Neonatal antithrombin III

Pre-operative coagulopathy management of a neonate with complex congenital heart disease: a case study

Severe coagulation defects often develop in neonates undergoing cardiac surgery, both as a result of the surgical intervention, and as pre-existing defects in the hemostatic mechanisms. The following case report describes a newborn patient with complex congenital heart disease and respiratory failure whose pre-operative coagulopathy was aggressively managed prior to surgical correction. A 5-day-old, 2.5 kg child presented with interrupted aortic arch, ventricular septal defect, atrial septal defect, and patent ductus arteriosus. On admission, he was in respiratory arrest suffering from profound acidemia. In addition, the child was hypothermic (30.1 degrees C), septic (Streptococcus viridans), and coagulopathic (disseminated intravascular coagulation-DIC). The patient was immediately intubated and initial coagulation assessment revealed the following: prothrombin time (PT) 48.9 s (international normalized ratio (INR) 15.7), activated partial thromboplastin time (aPTT) >106 s, platelet count 30,000 mm(3), fibrinogen 15 mg dL(-1) and antithrombin III (AT-III) 10%. Before cardiac surgery could be performed, the patient's DIC was corrected with the administration of cryoprecipitate (15 ml), fresh frozen plasma (300 ml), and platelets (195 ml). In spite of the large transfusion of fresh frozen plasma, the AT-III activity, measured as a percentage, remained depressed at 33. Initial thromboelastographic (TEG) determination revealed an index of +2.02, and following 100 IU administration of an AT-III concentrate, declined to -2.32. Sequential TEG profiles were performed over several days, with the results used to guide both transfusion and medical therapy. The congenital heart defect correction was subsequently performed with satisfactory initial results, but the patient developed a fungal infection and expired on the 16th post-operative day. The present case describes techniques of coagulation management for a newborn with both a severe hemostatic defect and congenital heart disease.

Normal levels of the natural anticoagulants (proteins C & S and antithrombin III) and the fibrinolytic factors (tPA and PAI) in Arab children

The diagnosis of many hemostatic defects in infancy and childhood depends on the establishment of normal levels of various hemostatic factors. In this study, measurements of the natural anticoagulants (proteins C, S, and antithrombin III), as well as the fibrinolytic factors (tPA and PAI) were undertaken in healthy neonates (cord blood; n = 56), as well as in healthy children, up to 12 years of age (n = 103). The results were compared to normal adult values obtained from blood donors (n = 49). Neonatal values were found to be 50% of those obtained in adults and their mean concentrations were as follows: ATIII antigen = 48.4%, ATIII activity = 61.6%, protein C antigen = 47.7%, protein C activity = 57.2%, total protein S = 41.8% and tPA = 1.9 ng/mL. PAI level (25.7 ng/mL) was similar to adult values. In the first three years of life, almost all the hemostatic factors, other than PAI, gained adults levels. The diminished concentrations of the natural anticoagulants, in addition to the hypofibrinolysis in neonates, shifts the hemostatic balance towards fibrin formation and safeguards effective hemostasis. The values obtained in this study may serve as local reference values.

Ligand-dependent enhancement of human antithrombin gene expression by retinoid X receptor alpha and thyroid hormone receptor beta

We studied potential modulators of antithrombin gene expression. A putative hormone response element (HRE) was identified by sequence similarity analysis of the antithrombin promoter, situated between nucleotides -92 and -54 relative to the transcription start site. This HRE contains three hexa-nucleotide motifs with an AGGTCA consensus, which are potential targets of members of the steroid/thyroid superfamily of nuclear receptors. Stimulation of the hepatoma cell line HepG2 with the receptor ligands L-3,5,3'-tri-iodothyronine, all-trans retinoic acid, or their combination, increased production of antithrombin into the culture medium by 1.3-, 1.6-, and 2.0-fold, respectively. In contrast, the receptor ligand 1,25-dihydroxy-cholecalciferol[1,25-(OH)2VitD3] did not influence antithrombin production. Analysis of promoter chloramphenicol acetyl-transferase (CAT) constructs, showed that the first 86 bp of the antithrombin promoter region are sufficient for basal transcription. The DNA length polymorphism of 32 bp or 108 bp, located upstream of position -276, did not influence anti-thrombin promoter activity. The antithrombin promoter activity dropped to background values when deleting the region -97/-49 of promoter fragment -453/+57. Transactivation of the antithrombin promoter by retinoid X receptor alpha (RXR alpha) (5-7-fold) or thyroid hormone receptor beta (TR beta) (4-5-fold) was only observed when at least -167/+57 bp of the promoter region is present in CAT constructs, and when the appropriate ligand of the nuclear receptor was added. This transactivation was not observed upon deletion of the antithrombin promoter region -97/-49. With three copies of the antithrombin promoter fragment -109/-42 in front of the thymidine kinase minimal promoter, transactivation was only obtained with RXR alpha, and not with TR beta. In conclusion, these results indicate that the ligand-dependent enhancement of antithrombin gene expression is regulated by RXR alpha as well as by TR beta. Transactivation of antithrombin gene expression by RXR alpha and TR beta appears to be dependent upon the presence of promoter region up to nucleotide -167. The HRE segment (-109/-42) only confers RXR alpha responsiveness to a heterologous promoter. Further study is needed to unravel the exact nature of this HRE and its 5'-flanking sequences.

