Hemostatic problems and thromboembolic complications in nephrotic children

Peculiaridades da terapia trombolítica na síndrome nefrótica pediátrica: monitorização do fator anti-Xa

OBJETIVO: Descrever a importância do tromboembolismo pulmonar (TEP) na síndrome nefrótica pediátrica e o uso da heparina de baixo peso molecular como opção terapêutica segura e eficaz. DESCRIÇÃO DO CASO: Menino de 5,7 anos com síndrome nefrótica córtico-resistente e glomérulo-esclerose segmentar e focal foi internado devido à diarréia, distúrbios eletrolíticos e anasarca. No 11º dia de internação, evoluiu com desconforto respiratório súbito, cuja investigação mostrou área de alta probabilidade de TEP na cintilografia pulmonar ventilação/perfusão e obstrução em veia jugular interna esquerda ao ultra-som doppler. Iniciado suporte ventilatório com nebulização de oxigênio e anticoagulação com enoxaparina (2mg/kg/dia). Após seis dias, evoluiu com sintomas neurológicos compatíveis com episódio isquêmico transitório, sem alteração na tomografia computadorizada de crânio. A monitorização do fator anti-Xa no soro demonstrou nível subterapêutico e a dose de enoxaparina foi ajustada para 3mg/kg/dia. O edema e os sintomas pulmonares melhoraram e o paciente recebeu alta hospitalar após 33 dias. COMENTÁRIOS: Embora o TEP seja raro em crianças, a síndrome nefrótica é uma condição pró-trombótica que favorece a complicação. A heparina de baixo peso molecular pode ser considerada no tratamento e na profilaxia secundária do TEP, sendo importante monitorizar o nível sérico do fator anti-Xa para ajustar sua dose e promover tratamento seguro e eficaz.

Protective effects of antithrombin on puromycin aminonucleoside nephrosis in rats

We investigated the effects of antithrombin, a plasma inhibitor of coagulation factors, in rats with puromycin aminonucleoside-induced nephrosis, which is an experimental model of human nephrotic syndrome. Antithrombin (50 or 500 IU/kg/i.v.) was administered to rats once a day for 10 days immediately after the injection of puromycin aminonucleoside (50 mg/kg/i.v.). Treatment with antithrombin attenuated the puromycin aminonucleoside-induced hematological abnormalities. Puromycin aminonucleoside-induced renal dysfunction and hyperlipidemia were also suppressed. Histopathological examination revealed severe renal damage such as proteinaceous casts in tubuli and tubular expansion in the kidney of control rats, while an improvement of the damage was seen in antithrombin-treated rats. In addition, antithrombin treatment markedly suppressed puromycin aminonucleoside-induced apoptosis of renal tubular epithelial cells. Furthermore, puromycin aminonucleoside-induced increases in renal cytokine content were also decreased. These findings suggest that thrombin plays an important role in the pathogenesis of puromycin aminonucleoside-induced nephrotic syndrome. Treatment with antithrombin may be clinically effective in patients with nephrotic syndrome.

Cerebral sinovenous thrombosis and idiopathic nephrotic syndrome in childhood: report of four new cases and review of the literature

INTRODUCTION

Nephrotic children are prone to develop thromboembolic complications secondary to an acquired hypercoagulable state. Cerebral sinovenous thrombosis (CSVT) is increasingly recognised in this population, but clinical characteristics and outcome are not well documented.

PATIENTS AND METHODS

The database of the Canadian Pediatric Ischemic Stroke Registry (Toronto Site) containing prospectively enrolled children from 1992-2004 with CSVT identified four children with NS. A pooled literature analysis retrieved 17 additional cases reports.

RESULTS

CSVT presented in the majority of cases during the first flare or within 6 months after the onset of NS and was found to occur more often in SSNS/SDNS (n=13) than in SRNS (n=4). Clinical manifestations were non-specific and consisted primarily of seizures (n=8) and signs of raised intracranial pressure (n=16). Imaging studies revealed a predilection for superior sagittal sinus involvement (n=21) and rare parenchymal lesions (n=4). The most consistent biological risk factors were a severe hypoalbuminaemia (n=14) and, to a lesser extent, decreased antithrombin (AT) levels (n=9/16). Deficiency of other coagulation inhibitors (protein S, protein C) was not identified. Inherited thrombophilia was documented in a single case, suggesting that acquired, more than genetic, coagulation factors are involved. Anticoagulation was safe, and the outcome was good in most patients, and no recurrence of thrombotic event was reported.

