Platelet dysfunction and coagulopathy in intraventricular hemorrhage in the premature infant

Decreased level of TREM like Transcript 1 (TLT-1) is associated with prematurity and promotes the in-utero inflammatory response to maternal lipopolysaccharide (LPS) exposure

PROBLEM

The occurrence of preterm birth is associated with multiple factors including bleeding, infection and inflammation. Platelets are mediators of hemostasis and can modulate inflammation through interactions with leukocytes. TREM like Transcript 1 (TLT-1) is a type 1 single Ig domain receptor on activated platelets. In adults, it plays a protective role by dampening the inflammatory response and facilitating platelet aggregation at sites of vascular injury. TLT-1 is expressed in human placenta and found in cord blood. We thus hypothesized that TLT-1 deficiency is associated with prematurity and fetal inflammation.

METHOD OF STUDY

To test this hypothesis, we examined cord blood levels of soluble TLT-1 (sTLT) in premature and term infants and compared the inflammatory response in C57BL/6 (WT) and TLT-1-/- (treml1-/- , KO) mice given intraperitoneal LPS mid-gestation RESULTS: The preterm infant cord blood level of sTLT was significantly lower than that found at term. On exposure to LPS, histology of KO (as compared to WT) placenta and decidua showed increased hemorrhage, and KO decidual RNA expression of IL-10 was significantly lower. KO fetal interface tissues (placenta, membranes, amniotic fluid) over time showed increased expression of inflammatory cytokines such as IL-6, IFN-γ, and TNF, but not MCP-1. However, fetal organs showed similar levels.

CONCLUSION

There is a potential association between insufficient TLT-1 expression and increased fetal inflammatory responses in the setting of prematurity. The data support further study of TLT-1 in the mechanistic link between bleeding, inflammation and preterm birth, and perhaps as a biomarker in human pregnancy.

Development of an integrated risk scale for prediction of shunt placement after neonatal intraventricular hemorrhage

OBJECTIVE

Neonatal intraventricular hemorrhage (IVH) is a major cause of mortality and morbidity, particularly following premature birth. Even after the acute phase, posthemorrhagic hydrocephalus is a long-term complication, frequently requiring permanent ventriculoperitoneal shunt (VPS) placement. Currently, there are no risk classification methods integrating the constellation of clinical data to predict short- and long-term prognosis in neonatal IVH. To address this need, the authors developed a two-part machine learning approach for predicting short- and long-term outcomes after diagnosis of neonatal IVH. Integrating both maternal and neonatal characteristics, they developed a binary classifier to predict short-term mortality risk and a clinical scale to predict the long-term risk of VPS placement.

METHODS

Neonates with IVH were identified from the Optum Clinformatics Data Mart administrative claims database. Matched maternal and childbirth characteristics were obtained for all patients. The primary endpoints of interest were short-term (30 day) mortality and long-term VPS placement. Classification of short-term mortality risk was evaluated using 5 different machine learning approaches and the best-performing method was validated using a withheld validation subset. Prediction of long-term shunt risk was performed using a multivariable Cox regression model with stepwise variable selection, which was subsequently converted to an easily applied integer risk scale.

RESULTS

A total of 5926 neonates with IVH were identified. Most patients were born before 32 weeks' gestation (67.2%) and with low birth weight (81.2%). Empirical 30-day mortality risk was 10.9% across all IVH grades and highest among grade IV IVH (34.3%). Among the neonates who survived > 30 days, actuarial 12-month postdiagnosis risk of shunt placement was 5.4% across all IVH grades and 31.3% for grade IV IVH. The optimal short-term risk classifier was a random forest model achieving an area under the receiver operating characteristic curve of 0.882 with important predictors ranging from gestational age to diverse comorbid medical conditions. Selected features for long-term shunt risk stratification were IVH grade, respiratory distress syndrome, disseminated intravascular coagulation, and maternal preeclampsia or eclampsia. An integer risk scale, termed the Shunt Prediction After IVH in Neonates (SPAIN) scale, was developed from these 4 features, which, evaluated on withheld cases, demonstrated improved risk stratification compared with IVH grade alone (Harrell's concordance index 0.869 vs 0.852).

CONCLUSIONS

In a large cohort of neonates with IVH, the authors developed a two-pronged, integrated, risk classification approach to anticipate short-term mortality and long-term shunt risk. The application of such approaches may improve the prognostication of outcomes and identification of higher-risk individuals who warrant careful surveillance and early intervention.

Age-Dependent Control of Collagen-Dependent Platelet Responses by Thrombospondin-1-Comparative Analysis of Platelets from Neonates, Children, Adolescents, and Adults

Platelet function is developmentally regulated. Healthy neonates do not spontaneously bleed, but their platelets are hypo-reactive to several agonists. The mechanisms underlying immature platelet function in neonates are incompletely understood. This critical issue remains challenging for the establishment of age-specific reference ranges. In this study, we evaluated platelet reactivity of five pediatric age categories, ranging from healthy full-term neonates up to adolescents (11–18 years) in comparison to healthy adults (>18 years) by flow cytometry. We confirmed that platelet hypo-reactivity detected by fibrinogen binding, P-selectin, and CD63 surface expression was most pronounced in neonates compared to other pediatric age groups. However, maturation of platelet responsiveness varied with age, agonist, and activation marker. In contrast to TRAP and ADP, collagen-induced platelet activation was nearly absent in neonates. Granule secretion markedly remained impaired at least up to 10 years of age compared to adults. We show for the first time that neonatal platelets are deficient in thrombospondin-1, and exogenous platelet-derived thrombospondin-1 allows platelet responsiveness to collagen. Platelets from all pediatric age groups normally responded to the C-terminal thrombospondin-1 peptide RFYVVMWK. Thus, thrombospondin-1 deficiency of neonatal platelets might contribute to the relatively impaired response to collagen, and platelet-derived thrombospondin-1 may control distinct collagen-induced platelet responses.

Genetic predictors of severe intraventricular hemorrhage in extremely low-birthweight infants

OBJECTIVE

To test associations between grades 3 or 4 (severe) intraventricular hemorrhage (IVH) and single nucleotide polymorphisms (SNPs) associated with coagulation, inflammation, angiogenesis, and organ development in an exploratory study.

STUDY DESIGN

Extremely low-birthweight (ELBW) infants enrolled in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network's (NRN) Cytokines Study were included if they had cranial ultrasound (CUS) and genotyping data available in the NRN Anonymized DNA Repository and Database. Associations between SNPs and IVH severity were tested with multivariable logistic regression analysis.

RESULT

One hundred thirty-nine infants with severe IVH and 687 infants with grade 1 or 0 IVH were included. One thousand two hundred seventy-nine SNPs were genotyped. Thirteen were preliminarily associated with severe IVH including five related to central nervous system (CNS) neuronal and neurovascular development.

CONCLUSION

Genetic variants for CNS neuronal and neurovascular development may be associated with severe IVH in premature infants.

Risk factors for severity of thrombocytopenia in full term infants: a single center study

Background

Neonatal thrombocytopenia (NT) (platelet count < 150 × 10⁹/L) is a common finding in the neonatal intensive care unit (NICU). The main aim of this study was to assess the prevalence, risk factors, and outcomes of severe NT in full term (FT) infants.