Fetal and neonatal development of antithrombin III plasma activity and liver messenger RNA levels in sheep

In healthy term human newborns a unique hemostatic balance exists with reduced plasma concentrations of several coagulant and anticoagulant proteins, including antithrombin III (AT III). In preterm newborns even lower AT III concentrations are observed, with an associated thromboembolic risk. As part of our study program on the gene regulation of AT III, we investigated whether the increase in plasma AT III activity during fetal and neonatal development is particularly controlled at the transcriptional level. Plasma AT III activity and liver AT III mRNA content between the 8th wk of gestation and the 4th wk after birth were determined in sheep. AT III activity gradually increased from 34% of the mean adult level at 8-10 wk of gestation to 86% (2.5-fold) at term (21 wk), and remained in the adult range after birth. The mean body weight, and thus plasma volume, increased 57-fold. Therefore, the total plasma AT III activity increased 140-fold. The total liver AT III mRNA content increased only 14-fold between these fetal stages, mainly due to increased liver weight. Therefore, the total plasma AT III activity increased 10-fold more than the liver AT III mRNA content. In the neonatal period between d 1-3 and 28, the total plasma AT III activity increased only 2-fold more than the liver AT III mRNA content. We conclude that the increase in plasma AT III activity during the fetal period, and similarly the neonatal period, is not regulated at the transcriptional level. Furthermore, a unique fetal isoform of AT III was detected in sheep. This isoform had a 2500-D higher molecular mass compared with the other fetal, neonatal, and adult AT III isoform, and disappeared from the circulation between d 2 and 7 after birth. These AT III isoforms differ in their carbohydrate moiety.

Hemostatic indices in healthy foals from birth to one month of age

Hemostatic indices were determined in 45 healthy light breed foals, from birth to 1 month of age, and in 20 healthy adult (> 2 years of age) light breed horses. Blood samples were obtained from each foal at 4 ages: 1) < 24 hours, 2) 4-7 days, 3) 10-14 days, and 4) 25-30 days. The following hemostatic indices were determined: platelet count; prothrombin and activated partial thromboplastin times; activity concentrations of protein C, antithrombin III, plasminogen, alpha-2 antiplasmin, tissue plasminogen activator, and plasminogen activator inhibitor-1; plasma protein C antigen and fibrinogen concentrations; and serum fibrin degradation products concentration. Prothrombin and activated partial thromboplastin times were significantly longer at birth than in older foals. The plasma concentrations of the following were significantly lower at birth than in older foals: antithrombin III, plasminogen and tissue plasminogen activator activities, protein C antigen, and fibrinogen. Concentrations of the following were significantly higher at birth than in older foals: protein C and plasminogen activator inhibitor-1 activities and fibrin degradation products. These results indicate that hemostatic indices of neonatal foals differ significantly from those of older foals and adults. With the exceptions of antithrombin III and tissue plasminogen activator activities, all hemostatic indices measured in foals at 1 month of age were equivalent to adult values.

Developmental expression of chicken antithrombin III is regulated by increased RNA abundance and intracellular processing

We isolated and sequenced a 432 bp cDNA to cAT-III, that encoded 115 nucleotides of 5' untranslated sequence, a 17 amino acid long signal peptide and residues 1-88 of the mature protein, and used it to prepare a probe for measuring and correlating the developmental changes of steady-state cAT-III mRNA levels with known changes in antigen levels. Densitometric analysis of nuclease protection (n = 2), Northern blot (n = 4), and slot blots (n = 3) of total RNA from chick livers of 16-day-old embryos to 6-day-old chicks showed a 2.6 +/- 0.5-fold increase in steady-state cAT-III mRNA levels. Assay of functional mRNA levels by in vitro translation of poly(A)+ RNA and specific immunoprecipitation of 35S-Met-labelled cAT-III was comparable to RNA analysis (16-day-old embryos vs. 10-day-old hatchlings). We evaluated whether there were developmental differences in post-translational secretion which may also contribute to the regulation of the circulating level of this protein. Pulse-chase studies of freshly-isolated hepatocytes from 16-day-old embryos and 10-day-old hatchlings maintained in suspension demonstrated a approx. 5.0-5.5-fold increase in cAT-III levels at steady-state secretion. The above findings indicate that changes in circulating cAT-III levels during late embryonic development are primarily due to increased abundance of cAT-III mRNA. In addition, we postulate that post-translational intracellular processing may account for further differences in circulating protein levels.

