Do Coagulation Screening Tests Detect Increased Generation of Thrombin and Plasmin in Sick Newborn Infants?

Disseminated intravascular coagulation in paediatrics

Disseminated intravascular coagulation (DIC) in paediatrics is associated with significant morbidity and mortality. Although there have been several recent advances in the pathophysiology of DIC, most of these studies were done in adults. Since the haemostatic system is very different in early life and changes dramatically with age, creating a variety of challenges for the clinician, delay in the diagnosis of DIC can happen until overt DIC is evident. In this review article, we report the aetiology, pathophysiology, clinical manifestations, diagnostic tests and a management algorithm to guide paediatricians when treating patients with DIC.

Enhanced thrombin generation and depressed anticoagulant function in children with pneumonia

AIMS

To clarify the status of the coagulation system in children with community-acquired pneumonia.

METHODS

Coagulation activation markers (prothrombin fragment F1 + 2, thrombin-antithrombin complexes, D-dimer), the natural anticoagulants (antithrombin, protein C and S) and tissue factor were measured in 28 consecutive children with pneumonia on admission to the hospital. Patients were divided into those with either bacterial-type pneumonia (at least two of the following three criteria: plasma C-reactive protein (CRP) >80 mg/L, white blood cell count >15 × 10(9) /L and alveolar infiltrates on the chest radiograph) or viral-type pneumonia.

RESULTS

The majority of the patients (79%) showed elevation of at least one of the three coagulation activation markers. Plasma CRP concentration correlated with F1 + 2 (R = 0.44, p < 0.05) and D-dimer (R = 0.71, p < 0.0001). Patients with bacterial-type pneumonia (n = 17) had higher D-dimer levels (p < 0.05) and lower levels of antithrombin (p = 0.005) and protein C (p = 0.08) than the patients with viral-type pneumonia.

CONCLUSIONS

Children with community-acquired bacterial-type pneumonia show distinctive changes in their coagulation system. The finding of coagulation system activation and depressed function of natural anticoagulants in uncomplicated pneumonia helps to understand the rapid and unpredictable changes observed in the coagulation status in patients with more severe forms of disease.

Staphylococcus aureus Septicemia with a fatal transmural myocardial infarction in a 27-week-gestation twin infant: a case study

Septicemia, one of the major causes of morbidity and mortality in the neonatal period, often has a rapid and fulminant course. Low-birth-weight infants with persistent Staphylococcus aureus septicemia, possibly associated with percutaneous central venous catheters, may develop metastatic infections including endocarditis with large vegetations. This article describes a neonate with S. aureus bacteremia that resolved with treatment who died secondary to decreased left ventricular function. At autopsy, organizing microthrombi were seen within both atria, the left ventricle, and the left coronary arterial system. Extensive infarcts were noted throughout the entire myocardium of the left ventricle. It was suspected, but not proven, that the thrombotic sequelae from septicemia caused this neonate's death.

A simple automatized audit system for following and managing practices of platelet and plasma transfusions in a neonatal intensive care unit

During neonatal intensive care, blood components are often used in clinical situations where both their efficacy and safety lack solid justification. A practical system to continuously analyse actual transfusion practices is a prerequisite for improvements of quality in transfusion therapy. We hypothesized that such a system would reveal inappropriate variations in clinical decision making and offer a means for staff education and quality improvement and assurance. The study consisted of three 120-152-day periods (P I, P II and P III) between January 2000 and October 2001 and involved 543 new patient admissions (141 patients with birth weight < 1501 g) and 6227 days of patient care at a single tertiary level NICU. P I was a control with no intervention, P II was after technically introducing the computer system and, the last period, P III was after presenting and discussing the results of P I and P II at a staff meeting. Upon an order of platelet or fresh frozen plasma (FFP) unit from the blood bank, a computer-based audit system compared the last platelet count or prothrombin time [expressed as percentage of normal clotting activity, prothrombin time (PT-%)] to predefined criteria. In the case of exceeding the preset thresholds, the system required additional information and recorded the pretransfusion laboratory values for later analysis. Thirty-two per cent of platelet transfusions were given with pretransfusion platelet count >49 x 10(9) L(-1), and 60% of these transfusions (19% of all platelet transfusions) could not be clinically justified in retrospective chart review. There was no significant change in this practice from P II to P III. FFP transfusions were given with significantly different pretransfusion PT-% values during P II and P III. The proportions of FFP transfusions with pretransfusion PT-% > 49% were 7.8% and 0.9% during P II and P III, respectively (P < 0.0001). In chart review, none of the FFP transfusions with pretransfusion PT-% > 49% could be justified by clinical grounds. Inappropriate transfusions of both platelets and plasma remain a significant challenge for quality assurance of neonatal intensive care. Automated recording of pretransfusion platelet count and prothrombin time reliably identified the poorly justified transfusions and thus offered a practical resource-saving tool for quality assurance of transfusion in the NICU. A significant shift towards more appropriate use of plasma was demonstrated after implementation of the audit system.