Methods

During the study period, all FT infants who met the inclusion criteria for NT on two occasions were included. Maternal data, such as maternal age, weight, gestational age, mode of delivery, and history of systemic diseases, including diabetes mellitus, pre-eclampsia, systemic lupus erythematosus, and immune thrombocytopenic purpura, were recorded. Furthermore, neonatal data, such as gender, neonatal weight, causes/duration of admission, types of respiratory support used, complete blood count measurements, and outcomes for neonates admitted to the NICU, were recorded.

Results

In total, 55 FT infants with NT met the inclusion criteria, and 29 (52.73%) cases had severe NT. The most common cause of NT was neonatal sepsis (20 cases, 36.35%), followed by a postoperative state (5 cases, 9.09%). Moreover, in cases of positive blood cultures, the most commonly isolated organism was Escherichia coli (6 cases, 10.90%), followed by Klebsiella (5 cases, 9.09%). Cases of severe NT needed more platelet transfusions (P = 0.001) and had higher rates of mortality (P = 0.001) when compared to cases of mild/moderate NT associated with signs of bleeding and pulmonary/intraventricular hemorrhage (IVH) (P = 0.001).

Conclusion

Severe NT compared to mild/moderate NT, associated with signs of bleeding and pulmonary/IVH, needed more platelet transfusions, and had increased mortality. Further research is needed to explain which of these complications related to severity of thrombocytopenia or were associated with original disease of the babies.

Hemostatic profile of infants with spontaneous prematurity: can we predict intraventricular hemorrhage development?

Background

Defining hemostatic profile for preterm infants is a challenge when severe bleedings are frequent.

Methods

The aim was to define the hemostatic profile at birth of infants with spontaneous prematurity and to evaluate whether characteristic profiles can predict the development of intraventricular hemorrhage (IVH) in prematures.

Results

We included 122 newborns with a median age of 31^5/7 gestational age (GA) [29^2/7;34^0/7] and median weight of 1145 g [785;1490]. Levels of fibrinogen, factor II (FII) and factor V (FV) rose with GA (p = 0.017,p = 0.009, p = 0.001). In the group of 23^0/7 – 28^6/7 GA, the 5th percentile was defined as 0.6 g/L for fibrinogen, 15 IU/dL for FII and 16 IU/dL for factor V (n = 30). In the group of 29^0/7–32^6/7 GA, the 5th percentile was defined as 1.0 g/L for fibrinogen, 24 IU/dL for FII and 41 IU/dL for factor V (n = 46). In the group of 33^0/7–36^6/7 GA, the 5th percentile was defined as 1.0 g/L for fibrinogen, 24 IU/dL for FII and 30 IU/dL for factor V (n = 46). Level of fibrinogen was higher in case of vaginal delivery and lower in case of IUGR. Only lower level of FV at birth was significantly associated with IVH (63.5 [46.0; 76.5] vs 74.0 [58.0; 89.0], p = 0.026) with an unadjusted OR per SD increase in FV of 0.57 (95%CI, 0.34 to 0.96). After adjustment for age, the association between FV level and IVH was slightly attenuated (adjusted OR, 0.70; 95%CI, 0.40 to 1.23) but remained not significant (p = 0.22).There was no correlation with FII and fibrinogen.

Conclusions

We can define hemostastic profile of prematures and corroborate references ranges for studied parameters. Further large studies are still called for, to correlate the grade of hemorrhage and the factor V level at birth.

Elevated International Normalized Ratio (INR) is Associated With an Increased Risk of Intraventricular Hemorrhage in Extremely Preterm Infants

INTRODUCTION

The international normalized ratio (INR), a standardized method of reporting the prothrombin time, can be a surrogate marker of the vitamin K-dependent coagulation pathways.

OBJECTIVE

To evaluate the relationship between INR measurements in the first 48 hours of life and subsequent development of intraventricular hemorrhage (IVH) in extremely preterm infants.

MATERIALS AND METHODS

A single-center retrospective, observational cohort study of infants born at <28 weeks gestation. The main outcome measure was defined as the degree of IVH seen on cranial ultrasound examinations at day 7 postnatal age.

RESULTS

Of 200 infants, 109 (mean gestational age, 25.2 wk [SD, 1.27]) had coagulation results available. Of 109, 26 developed IVH. Elevated INR was associated with increased risk of a severe IVH (odds ratio [OR] 6.50; 95% confidence interval [CI], 1.65-25.62; P=0.008) adjusted for gestation, birth weight, and sex. INR was significantly associated with severe IVH in infants who did not receive blood products (OR, 64.60; 95% CI, 1.35-3081.25; P=0.035), but not in those who did (OR, 2.93; 95% CI, 0.67-12.71; P=0.151) (Pinteraction=0.086).

CONCLUSION

An elevated INR in the first 48 hours of life may be useful to identify preterm infants at risk of severe IVH and may guide strategies to prevent the development, or limit the extension, of IVH.

An Analysis of Time to Improvement in Oxygenation in Japanese Preterm and Late Preterm or Term Neonates With Hypoxic Respiratory Failure and Pulmonary Hypertension

PURPOSE

We analyzed data from an ongoing registry to determine time to improvement in oxygenation in preterm and late preterm or term neonates with hypoxic respiratory failure and pulmonary hypertension receiving inhaled nitric oxide (iNO) in Japan.

METHODS

Registry neonates received iNO ≤7 days after birth (February 26, 2010, to October 9, 2012). Efficacy and safety profile data were collected up to 96 h after iNO initiation and, if necessary, every 24 h thereafter and before iNO discontinuation. Patients were stratified by gestational age (GA), oxygenation index (OI), and shunt direction at baseline.

FINDINGS

Data were evaluated for 1106 neonates (431 with a GA <34 weeks and 675 with a GA of ≥34 weeks). Sixty percent of patients had improved OI; rates were similar for those with GAs of <34 versus ≥34 weeks (61% vs 59%). Overall, mean time to improvement was 11.4 h and tended to be shorter in the groups with a GA <34 weeks versus ≥34 weeks (9.2 vs 12.9 h). Thirty percent of responding neonates required >1 h to achieve improvement in oxygenation. Neonates with higher baseline OI had the greatest decrease in OI during the first hour of treatment. The mortality rate was higher among iNO-treated patients with a baseline OI ≥25 versus those with OI ≥15 to <25 (25% vs 12%; P = 0.0073).

IMPLICATIONS

iNO treatment provided acute, sustained improvement in oxygenation in neonates with GAs <34 and ≥34 weeks; 70% of patients had improvement within 1 h, but the remaining 30% took >1 h to respond. Initiation of iNO at lower OIs was associated with reduced mortality compared with higher OI.

Selective prophylactic solvent-detergent plasma and cryoprecipitate transfusion to prevent intraventricular hemorrhage in extreme preterm infants: A case-historical control

BACKGROUND

Contradictory evidence exists whether a prophylactic coagulation factor transfusion in the first hours of life (HOL) prevents intraventricular hemorrhage (IVH) in extreme preterm infants (EPI, <28 weeks gestation). We aimed to determine whether selective prophylactic solvent-detergent plasma and cryoprecipitate transfusion within 12 hours of life (SP-SDP/Cryoprecipitate-T) could prevent IVH in EPI.

