Optimal use of intravenous tranexamic acid for hemorrhage prevention in pregnant women

Tranexamic acid - a promising hemostatic agent with limitations: a narrative review

Tranexamic acid (TXA) is a synthetic antifibrinolytic agent that has been used for several decades to reduce blood loss during surgery and after trauma. TXA was traditionally used to reduce bleeding in various clinical settings such as menorrhagia, hemophilia, or other bleeding disorder. Numerous studies have demonstrated the efficacy of TXA in reducing blood loss and the need for transfusions. Interest in the potential applications of TXA beyond its traditional use has been growing recently, with studies investigating the use of TXA in postpartum hemorrhage, cardiac surgery, trauma, neurosurgery, and orthopedic surgery. Despite its widespread use and expanding indications, data regarding the safe and appropriate use of TXA is lacking. Recent clinical trials have found various potential risks and limitations in the long-term benefits of TXA. This narrative review summarizes the clinical applications and limitations of TXA.

Prophylactic Tranexamic Acid Prevents Postpartum Hemorrhage and Transfusions in Cesarean Deliveries: A Systematic Review and Meta-analysis

Postpartum hemorrhage (PPH) is the leading cause of maternal mortality worldwide and PPH resulting in transfusion is the most common maternal morbidity in the United States. Literature demonstrates that tranexamic acid (TXA) can reduce blood loss in cesarean deliveries; however, there is little consensus on the impact on major morbidities like PPH and transfusions. We conducted a systematic review/meta-analysis of randomized controlled trials (RCTs) to evaluate if administration of prophylactic intravenous (IV) TXA prevents PPH and/or transfusions following low-risk cesarean delivery. PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines were followed. Five databases were searched: Cochrane, EBSCO, Ovid, PubMed, and ClinicalKey. RCTs published in English between January 2000 and December 2021 were included. Studies compared PPH and transfusions in cesarean deliveries between prophylactic IV TXA and control (placebo or no placebo). The primary outcome was PPH, and the secondary outcome was transfusions. Random effects models were used to calculate effect size (ES) of exposure in Mantel-Haenszel risk ratios (RR). All analysis was done at a confidence level (CI) of α = 0.5. Modeling showed that TXA led to significantly less risk of PPH than control (RR: 0.43; 95% CI: 0.28-0.67). The effect on transfusion was comparable (RR: 0.39; 95% CI: 0.21-0.73). Heterogeneity was minimal (I 2 = 0%). Due to the large sample sizes needed, many RCTs are not powered to interpret TXA's effect on PPH and transfusions. Pooling these studies in a meta-analysis allows for more power and analysis but is limited by the heterogeneity of studies. Our results minimize heterogeneity while demonstrating that prophylactic TXA can lower PPH occurrence and reduce the need for blood transfusion. We suggest considering prophylactic IV TXA as the standard of care in low-risk cesarean deliveries. KEY POINTS: · Consider TXA prior to incision for singleton, term pregnancies undergoing elective cesarean.. · Prophylactic TXA is effective in preventing PPH and blood transfusions.. · Routine use of TXA has the potential to decrease transfusion-related complications and costs..

Persistent hypofibrinolysis in severe COVID-19 associated with elevated fibrinolysis inhibitors activity

Hypercoagulability and reduced fibrinolysis are well-established complications associated with COVID-19. However, the timelines for the onset and resolution of these complications remain unclear. The aim of this study was to evaluate, in a cohort of COVID-19 patients, changes in coagulation and fibrinolytic activity through ROTEM assay at different time points during the initial 30 days following the onset of symptoms in both mild and severe cases. Blood samples were collected at five intervals after symptoms onset: 6-10 days, 11-15 days, 16-20 days, 21-25 days, and 26-30 days. In addition, fibrinogen, plasminogen, PAI-1, and alpha 2-antiplasmin activities were determined. Out of 85 participants, 71% had mild COVID-19. Twenty uninfected individuals were evaluated as controls. ROTEM parameters showed a hypercoagulable state among mild COVID-19 patients beginning in the second week of symptoms onset, with a trend towards reversal after the third week of symptoms. In severe COVID-19 cases, hypercoagulability was observed since the first few days of symptoms, with a tendency towards reversal after the fourth week of symptoms onset. A hypofibrinolytic state was identified in severe COVID-19 patients from early stages and persisted even after 30 days of symptoms. Elevated activity of PAI-1 and alpha 2-antiplasmin was also detected in severe COVID-19 patients. In conclusion, both mild and severe cases of COVID-19 exhibited transient hypercoagulability, reverted by the end of the first month. However, severe COVID-19 cases sustain hypofibrinolysis throughout the course of the disease, which is associated with elevated activity of fibrinolysis inhibitors. Persistent hypofibrinolysis could contribute to long COVID-19 manifestations.

