A histomorphometric comparison of the effects of heparin and low-molecular-weight heparin on cancellous bone in rats

Long-term heparin treatment causes osteoporosis through, an as yet, undefined mechanism. To investigate this phenomenon and to determine the relative benefits of low-molecular-weight heparin (LMWH) use, we treated rats with once daily subcutaneous injections of either unfractionated heparin (1.0 U/g or 0.5 U/g), the LMWH, Tinzaparin (1.0 U/g or 0.5 U/g), or placebo (saline) for a period of 32 days. The effects on bone were then compared both histomorphometrically and biochemically by measuring urinary type I collagen cross-linked pyridinoline (PYD) and serum alkaline phosphatase, markers of bone resorption and formation, respectively. Histomorphometric analysis of the distal third of the right femur, in the region proximal to the epiphyseal growth plate, demonstrated that both heparin and LMWH decrease cancellous bone volume in a dose-dependent fashion, but that heparin causes significantly more cancellous bone loss than does LMWH. Although both heparin and LMWH decrease osteoblast and osteoid surface to a similar extent, only heparin increases osteoclast surface. In support of these histomorphometric findings, biochemical markers of bone turnover demonstrated that both heparin and LMWH treatment produce a dose-dependent decrease in serum alkaline phosphatase, consistent with reduced bone formation, whereas only heparin causes a transient increase in urinary PYD, consistent with an increase in bone resorption. Based on these observations, we conclude that heparin decreases cancellous bone volume both by decreasing the rate of bone formation and increasing the rate of bone resorption. In contrast, LMWH, causes less osteopenia than heparin because it only decreases the rate of bone formation.

Coagulation and fibrinolytic profile of paediatric patients undergoing cardiopulmonary bypass

The haemostatic system and the use of heparin during cardiopulmonary bypass (CPB) have been studied extensively in adults but not in children. Results from adult trials cannot be extrapolated to children because of age-dependent physiologic differences in haemostasis. We studied 22 consecutive paediatric patients who underwent CPB at The Hospital for Sick Children, Toronto. Fibrinogen, factors II, V, VII, VIII, IX, XII, prekallikrein, protein C, protein S, antithrombin (AT), heparin cofactor II, alpha 2-macroglobulin, plasminogen, alpha 2-antiplasmin, tissue plasminogen activator (tPA), plasminogen activator inhibitor, thrombin-AT complexes (TAT), D-dimer, heparin (by both anti-factor Xa assay and protamine titration) and activated clotting time (ACT) were assayed perioperatively. The timing of the sampling was: pre heparin, post heparin, after initiation of CPB, during hypothermia, post hypothermia, post protamine reversal and 24 h post CPB. Plasma concentrations of all haemostatic proteins decreased by an average of 56% immediately following the initiation of CPB due to haemodilution. During CPB, the majority of procoagulants, inhibitors and some components of the fibrinolytic system (plasminogen, alpha 2 AP) remained stable. However, plasma concentrations of TAT and D-dimers increased during CPB showing that significant activation of the coagulation and fibrinolytic systems occurred. Mechanisms responsible for the activation of haemostasis are likely complex. However, low plasma concentrations of heparin (< 2.0 units/ml in 45% of patients) during CPB were likely a major contributing etiology. ACT values showed a poor correlation (r = 0.38) with heparin concentrations likely due to concurrent haemodilution of haemostatic factors, activation of haemostatic system, hypothermia and activation of platelets. In conclusion, CPB in paediatric patients causes global decreases of components of the coagulation and fibrinolytic systems, primarily by haemodilution and secondarily by consumption.

Hyperekplexia: abnormal startle response due to glycine receptor mutations

BACKGROUND

Hyperekplexia is a rare but well-delineated clinical syndrome of pathological startle response and neonatal hypertonia. Many cases result from mutations in the alpha 1 subunit of the glycine receptor (GLRA 1).

METHOD

The clinical features, management and recent genetic studies of hyperekplexia are reviewed.

RESULTS

Diagnosis of the disorder should not be difficult, if one is aware of the syndrome. The treatment of first choice is with the benzodiazepine drug clonazepam, which often causes a dramatic although incomplete diminution of startle. Both recessive and dominant mutations in GLRA 1 have been found in affected individuals. The study of mouse mutants with startle phenotypes suggests that the remainder of cases may well be due to mutations in the beta subunit of the glycine receptor.

CONCLUSIONS

Hyperekplexia is the first human disease shown to result from mutations within a neurotransmitter gene. The demonstration of both dominant and recessive inheritance resulting from different mutations in the same gene is of considerable interest, as other neuropsychiatric disorders may result from mutations in ligand-gated ion channels. Mutation analysis of GLRA 1 is also likely to be useful as an aid to genetic counselling and in diagnostic evaluation of neonatal hypertonia.

The relevance of developmental hemostasis to hemorrhagic disorders of newborns

The hemostatic system is a dynamic evolving process that is age-dependent. Components of the hemostatic system are synthesized in early fetal life and do not cross the placenta from mother to fetus. However, plasma concentrations of proteins involved in hemostasis significantly differ from adults. Physiological reference ranges are available for premature infants, full-term infants and children from ages 1 to 16 years. In the coagulation system, plasma concentrations of the vitamin K-dependent and contact factors are decreased at birth, whereas other factors such as fibrinogen, FV, FVIII, and FXIII are similar or increased compared with adults at birth. In the fibrinolytic system, plasma concentrations of plasminogen are decreased at birth, whereas tissue plasminogen activator and plasminogen activator inhibitor are increased. Clinically, the hemostatic system of the young is effective and healthy infants do not suffer from spontaneous hemorrhagic complications. However, infants are more vulnerable, compared with older patients, for bleeding in the presence of either congenital or acquired haemostatic defects. Severe congenital bleeding disorders, although rare, frequently present in the newborn period. The most common acquired causes of bleeding newborns include disseminated intravascular coagulation, vitamin K deficiency, and liver disease. A description of these disorders and treatment guidelines are provided.

Heparin therapy in pediatric patients

Advances in tertiary care pediatrics have resulted in heparin being one of the most frequently prescribed drugs in children's hospitals. Heparin is essential for cardiopulmonary bypass, extracorporeal membrane oxygenation, renal dialyses, maintenance of patency of venous and arterial catheters, and treatment of thromboembolic events. Currently, protocols validated in adults are used for children. However, optimal use of heparin in pediatric patients will likely differ from adults because of age-dependent physiologic and pathologic differences in hemostasis that influence the activities of heparin. The following review summarizes the influence of age on heparin anticoagulant activities, and pharmacokinetics. The indications, monitoring, therapeutic range, factors influencing dose-response relationships, and side effects of heparin therapy in pediatric patients are discussed. Finally the current and future indications for low-molecular-weight heparins in pediatric patients are summarized. Multi-centered, international clinical trials are urgently needed to assess and optimize the use of heparin in pediatric patients in a variety of clinical settings. Until these studies are completed, recommendations for adults provide guidelines for children.

