Coagulation changes in the newborn with respiratory failure

Thromboelastometry in Neonates with Respiratory Distress Syndrome: A Pilot Study

BACKGROUND

Although respiratory distress syndrome (RDS) constitutes a postnatal risk factor for bleeding and thromboembolic events in neonates, few studies have addressed this issue. We aimed to evaluate the hemostatic profile of neonates with RDS using rotational thromboelastometry (ROTEM).

METHODS

An observational study was conducted from November 2018 to November 2020 in the NICU of General Hospital of Nikaia "Aghios Panteleimon". Preterm and term neonates with RDS hospitalized in the NICU were included and EXTEM (tissue factor-triggered extrinsic pathway), INTEM (ellagic acid activated intrinsic pathway), and FIBTEM (with platelet inhibitor cytochalasin D) assays were performed at the onset of the disease.

RESULTS

A hypocoagulable profile was noted in neonates with RDS compared to controls, expressed as significant prolongation of EXTEM CT (clotting time) and CFT (clot formation time), lower EXTEM A10 (amplitude at 10 min), MCF (maximum clot firmness), and LI60 (lysis index). Furthermore, prolongation of INTEM CFT and FIBTEM CT, and decreased INTEM and FIBTEM A10 and MCF were found in neonates with RDS. Multivariable logistic regression analysis showed that RDS is an independent factor for the recorded alterations in ROTEM variables.

CONCLUSIONS

RDS is associated with a hypocoagulable profile and greater hyperfibrinolytic potential compared to healthy neonates.

The relevance of developmental hemostasis to hemorrhagic disorders of newborns

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

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

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

Severe neonatal protein C deficiency: prevalence and thrombotic risk

Severe deficiencies of protein C, a pivotal coagulation-regulatory protein, have been reported in neonates as an apparently transient condition. In this prospective study, cord blood was collected at 193 deliveries and assays of protein C were correlated with clinical status, other coagulation results, and outcome. Protein C levels of less than 0.1 unit/ml were found most frequently in preterm infants with respiratory distress, infants of diabetic mothers, and infants of twin gestations. Levels of protein C correlated with levels of factor VIII activity but did not correlate with markers of consumptive coagulopathy. A protein C level less than 0.1 unit/ml was significantly correlated with the subsequent onset of thrombosis, even when the effects of gestational age and birth weight were excluded. Low cord blood levels of protein C may reflect delayed maturation or increased turnover in certain infants and appear to convey an independent risk of thrombosis, but the critical concentration of protein C necessary to maintain neonatal hemostasis is not known.

Neonatal antithrombin III deficiency

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

Low antithrombin III: accurate predictor of idiopathic respiratory distress syndrome in premature neonates

A prospective study was performed in premature neonates to determine the predictive values of antithrombin III (AT III) deficiency immediately after birth, for the subsequent development of idiopathic respiratory distress syndrome (IRDS), intraventricular haemorrhage (IVH) and death. Of the 81 premature infants studied, 24 developed IRDS (30%). Of these 24 premature infants, 8 also developed IVH and 9 infants died within the follow-up period of 7 days. The mean plasma AT III level was significantly lower in the infants developing IRDS (0.23 U/ml vs 0.35 U/ml, P less than 0.0005). Within this study group 33 neonates of less than 30 weeks' gestation showed a prevalence for IRDS of 48%. In this group, AT III activity levels below 0.30 U/ml were 8.5 times as likely to result from infants with IRDS than from infants without IRDS. The diagnostic accuracy indices of criteria for the development of IRDS were: a sensitivity of 100%, a specificity of 88%, a positive predictive value of 89% and a negative predictive value of 100%. The predictive values for the development of IVH and occurrence of death were insignificant. Therefore, in premature neonates the combination of less than 30 weeks' gestation and an AT III below 0.30 U/ml is highly suggestive of IRDS and may facilitate the evaluation of early treatment.