Optimal starting dosing regimen of intravenous oxytocin for labor induction based on the population kinetic-pharmacodynamic model of uterine contraction frequency

BACKGROUND

Intravenous oxytocin is commonly used for labor induction. However, a consensus on the initial dosing regimen is lac with conflicting research findings and varying guidelines. This study aimed to develop a population kinetic-pharmacodynamic (K-PD) model for oxytocin-induced uterine contractions considering real-world data and relevant influencing factors to establish an optimal starting dosing regimen for intravenous oxytocin.

METHODS

This retrospective study included pregnant women who underwent labor induction with intravenous oxytocin at Peking University Third Hospital in 2020. A  population K-PD model was developed to depict the time course of uterine contraction frequency (UCF), and covariate screening identified significant factors affecting the pharmacokinetics and pharmacodynamics of oxytocin. Model-based simulations were used to optimize the current starting regimen based on specific guidelines.

RESULTS

Data from 77 pregnant women with 1095 UCF observations were described well by the K-PD model. Parity, cervical dilation, and membrane integrity are significant factors influencing the effectiveness of oxytocin. Based on the model-based simulations, the current regimens showed prolonged onset times and high infusion rates. This study proposed a revised approach, beginning with a rapid infusion followed by a reduced infusion rate, enabling most women to achieve the target UCF within approximately 30 min with the lowest possible infusion rate.

CONCLUSION

The K-PD model of oxytocin effectively described the changes in UCF during labor induction. Furthermore, it revealed that parity, cervical dilation, and membrane integrity are key factors that influence the effectiveness of oxytocin. The optimal starting dosing regimens obtained through model simulations provide valuable clinical references for oxytocin treatment.

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.

Management of pregnant women who have bleeding disorders

Bleeding disorders, including von Willebrand disease (VWD), hemophilia, other coagulation factor deficiencies, platelet disorders, defects of fibrinolysis, and connective tissue disorders, have both maternal and fetal implications. Successful management of bleeding disorders in pregnant women requires not only an understanding of bleeding disorders but also an understanding of when and how bleeding occurs in pregnancy. Bleeding does not occur during a normal pregnancy with a healthy placenta. Bleeding occurs during pregnancy when there is an interruption of the normal utero-placental interface, during miscarriage, during an ectopic pregnancy, or at the time of placental separation at the conclusion of pregnancy. Although mild platelet defects may be more prevalent, the most commonly diagnosed bleeding disorder among women is VWD. Other bleeding disorders are less common, but hemophilia carriers are unique in that they are at risk of bleeding themselves and of giving birth to an affected male infant. General guidance for maternal management of a woman who is moderately or severely affected includes obtaining coagulation factor levels at a minimum in the third trimester; planning for delivery at a center with hemostasis expertise; and anticipating the need for hemostatic agents. General guidance for fetal management includes pre-pregnancy counseling; the option of preimplantation genetic testing for hemophilia; delivery at a tertiary care center with pediatric hematology and newborn intensive care; consideration of cesarean delivery of a potentially severely affected infant; and avoidance of invasive procedures such as scalp electrodes and operative vaginal delivery in any potentially affected infant.

Efficacy and safety of tranexamic acid in prevention of postpartum hemorrhage: a systematic review and meta-analysis of 18,649 patients

BACKGROUND

In this meta-analysis, we aimed to update the clinical evidence regarding the efficacy and safety of TXA in the prevention of PPH.

