm that is relevant for therapeutic fibrinolysis.

One-step thickness shear mode acoustic assay for plasminogen activators

A new procedure is presented for the measurement of plasminogen activators using a thickness shear mode sensor and a modified version of the fibrin plate assay at the micro-scale. Separate, well-mixed solutions of the substrates fibrinogen and plasminogen, and enzymes thrombin and the plasminogen activator sample were mixed together and placed on the sensor surface. The temperature and evaporation were controlled during the assay. The clot dissolution time correlated well with the quantity of the plasminogen activator in the sample. The average relative standard deviation was 12.5%.

Cardiopulmonary bypass parameters and hemostatic response to cardiopulmonary bypass in infants versus children

OBJECTIVE

Because infants have relatively more blood loss (mL/kg) than older children during cardiac surgery involving cardiopulmonary bypass (CPB), the authors compared hemostatic activation between infants and older children undergoing cardiac surgery.

DESIGN

Observational study.

SETTING

University-affiliated children's hospital.

PARTICIPANTS

Twenty-eight children (18 infants <1 year and 10 children >1 year) undergoing cardiac surgery with CPB.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Markers of coagulation and fibrinolysis were evaluated at 9 sample points before, during, and after CPB in the 28 children. Infants had greater chest tube output, longer CPB times, and a larger drop in platelet counts during CPB than children. Active tissue plasminogen activator (tPA) increased during CPB in both groups, with infants showing lower levels than children (p < 0.001). In both groups, active plasminogen activator inhibitor type 1 (PAI-1) first decreased during CPB and then increased above baseline postoperatively. Infants had higher PAI-1 than children near the end of CPB (p = 0.01). Thrombin-antithrombin complex levels increased during and after CPB, with infants showing lower levels only during CPB (p = 0.01). D-dimer and prothrombin activation peptide (F1.2) levels increased in a similar pattern for both groups during and after CPB. The length of aortic cross-clamp time and the level of F1.2 after protamine administration correlated significantly and independently with 12-hour chest tube output.

CONCLUSIONS

Compared with children, infants had greater blood loss (mL/kg), greater drop in platelets during CPB, lower active tPA, and higher active PAI-1. Cumulative thrombin generation after CPB, indicated by F1.2 levels, correlated with early blood loss.

Postmenopausal oral estrogen therapy affects hemostatic factors, but does not account for reduction in the progression of subclinical atherosclerosis

BACKGROUND

Hemostatic factors influenced by postmenopausal hormone therapy may contribute to atherosclerosis. The Estrogen in the Prevention of Atherosclerosis Trial (EPAT), a 2-year, randomized, double-blind, placebo-controlled trial, demonstrated reduced subclinical atherosclerosis progression measured by change in common carotid artery intima-media thickness (CIMT) with unopposed oral 17beta-estradiol.

OBJECTIVES

To assess the effect of postmenopausal hormone therapy on the levels of several hemostatic factors, and the relationship between these factors and the progression of subclinical atherosclerosis.

PATIENTS AND METHODS

We measured tissue plasminogen activator (t-PA) antigen, factor (F) VII, D-dimer and albumin longitudinally, and plasminogen activator inhibitor type 1 (PAI-1) and fibrinogen at trial-end, in 186 postmenopausal women.

RESULTS

Estradiol vs. placebo was associated with greater FVII and lower t-PA, albumin, PAI-1 and fibrinogen (all P < or = 0.001), with no estradiol effect on D-dimer (P = 0.42). Only mean on-trial t-PA was positively associated with the absolute level of CIMT on-trial (r = 0.29, P < 0.0001), but this was attenuated with age and body mass index adjustment. No longitudinally measured hemostatic factor was associated with CIMT progression. However, higher CIMT during the trial was significantly related to increases in t-PA.

CONCLUSIONS

These results confirm previous findings regarding estrogen's effect on hemostatic factors and show that albumin is negatively associated with estrogen therapy. These hemostatic factors did not account for the reduction of CIMT progression with 17beta-estradiol seen in EPAT. Atherosclerosis itself may affect levels of hemostatic factors (reverse causality), with subsequent involvement in atherosclerosis-associated thrombosis.

