Effective tranexamic acid concentration for 95% inhibition of tissue-type plasminogen activator-induced hyperfibrinolysis in full-term pregnant women: a prospective interventional study

Variability of fibrinolytic activity in pregnant patients exposed to tissue plasminogen activator: an in vitro study utilizing rotational thromboelastometry

BACKGROUND

The investigation into the variability of fibrinolysis in obstetric patients is notably limited despite its relevance to postpartum hemorrhage. We investigate an in vitro model of fibrinolysis measured by rotational thromboelastrometry (ROTEM) in maternal blood samples with lysis stimulated by tissue plasminogen activator (tPA).

METHODS

Written informed consent was obtained from 19 patients at term pregnancy during admission to the labor and delivery unit. Patients who were taking medication affecting coagulation were excluded. Tissue plasminogen activator was added to whole blood samples to a final concentration of 100 or 220 ng/mL prior to ROTEM testing.

RESULTS

The addition of tPA produced high intra-individual fibrinolytic variability for clot firmness and lysis parameters. Patients responded differently to each tPA dose ranging from clot lysis within the range of 0 ng/mL tPA group to complete clot lysis. The coefficient of variation (CV) values for the 220 ng/mL tPA group were: EXTEM MCF 0.510, EXTEM LI30 1.601, FIBTEM MCF 0.349, FIBTEM LI30 2.097. CV values for the 100 ng/mL tPA group were: EXTEM MCF 0.144, EXTEM LI30 1.038, FIBTEM MCF 0.096, FIBTEM LI30 1.238.

CONCLUSION

We demonstrate a wide range of fibrinolytic response in the obstetric population to exogeneous tPA. We found subgroups of patients that were very responsive to tPA and insensitive to tPA. This study represents a preliminary exploration into classifying the obstetric fibrinolytic phenotypes. Further research will integrate relevant coagulation factors to establish a predictive model for testing susceptibility to lysis that can be applied at the point of care.

Evaluating tranexamic acid for the prevention and treatment of obstetric hemorrhage

PURPOSE OF REVIEW

Tranexamic acid (TXA) has emerged as a promising pharmacological adjunct to treat and prevent postpartum hemorrhage (PPH). We provide an overview of TXA, including its pharmacology, key findings of randomized trials and observational studies, and critical patient safety information.

RECENT FINDINGS

Pharmacokinetic data indicate that TXA infusions result in peak plasma concentration within 3 min (range: 1-6.6 min). Ex-vivo pharmacodynamic data suggest that low-dose TXA (5 mg/kg) inhibits maximum lysis for at least 1 h. In predominantly developing countries, TXA has demonstrated a 19% reduction in the risk of bleeding-related death among patients with PPH. Based on high-quality randomized trials, TXA prophylaxis does not effectively reduce the risk of PPH during vaginal delivery and is likely ineffective in reducing the PPH risk during cesarean delivery. TXA exposure does not increase the risk of maternal thrombotic events. Maternal deaths have occurred from accidental intrathecal TXA injection from look-alike medication errors.

SUMMARY

TXA has shown promise as an important adjunct for PPH treatment, especially in low-resource settings. However, TXA is not recommended as PPH prophylaxis during vaginal or cesarean delivery. Patient safety initiatives should be prioritized to prevent maternal death from accidental intrathecal TXA injection.

Tranexamic acid administered during cesarean delivery in high-risk patients: maternal pharmacokinetics, pharmacodynamics, and coagulation status

BACKGROUND

Tranexamic acid is frequently administered for postpartum hemorrhage. The World Health Organization recommends 1 g intravenous dosing, repeated once after 30 minutes for ongoing bleeding. Understanding the pharmacokinetics and pharmacodynamics of tranexamic acid in patients at high risk of postpartum hemorrhage may enable dosage tailoring for optimal antifibrinolysis with minimal adverse events, such as thrombosis or renal cortical necrosis.

OBJECTIVE

This study aimed to report tranexamic acid pharmacokinetics and pharmacodynamics after 1 g intravenous dosing during cesarean delivery in patients at risk of hemorrhage. The primary endpoint was tranexamic acid plasma concentration of >10 μg/mL, known to inhibit 80% of fibrinolysis. In addition, the correlation between patient demographics and rotational thromboelastometry coagulation changes were analyzed.

STUDY DESIGN

In this prospective study, 20 women aged 18 to 50 years, ≥23 weeks of gestation undergoing cesarean delivery with at least 1 major (placenta previa, suspected placenta accreta spectrum, or active bleeding) or 2 minor (≥2 previous cesarean deliveries, previous postpartum hemorrhage, chorioamnionitis, polyhydramnios, macrosomia, obesity, or suspected placental abruption) risk factors for postpartum hemorrhage were recruited. The exclusion criteria were allergy to tranexamic acid, inherited thrombophilia, previous or current thrombosis, seizure history, renal or liver dysfunction, anticoagulation, or category III fetal heart tracing. Tranexamic acid 1 g was administered after umbilical cord clamping. Blood samples were drawn at 3, 7, 15, and 30 minutes and then at 30-minute intervals up to 5 hours. Plasma concentrations were evaluated as mean (standard error). Serial rotational thromboelastometry was performed and correlated with tranexamic acid plasma concentrations.

