Postpartum Hemorrhage: Wherefore Art Thou, Hyperfibrinolysis?

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.

When to use tranexamic acid for the treatment of major bleeding?

Tranexamic acid (TXA) is an antifibrinolytic agent originally developed for the management of bleeding in the setting of postpartum hemorrhage (PPH). Over the last 15 years, there has been accumulating evidence on the use of TXA for the treatment of active bleeding in a variety of clinical contexts. Clinical trials have shown that the efficacy and safety of TXA for the treatment of bleeding differ according to the clinical context in which it is being administered, timing of administration, and dose. Early administration is important for efficacy, particularly in trauma and PPH. Further studies are needed to understand the mechanisms by which TXA provides benefit, optimal modes of administration and dosing, and its effect in some clinical settings, such as spontaneous intracerebral hemorrhage. There is no evidence that TXA increases the risk of thrombotic events in patients with major bleeding overall. However, there is evidence of increased risk of venous thrombosis in patients with gastrointestinal bleeding. There is also evidence of increased risk of seizures with the use of higher doses. This review summarizes the current evidence for the use of TXA for patients with active bleeding and highlights the importance of generating evidence of efficacy and safety of hemostatic interventions specific to the bleeding contexts-as findings from 1 clinical setting may not be generalizable to other contexts-and that of individual patient assessment for bleeding, thrombotic, and other risks, as well as important logistical and other practical considerations, to optimize care and outcomes in these settings.

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.

Hemostatic Effects of Tranexamic Acid in Cesarean Delivery: An Ancillary Study of the TRAAP2 Study

BACKGROUND

 Fibrinolysis activation during delivery contributes to postpartum hemorrhage (PPH). Clot lysis time studied with the global fibrinolytic capacity device (GFC/LT) is a functional test which rapidly assesses fibrinolytic profile. Tranexamic acid (TXA) is an efficient antifibrinolytic therapy.

METHODS

 We prospectively studied fibrinolysis and coagulation in 33 women included in the TRAAP2 trial, which aimed to assess the impact of TXA in preventing PPH following a cesarean delivery. TXA or placebo was randomly administered after childbirth as part of the TRAAP2 trial's protocol. Fibrinolytic (GFC/LT, plasma concentration of fibrinolysis activators and inhibitors) and hemostatic parameters were assayed at three sample times (TREF [T-reference] after anesthesia, T15 and T120minutes after TXA, or placebo administration).

RESULTS

 All cesarean deliveries were elective. In the placebo group, the clot lysis time assessed with GFC/LT significantly decreased between TREF and T120, indicating an activated fibrinolysis (44 [interquartile range, IQR: 40-48] vs. 34 [IQR: 30-36] minutes, p<0.001). In both TXA and placebo groups, significant fluctuations of the plasmatic concentrations of fibrinolytic mediators were noticed over time, suggesting fibrinolysis activation. Clot lysis time measured by GFC/LT was significantly increased in women of the TXA group as compared with those in the placebo group at T15 (120 [120-120] vs. 36 [34-41] minutes, p<0.001) and T120minutes (113 [99-120] vs. 34 [30-36] minutes, p<0.001) after drug administration, indicating a decreased in fibrinolysis in those women.

CONCLUSIONS

 GFC/LT evidenced fibrinolysis activation during cesarean delivery, linked to a decrease in fibrinolytic inhibitors. GFC/LT revealed a significant antifibrinolytic effect of TXA compared with placebo.

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.

Latest advances in postpartum hemorrhage management

Hemorrhage is the leading cause of maternal mortality worldwide. A maternal health priority is improving how healthcare providers prevent and manage postpartum hemorrhage (PPH). Because anesthesiologists can help facilitate how hospitals develop approaches for PPH prevention and anticipatory planning, we review the potential utility of PPH risk-assessment tools, bundles, and protocols. Anesthesiologists rely on clinical and diagnostic information for initiating and evaluating medical management. Therefore, we review modalities for measuring blood loss after delivery, which includes visual, volumetric, gravimetric, and colorimetric approaches. Point-of-care technologies for assessing changes in central hemodynamics (ultrasonography) and coagulation profiles (rotational thromboelastometry and thromboelastography) are also discussed. Anesthesiologists play a critical role in the medical and transfusion management of PPH. Therefore, we review blood ordering and massive transfusion protocols, fixed-ratio vs. goal-directed transfusion approaches, coagulation changes during PPH, and the potential clinical utility of the pharmacological adjuncts, tranexamic acid, and fibrinogen concentrate.