Effect of Polymer Coating (Poly 2-Methoxyethylacrylate) of the Oxygenator on Hemostatic Markers During Cardiopulmonary Bypass in Children

OBJECTIVE

Heparin and other oxygenator coatings have been used in attempts to reduce hemostatic activation during cardiopulmonary bypass (CPB). This study evaluated whether an oxygenator coated with poly 2-methoxyethylacrylate (PMEA) (X-coating; Terumo Corporation, Tokyo, Japan) would cause less activation of coagulation and fibrinolytic systems during CPB in children than a noncoated oxygenator.

DESIGN

Observational study.

SETTING

University-affiliated children's hospital.

PATIENTS

Twenty-six patients, 3 months to 5 years old, who underwent congenital heart surgery for repair of a ventricular septal defect, atrial septal defect, or both.

INTERVENTIONS

Patients were divided into 2 age-matched groups based on the type of oxygenator used: a noncoated oxygenator (group NC) versus a PMEA-coated oxygenator (group C).

MEASUREMENTS AND MAIN RESULTS

Blood samples for coagulation and fibrinolytic markers were compared before, during, and after CPB. Despite increases in thrombin generation markers (F1.2 and TAT) at certain times during CPB in group C compared to group NC, a comparison over all times during CPB were not statistically different between groups. Overall D-dimer concentrations during CPB were elevated in group C compared to group NC (p = 0.02). Active tPA and active PAI-1 were not different between groups during or after CPB. Group C had higher platelet counts (181,000 +/- 29,000) during CPB than group NC (155,000 +/- 57,000, p = 0.04) but not postoperatively. Twelve hours postoperatively, chest tube outputs were 8.8 +/- 3 mL/kg in group C and 19.1 +/- 12 mL/kg in group NC (p = 0.003). The corresponding outputs 24 hours after surgery were 12.4 +/- 3 mL/kg and 24 +/- 11 mL/kg, respectively (p = 0.005).

CONCLUSIONS

Except for a somewhat higher platelet count during CPB, there was no indication that PMEA coating resulted in less activation of coagulation and fibrinolytic systems. The lower postoperative chest tube output observed after CPB with PMEA-coated oxygenators needs to be studied further.

Measures of Thrombosis and Fibrinolysis

Our recent understanding of acute coronary syndrome as an atherothrombotic process has led to research efforts in the development of markers of thrombosis and fibrinolysis for risk prediction in cardiovascular heart disease. Although American Heart Association/American College of Cardiology guidelines recommend fibrinogen as a category I risk factor and also suggest factor VII, plasminogen activator inhibitor-1, tissue-type plasminogen activator, and von Willebrand factor as other potentially clinically useful markers, these tests have not come into routine clinical use. Their development as predictors of risk may be hampered by inconsistent laboratory methodology, which causes difficulty in comparing result interpretation with published trial studies. This article presents the history of development for these tests, proper laboratory handling, the best trial data that present evidence of their accuracy, and current guidelines for clinical use.

Increased tissue-type plasminogen activator: a facade in the fibrinolytic system in type 2 diabetes

To determine whether the increased concentration in blood of total tissue-type plasminogen activator (t-PA), accompanying increased plasminogen activator inhibitor type-1 (PAI-1) seen with diabetes reflects increased free t-PA and hence activity or simply increased t-PA complexed with PAI-1, we measured each in 39 people with type 2 diabetes. The increased total t-PA occurred in the absence of an increase in t-PA activity detectable in venous blood samples despite the increase in the concentration of total t-PA protein.

BACKGROUND

Type 2 diabetes is known to be associated with increased concentrations in blood of total tissue-type plasminogen activator (t-PA) [free t-PA plus t-PA complexed with plasminogen activator inhibitor type-1 (PAI-1)] and PAI-1. This study was performed to determine whether the increased total t-PA is indicative of increased t-PA activity attributable to free t-PA or whether it is simply a manifestation of compensatory processes maintaining t-PA activity detectable in venous blood samples at normal or subnormal levels.