METHODS

A literature search of PubMed, Scopus, Web of Science, Google Scholar, and Cochrane Library from inception until December 2022 was conducted. We included randomized controlled trials (RCTs) comparing TXA with a placebo among pregnant women. All relevant outcomes, such as total blood loss, the occurrence of nausea and/or vomiting, and changes in hemoglobin, were combined as odds ratios (OR) or mean differences (MD) in the meta-analysis models using STATA 17 MP.

RESULTS

We included 59 RCTs (18,649 patients) in this meta-analysis. For cesarean birth, TXA was favored over the placebo in reducing total blood loss (MD= -2.11 mL, 95%CI [-3.09 to -1.14], P < 0.001), and occurrence of nausea or/and vomiting (OR = 1.36, 95%CI [1.07 to 1.74], P = 0.01). For vaginal birth, the prophylactic use of TXA was associated with lower total blood loss, and higher occurrence of nausea and/or vomiting (MD= -0.89 mL, 95%CI [-1.47 to -0.31], OR = 2.36, 95%CI [1.32 to 4.21], P = 0.02), respectively. However, there were no differences between the groups in changes in hemoglobin during vaginal birth (MD = 0.20 g/dl, 95%CI [-0.07 to 0.48], P = 0.15). The overall risk of bias among the included studies varies from low to high risk of bias using ROB-II tool for RCTs.

CONCLUSIONS

This meta-analysis suggested that TXA administration is effective among women undergoing cesarean birth or vaginal birth in lowering total blood loss and limiting the occurrence of PPH. Further clinical trials are recommended to test its efficacy on high-risk populations.

Bacteriosynthetic Degradable Tranexamic Acid-Functionalized Short Fibers for Inhibiting Invisible Hemorrhage

Current research on hemostatic materials have focused on the inhibition of visible hemorrhage, however, invisible hemorrhage is the unavoidable internal bleeding that occurs after trauma or surgery, leading directly to a dramatic drop in hemoglobin and then to anemia and even death. In this study, bacterial nanocellulose (BNC) was synthesized and oxidized from the primary alcohols to carboxyl groups, and then grafted with tranexamic acid through amide bonds to construct degradable nanoscale short fibers (OBNC-TXA), which rapidly activated the coagulation response. The hemostatic material is made up of nanoscale short fibers that can be constructed into different forms such as emulsions, gels, powders, and sponges to meet different clinical applications. In the hemostatic experiments in vitro, the composites had significantly superior pro-coagulant properties due to the rapid aggregation of blood cells. In the coagulation experiments with rat tail amputation and liver trauma hemorrhage models, the group treated with OBNC-TXA1 sponge showed low hemorrhage and inhibited invisible hemorrhage in rectus abdominis muscle defect hemorrhage models, with a rapid recovery of hemoglobin values from 128±5.5 to 165±2.6 g L-1 within 4 days. In conclusion, the degradable short fibers constructed from bacterial nano-cellulose achieved inhibition of invisible hemorrhage in vivo.

Women with severe postpartum hemorrhage have a decreased endogenous thrombin potential before delivery

BACKGROUND

Severe postpartum hemorrhage (PPH), defined as a blood loss ≥1000 mL, is associated with maternal morbidity and mortality.

OBJECTIVES

We aimed at characterizing coagulation properties of predelivery plasmas from pregnant women with thrombin generation assay and hemostatic biomarkers (plasminogen activator inhibitor-1, tissue factor [TF], and thrombomodulin).

METHODS

A nested case-control study was conducted within the "Study of Biological Determinants of Bleeding Postpartum," a French prospective cohort study, in order to compare women with severe PPH (cases) and controls matched for age, body mass index, term, and mode of delivery. Plasma was collected at entry in the delivery room, and blood loss was measured objectively. The predelivery endogenous thrombin generation potential (ETP) was measured in plasma using calibrated automated thrombinography and low TF concentration. Hemostatic biomarkers were measured using ELISA kits.

RESULTS

A total of 142 women (71 cases and 71 controls) were investigated. There was no difference in the median lag phase, thrombin peak, and time to peak between cases and controls. However, median predelivery ETP was lower in cases than in controls (2170 vs 2408 nM.min, P < .0001), independently of mode of delivery and PPH etiology. Median plasminogen activator inhibitor-1 and TF levels were higher in cases compared with controls (107.4 vs 68.1 ng/mL, P = .0003; 34.4 vs 27.4 pg/mL, P = .007), whereas thrombomodulin levels did not differ between the 2 groups.