DISCUSSION

In conclusion, CSVT is now a well-described complication of NS with potential morbidity. A high index of suspicion is required, especially in young children with NS presenting neurological symptoms. Reliable biological predictors of CSVT are lacking.

Low protein Z levels in children with nephrotic syndrome

Acquired deficiency of anticoagulant proteins, due to loss in the urine, has been proposed as one of the major thrombogenic alterations in nephrotic syndrome (NS). Protein Z (PZ) is a single-chain vitamin K-dependent glycoprotein. Low PZ levels are reported to be a risk factor for thrombosis. The aim of this study was to investigate protein Z and other natural anticoagulant levels in children with NS. Thirty children aged between 1.5 and 12 years with NS (Groups I and II) and 19 age-and-sex-matched healthy controls (Group III) were enrolled into the study. Patients were divided into two groups: Group I (proteinuria >40 mg/m2/hr) and Group II (patients in remission). Plasma PZ levels in Group I were significantly lower than Group II (p=0.009) and group III (p=0.018). Plasma levels of AT III for Group I were significantly lower than for Groups II and III (p=0.009, p=0.005, respectively). Protein C levels in Group I were higher than in Group II and Group III (p=0.002, p=0.000, respectively). Protein Z levels positively correlated with serum total protein and albumin levels (p=0.003, p=0.003, respectively) and negatively with the degree of proteinuria (p=0.000). Protein Z levels were positively correlated with AT III (r=0.037, p=0.04). Along with the other coagulation abnormalities, decreased protein Z may contribute to increased risk of thromboembolic complications in children with NS. The negative correlation between proteinuria and PZ level suggests the possibility of renal PZ loss. Further studies are needed to investigate the mechanism and role of decreased PZ in NS.

Tissue factor pathway inhibitor in childhood nephrotic syndrome

It is now recognised that the extrinsic tissue factor pathway is the main trigger to the coagulation system in vivo. Its main inhibitor, tissue factor pathway inhibitor (TFPI), has never been studied in childhood nephrotic syndrome. The aim of the study was to monitor the level of TFPI in childhood nephrotic syndrome. One hundred and thirty-nine nephrotic children were classified into the following groups: group 1 (n=25), in relapse and receiving no treatment; group 2 (n=37), in relapse but receiving steroid treatment; group 3 (n= 45), in early remission and on steroids; group 4 (n=24), in established remission and receiving no steroids; group 5 (n=8), steroid-resistant. The controls (n=84) were healthy and age-matched. There was significant elevation of total TFPI levels in groups 1 and 2 and 3; levels were comparable to those of the healthy controls in group 4. The highest levels of total TFPI were recorded in group 5. Like total TFPI, the levels of the free form of TFPI showed a statistically significant increase in groups 1, 2, 3 and 4, when compared with levels in healthy controls. The highest levels of free TFPI were recorded group 5. We concluded that the elevated levels of both the total and free TFPI in various phases of nephrotic syndrome add another natural anticoagulant mechanism, which will attenuate the hypercoagulability of childhood nephrotic syndrome.

Chemical-induced atrial thrombosis in NTP rodent studies

Cardiac thrombosis, one of the causes of sudden death throughout the world, plays a principal role in several cardiovascular diseases, such as myocardial infarction and stroke in humans. Data from studies of induction of chemical thrombosis in rodents help to identify substances in our environment that may contribute to cardiac thrombosis. Results for more than 500 chemicals tested in rodents in 2-year bioassays have been published as Technical Reports of the National Toxicology Program (NTP) http://ntp-server.niehs.nih.gov/index. We evaluated atrial thrombosis induced by these chemical exposures and compared it to similarly induced lesions reported in the literature. Spontaneous rates of cardiac thrombosis were determined for control Fischer 344 rats and B6C3F1 mice: 0% in rats and mice in 90-day studies and, in 2-year studies, 0.7% in both genders of mice, 4% in male rats, and 1% in female rats. Incidences of atrial thrombosis were increased in high-dosed groups involving 13 compounds (incidence rate: 20-100%): 2-butoxyethanol, C.I. Direct Blue 15, bis(2-chloroethoxy)methane, diazoaminobenzene, diethanolamine, 3,3'-dimethoxybenzidine dihydrochloride, hexachloroethane, isobutene, methyleugenol, oxazepam, C.I. Pigment Red 23, C.I. Acid Red 114, and 4,4'-thiobis(6-t-butyl-m-cresol). The main localization of spontaneously occurring and chemically induced thromboses occurred in the left atrium. The literature survey suggested that chemical-induced atrial thrombosis might be closely related to myocardial injury, endothelial injury, circulatory stasis, hypercoagulability, and impaired atrial mechanical activity, such as atrial fibrillation, which could cause stasis of blood within the left atrial appendage, contributing to left atrial thrombosis. Supplementary data referenced in this paper are not printed in this issue of Toxicologic Pathology. They are available as downloadable files at http://taylorandfrancis.metapress.com/openurl.asp?genre=journal&issn=0192-6233. To access them, click on the issue link for 33(5), then select this article. A download option appears at the bottom of this abstract. In order to access the full article online, you must either have an individual subscription or a member subscription accessed through www.toxpath.org.