Short-term use of umbilical artery catheters may not be associated with increased risk for thrombosis

OBJECTIVE

Umbilical arterial catheters (UACs) have rare but serious complications related to thrombus formation. Two specific serum markers of thrombogenesis--prothrombin fragment (F1.2) and thrombin-antithrombin (TAT)--can be assayed and correlated with abdominal ultrasound visualization of UAC thrombosis. Levels of these markers of thrombogenesis have not been studied in infants with UACs. The objective of this study was to determine F1.2 and TAT levels longitudinally and compare the levels with platelet counts and ultrasound evidence of thrombi during the first week of life in infants with UACs.

METHODS

This study was conducted as a prospective, nonblinded, observational study performed between June 2001 and January 2002 at Christiana Care Hospital, a level III neonatal intensive care unit. Infants with a UAC in place in the first 24 hours of life were studied. All received equal amounts of heparin in the UAC. F1.2, TAT, platelet counts, and abdominal aorta ultrasounds were examined every other day starting within 24 hours of life. Studies were not done when the UAC was removed within the 5-day study period. Enzyme-linked immunosorbent assay for TAT and F1.2 was performed using a commercially available kit from Enzyngost. Data were analyzed with repeated measures analysis of variance evaluating TAT, F1.2, and platelet count over time.

RESULTS

Thirty-three patients were investigated (mean +/- standard deviation; gestational age: 27.4 +/- 3.5 weeks; birth weight: 1139 +/- 729 g). A total of 66 measurements of TAT, F1.2, and platelet counts were obtained. Sixty-one abdominal ultrasounds were performed; only 1 study was positive for UAC thrombus. There was no significant difference between F1.2 and TAT over time during the study period. Platelet counts seemed to fall over the 5-day study period, although this decrease did not reach statistical significance.

CONCLUSION

Indwelling UACs in sick infants may not carry an increased risk of thrombosis during the first 5 days of use.

Cerebral venous thrombosis and Escherichia coli infection in neonates

AIM

To present a possible association between cerebral venous thrombosis (CVT) and infection with Escherichia coli.

METHODS

Four neonates with deep CVT occurring during an E. coli infection are presented.

RESULTS

In these patients the thrombotic disease was found by Doppler ultrasonography. The thrombosis involved at least the sagittal sinus and the transverse sinus according to subsequent MRI scans. The E. coli strains did not produce verotoxin or haemolysin. Disseminated intravascular coagulation was not demonstrated. Three patients presented with seizures. At discharge, all of the patients had signs of neurological damage, but two of them have improved significantly since then. None of the patients has had recurrent (venous) thrombosis.

CONCLUSION

E. coli infections in neonates may predispose to CVT, a finding that has clinical implications.

Fresh frozen plasma reduces thrombin formation in newborn infants

BACKGROUND

Newborn infants undergoing intensive care are at risk of bleeding and thrombotic complications. Fresh frozen plasma (FFP) is used in hope of preventing these complications, despite poorly defined effects on the coagulation system and lack of proven clinical efficacy.

OBJECTIVES AND METHODS

We prospectively evaluated coagulopathy and the effect of standardized amount of FFP transfusion (10 mL kg-1 + 4 mL in 2 h) on various coagulation markers in 33 newborn infants during the first 24 h of intensive care.

RESULTS

Increased levels of prothrombin fragment F1+2, thrombin-antithrombin complexes (TAT), and d-dimer were found prior to the transfusion in 97%, 81%, and 100% of the patients, respectively. FFP transfusion was associated with a decrease in F1+2 level in 26/32 (81%) of the patients. The extent of F1+2 decrease correlated with the pretransfusion F1+2 level (R = 0.65, P < 0.0001). The patient series was divided into two groups according to increasing pretransfusional F1+2 level: Group 1 (preFFP F1+2 > or = 2.35 nm, n = 16), Group 2 (F1+2 <2.35 nm, n = 16). In Group 1, F1+2 decreased on average 1.58 nm (P < 0.01) from the baseline during FFP transfusion but no significant change in the level of F1+2 during the transfusion was observed in Group 2. Pretransfusional levels of individual factors or prothrombin time (PT) did not correlate with the FFP-associated decrease in F1+2 level.