CONCLUSION

Among thrombin generation assay parameters, predelivery ETP levels may have a predictive value for severe PPH.

An update to tranexamic acid trends during the peripartum period in the United States, 2019 to 2021

BACKGROUND

Results from the 2017 World Maternal Antifibrinolytic trial found that patients who received tranexamic acid during delivery had significantly lower rates of death and hysterectomy. Several months after the World Maternal Antifibrinolytic trial publication, American College of Obstetricians and Gynecologists endorsed the consideration of tranexamic acid usage when traditional uterotonics fail during postpartum hemorrhage. Since then, tranexamic acid usage has become more mainstream for the treatment of postpartum hemorrhage.

OBJECTIVE

This study aimed to evaluate tranexamic acid trends in obstetrics both temporally and geographically within the United States. Additional outcomes included patient demographics and perinatal outcomes.

STUDY DESIGN

This retrospective cohort study included 19 hospitals divided into East, Central, and West geographic regions within the Universal Health Services, Incorporated network. Rates of tranexamic acid use were compared from July 2019 through June 2021. Patient demographics and perinatal outcomes were analyzed for tranexamic acid recipients.

RESULTS

During the two-year study period, 3.2% (1580/50,150) of patients received tranexamic acid during delivery. The western region of the United States demonstrated increased tranexamic acid use over the 2-year study period. Recipients of tranexamic acid were more likely to have a history of postpartum hemorrhage (P<.0001), chronic hypertension (P<.0001), preeclampsia (P<.0001), and/or diabetes (P=.004). Patients who received tranexamic acid did not have an increased likelihood of venous thromboembolism in comparison with those who did not receive tranexamic acid (8 [0.5%] vs 226 [0.5%]; P=.77). Of those who received tranexamic acid, 53.2% (840/1580) had an estimated blood loss <1000 mL.

CONCLUSION

Nationally, a higher percentage of patients received tranexamic acid without a postpartum hemorrhage diagnosis compared with previous studies, and the western region of the United States had an overall increased use of tranexamic acid during delivery compared with previous years. There was no increased risk of venous thromboembolism in those who received tranexamic acid, regardless of postpartum hemorrhage diagnosis.

Tranexamic Acid to Prevent Obstetrical Hemorrhage after Cesarean Delivery

BACKGROUND

Prophylactic use of tranexamic acid at the time of cesarean delivery has been shown to decrease the calculated blood loss, but the effect on the need for blood transfusions is unclear.

METHODS

We randomly assigned patients undergoing cesarean delivery at 31 U.S. hospitals to receive either tranexamic acid or placebo after umbilical-cord clamping. The primary outcome was a composite of maternal death or blood transfusion by hospital discharge or 7 days post partum, whichever came first. Key secondary outcomes were estimated intraoperative blood loss of more than 1 liter (prespecified as a major secondary outcome), interventions for bleeding and related complications, the preoperative-to-postoperative change in the hemoglobin level, and postpartum infectious complications. Adverse events were assessed.

RESULTS

A total of 11,000 participants underwent randomization (5529 to the tranexamic acid group and 5471 to the placebo group); scheduled cesarean delivery accounted for 50.1% and 49.2% of the deliveries in the respective groups. A primary-outcome event occurred in 201 of 5525 participants (3.6%) in the tranexamic acid group and in 233 of 5470 (4.3%) in the placebo group (adjusted relative risk, 0.89; 95.26% confidence interval [CI], 0.74 to 1.07; P = 0.19). Estimated intraoperative blood loss of more than 1 liter occurred in 7.3% of the participants in the tranexamic acid group and in 8.0% of those in the placebo group (relative risk, 0.91; 95% CI, 0.79 to 1.05). Interventions for bleeding complications occurred in 16.1% of the participants in the tranexamic acid group and in 18.0% of those in the placebo group (relative risk, 0.90; 95% CI, 0.82 to 0.97); the change in the hemoglobin level was -1.8 g per deciliter and -1.9 g per deciliter, respectively (mean difference, -0.1 g per deciliter; 95% CI, -0.2 to -0.1); and postpartum infectious complications occurred in 3.2% and 2.5% of the participants, respectively (relative risk, 1.28; 95% CI, 1.02 to 1.61). The frequencies of thromboembolic events and other adverse events were similar in the two groups.