Coping with the absurd: a first-time educational researcher's reflection

Learning research through doing it often left me feeling confused, but I also experienced a well defined sense of 'well that's exactly what I thought all along', as I sought to clarify my uncertainties by turning to the literature. This feeling is, according to Schön & Bamberger, a type of historical revisionism where the student attributes insight to the moment when it occurs. They suggest that when the insight occurs, the 'moves on the way, tend to disappear' (1991, p207). This paper attempts to set down these moves and concludes with an exhortation to keep educational research rooted in the experience and interest of the student.

Histomorphometric analysis of the effects of standard heparin on trabecular bone in vivo

Long-term heparin treatment causes osteoporosis through an as yet undefined mechanism. To investigate this phenomenon, we treated rats with once daily subcutaneous injections of heparin (in doses ranging from 0.25 to 1.0 U/g) or saline for 8 to 32 days and monitored the effects on bone both histomorphometrically and by serial measurements of urinary type 1 collagen cross linked-pyridinoline (PYD) and serum alkaline phosphatase, markers of bone resorption and formation, respectively. Histomorphometric analysis of the distal third of the right femur in the region proximal to the epiphyseal growth plate showed that heparin induces both a time- and dose-dependent decreased in trabecular bone volume, with the majority of trabecular bone loss occurring within the first 8 days of treatment. Thus, heparin doses of 1.0 U/g/d resulted in a 32% loss of trabecular bone. Heparin-treated rats also showed a 37% decrease in osteoblast surface as well as a 75% decrease in osteoid surface. In contrast, heparin treatment had the opposite effect on osteoclast surface, which was 43% higher in heparin-treated rats, as compared with that in control rats. Biochemical markers of bone turnover showed that heparin treatment produced a dose-dependent decrease in serum alkaline phosphatase and a transient increase in urinary PYD, thus confirming the histomorphometric data. Based on these observations, we conclude that heparin decreases trabecular bone volume both by decreasing the rate of bone formation and increasing the rate of bone resorption.

Age-related changes in factor VII proteolysis in vivo

Previous studies have reported that pre-operative plasmas of patients over the age of 40 years who developed post-operative deep vein thrombosis (DVT) had approximately twice the amount of proteolysed factor VII found in plasmas of patients in whom prophylaxis with heparin or low M(r) heparin was successful. These and other studies also reported higher concentrations of thrombin-antithrombin III in pre- and post-operative plasmas of patients who developed post-operative thrombosis than in plasmas of patients in whom prophylaxis was successful. Whether the extent of factor VII proteolysis seen in the patients who developed post-operative DVT is related to the severity of their disease or age is not known. This report investigated age-related changes in the concentrations of total factor VII protein, factor VII zymogen, factor VIIa, tissue factor pathway inhibitor, thrombin-antithrombin III, and prothrombin fragment 1 + 2 in normal plasmas and the relationships between these parameters. With the exception of thrombin-antithrombin III, statistically significant increases in the concentrations of these parameters with age were found. Additionally, the differences between the concentrations of total factor VII protein and factor VII zymogen, an index factor VII proteolysis in vivo, were statistically significant only for individuals over age 40. Using linear regression analysis, a significant correlation was found to exist between the concentrations of plasma factor VIIa and prothrombin fragment 1 + 2. Since factor VIIa-tissue factor probably initiates coagulation in vivo, we hypothesize that the elevated plasma factor VIIa (reflecting a less tightly regulated tissue factor activity and therefore increased thrombin production in vivo) accounts for the high risk for post-operative thrombosis seen in individuals over the age of 40.

The application of EMLA and glyceryl trinitrate ointment prior to venepuncture

The efficacy of EMLA cream combined with glyceryl trinitrate (GTN) ointment was assessed by a double-blind prospective study. Adult female patients were randomly allocated to receive either EMLA 1 ml or 2 ml combined with GTN 2 mg, or EMLA 2 ml only. The difference in pain scores between the three groups was not statistically significant. When GTN was used with EMLA, the quality of the veins was superior and aided intravenous cannulation. There were no significant side-effects. It is concluded that if GTN is used with EMLA, the dose of EMLA can be reduced and intravenous cannulation is technically easier compared with EMLA alone.

Decreased thrombin activity of fibrin clots prepared in cord plasma compared with adult plasma

We hypothesized that the immaturity of the newborn coagulation system may influence the procoagulant activity of clotbound thrombin. 125I-Labeled fibrin clots were prepared from adult and cord plasma, incubated in their respective plasmas, and fibrinopeptide A (FPA) production was measured. Cord plasma clots generated significantly less FPA compared with adult plasma clots (p < 0.001). Cord plasma clots incubated in adult plasma generated similar amounts of FPA as cord plasma clots in cord plasma. Adult plasma clots incubated in cord plasma clots generated more FPA than adult plasma clots in adult plasma. Adult and cord plasma clots were then incubated with purified human adult fibrinogen, and the discrepancy between adult and newborn plasma clots remained (p < 0.01). To compare the amount of clot bound thrombin, adult and cord plasma clots were sonicated and incubated with fibrinogen. Again, significantly less thrombin was seen in cord clots compared with adult clots (p < 0.01). Because cord plasma has lower prothrombin concentrations (0.5 U/mL) we increased cord plasma prothrombin concentration by the addition of purified prothrombin. Prothrombin supplemented cord plasma clots generated more thrombin than unsupplemented clots (p < 0.01) and in amounts similar to the adult system. In conclusion, decreased amounts of thrombin present in cord plasma clots compared with adult plasma clots results in less FPA production. The low plasma concentration of prothrombin in cord plasma is responsible for this phenomenon.

Low-molecular-weight heparin in pediatric patients with thrombotic disease: a dose finding study

OBJECTIVE

To compare low-molecular-weight preparations of heparin (LMWH) with standard heparin in children requiring anticoagulant treatment for thromboembolic disease.

METHODS

We treated 25 children who required heparin, but were at significant risk of bleeding, with LMWH (enoxaparin, Rhone-Poulenc Rorer). The median age was 4 years (range, newborn to 17 years), with nine infants less than 2 months of age. Fourteen children had a deep vein thrombosis or pulmonary embolism, nine had thrombotic complications in the central nervous system, and two had complex congenital heart disease, for which they received prophylaxis at a lower dosage (0.5 mg/kg given subcutaneously twice a day). The remaining 23 children received an initial dose of 1 mg/kg, every 12 hours subcutaneously, with subsequent doses adjusted to achieve a 4-hour anti-factor Xa level between 0.5 and 1.0 unit/ml.