METHODS

Total t-PA, free t-PA, and PAI-1 antigen and activity were measured by enzyme-linked immunosorbent assay and immunofunctional chromogenic substrate kinetic assays in peripheral venous blood samples obtained under fasting conditions from 39 people with type 2 diabetes.

RESULTS

The results indicate that both PAI-1 and total t-PA antigen concentrations were increased in association with diabetes but the concentration of free t-PA and hence the t-PA activity was not. Thus, the increased total t-PA is a facade potentially masking the impaired fibrinolytic system activity associated with type 2 diabetes.

CONCLUSIONS

The results indicate that the increase in the concentration of total t-PA protein in blood of people with diabetes occurs in the absence of an increase in free t-PA. Hence t-PA activity detectable in peripheral venous blood samples does not increase and may even decline modestly.

The kinetics of plasmin inhibition by aprotinin in vivo

INTRODUCTION

The purpose of this study was to estimate, in patients undergoing cardiopulmonary bypass (CPB), the in vivo rates of tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1 (PAI-1) secretion, plasmin generation, fibrin degradation, and plasmin inhibition by aprotinin versus antiplasmin.

MATERIALS AND METHODS

Estimates of in vivo rates were based on measured levels of tPA, PAI-1, antiplasmin, plasmin-antiplasmin complex (PAP), total aprotinin, plasmin-aprotinin complex and D-dimer, combined with a computer model of each patient's vascular system that continuously accounted for secretion, clearance, hemodilution, blood loss and transfusion. Plasmin regulation was studied in nine control patients undergoing CPB without aprotinin versus six patients treated with aprotinin.

RESULTS

In controls, plasmin-antiplasmin levels rose from a baseline of 3.0+/-0.9 to a peak of 8.1+/-2.7 nmol/L after CPB due to an average 44-fold rise in the plasmin generation rate. This rise in plasmin generation during CPB lead to increased fibrin degradation causing D-dimer levels to increase from a baseline of 1.2+/-0.6 to a peak of 9.7+/-4.4 nmol/L due to an average 74-fold rise in the D-dimer generation rate. During CPB in the aprotinin group, plasmin-antiplasmin levels dropped, plasmin-aprotinin complex levels rose, while D-dimer levels remained unchanged from baseline. Compared to controls, the aprotinin group showed similar rates of plasmin generation during CPB, but an 11-fold faster plasmin inhibition rate and a 10-fold lower D-dimer generation rate.

CONCLUSIONS

The rise in plasmin generation and fibrin degradation that occurs during standard CPB is suppressed by the addition of aprotinin, which returns the patient to near baseline fibrin degradation rates during CPB.

Regulation of local availability of active tissue-type plasminogen activator in vivo in man

Free, biologically active tissue-type plasminogen activator (tPA) is the main initiator of intravascular fibrinolysis, but little is known about the regulation of active tPA on the organ level. The aim was to investigate if the local availability of active tPA on the organ level depends on the local release rate of tPA or the arterial input of tPA and plasminogen activator inhibitor type 1 (PAI-1). Also, we wanted to evaluate if plasma levels predict capacity for endothelial release of fibrinolytic proteins. Invasive perfused-forearm studies were performed in 96 healthy subjects. Local release rates of fibrinolytic proteins were assessed at baseline and during endothelial stimulation. Stimulation by methacholine and desmopressin induced a 6- and 12-fold increase in total tPA release rates, respectively. With increasing local release rates of tPA a gradually closer correlation emerged between the total tPA secretion and the forearm output of active tPA (from r = 0.102, ns to r = 0.85, P < 0.0001). Forearm availability of active tPA was not related to arterial input of either tPA or PAI-1. Release rates and plasma levels of tPA were not correlated. Baseline release rates of active tPA increased to noon. The major determinant for the local availability of active tPA is the capacity of the endothelium to release tPA rather than the arterial input of PAI-1 or tPA. Despite a molar excess of PAI-1, the majority of tPA released during stimulation does not undergo local inactivation. The capacity to release tPA locally cannot be predicted from its plasma concentration.