CONCLUSIONS

Prophylactic use of tranexamic acid during cesarean delivery did not lead to a significantly lower risk of a composite outcome of maternal death or blood transfusion than placebo. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development; ClinicalTrials.gov number, NCT03364491.).

The diagnosis, natural history, and management of von Willebrand disease in women in the age of guidelines

INTRODUCTION

Women and girls with bleeding disorders face multiple bleeding challenges throughout their life. The most significant morbidity and mortality are due to heavy menstrual bleeding and postpartum hemorrhage in their reproductive years. The ASH/ISTH/NHF/WFH 2021 guidelines on diagnosing and managing von Willebrand disease (VWD) provide several new updates.

AREAS COVERED

Women with VWD have a higher prevalence of heavy menstrual bleeding. The subpopulation of adolescents is particularly vulnerable, as the diagnosis is often delayed with increased comorbidity of iron deficiency anemia and associated symptoms. A detailed review is done on the prevalence of bleeding-related complications, especially heavy menstrual bleeding (HMB) and post-partum hemorrhage (PPH). The management strategies are also reviewed in detail, with a specific focus on the target factor levels and the use of antifibrinolytics.

EXPERT OPINION

The 2021 ASH/ISTH/NHF/WFH diagnostic and management recommendations are reviewed with a specific focus on hormonal methods of HMB management and antifibrinolytics in this situation. The reviewed topics include neuraxial anesthesia, factor cutoff, and tranexamic acid use in the postpartum period.

The role of tranexamic acid in the management of postpartum haemorrhage

In the last decades, tranexamic acid (TXA) has emerged as an essential tool in blood loss management in obstetrics. TXA prophylaxis for postpartum haemorrhage (PPH) has been studied in double-blind, placebo-controlled, randomized clinical trials (RCTs). Given the small observed preventive effect, the systematic use of TXA for vaginal and/or caesarean deliveries remains controversial. The result of a pharmacokinetic modelling suggests that relative to intravenous administration, intramuscular administration may be an equally effective alternative route for preventing PPH and may enable access to this drug in low-resource countries. Prophylaxis is currently studied in high-risk populations, such as women with prepartum anaemia or placenta previa. TXA effectively reduces blood loss and PPH-related morbidity and mortality during active PPH, as demonstrated by high-grade evidence from large RCTs. The drug has a good safety profile: in most cases, only mild gastrointestinal or visual adverse events may be observed. TXA use does not increase the risk of serious adverse events, such as venous or arterial thromboembolism, seizures, or acute kidney injury. The TRACES in vivo analysis of biomarkers of TXA's antifibrinolytic effect have suggested that a dose of at least 1 g is required for the treatment of PPH. The TRACES pharmacokinetic model suggests that because TXA can be lost in the haemorrhaged blood, a second dose should be administered if the PPH continues or if severe coagulopathy occurs. Future pharmacodynamic analyses will focus on the appropriateness of TXA dosing regimens with regard to the intensity of fibrinolysis in catastrophic obstetric events.

Update on Applications and Limitations of Perioperative Tranexamic Acid

Tranexamic acid (TXA) is a potent antifibrinolytic with documented efficacy in reducing blood loss and allogeneic red blood cell transfusion in several clinical settings. With a growing emphasis on patient blood management, TXA has become an integral aspect of perioperative blood conservation strategies. While clinical applications of TXA in the perioperative period are expanding, routine use in select clinical scenarios should be supported by evidence for efficacy. Furthermore, questions regarding optimal dosing without increased risk of adverse events such as thrombosis or seizures should be answered. Therefore, ongoing investigations into TXA utilization in cardiac surgery, obstetrics, acute trauma, orthopedic surgery, neurosurgery, pediatric surgery, and other perioperative settings continue. The aim of this review is to provide an update on the current applications and limitations of TXA use in the perioperative period.

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.