RESULTS

Newborn infants had increased dose requirements; an average of 1.60 units/kg was required to achieve therapeutic heparin levels. For the remaining children, the initial dose of 1.0 mg/kg was sufficient. After the initial dose adjustment, LMWH was administered with twice-weekly monitoring. The median duration of therapy with LMWH was 14 days. Two children with previously documented gastrointestinal ulcers bled and required transfusion therapy. Therapy with LMWH was continued without further events. There were no new thrombotic events during the treatment with LMWH. The cost of administering LMWH compared with heparin was reduced by 30% because of decreased laboratory monitoring, blood sampling times, intravenous starts, and nursing time. Needle punctures were reduced with LMWH therapy by the placement of a subcutaneous catheter.

CONCLUSION

These results provide the basis for a randomized, controlled trial comparing LMWH with standard heparin in pediatric patients.

Hemostatic complications in renal disorders of the young

This review focuses on the hemorrhagic and thrombotic complications sometimes associated with the most common renal disorders in children. A Medline search of the literature was conducted from 1966 to January 1995, using combinations of key words appropriate for each disorder. Additional references were located through the bibliographies of the publications and recent journals were searched independently. The most common renal disorders with hemostatic complications in children were: renal vein thrombosis (268 children in 80 publications), hemolytic uremic syndrome (473 children in 29 publications), nephrotic syndrome (4,158 children in 51 publications), renal transplantation (3,976 children in 14 publications), glomerulonephritis (20 publications), end-stage renal disease, and dialysis (22 publications). The age distribution, clinical presentation, etiology, diagnosis, treatment, and outcome of the affected children were analyzed for each disorder. Children with inherited pre-thrombotic disorders usually do not present during childhood unless there is a secondary risk factor. Similarly, most children with renal disease do not develop thromboembolic complications. Therefore, when a child with a renal disorder develops a thromboembolic event, evaluation for an inherited pre-thrombotic disorder should be seriously considered. Guidelines for the use of heparin and warfarin in these children (both therapeutically and prophylactically) are given. At this time, the risk/benefit of thrombolytic therapy in children is not known and a general recommendation for thrombolytic therapy cannot be made.

Indications and drugs for anticoagulation therapy in children

The indications for using anticoagulants in children are reviewed. These include venous thromboembolic disease, thrombosis associated with central venous lines, inherited conditions, arterial thromboembolic disease and umbilical catheterization. The anticoagulants presently available for paediatric use consist of heparin and oral agents including low molecular weight heparin (LMWH). The problems associated with their use in children are examined and potential advantages described. Increasing numbers of children are now requiring anticoagulant therapy and the potential advantages of LMWHs makes it imperative that randomized, controlled trials be carried out in children in prophylactic as well as therapeutic situations.

Topography and immunogenicity of bluetongue virus VP7 epitopes

The core of bluetongue virus (BTV) consists of ten dsRNA viral genome segments and five proteins, including two major (VP7 and VP3) and three minor (VP1, VP4 and VP6) components. The major core protein VP7 is believed to be an important structural constituent because it interacts, not only with the underlying core protein VP3, but also with two outer capsid proteins (VP2 and VP5). In this communication we summarise data on the mapping of at least six different epitopes of VP7 distributed along the molecule. Two of the six epitopes have not been mapped previously. The accessibility of these epitopes in intact virions and core particles was analysed using immunoelectron microscopy. The epitope located near the N-terminus of VP7 was accessible at the surface of intact virions and core particles. Epitopes in other parts of the VP7 molecule were detected weakly in core particles but not in intact virions. These results support the proposal that VP7 molecules are orientated with their N-terminus accessible on the surface of either the particle or at least one of the three different channels observed by cryoelectron microscopy in the outer capsid layer. Analysis of the immune response to BTV-infected or -immunised sheep and rabbits to three selected epitopes, which are located in different regions of the VP7 molecule, demonstrated that all of them were recognised by the animals tested. These results provided further molecular evidence suggesting that VP7 is indeed a major immunogenic antigen ideal for BTV antibody detection.

Hemostasis in childhood acute lymphoblastic leukemia: coagulopathy induced by disease and treatment

Thromboembolic events (TE) are serious complications of treatment for childhood acute lymphoblastic leukemia (ALL) that result in significant morbidity and occasionally mortality. These events are strongly associated with the administration of L'asparaginase (ASP). There have been many studies reporting TE and assessing the coagulopathy associated with treatment. The intention of these studies was to determine a potential mechanism for thrombosis. This article reviews the current literature in this area. First, data on thrombotic complications in terms of incidence, location, diagnosis, and timing of events are summarized. The second section discusses the coagulopathy associated with the disease and treatment. To minimize the effects of confounding treatments, the data are divided into sections covering pretreatment, after ASP only, after combination chemotherapy without ASP, and after combination chemotherapy with ASP. In addition, the effects of glucocorticoid steroids on the hemostatic system are discussed. As thrombin regulation is critically important to hemostasis, the next section of the review discusses the regulation of thrombin in children with ALL, both in vitro and in vivo, and the link between impaired thrombin regulation and TE in this population. Finally current hypothesis on mechanisms for TE and proposed preventative strategies are examined.

Developmental hemostasis: relevance to hemostatic problems during childhood

Congenital and acquired hemostatic disorders present during childhood. An accurate diagnosis is critically important in order to implement optimal therapy. Over the last century, several investigators have measured plasma concentrations of hemostatic components in newborns and compared the results to adult values. Clinically significant differences exist for many hemostatic components. Recently, three large studies in more than 400 healthy children have provided reference ranges for hemostatic components throughout childhood. Together, these studies provide insight into the regulation of coagulation and fibrinolysis in children in physiologic and pathologic states. Some examples of the influence of age on hemostasis are: (1) the diagnosis of some congenital factor deficiencies, based on plasma levels, can be difficult due to physiologically low values; (2) despite very low levels of many inhibitors of hemostasis, thrombotic complications are rare; (3) the interaction of anti-coagulants and thrombolytic agents is profoundly influenced by the relative immaturity of hemostasis at birth; and (4) in contrast to the risk of thrombosis, healthy infants are at risk for vitamin K deficiency bleeding due to poor transport of vitamin K across the placenta and plasma concentrations of the vitamin K dependent proteins of less than 50% of adults values. The following review discusses the age dependency of hemostasis during childhood and the effect of the physiologically immature system on the diagnosis and treatment of hemostatic disorders.