Reducing Hemostatic Activation During Cardiopulmonary Bypass: A Combined Approach

Interventions such as heparin-coated circuits, epsilon-aminocaproic acid, and reduced shed blood reinfusion have shown mixed results when applied individually for limiting hemostatic activation during cardiopulmonary bypass (CPB). We compared coagulation and fibrinolytic activation during conventional CPB (control) (CTRL) using noncoated circuits, no antifibrinolytics, and open cardiotomy with a combined strategy (HAC) that used heparin-coated circuits, epsilon-aminocaproic acid, and closed cardiotomy. Blood samples were drawn before, during, and after CPB for primary coronary bypass grafting surgery from 9 CTRL patients and 10 HAC patients. Thrombin-antithrombin complex and fibrinopeptide A levels (markers of thrombin and fibrin generation) were reduced in the HAC versus CTRL group after 30 min of CPB (P < 0.05). Average tissue plasminogen activator (tPA) levels were significantly lower in the HAC group by 30 min on CPB (P < 0.05), resulting in preservation of plasminogen activator inhibitor (PAI)-1 during CPB (P < 0.05). D-Dimer, a measure of intravascular fibrin formation and removal, was reduced in the HAC group during and after CPB (P < 0.005). Overall, the combined strategy was associated with a reduction in CPB-induced increases in markers of thrombin generation, fibrin formation, tPA release, and fibrin degradation and better preservation of PAI-1.

IMPLICATIONS

A combined approach during cardiopulmonary bypass (CPB) that uses heparin-coated circuits, epsilon-aminocaproic acid, and limited reinfusion of shed pericardial blood is associated with reduced activation of the coagulation and fibrinolytic systems that typically occurs during conventional CPB.

The effect of red palm olein and refined palm olein on lipids and haemostatic factors in hyperfibrinogenaemic subjects

Little is known about the physiological effects of red palm olein (RPO). The effects of red palm olein and palm olein (POL) compared to sunflower oil (SFO), on lipids, haemostatic factors and fibrin network characteristics in hyperfibrinogenaemic volunteers were investigated. Fifty-nine free-living, hyperfibrinogenaemic volunteers participated in this randomized, controlled, single blind parallel study. After a 4-week run-in, during which subjects received sunflower oil products, they were paired and randomly assigned to one of three intervention groups receiving products containing 25 g/day ( approximately 12% of total energy intake) of either red palm olein, palm olein or sunflower oil for another 4 weeks. Anthropometric measurements, blood samples and dietary intakes were measured before run-in, and before and after intervention. The differences in changes in total serum cholesterol response between palm olein and red palm olein (+0.59 vs. +0.18 mmol/l; p=0.053), and between palm olein and sunflower oil (+0.59 vs. -0.003 mmol/l; p < or =0.01) were significant. The low-density lipoprotein cholesterol (LDLC) response in the palm olein-and sunflower oil-groups also differed significantly (+0.42 vs. -0.11 mmol/l; p < or =0.01). Tissue plasminogen activator antigen (tPA(ag)) decreased significantly in the red palm olein group compared to the palm olein-and sunflower oil-groups. No effects were found in other haemostatic variables. Palm olein and red palm olein had no independent effect on fibrin network characteristics. In conclusion, compared to palm olein, red palm olein had less detrimental effects on the lipid profile and decreased tissue plasminogen activator antigen. Studies in larger groups are advised for confirmation of results, elucidation of mechanisms and effects of nonglyceride constituents of red palm oil (PO).

Failure of peripheral arterial thrombolysis due to elevated plasminogen activator inhibitor type 1