METHOD

This is a retrospective analysis, case-historical control, of prospectively collected data from a pre-existing electronic neonatal database at a Saudi tertiary neonatal intensive care unit. We compared the IVH rate in EPI born in the first 4 years (Jan 2010-Dec 2013) of the SP-SDP/Cryoprecipitate-T period with that of EPI born during the last 4 years (Jan 2006-Dec 2009) of the rescue SDP/Cryoprecipitate-T period.

RESULTS

The IVH rate was lower in the SP compared to the rescue- SDP/Cryoprecipitate-T period (30.8% versus 51.2%, odds ratio 0.42, 95% confidence interval 0.21, 0.88, p = 0.02). This difference remained significant after controlling for six other IVH risk factors.

CONCLUSIONS

Early SP-SDP/Cryoprecipitate-T may reduce the IVH rate in EPI. A large multicenter clinical trial is required for confirm the short and long-term benefit and risk of this intervention. Until then, early SP-SDP/Cryoprecipitate-T may be considered by an institution with a persistently high IVH rate.

Efficacy of inhaled nitric oxide in neonates with hypoxic respiratory failure and pulmonary hypertension: the Japanese experience

OBJECTIVE

To analyze data from a registry of Japanese neonates with hypoxic respiratory failure associated with pulmonary hypertension (PH) to compare the effectiveness of inhaled nitric oxide (iNO) in neonates born <34 weeks vs. ≥34 weeks gestational age (GA).

MATERIALS AND METHODS

iNO was administered according to approved Japanese product labeling. Study data were collected before iNO administration and at predefined intervals until discontinuation.

RESULTS

A total of 1,114 neonates were included (n=431, <34 weeks GA; n=675, ≥34 weeks GA; n=8, missing age data). Mean decrease from baseline oxygenation index (OI) was similar in both age groups. OI reduction was more pronounced in the <34 weeks subgroups with baseline OI ≥25. Survival rates were similar in the <34 weeks GA and ≥34 weeks GA groups stratified by baseline OI (OI<15, 89% vs. 93%; 15≤OI<25, 85% vs. 91%; 25≤OI≤40, 73% vs. 79%; OI>40, 64% vs. 66%).

CONCLUSION

iNO improved oxygenation in preterm neonates as effectively as in late preterm and term neonates, without negative impact on survival. If clinically significant PH is present, as measured by pulse oximetry or echocardiography, a therapeutic trial of iNO might be indicated for preterm neonates.

Significant Hypo-Responsiveness to GPVI and CLEC-2 Agonists in Pre-Term and Full-Term Neonatal Platelets and following Immune Thrombocytopenia

Neonatal platelets are hypo-reactive to the tyrosine kinase-linked receptor agonist collagen. Here, we have investigated whether the hypo-responsiveness is related to altered levels of glycoprotein VI (GPVI) and integrin α2β1, or to defects in downstream signalling events by comparison to platelet activation by C-type lectin-like receptor 2 (CLEC-2). GPVI and CLEC-2 activate a Src- and Syk-dependent signalling pathway upstream of phospholipase C (PLC) γ2. Phosphorylation of a conserved YxxL sequence known as a (hemi) immunotyrosine-based-activation-motif (ITAM) in both receptors is critical for Syk activation. Platelets from human pre-term and full-term neonates display mildly reduced expression of GPVI and CLEC-2, as well as integrin αIIbβ3, accounted for at the transcriptional level. They are also hypo-responsive to the two ITAM receptors, as shown by measurement of integrin αIIbβ3 activation, P-selectin expression and Syk and PLCγ2 phosphorylation. Mouse platelets are also hypo-responsive to GPVI and CLEC-2 from late gestation to 2 weeks of age, as determined by measurement of integrin αIIbβ3 activation. In contrast, the response to G protein-coupled receptor agonists was only mildly reduced and in some cases not altered in neonatal platelets of both species. A reduction in response to GPVI and CLEC-2, but not protease-activated receptor 4 (PAR-4) peptide, was also observed in adult mouse platelets following immune thrombocytopenia, whereas receptor expression was not impaired. Our results demonstrate developmental differences in platelet responsiveness to GPVI and CLEC-2, and also following immune platelet depletion leading to reduced Syk activation. The rapid generation of platelets during development or following platelet depletion is achieved at the expense of signalling by ITAM-coupled receptors.

Platelet function testing in pediatric patients

INTRODUCTION

Platelets play a key role in primary hemostasis and are also intricately linked to secondary hemostasis. Investigation of platelet function in children, especially in neonates, is seriously challenged by the volumes required to perform the majority of platelet function tests and due to the lack of standardization of these tests for use in children. Areas covered: The present review summarizes developmental hemostasis with a focus on the differences in platelet adhesion, activation and aggregation, between preterm neonates, full-term neonates, during childhood and in adults. Some of the most widely used platelet function tests are presented, including novel tests requiring only a small blood volume. Expert commentary: Currently available platelet function tests are limited as regards to investigation of neonates due to difficulties in obtaining adequate blood volume, poor standardization, lack of reference intervals for neonates and children, and an incomplete understanding of the functional phenotype of neonatal platelets, especially preterm neonatal platelets.

Platelet Transfusion Practices Among Very-Low-Birth-Weight Infants

IMPORTANCE

Thrombocytopenia and intraventricular hemorrhage (IVH) are common among very-low-birth-weight (VLBW) infants. Survey results suggest that US neonatologists frequently administer platelet transfusions to VLBW infants with mild to moderate thrombocytopenia.

OBJECTIVES

To characterize platelet transfusion practices in US neonatal intensive care units (NICUs), to determine whether severity of illness influences platelet transfusion decisions, and to examine the association between platelet count (PCT) and the risk for IVH in the first 7 days of life.

DESIGN, SETTING, AND PARTICIPANTS

This multicenter, retrospective cohort study included 972 VLBW infants treated in 6 US NICUs, with admission dates from January 1, 2006, to December 31, 2007. Data were collected from all infants until NICU discharge or death (last day of data collected, December 4, 2008). Data were entered into the central database, cleaned, and analyzed from May 1, 2009, to February 11, 2016.

INTERVENTION

Platelet transfusion.

MAIN OUTCOMES AND MEASURES

Number of platelet transfusions and incidence of IVH.

RESULTS

Among the 972 VLBW infants (520 [53.5%] male; mean [SD] gestational age, 28.2 [2.9] weeks), 231 received 1002 platelet transfusions (mean [SD], 4.3 [6.0] per infant; range, 1-63 per infant). The pretransfusion PCT was at least 50 000/μL for 653 of 998 transfusions (65.4%) with this information. Two hundred eighty-one transfusions (28.0%) were given during the first 7 days of life. During that period, platelet transfusions were given on 35 of 53 days (66.0%) when the patient had a PCT less than 50 000/μL and on 203 of 436 days (46.6%) when the patient had a PCT of 50 000/μL to 99 000/μL. At least 1 marker of severe illness was present on 198 of 212 patient-days (93.4%) with thrombocytopenia (PCT, <100 000/μL) when a platelet transfusion was given compared with 113 of 190 patient-days (59.5%) with thrombocytopenia when no platelet transfusion was given. Thrombocytopenia was a risk factor for intraventricular hemorrhage during the first 7 days of life (hazard ratio, 2.17; 95% CI, 1.53-3.08; P < .001). However, no correlation was found between severity of thrombocytopenia and risk for IVH. After controlling for significant clinical factors and thrombocytopenia, platelet transfusions did not have a significant effect on the incidence of IVH (hazard ratio, 0.92; 95% CI, 0.49-1.73; P = .80).