Thromboembolic complications in the nephrotic syndrome: Pathophysiology and clinical management

Patients with the nephrotic syndrome are at increased risk of developing venous and arterial thromboembolism, the most common of which is renal vein thrombosis. There are several unanswered or controversial issues relating to the nephrotic syndrome and thromboembolism, which include the mechanism of thromboembolism, and optimal diagnostic and anticoagulant management strategies. This review will discuss several of these issues: the epidemiology and clinical spectrum of thromboembolic disease occurring in patients with the nephrotic syndrome; the pathophysiology of the hypercoagulable state associated with the nephrotic syndrome; the diagnosis of renal vein thrombosis in the nephrotic syndrome; and the evidence for prophylactic and therapeutic anticoagulation strategies in such patients.

Lung scintigraphy in the diagnosis and follow-up of pulmonary thromboembolism in children with nephrotic syndrome

Thromboembolic phenomenon and pulmonary embolism is quite frequent in children with nephrotic syndrome (NS). The incidence of pulmonary thromboembolism in children with NS is as common as in adults, and severity is also reported to be relatively high. The mortality rate in NS with thromboembolic complications may be significantly increased if not diagnosed and treated well in time. For establishing the diagnosis of pulmonary embolism, although the combined use of magnetic resonance venography and CT angiography has been proposed, V/Q scan is still the best modality. We performed serial lung perfusion scans in two young patients with NS who developed sudden onset tachypnea during their stay in the hospital. Initial lung perfusion scans showing marked perfusion defects and normal chest X-rays indicated a high probability for pulmonary embolism. The patients were treated with streptokinase, and the study was repeated. Marked improvement was seen in lung perfusion, thereby highlighting the importance of lung perfusion scan in the follow-up of such patients.

Hypercoagulability risk factors in children with minimal change disease and the protective role of protein-C activity

It is believed that thrombotic activity in nephrotic syndrome is due to an imbalance between procoagulant/thrombotic and anticoagulant/antithrombotic factors in plasma. The aim of this study was to investigate the hypercoagulability risk in childhood minimal change disease and to find possible protective mechanisms with respect to hemostasis. Twenty-six children with minimal change disease were enrolled in this study. All patients were evaluated during an attack and on remission. The control group consisted of 33 healthy children. During the attack period, prothrombosis parameters, total lipid, cholesterol, fibrinogen levels and platelet count increased significantly compared to levels in the remission period. This denotes that hyperviscosity increases thrombosis tendency. In the attack period, the significant increase of prothrombin fragments 1 + 2 which shows thrombin formation and thrombin-antithrombin complex which causes prothrombin activation, are an indication of increased thrombosis risk. Five patients with lupus anticoagulant present and 7 patients with, activated protein-C resistance ratios carried an increased thrombosis risk. D-dimer level of fibrinolytic factors significantly increased during the attack period. These findings emphasize the existence of thrombotic activity causing the activation of the fibrinolytic system. The significant increase in protein-C activity in these patients represents one of the protective mechanisms against thrombosis. The decrease in tissue plasminogen activator and antiplasmin indicates the protective role of fibrinolytic activity. Consequently, an increase in the protein-C activity is one of the protective mechanisms. The fibrinolytic system also plays an important role in preventing thrombotic activity in these patients.

Superior sagittal sinus thrombosis in steroid-resistant nephrotic syndrome

An 8(1/2)-year-old-female child with steroid-resistant nephrotic syndrome developed sagittal sinus thrombosis while on pulse therapy with corticosteroids, presenting with recurrent vomiting, headache, and impaired consciousness. The diagnosis was established by cranial computed tomography, magnetic resonance imaging, and magnetic resonance angiography. She gradually recovered without neurologic sequelae while being treated with low-molecular-weight heparin (2 mg/kg/day). Sagittal sinus thrombosis consists of a rare and probably underdiagnosed complication of childhood nephrotic syndrome.