Tranexamic acid for the prevention of postpartum hemorrhage in women undergoing cesarean delivery: an updated meta-analysis

OBJECTIVE

This study aimed to assess the efficacy and safety of prophylactic tranexamic acid administration vs standard uterotonic agents alone among women undergoing cesarean delivery.

DATA SOURCES

MEDLINE, Scopus, Web of Science, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, and Google Scholar were systematically searched from inception to June 30, 2021.

STUDY ELIGIBILITY CRITERIA

Randomized controlled trials comparing intravenous tranexamic acid administration with placebo in women undergoing cesarean delivery and receiving standard prophylactic uterotonic agents were held eligible.

STUDY APPRAISAL AND SYNTHESIS METHODS

The risk of bias of individual studies was appraised with the Risk of Bias 2 tool. Meta-analysis was conducted by fitting random-effects models using restricted maximum likelihood. Subgroup analysis was performed on the basis of country, protocol availability, double-blinding, risk of bias, sample size, and tranexamic acid dose. A 1-stage meta-analysis was performed as a sensitivity analysis. The credibility of outcomes was appraised with the Grading of Recommendations Assessment, Development and Evaluation approach.

RESULTS

Overall, 36 studies with 10,659 women were included. Tranexamic acid administration was associated with significantly lower total blood loss (mean difference, -189.44 mL; 95% confidence intervals, -218.63 to -160.25), lower hemoglobin drop (mean difference, 8.22%; 95% confidence interval, 5.54-10.90), decreased risk of blood loss of >1000 mL (odds ratio, 0.37; 95% confidence interval, 0.22-0.60), transfusion requirement (odds ratio, 0.41; 95% confidence interval, 0.26-0.65), and need of additional uterotonics (odds ratio, 0.36; 95% confidence interval, 0.25-0.52). Subgroup analysis indicated a greater effect of tranexamic acid on total blood loss reduction in low-middle income countries. The outcomes remained stable by separately evaluating women at low bleeding risk. The 1-stage meta-analysis demonstrated similar outcomes with the primary analysis. The quality of evidence was judged to be moderate regarding total blood loss and hemoglobin percentage change and low for the other outcomes.

CONCLUSION

This meta-analysis suggested that prophylactic tranexamic acid administration is effective among women undergoing cesarean delivery in lowering postpartum blood loss and limiting hemoglobin drop. Further research is needed to test its efficacy in high-risk populations and verify its safety profile.

Population pharmacokinetics and pharmacodynamics of Tranexamic acid in women undergoing caesarean delivery

AIMS

The population pharmacokinetics (PK) and pharmacodynamics (PD) of tranexamic acid (TXA) have not been studied to prevent postpartum haemorrhage (PPH) in pregnant women. It is unclear which TXA dose assures sufficient PPH prevention. This study investigated population PK/PD of TXA in pregnant women who underwent caesarean delivery to determine the optimal prophylactic doses of TXA for future studies.

METHODS

We analysed concentration (PK) and maximum lysis (PD) data from 30 pregnant women scheduled for caesarean delivery who received 5, 10 or 15 mg/kg of TXA intravenously using population approach.

RESULTS

TXA PK was best described by a two-compartment model with first-order elimination and the following parameters: clearance (between-subject variability) of 9.4 L/h (27.7%), central volume of 10.1 L (47.4%), intercompartmental clearance of 22.4 L/h (66.7%), peripheral volume of 14.0 L (13.1%) and additive error of 1.4 mg/L. The relationship between TXA concentration and maximum lysis was characterized by a sigmoid Emax model with baseline lysis of 97%, maximum inhibition of 89%, IC50 of 6.0 mg/L (65.3%), hill factor of 8.5 (86.3%) and additive error of 7.3%. Simulations demonstrated that 500 and 650 mg of TXA maintained therapeutic targets for 30 minutes and 1 hour, respectively, in 90% of patients.

CONCLUSION

This is the first population PK and PD study of TXA in pregnant women undergoing caesarean delivery. Our analysis suggests that a 650 mg dose provides adequate PPH prophylaxis up to 1 hour, which is less than the currently used 1000 mg of TXA in pregnant women.