CONCLUSIONS AND RELEVANCE

A large proportion of platelet transfusions were given to VLBW infants with PCT greater than 50 000/μL. Severity of illness influenced transfusion decisions. However, the severity of thrombocytopenia did not correlate with the risk for IVH, and platelet transfusions did not reduce this risk.

Thrombocytopenia and platelet transfusion in the neonate

Neonatal thrombocytopenia is widespread in preterm and term neonates admitted to neonatal intensive care units, with up to one-third of infants demonstrating platelet counts <150 × 10(9)/L. Thrombocytopenia may arise from maternal, placental or fetal/neonatal origins featuring decreased platelet production, increased consumption, or both mechanisms. Over the past years, innovations in managing neonatal thrombocytopenia were achieved from prospectively obtained clinical data on thrombocytopenia and bleeding events, animal studies on platelet life span and production rate and clinical use of fully automated measurement of reticulated platelets (immature platelet fraction). This review summarizes the pathophysiology of neonatal thrombocytopenia, current management including platelet transfusion thresholds and recent developments in megakaryopoietic agents. Furthermore, we propose a novel index score for bleeding risk in thrombocytopenic neonates to facilitate clinician's decision-making when to transfuse platelets.

Cellular and humoral coagulation profiles and occurrence of IVH in VLBW and ELWB infants

BACKGROUND AND STUDY PURPOSE

Intraventricular hemorrhage (IVH) is a major complication in preterm neonates with significant long-term morbidity and an increased mortality rate. The role of the immature coagulation system in the pathogenesis of IVH in these infants is still under debate. The aim of this study was to provide reference values for coagulation studies within the first 24h of life, and to relate these findings to the incidence of IVH.

PATIENTS AND METHODS

In this retrospective study, a total of 250 (male: 123/female: 127; VLBW: 150 and ELBW: 100) infants were included over a 4-year-period. Coagulation studies were performed within the first 24h of life in all infants. Multiple regression analysis was employed to demonstrate a potential association between IVH and a number of known risk and protective factors for IVH (antenatal steroids, birth weight, gender, IUGR, APGAR score at 10minutes, platelet count, INR, PTT, fibrinogen).

RESULTS

Mean birth weight was 1047.9±305.6 (range: 320-1490g). Both cellular (platelets, nucleated red blood cells) and plasmatic coagulation parameters (INR, fibrinogen and antithrombin III) were dependent on birth weight. Moreover, INR levels (p<0.05) were significantly increased in neonates with IVH of any grade. Also, INR was positively correlated with the severity of IVH (Spearman's correlation coefficient: 0.193; p=0.003). While overall fibrinogen levels were not associated with IVH, a fibrinogen level<100mg/dL significantly increased the risk for IVH (p<0.01).

CONCLUSIONS

Our data provide a robust set of reference values for both cellular and humoral coagulation studies in VLBW and ELBW infants for the first 24h of life. The results of our study indicate that abnormal INR levels and fibrinogen levels<100mg/dL are significantly associated with the occurrence of IVH in this susceptible cohort.

Prognostic significance of early platelet count decline in preterm newborns

OBJECTIVES

Decline of platelets with or without thrombocytopenia is observed in critically ill preterm newborns. Prognostic significance of platelets count in Neonatal Intensive Care Unit focused on outcome after thrombocytopenia. We aimed to estimate the changes in platelets count within the first 7 days of life in preterm newborns and its relation to final outcomes.

METHODS

Retrospectively, the platelets count during the first 7 days of life, and its association with mortality, length of stay among survivors (LOS), and later severe morbidities were determined. Appropriate regression analyses were used to examine possible relations between studied variables.

RESULTS AND DISCUSSION

Platelets drop that did not reach thrombocytopenia level in the first 7 days of life happened in 61.7%. Platelets count drop in the first 7 days of life was a predictor of mortality, LOS, and major morbidities such as intraventricular hemorrhage and necrotizing enterocolitis.

CONCLUSIONS

Platelets count drop within the first 7 days of life independent of thrombocytopenia can be used to predict increased mortality, LOS, and the development of later severe morbidities in critically ill preterm neonates.

Superior vena cava flow and intraventricular haemorrhage in extremely preterm infants

OBJECTIVE

To evaluate the relationship between superior vena cava flow (SVCF) measurements within the first 24 h of life, and development of intraventricular haemorrhage (IVH) in extremely preterm infants.

STUDY DESIGN

Single centre retrospective cohort study of 108 preterm infants born less than 28 weeks' gestation. Main outcome measure was degree of IVH at day 7 postnatal age.

RESULTS

The mean GA of the study group was 25.4 weeks. Mean SVCF was lower (75 ml/kg/min) in infants later diagnosed with IVH (n = 46) compared to infants, who did not develop IVH (87.7 ml/kg/min, p = 0.055). PDA diameter was inversely associated with SVCF (p = 0.024) and reversal of flow in the descending aorta (p = 0.001). Sensitivity analysis did not confirm an independent association of SVCF with development of IVH [OR 0.990 (0.978-1.002), p = 0.115].

CONCLUSION

Our study describes early SVCF in extremely preterm infants is associated with the extent of ductal shunting, but insensitive in predicting IVH.

One size will never fit all: the future of research in pediatric transfusion medicine

There is concern at the National Heart, Lung, and Blood Institute (NHLBI) and among transfusion medicine specialists regarding the small number of investigators and studies in the field of pediatric transfusion medicine (PTM). Accordingly, the objective of this article is to provide a snapshot of the clinical and translational PTM research considered to be of high priority by pediatricians, neonatologists, and transfusion medicine specialists. Included is a targeted review of three research areas of importance: (i) transfusion strategies, (ii) short- and long-term clinical consequences, and (iii) transfusion-transmitted infectious diseases. The recommendations by PTM and transfusion medicine specialists represent opportunities and innovative strategies to execute translational research, observational studies, and clinical trials of high relevance to PTM. With the explosion of new biomedical knowledge and increasingly sophisticated methodologies over the past decade, this is an exciting time to consider transfusion medicine as a paradigm for addressing questions related to fields such as cell biology, immunology, neurodevelopment, outcomes research, and many others. Increased awareness of PTM as an important, fertile field and the promotion of accompanying opportunities will help establish PTM as a viable career option and advance basic and clinical investigation to improve the health and wellbeing of children.

Platelets in neonates: central mediators in haemostasis, antimicrobial defence and inflammation

Platelets are not only centrally involved in haemostasis, but also in antimicrobial defence and inflammation. Since evaluation of platelet physiology in the particular patient group of preterm and term neonatal infants is highly restricted for ethical reasons, there are hardly any data available in healthy and much less in extremely immature or ill neonates. By summarising current knowledge and addressing both platelet researchers and neonatologists, we describe neonatal platelet count and morphology, report on previous analyses of neonatal platelet function in primary haemostasis and provide insights into recent advances in platelet immunology that considerably impacts our clinical view on the critically ill neonatal infant. We conclude that neonatal platelets, originating from liver megakaryocytes, substantially differ from adult platelets and may play a pivotal role in the pathophysiology of neonatal sepsis or intraventricular haemorrhage, both complications which seriously augment perinatal morbidity and mortality.