RESULTS

The median age of participants was 37.5 years (interquartile range, 35.0-39.5), and the median body mass index was 28.6 kg/m2 (interquartile range, 24.9-35.0). The median blood loss (estimated or quantitative) was 1500 mL (interquartile range, 898.5-2076.0). Of note, 9 of 20 (45%) received a transfusion of packed red blood cells. The mean peak tranexamic acid plasma concentration at 3 minutes was 59.8±4.7 μg/mL. All patients had a plasma concentration >10 μg/mL for 1 hour after infusion. Plasma concentration was >10 μg/mL in more than half of the patients at 3 hours and fell <10 μg/mL in all patients at 5 hours. There was a moderate negative correlation between body mass index and the plasma concentration area under the curve (r=-0.49; 95% confidence interval, -0.77 to -0.07; P=.026). Rotational thromboelastometry EXTEM maximum clot firmness had a weak positive correlation with longitudinal plasma concentration (r=0.32; 95% confidence interval, 0.21-0.46; P<.001). EXTEM maximum clot lysis was 0% after infusion in 18 patients (90%), and no patient in the study demonstrated a maximum lysis of >15% at any interval from 3 minutes to 5 hours. There was no significant correlation between EXTEM clot lysis at 30 minutes and longitudinal tranexamic acid plasma concentrations (r=0.10; 95% confidence interval, -0.20 to 0.19; P=.252).

CONCLUSION

After standard 1 g intravenous dosing of tranexamic acid during cesarean delivery in patients at high risk of hemorrhage, a plasma concentration of ≥10 μg/mL was sustained for at least 60 minutes. Plasma tranexamic acid levels correlated inversely with body mass index. The concurrent use of rotational thromboelastometry may demonstrate tranexamic acid's impact on clot firmness but not a hyperfibrinolysis-derived trigger for therapy.

Alternative routes to intravenous tranexamic acid for postpartum hemorrhage: A systematic search and narrative review

OBJECTIVE

To review available data on tranexamic acid (TXA) plasma concentration needed to inhibit fibrinolysis and the time to achieve this concentration when giving TXA by different routes in humans. To identify ongoing trials assessing alternatives to intravenous TXA administration.

METHODS

We updated two previous systematic reviews by searching MEDLINE, EMBASE, OviSP, and ISI Web of Science from database inception to July 2021. We also searched the WHO International Clinical Trials Registry Platform for ongoing trials to July 2021. Titles and abstracts were screened for relevant trials. Two reviewers independently reviewed and agreed the trials to be included.

RESULTS

Plasma TXA concentrations over 10 mg/L provide near maximal inhibition of fibrinolysis, with concentrations over 5 mg/L providing partial inhibition. Oral TXA tablets take about 1 h to reach a plasma concentration of 5 mg/L in postpartum women. Studies in healthy volunteers and shocked trauma patients show that intramuscular TXA achieves a plasma level of over 10 mg/L within 15 min. One trial is ongoing to determine the pharmacokinetics of intramuscular and oral solution TXA in pregnant women.

CONCLUSION

Intramuscular TXA in healthy volunteers and shocked trauma patients reaches therapeutic concentration rapidly. Oral TXA tablets take too long to reach the minimum therapeutic concentration in postpartum women.

The Non-Activated Thromboelastometry (NATEM) Assay's Application among Adults and Neonatal/Pediatric Population: A Systematic Review

The non-activated thromboelastometry (NATEM) assay is a point-of-care assay that can provide a comprehensive insight into the actual hemostatic mechanism. However, there are very limited data about its use in clinical practice. The aim of this study was to systematically review the literature for any data regarding the use of NATEM in several clinical settings. A systematic review of PubMed and Scopus databases was conducted through 20 January 2022 for studies evaluating the use of the NATEM assay in different clinical settings. The literature search yielded a total of 47 publications, 30 of which met the eligibility criteria for this review. Evaluation of NATEM’s detecting ability for hemostasis disorders is limited in the literature. The results of the included studies indicate that NATEM seems to be a sensitive method for the detection of hyperfibrinolysis and may have an advantage in the diagnosis of hemostatic disorders. It could be more informative than the other ROTEM assays for detecting changes in coagulation parameters in patients who receive anticoagulants. However, the reported outcomes are highly varying among the included studies. NATEM has a high sensitivity to detect hypo- or hypercoagulability and provides a detailed insight into the whole hemostatic process from clot formation to clot breakdown. It could be a useful technique in variable fields of medicine, not only in adults, but also in pediatric and neonatal populations, to guide different hemostatic treatments and predict coagulation disorders or mortality/morbidity; this issue remains to be further investigated.