Viscoelastic haemostatic point-of-care assays in the management of postpartum haemorrhage: a narrative review

Viscoelastic haemostatic assays provide rapid testing at the bed-side that identify all phases of haemostasis, from initial fibrin formation to clot lysis. In obstetric patients, altered haemostasis is common as pregnancy is associated with coagulation changes that may contribute to bleeding events such as postpartum haemorrhage, as well as thrombosis events. In this narrative review, we examine the potential clinical utility of viscoelastic haemostatic assays in postpartum haemorrhage and consider the current recommendations for their use in obstetric patients. We discuss the clinical benefits associated with the use of viscoelastic haemostatic assays due to the provision of (near) real-time readouts with a short turnaround, coupled with the identification of coagulation defects such as hypofibrinogenaemia. The use of viscoelastic haemostatic assay-guided algorithms may be beneficial to diagnose coagulopathy, predict postpartum haemorrhage, reduce transfusion requirements and monitor fibrinolysis in women with obstetric haemorrhage. Further studies are required to assess whether viscoelastic haemostatic assay-guided treatment improves clinical outcomes, and to confirm the utility of prepartum viscoelastic haemostatic assay measurements for identifying patients at risk of postpartum haemorrhage.

Tranexamic Acid for Prevention of Hemorrhage in Elective Repeat Cesarean Delivery - A Randomized Study

BACKGROUND

The American College of Obstetricians and Gynecologists states that data is insufficient to recommend Tranexamic acid (TXA) prophylaxis for postpartum hemorrhage.

OBJECTIVE

This study's objective was to evaluate if prophylactic TXA reduces calculated blood loss versus placebo in women undergoing elective repeat cesarean delivery.

STUDY DESIGN

A double-blind, randomized, placebo-controlled trial, examining calculated blood loss with prophylactic doses of 1-gram of TXA given before skin incision and after placental delivery and standard uterotonics in women with singleton pregnancies at least 37 weeks' gestation, presenting for their second or third cesarean delivery under neuraxial anesthesia. The primary outcome was calculated blood loss at 24 hours. The calculation was based on the participant's height, weight, and the difference in hematocrit before the start of surgery and 24 hours after delivery. Prespecified secondary outcomes were quantification of maternal coagulation activity during the perioperative course. A sample size of 50 women per group was planned (N=100), based on a meta-analysis of mean reduction in blood loss after TXA.

RESULTS

723 women were screened, and 110 women were randomized as follows: 55 to TXA and 55 to placebo. The primary outcome of mean calculated blood for TXA (2274 ± 469 mL) and the placebo group (2407 ± 388 mL), p > 0.05. In the secondary outcomes, D-dimer levels were lower in the TXA group than the placebo group 24 hours after delivery (2.1 ± 1.2 µg/mL versus 4.3 ± 2.4 µg/mL), p < 0.001.

CONCLUSIONS

Prophylactic tranexamic acid did not decrease mean calculated blood loss. Significantly less participants had calculated blood loss greater than 2000 mL in the tranexamic acid group compared to the placebo group with lower levels of D-dimer at 24 hours.

Viscoelastic Hemostatic Assays for Postpartum Hemorrhage

This article discusses the importance and effectiveness of viscoelastic hemostatic assays (VHAs) in assessing hemostatic competence and guiding blood component therapy (BCT) in patients with postpartum hemorrhage (PPH). In recent years, VHAs such as thromboelastography and rotational thromboelastometry have increasingly been used to guide BCT, hemostatic adjunctive therapy and prohemostatic agents in PPH. The three pillars of identifying hemostatic competence include clinical observation, common coagulation tests, and VHAs. VHAs are advantageous because they assess the cumulative contribution of all components of the blood throughout the entire formation of a clot, have fast turnaround times, and are point-of-care tests that can be followed serially. Despite these advantages, VHAs are underused due to poor understanding of correct technique and result interpretation, a paucity of widespread standardization, and a lack of large clinical trials. These VHAs can also be used in cases of uterine atony, preeclampsia, acute fatty liver of pregnancy, amniotic fluid embolism, placental abruption, genital tract trauma, surgical trauma, and inherited and prepartum acquired coagulopathies. There exists an immediate need for a point-of-care test that can equip obstetricians with rapid results on developing coagulopathic states. The use of VHAs in predicting and treating PPH, although in an incipient state, can fulfill this need.

Tranexamic acid and obstetric hemorrhage: give empirically or selectively?

Antifibrinolytic agents such as tranexamic acid (TXA) inhibit the fibrinolytic pathway and protect blood clots from being degraded, thereby promoting hemostasis. They have been used to reduce blood loss in various settings including obstetrics. Based on current evidence, TXA can be considered as a therapeutic adjunct to control postpartum hemorrhage (PPH) after vaginal and cesarean deliveries, with earlier administration preferred. This strategy has been demonstrated to reduce mortality due to bleeding (but not the incidence of transfusion) in developing countries. On the other hand, the benefit-risk ratio of TXA has not been fully assessed in developed countries which have much lower PPH-related mortality rates and better access to other management modalities. As a proposed prophylactic agent to prevent PPH, the level of evidence is currently insufficient to recommend the routine use of TXA to prevent blood loss after vaginal and cesarean deliveries. The results of large new multicenter studies assessing the impact of TXA on maternal blood loss-related outcomes after cesarean delivery are awaited. While most studies to date have focused on empirical and one-size-fit-all dosing of TXA, more selective and individualized treatment protocols (possibly guided by functional coagulation assays) are needed to pave the way for safer and more effective use of this inexpensive and widely used medication.