Preventing germinal matrix layer rupture and intraventricular hemorrhage

The etiology of intraventricular hemorrhage (IVH) in extremely low birth weight preterm infants is multifactorial with circulatory instability and hemostasis being preeminent. This study sought to determine if the germinal matrix layer remained intact when platelets were above 200 × 10(9)/L, a near normal level, and fell below that when IVH occurred. This was a retrospective study of platelets and head ultrasounds (HUS) in infants 23-28 weeks gestation. Analyses were descriptive, one way analysis of variance, Pearson Chi-square tests, and t-tests. Platelet counts and HUS were linked in 114 infants during the first 3 days when 90% of IVHs occur. Mean platelet levels were >200 × 10(9)/L in 68% of infant 23-24 weeks gestation and 78% of those 25-26 weeks when there were no IVHs. These findings, if confirmed, suggest that improving hemostasis in high risk preterm infants by keeping platelet levels >200 × 10(9)/L may maintain the integrity of the germinal matrix layer and prevent IVHs.

Platelet transfusions in neonates: practices in the United States vary significantly from those in Austria, Germany, and Switzerland

BACKGROUND

Thrombocytopenia affects 20% to 35% of patients admitted to neonatal intensive care units (NICUs). Platelet (PLT) transfusions are usually administered to neonates with thrombocytopenia at higher thresholds than those used for older children or adults, although there is a paucity of evidence to guide these decisions.

STUDY DESIGN AND METHODS

In this study, we used a Web-based survey to investigate the PLT transfusion thresholds used in Level 1 NICUs (equivalent to Level 3 in the US) in three European countries (Austria, Germany, and Switzerland [AUT/GER/SUI]). This survey was identical to the one that was previously sent to US neonatologists, thus allowing for a direct comparison of their responses to 11 case-based scenarios.

RESULTS

In nine of the scenarios, AUT/GER/SUI neonatologists selected substantially lower PLT transfusion thresholds than US neonatologists (p < 0.0001). Transfusion thresholds were more similar when treating neonatal alloimmune thrombocytopenia and before invasive procedures. The clinical impact of these differences was estimated by extrapolating the AUT/GER/SUI versus the US answers to a cohort of neonates with a birth weight below 1000 g. This suggested that, in AUT/GER/SUI, these neonates would receive 167 PLT transfusions per 1000 infants, compared to 299 PLT transfusions in the United States.

CONCLUSION

This first international comparative survey on PLT transfusion practice in neonates reveals substantially higher transfusion thresholds in the United States than in AUT/GER/SUI. Well-designed clinical studies are needed to address the risks and/or benefits of these different approaches.

Vitamin K the basics--what's new?

Relatively little is known about the vitamin K status and requirements in term and preterm infants, though hemorrhagic disease of the newborn infant continues to be a worldwide problem. This brief review of vitamin K metabolism, vitamin K dependent proteins, and the vitamin K cycle covers some new thoughts about the importance of vitamin K to human health including the preterm infant. A review of perinatal vitamin K metabolism concludes that little vitamin K actually crosses the placenta from mother to infant. The neonatal sources of vitamin K are generally limited to the vitamin K prophylaxis given at the time of birth, dietary sources, and questionable amounts from vitamin K present in the intestinal tract synthesized from bacteria. Preterm infants receive large quantities of vitamin K from prophylaxis, TPN solutions, infant formula and breast milk fortifiers. Thus, vitamin serum concentration in preterm infants is up to one hundred times higher than those found in adults and 10-20 times those found in term formula-fed infants. Though no toxicity has been reported, the elevation of epoxide reductase (VKOR) from the vitamin K cycle found in the serum of preterm infants is worthy of additional study. PIVKA-II (abnormal prothrombin) is not a reliable indicator of vitamin K deficiency in preterm or term infants.

Intracranial hemorrhage in the preterm infant: understanding it, preventing it

New discoveries in neonatal imaging, cerebral monitoring, and hemodynamics, and greater understanding of inflammatory and genetic mechanisms involved in intracranial hemorrhage (ICH) in the preterm infant are creating opportunities for innovative early detection and prevention approaches. This article covers the spectrum of ICH in the preterm infant, including germinal matrix intraventricular hemorrhage, its complications, and associated phenomena, such as the emerging role of cerebellar hemorrhage. The overall aim of this article is to review the current knowledge of the mechanisms, diagnosis, outcome, and management of preterm ICH; to revisit the origins from which they develop; and to discuss future expectations.

Severe Thrombocytopenia in the NICU

OBJECTIVE

Severe thrombocytopenia (platelets <or= 50000/microL) in a NICU patient can have significant consequences; however, previous reports have not focused exclusively on NICU patients with counts this low.

METHODS

We identified all patients with severe thrombocytopenia who were cared for in the Intermountain Healthcare level III NICUs from 2003-2007.

RESULTS

Among 11281 NICU admissions, severe thrombocytopenia was identified in 273 (2.4%). Just over 30% of these presented in the first three days of life. Half presented by day 10, 75% by day 27, and 95% by day 100. The prevalence was inversely related to birth weight. Cutaneous bleeding was more common in patients with platelet counts of <20000/microL; however, no statistically significant correlation was found between platelet counts and pulmonary, gastrointestinal, or intraventricular bleeding. The most common explanations for severe thrombocytopenia were acquired varieties of consumptive thrombocytopenia. Platelet transfusions (median 5, range 0-76) were administered to 86% of the patients. No deaths were ascribed to exsanguinations. The mortality rate did not correlate with the lowest platelet count but was proportionate to the number of platelet transfusions.

CONCLUSION

The prevalence of severe thrombocytopenia in the NICU is inversely proportional to birth weight and most cases are acquired consumptive thrombocytopenias. We speculate that very low platelet counts are a causal factor in cutaneous bleeding, but pulmonary, gastrointestinal, and intraventricular bleeding are less influenced by the platelet count and occur primarily from causes other than severe thrombocytopenia. The lowest platelet count does not predict the mortality rate but the number of platelet transfusions received does.

Platelets, frozen plasma, and cryoprecipitate: what is the clinical evidence for their use in the neonatal intensive care unit?

Transfusion of blood components such as platelets, frozen plasma, and cryoprecipitate is a common practice in the neonatal intensive care unit. Although it is intuitive that these components would be transfused in the context of bleeding, their use in neonatology has often been on a prophylactic basis. Due to a lack of consensus guidelines regarding indications for transfusion, however, the neonatologist is left to his/her opinion as to when to transfuse. This article seeks to review the available evidence regarding the use of platelets, frozen plasma, and cryoprecipitate in neonates, as well as the risks associated with the administration of these products.