To reduce the risk of intracerebral hemorrhage during thrombolytic therapy, a lower dose of tissue plasminogen activator (t-PA) or urokinase is used for acute peripheral arterial thrombi versus coronary thrombi. We hypothesized that elevated plasminogen activator inhibitor-1 (PAI-1) activity could neutralize infused t-PA or urokinase, resulting in lysis failure. Active PAI-1, active t-PA and total t-PA antigen were measured in 20 patients receiving t-PA, and active PAI-1 was measured in four patients receiving urokinase for acute peripheral arterial thrombosis. The 18 patients that successfully lysed their thrombi all had low active PAI-1 levels (10 +/- 19 pmol/l) during infusion of thrombolytic therapy, while six patients that failed to lyse their thrombi had high active PAI-1 levels (1533 +/- 1384 pmol/l, P = 0.00007) during infusion. Active t-PA levels during t-PA infusion were higher in the group that lysed their thrombi (536 +/- 423 pmol/l versus 42 +/- 45 pmol/l, P = 0.04) even though total t-PA levels were lower (1240 +/- 493 pmol/l versus 1956 +/- 709 pmol/l, P = 0.03). In the patients that failed to lysed their thrombi, > 95% of infused t-PA was neutralized by PAI-1. We conclude that elevated PAI-1 during acute peripheral arterial thrombolysis is associated with an increased risk of lysis failure due to reduced levels of circulating active t-PA or urokinase.

Secretion of tissue plasminogen activator and plasminogen activator inhibitor 1 during cardiopulmonary bypass

INTRODUCTION

Cardiopulmonary bypass (CPB) is associated with elevated tissue plasminogen activator (t-PA) levels during CPB and increased plasminogen activator inhibitor 1 (PAI-1) levels post-operatively. The goal of this study was to estimate the rate of t-PA and PAI-1 secretion in vivo, before, during and after CPB.

MATERIALS AND METHODS

Estimated rates of t-PA and PAI-1 secretion were based on measured levels of active and total t-PA, and active and total PAI-1, obtained before, during and after CPB from nine males, combined with a computer model of each patient's vascular system that continuously accounted for secretion, clearance, hemodilution, blood loss and transfusion.

RESULTS AND CONCLUSIONS

At baseline, the average t-PA and PAI-1 secretion rates were 0.74+/-0.33 and 1.28+/-0.74 pmol/s, respectively. Within 5 min of CPB initiation, t-PA secretion increased six-fold to 4.41+/-2.58 pmol/s, while PAI-1 secretion was unchanged, resulting in a six-fold increase in active t-PA levels. t-PA secretion remained elevated throughout CPB and into the early post-operative period. Average PAI-1 secretion did not start to increase until the end of CPB. By 2 h after surgery, average PAI-1 secretion had increased 15-fold to 19.60+/-17.10 pmol/s, resulting in reduced levels of active t-PA even though t-PA secretion was still elevated. We conclude that CPB induces an immediate sustained increase in t-PA secretion followed by a delayed progressive increase in PAI-1 production. Variations in the level of active t-PA are a function of the relative rates of t-PA versus PAI-1 secretion at different times during and after surgery.

Prothrombotic coagulation abnormalities preceding the hemolytic-uremic syndrome

BACKGROUND

The hemolytic-uremic syndrome is a thrombotic complication of Escherichia coli O157:H7 infection. It is not known whether the coagulation abnormalities precede, and potentially cause, this disorder.

METHODS

In 53 children infected with E. coli O157:H7, we measured a panel of markers indicating activation of the clotting cascade and renal function within four days after the onset of illness. These markers were measured again in as many as possible of the 16 children in whom the hemolytic-uremic syndrome developed.

RESULTS

The children in whom the hemolytic-uremic syndrome subsequently developed had significantly higher median plasma concentrations of prothrombin fragment 1+2, tissue plasminogen activator (t-PA) antigen, t-PA-plasminogen-activator inhibitor type 1 (PAI-1) complex, and D-dimer than children with uncomplicated infection. These abnormalities preceded the development of azotemia and thrombocytopenia. When the hemolytic-uremic syndrome developed, the urinary concentrations of beta2-microglobulin and N-acetyl-beta-glucosaminidase rose significantly (P=0.03 for both increases); the plasma concentrations of t-PA antigen, t-PA-PAI-1 complex, D-dimer, and plasmin-antiplasmin complex also increased significantly. The concentration of t-PA antigen correlated with that of the t-PA-PAI-1 complex in a linear regression model (squared correlation coefficient, 0.80; P<0.001).

CONCLUSIONS

In the hemolytic-uremic syndrome, thrombin generation (probably due to accelerated thrombogenesis) and inhibition of fibrinolysis precede renal injury and may be the cause of such injury.