Home monitoring of warfarin therapy in children with a whole blood prothrombin time monitor

We prospectively evaluated a capillary whole blood prothrombin time (PT) monitor (Biotrack, Ciba Corning) in an outpatient pediatric anticoagulation clinic (40 clinic patients) and in age-matched healthy subjects (30 control subjects). Subsequently, 23 children requiring warfarin therapy were placed on a home program (home patients) using the PT monitor; their parents were trained and the results followed by clinic staff. The PT results were reported as internationalized normalized ratios (INRs). The laboratory and PT-monitor INR values were similar for the clinic patients and the control subjects (y = 0.76x + 0.38; r = 0.93; p < 0.001). The accuracy of the PT monitor (the difference between INR values and the laboratory INR) was best at an INR of 2.5 to 3.5; 90% of paired INR values were within 0.8 INR units. The average duration of monitoring for home patients was 13 months (range, 2 to 60 months). They had an average of 3 dose measurements (range, 1 to 11 measurements) and 1.8 dose changes (range, 0.6 to 4.5 changes) per month. Of the 599 measurements, 63% were within the therapeutic range, similar to those for clinic patients; the dose requirements were also similar. There was 1 significant bleeding event, a subdural hematoma in a patient with an INR of 4.1, and 1 catheter-related thrombotic event with an INR of 1.2; both children recovered. Of the 23 families, one discontinued home monitoring because of parental discomfort, 2 children died of their primary disease, 6 completed warfarin therapy, and 14 remain on the home program. We conclude that the whole blood PT/INR monitor is safe and offers practical advantages to children requiring anticoagulation.

Circulating dermatan sulfate and heparan sulfate/heparin proteoglycans in children undergoing liver transplantation

The liver produces dermatan sulfate (DS), heparan sulfate (HS) and heparin glycosaminoglycans (GAG) and in the presence of hepatic disease, tissue levels of the DS GAG increase dramatically. We hypothesized that in children undergoing liver transplantation plasma levels of DS would be increased. Plasma from children undergoing liver transplantation were tested preoperative, intra operative and post operative at 24-48 h, and 1-3 weeks. Fluctuating levels of DS, HS and heparin anticoagulant activity were detected at all timepoints. The anticoagulant activity was purified and gel chromatography of the material displayed a mean Mr 110,000 D. Reductive elimination decreased the mean Mr 24,000 D indicating the activity resides on a proteoglycan (PG). The purified material was subjected to further chromatography and two peaks of anticoagulant activity resolved, compatible with at least two separate PGs, one with DS GAG chains and the additional PG(s) with HS and heparin GAG chains.

Changes in diurnal blood pressure variation and red cell and plasma volumes in patients with renal failure who develop erythropoietin-induced hypertension

Hypertension is the most common side-effect of treatment with recombinant human erythropoietin (EPO) for the anemia of chronic renal failure. To elucidate why this occurs in some patients we measured changes in blood volumes and diurnal blood pressure (BP) variation during treatment. Isotope labelled measurements of red cell and plasma volume (RCV and PV) were carried out along with ambulatory BP monitoring before starting EPO and after target hemoglobin (Hb) was reached. RCV did not differ between the patient group developing EPO-induced hypertension (EpHT, n = 11) and the group with no change in BP (NC, n = 13) either before or after treatment. However PV was significantly lower in the EpHT group after treatment (2.97 vs 3.92 litres; p < 0.025). Mean BPs differed little between groups because antihypertensive medications were increased as necessary for clinical safety but after achieving target Hb, day-night difference in diastolic BP was greater in the EpHT than the NC group (11.5 vs 4.6 mmHg; p < 0.025) due to a greater rise in daytime BP. There were significant correlations between high day-night diastolic BP differences after EPO in all the studied patients and low plasma volumes either pre- or post-EPO. The study group was heterogeneous but the changes were in the same direction irrespective of type of renal replacement therapy. These results suggest that EPO-induced hypertension is associated with increased daytime vasoconstriction and greater hemoconcentration due to lower plasma volume.

Antigen specificity of the ovine cytotoxic T lymphocyte response to bluetongue virus

Bluetongue virus (BTV), an arbovirus transmitted by midges, can cause serious disease in sheep. Both virus neutralizing antibody and cytotoxic T lymphocytes (CTL) have been shown to have a role in protective immunity. In this study, the antigen specificity of CTL from BTV-immune sheep has been determined using recombinant vaccinia viruses expressing individual BTV antigens. The results show that, in the sheep studied thus far, the serotype-specific outer coat protein, VP2, and the non-structural protein, NS1 are major immunogens for CTL, with VP5 (an outer coat protein) and NS3 being minor immunogens. No VP7 (a major group-reactive inner coat protein) specific CTL were detected. The CTL from sheep immunized with serotype 1 were cross-reactive and able to recognize target cells infected with other BTV serotypes. Further work demonstrated that the cross-reactive CTL recognized NS1, but not VP2.

Cerebral vein thrombosis in childhood systemic lupus erythematosus

We describe three cases of cerebral vein thrombosis (CVT) in girls with systemic lupus erythematosus. Severe, persistent, unremitting headache was a common manifestation. In the first patient, although the clinical features were suggestive of CVT, the diagnosis was delayed and she had a significant cerebral infarct. In the other two patients the diagnosis was made earlier and led to more rapid treatment; the institution of early therapy may have prevented further sequelae. The CVT was diagnosed in all patients with a combination of computed tomography and magnetic resonance imaging studies without the need for angiography. All patients were treated for their underlying systemic lupus erythematosus and with anticoagulation. All are receiving long-term low doses of warfarin and have not had any recurrences.

Cognitive function, thyroid status and postpartum depression

Impairment of cognitive function can occur with thyroid disorder and also with depression. Since depression occurs in conjunction with postpartum autoimmune thyroiditis, the question arises as to whether any impairment of cognitive function in postpartum women is related to change in thyroid status or to depressed mood. A total of 242 women (110 thyroid antibody-positive and 132 antibody-negative) were assessed at 8, 12, 20 and 28 weeks postpartum in the outpatients of a district general hospital. Thyroid antibody levels (antimicrosomal and antithyroglobulin) were monitored at monthly intervals, together with plasma T3, T4 and thyroid-stimulating hormone. The main outcome measures were Research Diagnostic Criteria for depression, the 17-item Hamilton Depression Rating Scale and the Edinburgh Postnatal Depression Scale, together with reaction time and digit span. Subjects with postnatal depression showed detectable cognitive impairment independent of thyroid antibody status and actual thyroid dysfunction.

INR reporting in Canadian medical laboratories. Thrombosis Interest Group of Canada

A written survey of all licensed medical laboratories in Canada performing coagulation testing was performed to investigate the level of knowledge and overall usage of the INR system for reporting prothrombin time results in medical laboratories. There was an overall response rate of 857 of 1,228 laboratories surveyed. Fifty-seven percent of responding laboratories utilized some format of INR reporting. The ISI of the individual thromboplastin utilized was known by 89% of laboratories. The ISI of the thromboplastin utilized was known to be specific for the particular reagent/instrument combination in 44% of cases. Fifty-five percent of client physicians preferred PT results to be reported in seconds while 42% desired an INR format. The situation in Canada is similar to the United States in that further education regarding the INR system for PT reporting is required by both medical laboratories and physicians.