Platelet transfusion practices among neonatologists in the United States and Canada: results of a survey

OBJECTIVE

In the absence of scientific evidence, current neonatal platelet transfusion practices are based on physicians' preferences, expert advice, or consensus-driven recommendations. We hypothesized that there would be significant diversity in platelet transfusion triggers, product selection, and dosing among neonatologists in the United States and Canada.

METHODS

A Web-based survey on neonatal platelet transfusion practices was distributed to all members of the American Academy of Pediatrics Perinatal Section in the United States and to all physicians listed in the 2005 Canadian Neonatology Directory.

RESULTS

The overall response rate was 37% (1060 of 2875). In the United States, 37% (1007 of 2700) responded, of which 52% practiced at academic centers. Thirty percent (53 of 175) of Canadians responded, of whom 94% practiced at academic centers. As hypothesized, there was significant practice diversity in both countries. The survey also revealed that platelet transfusions are frequently administered to nonbleeding neonates with platelet counts of >50 x 10(9)/L. This practice is particularly prevalent among neonates with specific clinical conditions, including indomethacin treatment, preceding procedures, in the postoperative period, or with intraventricular hemorrhages.

CONCLUSIONS

There is great variability in platelet transfusion practices among US and Canadian neonatologists, suggesting clinical equipoise in many clinical scenarios. Prospective randomized clinical trials to generate evidence-based neonatal platelet transfusion guidelines are needed.

Template bleeding times of 240 neonates born at 24 to 41 weeks gestation

OBJECTIVE

The template bleeding time is a test used to assess the hemostatic effectiveness of platelet/endothelial interactions. A modified template bleeding time, described over 15 years ago by Andrew et al., has been used to test this aspect of hemostasis in term and preterm infants, but questions remain regarding the effect of gestational age and postnatal age on results. The effect of the platelet count (platelets per microliter blood) and the circulating platelet mass (nl platelets per microliter blood) on the bleeding time of neonatal intensive care unit (NICU) patients also require better definition.

STUDY DESIGN

We measured template bleeding times on 240 neonates at Ospedale A Perrino, in Brindisi, Italy; studying groups of n=60 at the following gestational ages; <28 weeks, 29 to 32 weeks, 33 to 37 weeks and > or =38 weeks. In each group of 60 neonates, 20 were studied on the first day after birth, 20 were studied on day 10 and 20 were studied on day 30. A multivariate analysis was performed to examine various associations with bleeding time.

RESULT

Bleeding times, on the first day of life, were shorter as gestational age increased. Those born <33 weeks gestation had bleeding times about twice that of those > or =38 weeks (P<0.001). Bleeding times tended to shorten between days 1 and 10. Little or no further shortening occurred between days 10 and 30, and by day 30 they were not statistically different between the various gestational age groups. No independent effect on bleeding time could be ascribed to gender, platelet count or circulating platelet mass, but independent effects were found for hematocrit (P<0.02) and gestational age (P<0.001).

CONCLUSION

On the first day of life, preterm neonates have a longer bleeding time than do term neonates. By day of life 10, the bleeding times at all gestational ages are shorter and are indistinguishable on the basis of gestational age at birth. Additionally, since platelet counts as low as 110 000 per microliter did not prolong the bleeding time, we see no benefit of administering a platelet transfusion to a stable, nonbleeding, NICU patient with mild thrombocytopenia (platelet count 100 000 to 150 000 per microliter).

TEMPORAL PLATELET AGGREGATORY FUNCTION IN HYPOXIC NEWBORN PIGLETS REOXYGENATED WITH 18%, 21%, AND 100% OXYGEN

Thromboembolic and bleeding complications are common after asphyxia. We studied the temporal effects of different oxygen concentrations used in resuscitating hypoxic newborn piglets on platelet aggregatory function. Alveolar normocapnic hypoxia (fractional inspired oxygen concentration = 0.15) was induced in piglets (1-4 d, 1.7-2.5 kg) for 2 h, followed by reoxygenation with 18%, 21%, or 100% oxygen for 1 h and then 21% for 2 h (n = 8-9 per group). Control piglets underwent surgery with no hypoxia-reoxygenation (n = 5). Platelet counts and collagen-stimulated (2-10 microg/mL) whole blood aggregation were studied at normoxic baseline and at 3 h, 2 d, and 4 d of recovery. Platelet activation markers including plasma thromboxane B2 and matrix metalloproteinase 2 and 9 levels were measured. At 2 h hypoxia (mean PaO2 30-35 mmHg), all piglets were hypotensive and acidotic (mean pH 7.19-7.24). In 100% reoxygenation piglets, the concentration-response curves of collagen-stimulated platelet aggregation were significantly shifted upward at 3 h and 2 d of recovery with no differences in the collagen concentration required to induce 50% of maximum aggregation, and this normalized to baseline on 4 d. In the 18% and 21% reoxygenated groups, there were no changes in platelet aggregation during the experiment. Platelet counts were not different between groups and over time. Hypoxic-reoxygenated piglets had increased plasma thromboxane B2 (100% group) and matrix metalloproteinase-2 levels (21% and 100% groups) (versus respective baseline, P < 0.05), with no difference between experimental groups. These findings suggest transient platelet activation in hypoxic newborn piglets resuscitated with 100% but not with 18% and 21% oxygen, of which the clinical significance requires further investigation.

Thrombocytopenia related neonatal outcome in preterms

OBJECTIVE

To investigate the thrombocytopenia and platelet transfusion related outcome in very preterm infants.

METHODS

Cases (n=94) with at least one episode of thrombocytopenia (platelet counts < 150 x 10(9)/L) and controls (n=70) were identified from a database of 1054 neonates with gestational age < or = 32 weeks admitted to a level III NICU. Thrombocytopenia and platelet transfusion related morbidity (IVH, sepsis, NEC, and bleeding) and mortality were analyzed with respect to gestational age (< 28 weeks and 28-32 weeks), severity of thrombocytopenia (mild if platelet count > or = 100 and < 150 x 10(9)/L, moderate if count > or = 50 and < 100 x 10(9)/L, and severe if platelets < 50 x 10(9)/L), age of thrombocytopenia onset (early < 72 hours and late > or =72 hours).

RESULTS

The majority of thrombocytopenia (67.0%) was diagnosed after 72 hours of age, and was mild in 12.8%, moderate in 36.2% and severe in 51.0% of the cases. Neonates with severe and moderate thrombocytopenia were more frequently born at lower gestational age and birth weight. NEC and sepsis especially that caused by Candida infection, were associated with severe thrombocytopenic events. The development of IVH was strongly associated with lower gestational age but not the severity and age of thrombocytopenia onset. Mucocutaneous bleeding complicated 18.4% of cases with severe and late-onset thrombocytopenia (7/38). Platelets were transfused to 85.4% of infants with severe and 64.7% of infants with moderate thrombocytopenia (P< 0.02). The gestational age of the majority of the platelet transfused neonates (49/60, 81.7%) was < 28 weeks. Mean gestational age and birth weight, and rates of severe thrombocytopenia, IVH, sepsis and mortality were comparable in transfused vs not-transfused infants with gestational age 28-32 weeks. Platelet transfused neonates with gestational age < 28 weeks had lower birth weights, were more often severely thrombocytopenic, and died more frequently than infants of a similar gestational age who were not transfused.