Cyclosporin A does not affect platelets in children with idiopathic nephrotic syndrome

The immunosuppressive agents administered to maintain the remission of idiopathic nephrotic syndrome (INS) may have a deleterious effect on several cell types. The aim of this study was to analyze platelet activation and reactivity in children with INS treated with cyclosporin A (CyA). The study groups comprised 16 children with remission of INS induced by CyA and 16 children with glucocorticosteroid-induced remission 8 weeks from the onset of INS relapse. Fifteen healthy children served as controls. Surface expression of CD61, CD62P, and CD42b on resting and thrombin-stimulated platelets was analyzed with flow cytometry. No differences between groups were found in CD61, CD62P, and CD42b surface expression, but markers of the coagulation cascade and fibrinolysis or endothelial injury (F1+2 prothrombin fragments, tissue plasminogen activator inhibitor 1) were elevated in patients treated with CyA compared with children on steroids and healthy controls. No correlations between markers of platelet function and CyA concentration were found. We postulate that CyA administration in nephrotic patients causes an activation of thrombinogenesis but does not influence platelet activation and reactivity in INS.

Increased pulmonary arterial pressure in children with nephrotic syndrome

AIMS

To evaluate the pulmonary arterial pressure in children with nephrotic syndrome (NS).

METHODS

Doppler echocardiography was performed in 40 children with NS (aged 1.5-13 years) at NS onset (n = 28) or relapse (n = 12), and 40 normal controls. Pulmonary pressure was estimated by: (1) measuring the systolic transtricuspid gradient from tricuspid regurgitation; and (2) measuring the time to peak velocity of pulmonary flow.

RESULTS

Thirty five of the 40 patients with NS had measurable tricuspid regurgitation with a pulmonary systolic pressure ranging from 21 to 48 mm Hg. Pulmonary systolic pressure was >40 mm Hg in seven patients. The pulmonary time to peak velocity was shortened and the ratio of time to peak velocity and right ventricular ejection time decreased compared with controls. The patients with increased pulmonary pressure had a longer time since onset of NS. One patient developed thrombus in the inferior vena cava during hospitalisation.

CONCLUSION

Pulmonary arterial pressure was increased in children with NS. Further work is needed to evaluate the aetiology and clinical implications of this abnormality.

Mesenteric thrombosis causing short bowel syndrome in nephrotic syndrome

Nephrotic patients are at risk of developing venous and arterial thrombotic complications. Pulmonary embolism due to affected deep leg veins is by far the most common event. Renal or cerebral vein thromboses have been described. Thrombosis of arterial vessels is less frequent. Mesenteric infarction is a rare but severe complication in patients with nephrotic syndrome (NS). We report a 7-year-old boy with a steroid-dependent (SD) NS and a homozygous mutation of methylenetetrahydrofolate reductase, increasing the risk of thromboembolic events. He developed a thrombosis of his superior mesenteric artery during his ninth relapse, which was responsible for a necrosis of 240 cm of his small bowel, necessitating resection of necrotic parts and double external ostomy diversion. Remission was achieved with pulse prednisolone therapy. Corticoids were reduced over 4 months progressively. Oral cyclosporin A (CyA) was initiated for long-term treatment. Due to a short bowel syndrome with severe malabsorption, even oral administration of 22.5 mg/kg per day CyA did not lead to sufficient plasma levels. Intravenous cyclophosphamide pulse therapy over 6 months led to a complete remission. No relapse occurred over a period of more than 5 months after the last cyclophosphamide pulse. Anticoagulation and screening for increased susceptibility for thrombotic events are necessary in every nephrotic patient. Intravenous cyclophosphamide pulse therapy is a useful alternative in SDNS with impaired intestinal absorption of applied immunosuppressive drugs.

Nephrotic syndrome in childhood

Childhood nephrotic syndromes are most commonly caused by one of two idiopathic diseases: minimal-change nephrotic syndrome (MCNS) and focal segmental glomerulosclerosis (FSGS). A third distinct type, membranous nephropathy, is rare in children. Other causes of isolated nephrotic syndrome can be subdivided into two major categories: rare genetic disorders, and secondary diseases associated with drugs, infections, or neoplasia. The cause of idiopathic nephrotic syndrome remains unknown, but evidence suggests it may be a primary T-cell disorder that leads to glomerular podocyte dysfunction. Genetic studies in children with familial nephrotic syndrome have identified mutations in genes that encode important podocyte proteins. Patients with idiopathic nephrotic syndrome are initially treated with corticosteroids. Steroid-responsiveness is of greater prognostic use than renal histology. Several second-line drugs, including alkylating agents, ciclosporin, and levamisole, may be effective for complicated and steroid-unresponsive MCNS and FSGS patients. Nephrotic syndrome is associated with several medical complications, the most severe and potentially fatal being bacterial infections and thromboembolism. Idiopathic nephrotic syndrome is a chronic relapsing disease for most steroid-responsive patients, whereas most children with refractory FSGS ultimately develop end-stage renal disease. Research is being done to further elucidate the disorder's molecular pathogenesis, identify new prognostic indicators, and to develop better approaches to treatment.