A cross-sectional study of catheter-related thrombosis in children receiving total parenteral nutrition at home

We performed a cross-sectional evaluation of deep vein thrombosis (DVT) related to the use of central venous lines (CVLs) in all pediatric patients receiving home total parenteral nutrition at our institution (N = 12). All children (5 months to 17 years of age) were examined with bilateral upper limb venography. All CVLs were flushed daily with heparin (200 units). At the time of evaluation, 49 CVLs had been placed in the 12 children. Of the 39 CVLs removed, 27 (66%) were blocked; venograms had not been previously obtained except of one child. Eight children had clinical evidence of superficial collateral circulation in the upper portion of the chest and the upper extremities; five had intermittent symptoms of superior vena cava obstruction. On venography, 8 of the 12 children had extensive evidence of DVT; two were unilateral and six bilateral. Five children were treated with warfarin (0.12 to 0.28 mg/kg per day) to achieve an international normalized ratio of 1.4 to 1.8. Neither bleeding nor further CVL-related DVT has occurred. We conclude that the risk of CVL-related DVT in children requiring home total parenteral nutrition is high, and that venography should be performed early in the event of CVL blockage. A multicenter, controlled trial assessing optimal warfarin therapy in this patient population is indicated.

Inhibition of thrombin by antithrombin III and heparin cofactor II in vivo

The critical role of thrombin in the pathogenesis of venous and arterial thrombosis, and the effectiveness of glycosaminoglycans as antithrombotic drugs are well known. Antithrombin III is a major inhibitor of thrombin and augmentation of its inhibitory actions by heparin is the basis for the clinical uses of heparin. Recent clinical and experimental studies have demonstrated that another glycosaminoglycan, dermatan sulfate, is an effective antithrombotic drug. Dermatan sulfate catalyses the inhibition of thrombin by heparin cofactor II. The concentrations of heparin cofactor II are higher in the plasmas of individuals with congenital antithrombin III deficiency and pregnant women than controls. The role of heparin cofactor II as a physiologic thrombin inhibitor is unknown. Enzyme-linked immunosorbent assays were used to quantify thrombin-heparin cofactor II and thrombin-antithrombin III endogenous to the plasmas of adult antithrombin III-Hamilton deficient subjects, their siblings with normal antithrombin III levels, pregnant women at term and 3 to 5 days after delivery. Both thrombin-antithrombin III and thrombin-heparin cofactor II complexed with vitronectin were detected in all the plasmas. Significantly, the concentrations of thrombin-heparin cofactor II-vitronectin were higher in the plasmas of congenital antithrombin III deficient subjects and in pre- and post-delivery plasmas than those of normal subjects. In addition, the concentrations of thrombin-heparin cofactor II decreased 3 to 5 days after delivery, reflecting the disappearance of the catalytically active dermatan sulfate elaborated by the placenta. Thus, heparin cofactor II normally inactivates thrombin in vivo, with its role increasing in conditions associated with high levels of heparin cofactor II and/or dermatan sulfate.

alpha 2-Macroglobulin remains as important as antithrombin III for thrombin regulation in cord plasma in the presence of endothelial cell surfaces

Infants and children rarely develop thrombotic complications compared with adults, suggesting that there are protective mechanisms in place for the young. Because endothelial cell surfaces regulate thrombin formation and inhibition, we compared thrombin regulation by human umbilical vein endothelial cell surfaces exposed to defibrinated cord and adult plasmas. After activation by either 10% activated partial thromboplastin reagent (strong activator) or coagulant phospholipids (weak activator) the following were measured: free thrombin, thrombin bound to antithrombin III (ATIII), heparin cofactor II, alpha 2-macroglobulin (alpha 2M), and prothrombin concentration. Free thrombin activity was expressed as remaining activity, after subtraction of thrombin-alpha 2M activity. After 10% activated partial thromboplastin reagent, 100% of prothrombin was consumed and significant amounts of thrombin generated by 2 min. Cord plasma generated significantly less thrombin than adult plasma, reflecting the lower initial plasma concentration of prothrombin. correspondingly, concentrations of thrombin inhibitor complexes were significantly greater in adult plasma than in cord plasma. After coagulant phospholipids, 50% of prothrombin was consumed and negligible thrombin activity measured for both adult and cord plasma. Similar amounts of thrombin inhibitor complexes were formed. ATIII was the predominant inhibitor of thrombin in adult plasma, whereas alpha 2M was as important as ATIII in cord plasma for both activators. When cord plasma concentrations of ATIII were increased to adult values, the proportion complexed to alpha 2M decreased. We conclude that on human umbilical vein endothelial cells, the capacity to generate thrombin is decreased in adult and cord plasmas.(ABSTRACT TRUNCATED AT 250 WORDS)

[Guidelines for understanding and treating chronic obstructive lung diseases. Institute for Pharmacotherapy]

A group of chest physicians, general practitioners, clinical pharmacologist and pharmacists appointed by the Institute of Pharmacotherapy, University of Oslo has evaluated the present knowledge about treatment of chronic obstructive lung disease. The group discusses today's medical treatment of this rather numerous group of patients. It is stated that, to a high degree, the treatment of these patients lacks proper documentation, and that treatment needs to be tested out on an individual basis. The group proposes a flow chart for this purpose.

Thrombin regulation in children differs from adults in the absence and presence of heparin

The physiologic mechanisms that protect children from thromboembolic complications are not known. We investigated the regulation of thrombin in children because of its central importance to thrombosis. The capacity to generate thrombin in vitro (chromogenic assay) was decreased by 26% in plasmas from children (1-16 yrs; n = 102) compared to adults ([20-45 yrs; n = 20; p < 0.001]). The addition of purified prothrombin to plasmas from children increased thrombin generation to adult values. The capacity of plasmas to inhibit 125I-alpha-thrombin was increased by 21% in children compared to adults (p = 0.020), with significantly more thrombin complexed to alpha 2-macroglobulin (alpha 2M) in children. When DVT occur in children, adult guidelines for heparin therapy are used. At low heparin concentrations (0.1 and 0.2 U/ml), thrombin generation was decreased by 30% in children compared to adults (p < 0.001). At high heparin levels (0.4 U/ml), thrombin generation was negligible in all plasmas. ATIII inhibited over 95% of thrombin in all plasmas in the presence of heparin. In summary, thrombin regulation differs in children from adults and may protect children from thromboembolic complications. When DVT do occur, heparin requirements may differ in children compared to adults.