CONCLUSION

Platelet transfusions did not lower mortality in very premature born infants with moderate and severe thrombocytopenia during the NICU admission.

Prevention of intraventricular haemorrhage: a role for recombinant activated factor VII?

As the survival from extreme prematurity continues to improve, focus on the quality of this survival becomes increasingly important. Prevention of intraventricular haemorrhage (IVH) and its potential long-term sequelae remains one of the major challenges in the early management of these infants. Recombinant activated factor VII (rVIIa), a novel haemostatic agent with an ever-expanding list of potential applications, warrants consideration for use in this setting. This review examines the pathogenesis and prevention of IVH, current concepts of haemostasis both in adults and neonates, and the postulated mechanism of action and various uses of rVIIa. Published data specifically relating to use of rVIIa in neonates is summarised. The hypothesis that early (prophylactic) administration of rVIIa to extremely preterm infants (<28 weeks) would reduce the incidence of severe IVH is explored.

Platelet aggregation in term and preterm newborns

The platelets of newborns have a hyporeactive period. This period, during which the platelet count is normal but their functions are deficient, is called transient platelet hyporeactivity of newborns. The platelet functions and their normalizing process of term and preterm neonates are investigated. Twenty term and 20 preterm (gestational age <37 weeks) newborns were enrolled in the study. Twenty-eight healthy children aged 2 months to 3 years old participated in the study as the control group. Healthy newborns were followed for 15 days after birth longitudinally in 3 periods: period 1 (0-4 days), period 2 (5-9 days), period 3 (10-15 days). Aggregation studies were performed from whole blood samples. Whole blood aggregation was measured by the impedance method. Transient hyporeactivity of platelets was found in term and preterm groups, and there was no difference between term and preterms. Platelets of newborns gained their normal functions at postnatal 10-14 days. The results show that hyporeactivity of platelets during the first 9 days of life is physiological and transient.

Evaluation and treatment of thrombocytopenia in the neonatal intensive care unit

Phlebotomy-induced anaemia excepted, thrombocytopenia is the most common haematological abnormality in neonatal intensive care unit (NICU) patients. Roughly one-quarter of all NICU patients and half of all sick preterm neonates develop thrombocytopenia. Whereas a large number of varied precipitating conditions has been identified, early-onset thrombocytopenia (<72 h) is most commonly associated with fetomaternal conditions complicated by placental insufficiency and/or fetal hypoxia, e.g. maternal pre-eclampsia and fetal intrauterine growth restriction. The resulting neonatal thrombocytopenia is usually mild to moderate, resolves spontaneously and requires no specific therapy. Deviation from this pattern of thrombocytopenia suggests the presence of more significant precipitating conditions. The most important of these are the immune thrombocytopenias, and every NICU should develop investigation and treatment protocols to manage these cases promptly and avoid unnecessary risk of haemorrhage. In contrast, late-onset thrombocytopenia (>72 h) is almost always associated with sepsis or necrotizing enterocolitis and the associated thrombocytopenia is severe, prolonged and often requires treatment by platelet transfusion. Unfortunately, evidence-based guidelines for platelet transfusion therapy in NICU patients are currently unavailable, making it difficult to define widely accepted thresholds for transfusion and leading to a significant variation in transfusion practice between centres.

CONCLUSION

While improving this situation remains a pressing need, the growing evidence that impaired megakaryocytopoiesis and platelet production are major contributors to many neonatal thrombocytopenias suggests that recombinant haemopoietic growth factors, including thrombopoietin and interleukin-11, may be useful future therapies to ameliorate neonatal thrombocytopenia.

Interleukin-11 levels in healthy and thrombocytopenic neonates

Thrombocytopenia is common in sick neonates, and affected neonates have adverse outcomes compared with those without thrombocytopenia. As impaired platelet production underlies many neonatal thrombocytopenias, affected neonates are potential candidates for hemopoietic growth factor therapy. Although recombinant human (rh) thrombopoietin remains under therapeutic development, rhIL-11, which stimulates megakaryocytopoiesis and increases platelet counts after chemotherapy, is already licensed for clinical use. However, nothing is known about IL-11 in neonates. We therefore measured plasma IL-11 by ELISA in healthy term neonates, stable preterm neonates with or without thrombocytopenia, and preterm neonates with sepsis or necrotizing enterocolitis (NEC) with or without thrombocytopenia. At birth IL-11 was undetectable (<10 pg/mL) in healthy term neonates (n = 20) and 27 of 31 (87%) stable preterm neonates. Three stable preterm neonates with detectable IL-11 (mean+/-SD, 11.3 +/- 0.4 pg/mL; median, 11.6 pg/mL) suffered chorioamnionitis, the remaining neonate (IL-11, 14 pg/mL) being one of nine with early onset thrombocytopenia (present by <72 h of age). IL-11 was also measured in 58 preterm neonates with suspected sepsis or NEC. In 25 of 58, sepsis or NEC was unconfirmed and IL-11 was undetectable. By contrast, 14 of 33 with proven sepsis or NEC had elevated IL-11 (median, 14.9 pg/mL; range, 11.2-92.2 pg/mL). Of these 33 neonates, 19 developed thrombocytopenia: nine of 19 (47%) had detectable IL-11 and 10 of 19 (53%) did not (p > 0.05). Although its role in platelet production in neonates remains unclear, these data suggest that IL-11 is involved in the endogenous cytokine response to sepsis or NEC in preterm neonates. Further studies of IL-11 in neonates are warranted to assess its role both in platelet production and in mediation of the endogenous inflammatory response.

Association of thrombocytopenia and delivery method with intraventricular hemorrhage among very-low-birth-weight infants

OBJECTIVES

To investigate the significance of neonatal thrombocytopenia and delivery method on the incidence of intraventricular hemorrhage in infants weighing <1500 g.

STUDY DESIGN

A total of 1283 infants weighing <1500 g who were admitted to six neonatal intensive care units over 21 months were analyzed prospectively. Illness severity was measured by the Score for Neonatal Acute Physiology (SNAP).

RESULTS

Of the infants analyzed, 145 (11.3%) had thrombocytopenia (platelet count <100 x 10(9)/L). The incidence of intraventricular hemorrhage was greater among infants with thrombocytopenia than among those without (44.8% vs 23.9%, P <.0001). Non-thrombocytopenic infants who were delivered vaginally had a higher incidence of intraventricular hemorrhage than those delivered via cesarean section (35.8% vs 15.9%, P <.0001). Thrombocytopenic infants who were delivered vaginally had the highest incidence of intraventricular hemorrhage (63.4% vs 37.5% for cesarean section, P =.005). Vaginal delivery and platelets < 50 x 10(9)/L on day 1 were independent risk factors for intraventricular hemorrhage (OR 2.7, 95% CI 2.0-3.8 and OR 11.2, 95% CI 3.0-42.5, respectively).

CONCLUSIONS

This multicenter study confirms that thrombocytopenia and intraventricular hemorrhage are not uncommon in neonates who weigh <1500 g, and that the incidence of intraventricular hemorrhage is higher in those thrombocytopenic infants delivered vaginally.