Comparison of antithrombin III, protein C and protein S levels in capillary and venous blood of newborn infants

The plasma concentrations of antithrombin III, protein C and protein S in capillary and venous blood samples obtained simultaneously from 30 neonates were compared in order to determine the suitability of using capillary blood for estimation of these proteins with anticoagulant action. Our findings showed that while capillary and venous blood did not differ significantly in antithrombin III functional activity and protein C antigen levels, the capillary samples had significantly lower protein C functional activity and higher antithrombin III antigen level. Protein S antigen level was also significantly higher in the capillary samples although the difference was relatively small. The capillary and venous concentrations of the binding protein of protein S, C4b binding protein, were almost identical.

Incidence of thrombosis during central venous catheterization of newborns: a prospective study

Forty-two newborns were studied prospectively to determine the incidence of thrombosis due to central venous catheterization. Following Broviac catheter placement, the catheter tip, distal superior vena cava, and right atrium were evaluated by weekly two-dimensional echocardiograms. The presence of thrombosis was examined in relation to birth weight, gestational age, age and weight at the time of catheter placement, antithrombin III levels, and platelet counts. Six newborns (14%) were noted to have a thrombus by echocardiographic examination after the catheter had been in place for a median duration of 7 weeks. The infants with thrombus formation had significantly lower birth weights (887 +/- 231 v 1,409 +/- 766 g; P = .003) and gestational ages (27 +/- 2.4 v 30.3 +/- 4.3 weeks; P = .018) than those without thrombus. Their weights (757 +/- 203 v 1,832 +/- 1,098 g; P = .000) and ages (2.75 +/- 0.76 v 7.24 +/- 7.8 weeks; P = .002) at the time of catheter placement were also lower; the antithrombin III levels were lower at the time of catheter placement (0.32 +/- 0.08 v 0.06 +/- 0.31 U/mL; P = .001), but were normal for gestational and postnatal age. The presence of thrombosis was not related to the sex of the baby, the platelet count, or the duration of catheterization.

Acquired antithrombin III deficiency: laboratory diagnosis, incidence, clinical implications, and treatment with antithrombin III concentrate

Antithrombin III (ATIII) is the predominant naturally occurring inhibitor of serine proteases generated during blood coagulation [Rosenberg RD: Annu Rev Med 1978; 29: 367-378]. Since 1965, several assays have been developed that allow rapid and precise determination of ATIII in plasma. As a consequence, the existence of acquired ATIII deficiency in many pathologic conditions has been described. Acquired ATIII deficiency is based on decreased synthesis, increased loss or increased consumption, or induced by drugs. An inherited ATIII deficiency is associated with a lifelong tendency to venous thromboembolism. In contrast, the clinical significance of acquired ATIII deficiency has been less well defined. A precise estimate of the risk of thromboembolism in the acquired ATIII deficiency state cannot easily be provided, owing to the lack of studies in consecutive patients. In 1978, a purified human ATIII concentrate became available for clinical investigation. Despite numerous small studies, the value of ATIII replacement therapy in patients with acquired deficiency remains to be demonstrated.

Neonatal antithrombin III deficiency

Hemorrhagic and thrombotic complications are common in sick preterm infants and may reflect inadequate regulation of coagulation. All neonates have low levels of the pivotal regulator antithrombin III (ATIII) compared with adults. Plasma levels of ATIII are very low in preterm infants and are further diminished in infants with respiratory distress, necrotizing enterocolitis, sepsis, or disseminated intravascular coagulation. Babies with lower levels of ATIII in the cord blood have been shown to have a worse outcome than neonates with levels appropriate for gestational age, including higher mortality and increased incidence of intracranial hemorrhages and catheter-related thromboses. The origin of severe ATIII deficiency is unknown. Therapies with plasma replacement or anticoagulation have decreased the incidence and severity of hemorrhagic and thrombotic complications in high-risk infants in several clinical trials. These data lay the groundwork and rationale for potential use of ATIII replacement in deficient preterm infants.

Heparin cofactor II, antithrombin and protein C in plasma from term and preterm infants

The coagulation inhibitors heparin cofactor II (HC II), antithrombin (AT) and protein C (PC) were measured in healthy term and preterm infants in order to establish reference standards. The mean value for HC II in term infants was found to be about half of the adult values. Values below 25% in healthy infants may suggest hereditary deficiency states. One girl with congenital HC II deficiency was detected. Mean AT and PC levels were somewhat higher than HC II. Healthy preterm infants have significantly lower HC II and AT values than healthy term infants. Serial AT measurements have been used in monitoring seriously ill infants and used as a prognostic indicator. In a small number of unhealthy neonates HC II was reduced to an even greater extent than AT, and on recovery normalized more rapidly than AT.