Evidence for recessive as well as dominant forms of startle disease (hyperekplexia) caused by mutations in the alpha 1 subunit of the inhibitory glycine receptor

Startle disease, or hyperekplexia, is characterized by an exaggerated startle reflex and neonatal hypertonia. An autosomal dominant form of the disorder is associated with mutations in the same codon of the alpha 1 subunit of the inhibitory glycine receptor (GLRA 1) resulting in the substitution of an uncharged amino acid for Arg271 in the mature protein. However, recessive transmission is seen in the mouse mutant spasmodic which resembles startle disease phenotypically and is also associated with mutations in Glra 1. We have confirmed the finding of Arg271 mutations in individuals with startle disease in a UK family showing autosomal dominant transmission. In addition we describe an apparently sporadic case, the offspring of a consanguineous mating, who is homozygous for a novel mutation (T1112A) in GLRA 1, which results in the substitution of asparagine for isoleucine at position 244 of the mature protein. This suggests that human startle disease can display recessive as well as dominant inheritance resulting from different mutations in GLRA 1.

Randomised trial of intravenous immunoglobulin G, intravenous anti-D, and oral prednisone in childhood acute immune thrombocytopenic purpura

The most serious complication of childhood acute immune thrombocytopenic purpura (ITP), intracranial haemorrhage, occurs in about 1% of children with platelet counts below 20 x 10(9)/L. We conducted a randomised study to explore three treatment options in this high-risk group. 146 children (> 6 months and < 18 years old) with typical acute ITP and platelet counts of 20 x 10(9)/L or lower were randomised to receive high-dose intravenous immunoglobulin G (IVIgG) 1 g/kg on 2 consecutive days (n = 34), 0.8 g/kg once (n = 35), intravenous anti-D 25 micrograms/kg on 2 consecutive days (n = 38), or oral prednisone 4 mg/kg per day with tapering and discontinuation of prednisone by day 21 (n = 39). The rate of response as reflected by the number of days with platelet counts at 20 x 10(9)/L or lower and the time taken to achieve a platelet count 50 x 10(9)/L or more was significantly faster for both IVIgG groups than for the anti-D group (p < 0.05); the difference between prednisone and IVIgG was significant (p < 0.05) only for the IVIgG 0.8 g/kg group, and responses to the two IgG groups were similar. These differences in response rates were reflected in the percentages of children with platelet counts of 20 x 10(9)/L or lower at 72 hours following the start of treatment: 3% (IVIgG 0.8 g/kg x 1), 6% (IVIgG 1 g/kg x 2), 18% (anti-D), and 21% (oral prednisone 4 mg/kg/day). Treatment-associated toxicities included a fall in haemoglobin with anti-D (to less than 100 g/L in 24% of cases); weight gain with oral prednisone; and fever, nausea, vomiting, and headache with IVIgG. On the basis of these results, intravenous anti-D cannot be recommended as initial therapy for children with acute ITP and platelet counts of 20 x 10(9)/L or lower. A single dose of 0.8 g/kg IVIgG offers the fastest recovery for the least treatment; additional IgG or oral prednisone can be reserved for the one-third of children who continue to have platelet counts of 20 x 10(9)/L or less at 48-72 hours after the start of treatment.

Recombinant vaccinia viruses expressing interleukin-5 stimulate an earlier appearance of antibody-secreting cells in the lung

Interleukin-5 (IL-5) is a cytokine that participates in the regulation of antibody secretion, in particular promoting the secretion of IgA at mucosal sites. In this report, recombinant vaccinia viruses expressing IL-5 have been inoculated into mice and the appearance of antibody-secreting cells in the spleen and lungs investigated. Although vaccinia virus-expressed IL-5 did not increase the level of IgA in serum, antibody-secreting cells, measured in an enzyme-linked immunosorbent spot assay, appeared earlier in lungs when the immunizing virus expressed IL-5. These early B cells secreted either IgM or IgG1.

Age-dependent immune response in Merino sheep

The numerical and functional attributes of populations of lymphocytes were compared in the blood, lymph and skin of young and mature sheep. Young sheep, four to eight months old, had a lower proportion of CD4+ cells in blood, lymph and skin than mature sheep three to six years old. In contrast, B cells and T19+ cells were as prevalent or more prevalent in young sheep as in mature sheep. Blood lymphocytes from young sheep, cultured in vitro produced less interferon-gamma, both spontaneously and in the presence of concanavalin A than did lymphocytes from older sheep. The serum antibody responses of adult sheep to the T cell-independent antigen Brucella abortus lipopolysaccharide (LPS) were greater over a range of antigen doses, suggesting that an apparent excess of antigen could not overcome the relative immune deficiency of young sheep. The adjuvant Quil A corrected the depressed antibody response of young sheep to B abortus LPS, but dextran sulphate did not. The skin contact hypersensitivity of mature sheep to dinitrochlorobenzene was greater. However, the T cell phenotypes present in infiltrates of lymphocytes elicited by the intradermal injection of tetanus and diphtheria, but not tuberculin antigens, were comparable for the two age groups. The capacity of Quil A to raise the antibody responses of both young and mature sheep to a similar titre suggests that it may be possible to overcome the immunological hyporesponsiveness that may contribute to the disease susceptibility of young sheep.

Thrombin inhibition by fetal distal lung epithelium is different in fetal and adult plasma

Intra-alveolar fibrin deposition is a cardinal feature of neonatal respiratory distress syndrome and likely contributes to short-term and long-term morbidity. Previous studies have shown that fetal distal lung epithelial cell (FDLE) surfaces express procoagulant activity when incubated with adult plasma and may therefore provide one mechanism by which fibrin is generated. However, plasma concentrations of prothrombin and thrombin inhibitors differ significantly at birth and during the first weeks of life compared with adult values. Therefore, we measured thrombin-generating capacity and inhibitor complex formation in cord and adult plasma incubated in the presence of FDLE. Although starting cord plasma concentrations of prothrombin were 43% of adult values, the amount of thrombin generated was decreased by only 21%. When cord plasma concentrations of prothrombin were selectively increased to adult values, the amount of thrombin generated surpassed adult plasma by 89%. The latter observations suggested that thrombin inhibition was impaired in cord plasma compared with adult plasma and supplementation of cord plasma with antithrombin III (ATIII) as well as prothrombin returned thrombin generation to adult levels. However, the percentage of thrombin complexed to inhibitors (59%) at the completion of the experiments was similar in cord, cord plus prothrombin, cord plus prothrombin plus ATIII, and adult plasmas. Although a higher proportion of thrombin was inhibited by alpha 2-macroglobulin (alpha 2M) in cord plasma and cord plasma plus prothrombin, this did not compensate for the decreased amount of thrombin inhibited by ATIII. When cord plasma was supplemented with ATIII as well as prothrombin, the proportions of thrombin complexed by the different inhibitors were similar to those of adult plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of codeine analgesics in a general population. A Norwegian study of moderately strong analgesics