CONCLUSIONS

In the patients with the highest pretransfusional thrombin formation, FFP had an acute thrombin-reducing effect. Pretransfusion thrombin generation markers, rather than PT or individual pro- and anticoagulants, may be helpful in identifying the patient who will have measurable coagulational effects induced by FFP.

The effect of recombinant factor VIIa on coagulopathic pigs with grade V liver injuries

BACKGROUND

Recombinant factor VIIa (rFVIIa) has been used to decrease bleeding in a number of settings including hemophilia, liver transplantation, intractable bleeding, and cirrhosis. Experience in the trauma setting is limited. This study was performed to determine whether rFVIIa would reduce bleeding after a grade V liver injury in hypothermic, dilutionally coagulopathic pigs when used as an adjunct to abdominal packing and to determine whether increasing the dose of the drug increased its hemostatic efficacy.

METHODS

Thirty animals were randomized to receive 180 microg/kg of rFVIIa, 720 microg/kg of rFVIIa, or vehicle buffer control. After laparotomy and splenectomy, animals underwent a 60% blood volume isovolemic exchange transfusion with 5% human albumin. The animals' temperature was maintained at 33 degrees C and a standardized grade V liver injury was made with a liver clamp. Thirty seconds after injury, the abdomen was packed with laparotomy sponges, resuscitation was initiated, and blinded therapy was given. Animals were resuscitated to their baseline mean arterial pressure and the study was continued for 2 hours. Serial coagulation parameters were measured at the temperature they were drawn. After the study period, surviving animals were killed, posttreatment blood loss was measured, and an autopsy was performed.

RESULTS

Ten animals were randomized to each group. After administration of study drug, factor VII clotting activity (FVII:C) was higher in the 720 microg/kg group than in the 180 microg/kg group (p < 0.01). FVII:C was higher in both treatment groups than in the control group (p < 0.01). The mean prothrombin time was shorter in the treatment groups than in the control group (p < 0.05). Mean arterial pressure was lower in the control group than in the treatment groups throughout the study (p < 0.01). Mean blood loss was less in the treatment groups than in the control group (p = 0.03). Mortality was not different between groups. There were no differences between the groups that received rFVIIa in any measured parameters except for FVII:C. Liver injuries were similar between groups and there was no evidence of microthrombosis on lung histology.

CONCLUSION

rFVIIa reduces blood loss in hypothermic, dilutionally coagulopathic pigs with grade V injuries when used as an adjunct to packing. Increasing the dose does not enhance the hemostatic effect.

Increased risk of intraventricular hemorrhage in preterm infants with thrombophilia

The multifactorial etiology of cerebral intraventricular hemorrhage (IVH) may involve coagulation disturbances and venous infarction. We tested whether coagulation abnormalities associated with adult venous thrombosis would constitute a risk factor for IVH in newborn infants. In 22 infants (gestational age 24.3--39.9 wk, median 28.0 wk) with neonatal IVH grade II to IV, the frequencies of congenital resistance to activated protein C due to a point mutation in the factor V gene (Gln506-FV) and a polymorphism in the prothrombin gene (G20210A-FII) were assessed and compared with those observed in 29 premature newborn infants without IVH and in 302 (Gln506-FV) or 526 (G20210A-FII) healthy adults. In infants with IVH, four (18%) heterozygous carriers of Gln506-FV and one (5%) heterozygous carrier of G20210A-FII were found. One infant without IVH was heterozygous for Gln506-FV (3%). When compared with the frequency of Gln506-FV in the general population, the odds ratio for being a carrier of Gln506-FV for patients with IVH was 5.9 (95% confidence interval 1.7--20.3, p = 0.013) and for patients without IVH 0.9 (95% confidence interval 0.1--7.6, p > 0.99). The absolute risk of IVH in a newborn infant with heterozygous Gln506-FV and born before 30 wk of gestation was estimated at 80%, whereas the corresponding risk for all infants born before 30 wk was 14%. Gln506-FV was more common in newborn infants with IVH than in the general population, whereas there was no difference in the frequencies of Gln506-FV in infants without IVH and in the general population. Thus, Gln506-FV may be a risk factor of IVH. The risk of IVH in a premature infant with Gln506-FV or other established thrombophilic coagulation abnormality may be considerable.