Pediatric thrombosis

Although thrombosis is less frequent in children than in adults, it represents a significant source of morbidity and mortality. Multiple factors. both genetic and acquired. contribute to the development of thrombosis in chiidren. Thrombosis in a child warrants investigation of potential underlying prothrombotic conditions. The risk of thrombosis in children with heterozygous deficiencies is not clearly defined, but it appears that children who are heterozygous for more than one risk factor or who have a combination of inherited and acquired defects are at higher risk for thrombosis. Treatment of thrombosis primarily involves a rapidly acting anticoaguiant such as heparin or LMWH to prevent extension, and long-term anticoagulation with warfarin may be instituted to prevent recurrence. Thrombolytic therapy with recombinant tissue plasminogen activator also appears to be safe and effective in children. Prospective and multicenter studies are still needed to clarify the contribution of specific prothrombotic disorders to childhood TE so that evidence-based treatment recommendations can be made.

Arterial strokes in children

Pediatric stroke has received special attention in the recent literature. It is now recognized as an important cause of mortality and morbidity in pediatric population. Varied and poorly specific symptomatology as well as overlapping risk factors makes the diagnosis of stroke in childhood challenging. Therapy remains controversial. The use of anticoagulation and thrombolysis in the management of acute stroke in children has not been systematically studied. In this article, we discuss the natural history, investigation, and treatment of pediatric arterial hemorrhagic and ischemic strokes.

Statins and renal function

Renal disease is often associated with an increased risk of vascular events. Moreover, an accelerated form of atherosclerosis commonly occurs in these patients. The reasons for these associations are not clearly defined but include the widespread presence of several established risk factors (eg, dyslipidemia, hypertension, and diabetes). Other predictors of atherosclerotic disease may also be abnormally elevated (eg, homocysteine, fibrinogen, and lipoprotein a). In addition, there is evidence that impaired renal function per se predicts vascular risk. Despite this high-risk background, the potential benefit of treatment with statins has not been widely investigated in these patients. The present review considers the evidence (experimental and clinical) that statins exert beneficial effects in patients with different types of renal disease. This includes improved renal function, decreased microalbuminuria, and a fall in blood pressure. Statins may also improve renal allograft survival. The potential mechanisms mediating these effects are considered. The interactions between statins and several risk factors that may be present in patients with impaired renal function are also considered. There is an urgent need to define the role of statins in these high-risk patients. Which is the statin of choice? This question is relevant because impaired renal function can interfere with statin pharmacokinetics. Furthermore, other drugs administered to these patients may cause serious interactions with statins.

Venous thromboembolism in childhood: a prospective two-year registry in The Netherlands

OBJECTIVE

To study the incidence, signs and symptoms, diagnostic tests, risk factors, therapy, and complications of pediatric venous thromboembolism (VTE) in The Netherlands.

METHODS

A prospective 2-year registry of VTE in children aged < or = 18 years.

RESULTS

Ninety-nine patients were registered. The annual incidence of VTE was 0.14/10,000 children, 35% of whom were symptom free. Almost half of the patients were newborns. Neonatal VTE was almost exclusively catheter related, located in the upper venous system, and asymptomatic. In older children VTE was catheter related in approximately one third and more often was located in the lower venous system. In 85% of all patients, thrombosis developed while the patient was in the hospital. Diagnosis was usually made by ultrasonography. In 98% of all patients, at least 1 risk factor was present. Congenital prothrombotic disorders were more often present in older children (21%) than in neonates (6%). A variety of treatment modalities were used. Morbidity consisted of bleeding (7%) and recurrent thrombosis (7%). Two children died as result of VTE.

CONCLUSION

VTE is mostly diagnosed in hospitalized children, especially sick newborns with central venous catheters and older children with a combination of risk factors. Primary prevention, optimal treatment, and long-term outcome of pediatric symptomatic and asymptomatic VTE need to be studied.