The prescribing of controlled analgesics (codeine, buprenorphine and pentazocine preparations) was studied, using prescriptions from the three pharmacies in the municipality of Tromsø, Norway. All prescriptions dispensed during one year were analysed. The study sample comprised 3083 women (58%) and 2223 men (42%) between 10 and 99 years of age. About 8% of the population had obtained one or more prescriptions of controlled analgesics. Combined codeine preparations were by far the most frequently prescribed subgroups, and the average amount purchased during 1 year was 30 defined daily doses (DDD). The sporadic users were in the majority. A few users had purchased high amounts of controlled analgesics. The prevalence of use, the mean number of defined daily doses of analgesics, and the proportion of 'weekly' drug users was higher in women than men. The prevalence increased significantly with age, from 0.7 to 22.3% in women and from 0.5 to 14.1% in men. The mean number of DDD during one year also increased with age, from 12.6 to 50.6 DDD in women, and from 6.6 to 40.6 DDD in men. The users of buprenorphine and pentazocine differed in several aspects from the codeine users. The highest use of combined codeine preparations was seen in elderly people especially in women. Use of lower codeine doses or intermittent treatment with other drugs e.g. plain paracetamol in adequate doses, may be appropriate alternatives reducing the risk of adverse drug reactions such as nausea and constipation. Monitoring of prescribing and use of controlled analgesics according to certain criteria may uncover possible misuse.

Measles immunization of 2-year-olds in a rural southern state

OBJECTIVE

To assess the measles vaccine coverage of 2-year-old children living in Mississippi during the national measles epidemic of 1989 and 1990.

DESIGN

Survey of 2-year-olds randomly selected from the 1987 birth cohort. The status of measles-mumps-rubella (MMR) vaccination was determined by medical record reviews and family contacts.

SETTING

A predominantly rural state in the southeastern United States with a large black minority population (35%) and a low per capital income ($9827 to $12,899). Approximately 80% of MMR immunizations are given by public health service nurses working in nine health districts.

SUBJECTS

A total of 2450 preschool-aged children representing 6% of the 1987 birth cohort (n = 41,279). Three hundred forty-one children were considered ineligible, leaving 2109 in the final sample.

MAIN OUTCOME MEASURES

Confirmed vaccination by the age of 2 years. Rates of immunization were calculated for the entire state, its health districts, and subgroups based on population density, per capita income, type of clinic visited, and race.

RESULTS

The statewide immunization rate was 87% (95% confidence interval, 86% to 88%). Among the nine health districts, rates varied from 79% to 97% (median, 88%). They were similar for white and black children in each health district and within the state as a whole. The level of vaccine coverage was significantly higher in districts with lower population densities (89% vs 85%, P = .02) and in those with higher per capita incomes (89% vs 86%, P = .03). There were four minor outbreaks of measles during 1989 and 1990; half of the cases occurred in unimmunized children too young to receive the MMR vaccine.

CONCLUSION

A high rate of measles immunization is attainable among 2-year-olds living in a rural state with a large black minority population and limited economic resources.

Oral anticoagulation therapy in pediatric patients: a prospective study

There are no validated guidelines for administering or monitoring oral anticoagulant therapy in pediatric patients. A pediatric thromboembolism program at the Hospital for Sick Children, Toronto, prospectively monitored consecutive children requiring warfarin over an 18 month period. A uniform protocol was followed and dose adjustments based upon international normalized ratios (INRs). One hundred and fifteen consecutive children; 68 males and 47 females, received warfarin. The age distribution was: <1y (19); 1-5 ys (33); 6-10 ys (20); 11-18 ys (43). Warfarin was used for secondary prevention of venous thromboembolism (n = 56) and primary prevention of thromboembolism (n = 59). Underlying disorders included: congenital heart disease (CHD) without mechanical valves (MV) (49); CHD with MV (18); cancer (8); longterm total parenteral nutrition (7); renal disorders (10); other (23). Treatment length was considered as short term (3-6 mths) n = 37 (32%); longterm (> 6 mths) n = 38 (33%); and life-long n = 40 (35%) of children. While receiving warfarin, 95 children received concurrent longterm treatment with other drugs: 1 drug (28); 2 drugs (27); 3 drugs (21); 4 or more drugs (19). The amounts of warfarin/kg required to achieve INRs of 2 to 3 decreased with increasing age. Children <1 year of age required 0.32 +/- 0.05 mg/kg whereas children 11-18 yrs required 0.09 +/- 0.01 mg/kg; P < 0.001. Monitoring warfarin required an average of 4.0 measurements per month and 1.5 dose changes per month. Changes in warfarin doses were primarily precipitated by drugs, intermittent illness, and changes in diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Venous thromboembolic complications (VTE) in children: first analyses of the Canadian Registry of VTE

Deep vein thrombosis (DVT) and pulmonary embolism (PE) occur in pediatric patients; however, the incidence, associated morbidity, and mortality are unknown. A Canadian registry of DVT and PE in children (ages 1 month to 18 years) was established July 1, 1990 in 15 tertiary-care pediatric centers. One-hundred thirty-seven patients were identified prospectively and are the subject of this report. The incidence of DVT/PE was 5.3/10,000 hospital admissions or 0.07/10,000 children in Canada. Infants under 1 year old and teenagers predominated with equal numbers of both sexes. DVT were located in the upper (n = 50) and lower (n = 79) venous system, or as PE alone (n = 8). Central venous lines (CVLs) were present in approximately 33% of children with DVT (n = 45). Associated conditions were present in 96% of children and 90% of children had two or more associated conditions for DVT. DVT was diagnosed by venography (n = 83), duplex ultrasound (n = 37), and other combinations (n = 17). Twenty-two of the 31 ventilation/perfusion scans performed were interpreted as high-probability scans for PE. Therapy consisted of heparin (n = 115), thrombolysis (n = 15), surgical removal of a CVL or thrombus (n = 22), and oral anticoagulant therapy (n = 103). Significant bleeding complications did not occur. However, three (2.2%) children died as a direct consequence of their thromboembolic disease; DVT reoccurred in 23 children and postphlebitic syndrome (PPS) occurred in 26. In conclusion, DVTs occur in a significant number of hospitalized children with a mortality of 2.2%. Complications are not hemorrhagic, but thrombotic, and characterized by PE, recurrent disease, and PPS. In contrast to adults, the upper venous system is frequently affected because of the use of CVLs. The frequency of DVT/PE justifies controlled trials of primary prophylaxis in high-risk groups, and therapeutic trials to determine optimal treatment.