Association between pulmonary microthromboembolism and coagulation variables in hypercoagulable states: an autopsy study

OBJECTIVE

This autopsy study was carried out to investigate the relationship between the number of pulmonary microthromboemboli and coagulation tests in patients with coagulation abnormalities.

METHODOLOGY

Fifty-one patients in whom coagulation studies were performed within 2 days prior to death were studied. The coagulation tests included platelet counts, prothrombin times expressed as International Normalized Ratios (INR), activated partial thromboplastin times, fibrinogen concentrations, plasma fibrinogen/fibrin fragment E antigen levels, and plasma D-dimer levels. For microscopic analysis, five tissue blocks of the lung were taken from each subject and the number of pulmonary microthromboemboli per 20 cm2 of tissue sections was calculated.

RESULTS

Thirty-six of the 51 patients had pulmonary microthromboembolism. International Normalized Ratios were higher than 1.7 in 12 of 36 embolic and in two of 15 non-embolic patients (33.3% of sensitivity and 86.7% of specificity). There was no significant difference in D-dimer levels between the two groups. Multiple regression analysis identified that INR was significantly related to the number of microthromboemboli (P = 0.042).

CONCLUSIONS

D-dimer levels appear to be inappropriate as a single screening test for disseminated intravascular coagulation (DIC) in critically ill patients because the levels in these subjects are elevated irrespective of the presence of microthromboemboli. Because of the high specificity, INR could be a specific marker for microthromboemboli. The significant association between the number of microthromboemboli and INR might indicate the importance of the extrinsic pathway in the initiation of DIC.

Age-related reference values for activation markers of the coagulation and fibrinolytic systems in children

The physiology of the hemostatic system in infancy and childhood is different from that in adulthood. Despite differences in several components of the coagulation and fibrinolytic systems, there is no evidence that children are at greater risk for hemorrhagic or thrombotic problems compared with adults (1,2). Advances in understanding of the biochemistry of the hemostatic mechanism have led to the development of sensitive immunochemical methods for measuring peptides or enzyme-inhibitor complexes that are liberated with the activation of the coagulation and fibrinolytic systems in vivo (3). Activation markers of coagulation and fibrinolysis have been measured in newborns, infants and children with a variety of underlying disorders (4-16). However, reference ranges for children of different age groups have hitherto not been established. The aim of the present study was to document thrombin-antithrombin III-complex (TAT), prothrombin fragment 1 + 2 (F1 + 2), plasmin-alpha 2-antiplasmin-complex (PAP) and D-dimer in healthy children and to determine whether age-related differences can be demonstrated.

Activation of the clotting system during extracorporeal membrane oxygenation in term newborn infants

OBJECTIVES

To determine the degree of clotting activation that occurs with the usual anticoagulation regimen with systemic heparinization.

METHODS

To allow a standardized comparison of the patients, this study focused on the first 48 hours of extracorporeal membrane oxygenation (ECMO) in term newborn infants. The ECMO perfusion circuit consisted of a roller pump, silicone membrane lungs, and silicone rubber tubing. Coagulation was controlled routinely by measuring prothrombin time, fibrinogen, antithrombin III, and reptilase time. Platelet counts, activated clotting time, and heparin concentration were controlled regularly. The following specific activation markers of the clotting system were measured: prothrombin activation fragment 1 + 2(F1+2), thrombin-antithrombin III complexes, and D-dimer. Measurements were done before the start of ECMO, after 5 minutes, and at hours 1, 2, 3, 4, 6, 12, 24 and 48.

RESULTS

All seven term infants had excessively high levels of clotting activation markers within the first 2 hours of ECMO: F1+2, 11.6(+/- O.9) nmol/L (mean +/- SEM); thrombin-antithrombin, 920(+/- 2.2) microg/L; D-dimer, 15.522(+/- 3.689) ng/L. During the next 46 hours of ECMO, F1+2 and thrombin-antithrombin III complexes decreased from those high values, whereas D-dimer did not. The increase of activation markers was accompanied by low fibrinogen, low platelet counts. and prolongation of reptilase time.

CONCLUSIONS

These findings fit the pattern of consumptive coagulopathy during neonatal ECMO, especially in the first 24 hours.