Neonatal thrombocytopenia: new insights into pathogenesis and implications for clinical management

The healthy fetus has a platelet count of greater than 150 x 10(9)/L by the second trimester of pregnancy and only 2% of term infants are thrombocytopenic at birth. Severe thrombocytopenia (platelets < 50 x 10(9)/L) occurs in fewer than three per 1000 term infants, the most important cause being alloimmune thrombocytopenia. In contrast, in infants admitted to neonatal intensive care units, thrombocytopenia develops in 25% and in up to half of sick preterm infants. Recent evidence shows that these infants mostly have evidence of underlying impaired fetal megakaryocytopoiesis and platelet production following pregnancy complications characterized by placental insufficiency or fetal hypoxia. The mechanism of this is unknown. However, many neonatal complications exacerbate this thrombocytopenic potential and 20% of thrombocytopenias in neonatal intensive care unit patients are severe. Evidence-based guidelines for platelet transfusion therapy in these patients are yet to be defined, but as platelet underproduction underlies most neonatal thrombocytopenias, recombinant hemopoietic growth factors, including thrombopoietin and interkeukin-11, may be useful future therapies.

Performing and interpreting the bleeding time in the neonatal intensive care unit

In summary, the bleeding time is a helpful clinical tool to detect and investigate certain hemostatic defects in neonates and to evaluate the adequacy of treatments. A prolonged bleeding time alone is sometimes not sufficient to diagnose specific conditions requiring further investigations. Platelet hyporeactivity in the first days of life, gestational age, platelet dysfunction secondary to various neonatal or maternal pathologic conditions, neonatal or maternal drug administration, and hematocrit must be considered for the correct interpretation of the bleeding time test in neonates. In addition, reliable test results can be ensured only by the scrupulous execution of the procedure.

Vitamin metabolism and requirements in the micropremie

Vitamin metabolism and requirements are reviewed for the micropremie (1000 Pounds g birthweight), for parenteral and enteral feedings. Recommendations are presented in table format. Human milk fortifiers and special formulas for the preterm infant are reviewed. For parenteral nutrition, only MVI Pediatric is currently available in the United States. Two millimeters per kilogram is recommended for the micropremie as the most satisfactory method of providing supplemental vitamins in total parenteral nutrition solutions.

Inhaled nitric oxide does not affect adenosine 5'-diphosphate-dependent platelet activation in infants with persistent pulmonary hypertension of the newborn

OBJECTIVE

To investigate the effect of inhaled nitric oxide (NO) treatment in newborns with persistent pulmonary hypertension on adenosine 5'-diphosphate (ADP)-dependent platelet activation.

METHODS

After parental informed consent, infants with persistent pulmonary hypertension of the newborn were randomly assigned to receive conventional treatment (control group) or treatment with 40 parts per million of inhaled NO. Platelet activation was measured at time of entry and 30 minutes later by surface expression of P-selectin in response to increasing concentrations of the agonist ADP (0, 2, 5, 10, and 20 microM) using fluorescence-activated flow cytometry.

RESULTS

We examined 11 infants in the inhaled NO group and 13 in the control group. P-selectin expression, quantified as mean fluorescence, was not significantly different in the two groups of patients at baseline. Median percent change from baseline fluorescence was assessed using the Wilcoxon matched-pairs signed-rank test. At 30 minutes after enrollment there were no statistically significant changes from baseline fluorescence in either group of patients and at all ADP concentrations.

CONCLUSION

Thirty minutes of exposure to 40 ppm of inhaled NO does not inhibit ADP-dependent platelet activation as measured by surface expression of P-selectin in infants with persistent pulmonary hypertension of the newborn.

The outcome of very low birth weight neonates (</=1500 g) rescued by inhaled nitric oxide: neurodevelopment in early childhood

Although inhaled nitric oxide (INO) improves oxygenation in critically ill neonates, the neurodevelopmental outcome of premature neonates with severe hypoxemic respiratory failure treated with INO has not been reported. Mortality and prospective neurodevelopmental assessment in early childhood were studied in a cohort of 24 very low birth weight neonates (</=1500 g) consecutively admitted from 1993 to 1997 and rescued with INO because of severe hypoxemic respiratory failure (oxygenation index 28 to 52) unresponsive to aggressive conventional treatment. Significant improvements in arterial oxygen tension and oxygenation index with lower inspired oxygen concentration and less ventilator support after initiating INO were observed (P <.05, analysis of variance). Despite the dramatic improvement in systemic oxygenation, the mortality rate was high (14 of 24, 58%). Only 6 of 23 had normal cranial ultrasonographies. At 13 to 40 (22 +/- 10) months of adjusted age, 10 survivors had Bayley Scales mental and psychomotor developmental indexes of 81 +/- 21 and 64 +/- 22, respectively. Of the 10 children, 5 (50%) were disabled, 2 (20%) were developmentally delayed, and 3 (30%) had normal development. In view of the poor outcome in very low-birth-weight neonates rescued by INO, randomized controlled trials are required to examine the role of INO in premature neonates. Before, during, and after INO therapy, cranial ultrasonography is recommended.

Nitric oxide and platelet function: implications for neonatology

Nitric oxide (NO) is a mediator that modulates vessel wall tone and hemostatic-thrombotic balance. Platelet function is regulated by NO generated from platelets, endothelial cells and leukocytes. Nitric oxide has been shown to inhibit platelet adhesion, aggregation, and stimulate disaggregation of preformed platelet aggregates. Many of the effects of NO are mediated by its stimulation of guanylate cyclase and the formation of cyclic GMP and its subsequent transduction mechanism. In vivo, NO is likely to interact with prostacyclin, metabolites of ecto-nucleotidase, and lipoxygenase to modulate platelet function in a synergistic manner. An imbalance of NO production (deficiency or overproduction) has been implicated in the pathogenesis of various vascular disorders including thrombosis, atherosclerosis, septicemia, and ischemia-reperfusion injury. It is likely that some of detrimental effects of NO are mediated through its reaction with superoxide anion to form the potent oxidant, peroxynitrite. Nitric oxide gas and NO donors are used for the pharmacological treatment of various vascular disorders. Because inhaled NO has been documented to improve systemic oxygenation and reduce the need for extracorporeal membrane oxygenation, it has been widely used in neonates with severe hypoxemia. An inhibition of platelet function, resulting in a prolonged bleeding time, has been shown in adults receiving inhaled NO. Because bleeding complications may occur in high-risk infants, it is important to evaluate the effect of inhaled NO on platelet function and its correlation with clinical consequences such as intracranial hemorrhage. For these reasons, hemostasis should be carefully monitored during the administration of inhaled NO to critically ill neonates.

Platelet disorders in newborn infants: diagnosis and management

Platelets are small, disc-shaped, anucleated cells formed by fragmentation of megakaryocytes in the bone marrow. They circulate in blood with a lifespan of 7 to 10 days and, together with fibrin, form hemostatic plugs at sites of vessel injury. Abnormalities of platelets, either quantitative or qualitative, may cause clinically significant bleeding with resultant morbidity and, on occasion, mortality. This review will focus on platelet disorders in neonates, defined as infants of up to 4 months of age. Special emphasis will be given to the physiology of platelet function in healthy and sick newborn infants. The review will be divided into sections as follows: role of platelets in hemostasis, platelet function in newborn infants, quantitative platelet disorders, qualitative platelet disorders, and platelet transfusion therapy.