Coagulation standards in healthy newborns and infants.

BACKGROUND: The range of normal values for coagulation factors in the healthy newborn was described 30 years ago but since then the reagents, automated systems, and dosing techniques have changed considerably. For 30 years, several authors have tried to update the standards and references in children using updated reagents but the newborn and infant population in these studies has been quite small, limiting the findings. The aim of this study was to establish the normal coagulation standards in healthy newborns. METHODS: We included all consecutive healthy newborns with pyloric stenosis presenting to our reference center over a period of 5 years. We calculated the reference ranges defined as mean±2 SD. Normality of distribution was checked graphically and by using the Shapiro-Wilk test. Correlations between two continuous variables were assessed using Spearman's rank coefficient correlation. Statistical testing was done at the two-tailed α-level of 0.05. Data were analyzed using the SAS software package, release 9.4 (SAS Institute, Cary, NC). RESULTS: We included 112 healthy newborns and infants. The median age was 35.5 days (15.0-88.0), median weight was 4062g (2855-6040), and 90.2% were boys. Activated partial thromboplastin time (aPTT) and prothrombin time (PT) were not correlated with age (P=0.92 and P=0.21, respectively) or with weight (P=0.16 and P=0.90, respectively). The reference range was 28.6-46.2 s for aPTT, 0.91-1.49 for aPTT ratio, and 71.3-110.6 s for PT. Regarding fibrinogen (n=24), the median was 2.2g/L (1.2-3.2); the median for factor II was 67.0U/dL (51.0-130.0; n=20), and 101.5U/dL for factor V (68.0-233.0; n=20). Regarding factor VIII, the median was 75.0U/dL (45.0-152.0; n=25), 49.0U/dL for factor IX (32.0-96.0; n=25) and 53.0U/dL (29.0-112.0) for factor XI (n=23). CONCLUSION: This study can help to establish standards for coagulation testing in this very specific population. Indeed, our study represents the largest newborn population in a recent investigation of PT and aPTT using updated reagents.

Postpartum haemorrhage related early increase in D-dimers is inhibited by tranexamic acid: haemostasis parameters of a randomized controlled open labelled trial.

BACKGROUND: Beneficial effects of tranexamic acid (TA) have been established in surgery and trauma. In ongoing postpartum haemorrhage (PPH), a moderate reduction of blood loss was observed in a previously published randomized controlled trial. Analysis of haemostasis parameters obtained from samples collected as part of this study are presented. METHODS: Women with PPH >800 ml after vaginal delivery were assigned to receive either TA (4 g over 1 h, then 1 g per h over six h) (TA) or not (H). A non-haemorrhagic group (NH), <800 ml blood loss, was included as postpartum reference. At four time-points (enrolment, +30 min, +2 h, +6 h), haemostasis was assessed. Haemostasis assays were performed blinded to group allocation. Data were expressed as median [interquartiles] and compared with non-parametric tests. RESULTS: In H compared with NH group, D-dimers increase (3730 ng ml(-1) [2468-8493] vs 2649 [2667-4375]; P=0.0001) and fibrinogen and factor II decrease were observed at enrolment and became maximal 2 h later. When comparing TA to H patients, the increase in Plasmin-Antiplasmin-complexes at +30 min (486 ng ml(-1) [340-1116] vs 674 [548-1640]; P=0.03) and D-dimers at +2 h (3888 ng ml(-1) [2688-6172] vs 7495 [4400-15772]; P=0.0001) was blunted. TA had no effect on fibrinogen decrease. CONCLUSIONS: This study provides biological evidence of an early increase in D-dimers and plasmin-antiplasmin complexes associated with active post-partum haemorrhage and its attenuation by the early use of a clinically effective high dose of TA, opening the perspective of dose ranging studies to determinate the optimal dose and timing in this setting. CLINICAL TRIAL REGISTRATION: ISRCTN09968140.

The effect of AMP-activated kinase activation on gonadotrophin-releasing hormone secretion in GT1-7 cells and its potential role in hypothalamic regulation of the oestrous cyclicity in rats.

Hypothalamic AMP-activated kinase (AMPK) is a key regulator of food intake in mammals. Its role in reproduction at the central level and, more precisely, in gonadotrophin-releasing hormone (GnRH) release has never been investigated. We showed that each subunit of AMPK is present in immortalised GnRH neurones (GT1-7 cells). Treatment with 5-aminoimidazole-4-carboxamide-1-beta-D-ribonucleoside (AICAR) and metformin, two activators of AMPK, increased dose-dependent and time-dependent phosphorylation of AMPKalpha atThr172 in GT1-7 cells. Phosphorylation of acetyl-coenzyme A carboxylase at ser79 also increased. Treatment with AICAR (5 mM) or metformin (5 mM) for 4 h inhibited GnRH release in the presence or absence of GnRH (10(-8) M). Specific AMPK inhibitor compound C completely eliminated the effects of AICAR or metformin on GnRH release. Finally, we determined the central effects of AICAR in vivo on food intake and oestrous cyclicity. Ten-week-old female rats received a 50 microg AICAR or a saline i.c.v. injection. We detected increased AMPK and acetyl-CoA carboxylase phosphorylation, specifically in the hypothalamus, 30 min after AICAR injection. Food intake was significantly higher (P < 0.05) in animals treated with AICAR than in animals injected with saline, 24 h after injection. This effect was abolished after 1 week. Moreover, during the 4 weeks following injection, the interval between two oestrous stages was significantly lower in the AICAR group than in the saline group. Our findings suggest that AMPK activation may act directly at the hypothalamic level to affect fertility by modulating GnRH release and oestrous cyclicity.

Activin and inhibin receptor gene expression in the ewe pituitary throughout the oestrous cycle.

In mammals, activin and inhibin are important regulators of FSH secretion. Previous studies have demonstrated that primary ovine pituitary cells express different activin receptor subtypes: activin receptor-like (ALK)2, ALK4, activin type II receptor A (ActRIIA), ActRIIB and Smad proteins in vitro. Here, we have carried out physiological studies to investigate the pattern of mRNA expression of the activin receptor subunits in the ewe pituitary throughout the oestrous cycle. The oestrous cycles of ewes were synchronized with progestagen sponges. The animals were killed 36 h (before the preovulatory surge, n=4), 48 h (during the preovulatory surge, n=4), 72 h (during the second surge of FSH, n=6) and 192 h (during the luteal phase, n=4) after sponge removal. Using Northern blots, we have shown that the levels of ALK2, ALK4 and ActRIIB mRNA were significantly higher before the preovulatory surge and during the secondary surge of FSH as compared with both during the preovulatory surge and the luteal phase, whereas the level of the ActRIIA mRNA was similar throughout the oestrous cycle. Using Western blots we have also demonstrated that the level of phospho-Smad2 did not vary during the reproductive cycle. Inhibin binding protein (InhBP/p120) and the transforming growth factor-beta type III receptor, betaglycan, have been identified as putative inhibin co-receptors. In this study, we cloned a fragment of both InhBP/p120 and betaglycan cDNAs in the ewe and showed by Northern blot that pituitary betaglycan and InhBP/p120 mRNA levels did not fluctuate across the oestrous cycle nor did they correlate with serum FSH levels.