WOMAN-PharmacoTXA trial: Study protocol for a randomised controlled trial to assess the pharmacokinetics and pharmacodynamics of intramuscular, intravenous and oral administration of tranexamic acid in women giving birth by caesarean section

Background: Intravenous tranexamic acid (TXA) within 3 hours of birth significantly reduces death due to bleeding in women with postpartum haemorrhage (PPH). Most PPH deaths occur in the first hours after giving birth and treatment delay decreases survival.  One barrier to rapid TXA treatment is the need for intravenous injection. Intramuscular injection and oral solution of TXA would be easier and faster to administer and would require less training. However, the pharmacokinetics (PK), pharmacodynamics and safety of TXA administered by different routes in pregnant women have not been established. The main aim of this study is to ascertain whether IM and oral solution of TXA will be absorbed at levels sufficient to inhibit fibrinolysis in pregnant women.

Methods: WOMAN-PharmacoTXA is a prospective, randomised, open label trial to be conducted in Zambia and Pakistan.  Adult women undergoing caesarean section with at least one risk factor for PPH will be included.  Women will be randomised to receive one of the following about 1 hour prior to caesarean section: 1-gram TXA IV, 1-gram TXA IM, 4-grams TXA oral solution or no TXA. Randomisation will continue until 120 participants with at least six post randomisation PK samples are included. TXA concentration in maternal blood samples will be measured at baseline and at different time points during 24 hours after receipt of intervention. Blood TXA concentration will be measured from the umbilical cord and neonate.

The primary endpoint is maternal blood TXA concentrations over time. Secondary outcomes include umbilical cord and neonate TXA concentration D-dimer concentration, blood loss and clinical diagnosis of PPH, injection site reactions and maternal and neonate adverse events.

Discussion: The WOMAN-PharmacoTXA trial will provide important data on pharmacokinetics, pharmacodynamics and safety of TXA after IV, intramuscular and oral administration in women giving birth by caesarean section.

Trial registration: ClincalTrials.gov, NCT04274335 (18/02/2020).

Application of a plasmin generation assay to define pharmacodynamic effects of tranexamic acid in women undergoing cesarean delivery

Essentials Tranexamic acid (TXA) is an antifibrinolytic drug used to reduce bleeding. Assaying plasmin generation (PG) in plasma detects clinically relevant TXA levels in vitro and ex vivo. 3.1-16.2 µg/mL TXA half-maximally inhibits PG in plasma from women undergoing cesarean delivery. PG velocity shows the strongest dose-relationship at low TXA concentrations (≤10 µg/mL). ABSTRACT: Background Tranexamic acid (TXA) is used to reduce bleeding. TXA inhibits plasmin(ogen) binding to fibrin and reduces fibrinolysis. TXA antifibrinolytic activity is typically measured by clot lysis assays; however, effects on plasmin generation (PG) are unclear due to a lack of tools to measure PG in plasma. Aims Develop an assay to measure PG kinetics in human plasma. Determine effects of TXA on PG and compare with fibrinolysis measured by rotational thromboelastometry (ROTEM). Methods We characterized effects of plasminogen, tissue plasminogen activator, fibrinogen, and α2 -antiplasmin on PG in vitro. We also studied effects of TXA on PG in plasma from 30 pregnant women administered intravenous TXA (5, 10, or 15 mg/kg) during cesarean delivery. PG was measured by calibrated fluorescence. PG parameters were compared with TXA measured by mass spectrometry and ROTEM of whole blood. Results The PG assay is specific for plasmin and sensitive to tissue plasminogen activator, fibrin(ogen), and α2 -antiplasmin. Addition of TXA to plasma in vitro dose dependently prolonged the clot lysis time and delayed and reduced PG. For all doses of TXA administered intravenously, the PG assay detected delayed time-to-peak (≤3 hours) and reduced the velocity, peak, and endogenous plasmin potential (≤24 hours) in plasma samples obtained after infusion. The PG time-to-peak, velocity, and peak correlated significantly with TXA concentration and showed less variability than the ROTEM lysis index at 30 minutes or maximum lysis. Conclusions The PG assay detects pharmacologically relevant concentrations of TXA administered in vitro and in vivo, and demonstrates TXA-mediated inhibition of PG in women undergoing cesarean delivery.