Thrombin regulation in congenital heart disease after cardiopulmonary bypass operations

Children with cyanotic congenital heart disease who undergo operation with cardiopulmonary bypass are at increased risk of thromboembolic or hemorrhagic complications, or both. Regulation of thrombin, a key enzyme in coagulation, is essential in preventing these complications. We therefore examined the in vitro capacity of plasma from 15 children with cyanotic congenital heart disease to generate thrombin and to inhibit 125I-thrombin before and after cardiopulmonary bypass. We also assessed whether thrombin had been generated in vivo by assaying levels of fibrinogen, thrombin-antithrombin III complexes, and D-dimer. Plasma levels of the thrombin inhibitors, antithrombin III, alpha-2-macroglobulin, and heparin cofactor II were also measured. Thrombin regulation was normal before operation. After cardiopulmonary bypass, the in vitro capacity to generate thrombin decreased by 50%, and this was primarily a result of hemodilution (31%). Similar postoperative decreases were noted in the levels of antithrombin III, heparin cofactor II, and alpha-2-macroglobulin (26% to 45%). However, the total in vitro plasma thrombin inhibitory capacity decreased by only 13%. Levels of thrombin-antithrombin III and D-dimer increased after operation, indicating that thrombin had been generated and inhibited in vivo. Clinically, there were no thromboembolic complications although six patients required replacement therapy for excessive small-vessel bleeding. In conclusion, thrombin regulation is significantly altered after cardiopulmonary bypass. Although thrombin is generated in vivo, the total residual capacity to do so is impaired because of hemodilution. Despite a concomitant decrease in thrombin inhibitor levels, the total residual in vitro capacity of plasma to inhibit thrombin is relatively spared. This suggests that after cardiopulmonary bypass the risk of hemorrhagic complications after an additional hemostatic challenge is relatively greater than the risk of thrombotic complications. This might be reflected in the predominance of hemorrhagic complications in our patients.

[Use of antimicrobial agents in Norway 1980-92]

Use of systemic antimicrobial agents in Norway shows a moderate increase from 1980 to 1992, from 13.5 to 16.9 defined daily doses (DDDs) per 1,000 inhabitants per day. Comparing the Nordic countries, the use of these drugs is second lowest in Norway, after Denmark. In relative terms the use of tetracyclines is highest in Norway. Use of co-trimoxazole is also relatively high, while use of macrolides is low. The share of penicillin V and G is highest in Sweden. Several new and important antimicrobial agents have been introduced on the Norwegian market during the period, while almost as many have been withdrawn. Penicillin V and G constitutes the main subgroup. However, the use of tetracyclines is almost as high, for a short period in fact higher. Taking into account the development of drug resistance and adverse events, it is recommended that use of tetracyclines and co-trimoxazole be reduced, mainly to the advantage of penicillins. The use of cephalosporins seems to be reasonable, but penicillins should be considered more often as an alternative. The use of antimycotic and antiviral drugs is low in terms of DDDs. In 1992 the cost of antimicrobial agents for systemic use was in 1992 approx. NOK 400 million, retail price. The largest subgroup, cephalosporins, constituted almost 20%, as against only 2% of DDDs. Antimicrobial agents represent a substantial part of the total drug budget in hospitals. A shift from expensive to cheaper alternatives should be considered as a routine. Moreover, an optimal change from parenteral to oral administration could help to reduce costs.

Increased endogenous thrombin generation in children with acute lymphoblastic leukemia: risk of thrombotic complications in L'Asparaginase-induced antithrombin III deficiency

Pediatric patients with acute lymphoblastic leukemia (ALL) are at an increased risk of thromboembolic events. Potential responsible mechanisms include the disease process itself, treatment with chemotherapeutic agents (particularly L-Asparaginase [ASP]), or a combination of the disease and treatment. We studied thrombin regulation in 26 consecutive children with ALL and 14 healthy age-matched controls by: (1) plasma concentrations of prothrombin; (2) plasma inhibition of 125I-alpha-thrombin; and (3) four biochemical markers of in vivo thrombin activation (thrombin complexed to its inhibitor antithrombin III [ATIII; TAT], prothrombin fragment 1.2 (F1.2), activated protein C complexed to the inhibitors alpha 1 antitrypsin [APCAT]), and protein C inhibitor (APC-PCI). Measurements were made at presentation before treatment, after treatment with ASP alone, and during combination chemotherapy with and without ASP. At presentation, the capacity to generate thrombin (reflected by plasma prothrombin concentrations) and the capacity to inhibit thrombin (125I-alpha-thrombin--inhibitor complex formation) were similar in children with ALL compared with that for healthy children. After ASP alone or as part of combination chemotherapy, prothrombin levels were preserved, whereas plasma inhibition of 125I-alpha-thrombin decreased significantly because of a decrease in plasma concentrations of inhibitors, most importantly ATIII. After combination chemotherapy without ASP, plasma concentrations of ATIII and the capacity to inhibit 125I-alpha-thrombin returned to normal values, whereas prothrombin levels increased above control values. Thrombin generation in vivo also differed from healthy controls. At presentation, plasma concentrations of three of four markers of in vivo thrombin activity (TAT, F1.2, APCAT, but not APC-PCI) were increased in children with ALL. Neither ASP alone nor combination chemotherapy with or without ASP significantly altered values of these three markers. In summary, although the in vitro capacity to generate thrombin was preserved, the in vitro capacity to inhibit 125I-alpha-thrombin decreased after ASP therapy. Evidence for increased endogenous thrombin generation was documented in children with ALL at presentation and throughout treatment. We speculate that poor regulation of this thrombin may contribute to thrombotic complications in children with ALL.

Heparin therapy in pediatric patients: a prospective cohort study

Current guidelines for heparin therapy in pediatric patients have been extrapolated from trials in adult patients without rigorous evaluation of efficacy and safety. We prospectively monitored consecutive pediatric patients receiving systemic doses of heparin over 10 mo at one institution using a predetermined nomogram to monitor maintenance therapy. Sixty-five consecutive children; 38 males and 27 females, received systemic doses of heparin. Thirty children had deep venous thrombosis and/or pulmonary embolism; 11 had arterial thrombi, most frequently after diagnostic angiography; and the remaining 24 received heparin prophylactically, for congenital heart disease. Twenty-nine (45%) of the 65 patients were less than 1 y of age and 22 (34%) were 10 y or older. Congenital heart disease was the predominant diagnosis under 1 y and deep venous thrombosis in older children. After a bolus dose of 50 U/kg, 39% of children (n = 30) achieved a minimal level activated partial thromboplastin time (APTT). Sixty-eight percent of children achieved a minimal level APTT by 24 h and 81% by 48 h. For all 65 children, APTT values were within the therapeutic range 43% of the time. APTT values outside the therapeutic range were twice as likely to be low as high. The average amount of heparin required to maintain therapeutic APTT values for children was 22 U/kg/h: 28 U/kg/h for infants < 1 y and 20 U/kg/h for the rest. Bleeding was rare (2%) and mild. Documented recurrent thrombotic disease was more common (7%) with associated morbidity.(ABSTRACT TRUNCATED AT 250 WORDS)