2.1

Rationale for use of QBL

Cumulative and accurate assessment of blood loss is essential for the management of PPH. Quantification of blood loss is a key element of the NPMS bundle and is recommended for all deliveries by national societies, including the American College of Obstetricians and Gynecologists (ACOG), AWHONN, and the California Maternal Quality Care Collaborative (CMQCC) [ , ]. Delayed recognition of excessive blood loss and inaccurate estimated blood loss (EBL) precludes timely PPH treatment [ , ]. Increases in delivery blood loss volume above PPH thresholds should trigger the activation of a PPH protocol to promptly escalate care, as timely identification of PPH influences patient outcomes and morbidity.

Blood loss measurement is often inaccurate and underestimated after both vaginal and cesarean delivery when based on visual estimation alone, resulting in delayed PPH diagnosis and treatment [ ]. While visual EBL is readily available, feasible, and easy to perform, it has been shown to underestimate large volume loss while overestimating small volume loss. Toledo et al. found that visual EBL accuracy was improved with use of calibrated drapes compared to noncalibrated drapes in a simulation-based vaginal delivery study [ ]. Worse visual underestimation of blood loss occurred at larger, clinically significant blood volumes, with a 41% error at 2000 mL versus a 16% error at 300 mL using noncalibrated drapes [ ].

Quantitative assessment of postpartum blood loss is associated with enhanced recognition of PPH [ ]. In an observational study comparing visual and quantitative blood loss (QBL) measurements, Katz et al. compared the management and outcomes of 7618 deliveries [ ]. For vaginal deliveries utilizing the QBL method, there were fewer postpartum transfusions and greater use of secondary uterotonics. For cesarean deliveries, there was a decrease in the quantity of packed red blood cells (pRBCs) transfused when QBL was used [ ].

2.2

Summary of methods

There are multiple QBL methods including gravimetry, use of calibrated V-drapes or canisters, colorimetric techniques, or a combination. Each modality has its advantages and disadvantages ( Table 1 ) which must be considered for their influence on QBL accuracy.

• a.
  

  Gravimetry.

Gravimetry, first described by Wangensteen et al., is used to quantify blood loss by assessing the difference in weight of sponges before and after surgical use, yielding the total fluid weight [ ]. In gravimetry calculations, 1 g is equivalent to 1 mL of blood loss. Gravimetry can overestimate blood loss if sponge absorption of non-sanguineous fluids is not excluded (i.e., irrigation and/or amniotic fluid). In addition, blood loss may be underestimated if blood-saturated surgical drapes or under-body pads are not weighed [ ]. Doctorvaladan et al. compared visual EBL, gravimetric QBL, and colorimetric techniques to determine cesarean delivery blood loss [ ]. The study showed that visual EBL and gravimetric QBL were inferior to the colorimetric technique [ ]. A secondary study by Thurer et al. was performed to analyze sources of inaccuracy using the gravimetric method [ ]. Both over and underestimation occurred, diverging markedly from the calculated (hemoglobin assayed) blood loss [ ]. Gravimetry alone is considered a less optimal method of QBL quantitation [ ].

• b.
  

  Calibrated V-drape

The calibrated V-drape is a direct method for measuring blood loss when it collects in a calibrated collection pouch placed beneath the patient.

Zhang et al. evaluated the effectiveness of the calibrated V-drape in measuring blood loss and its role in reducing PPH incidence across 78 maternity units in 13 countries [ ]. The authors hypothesized that direct, objectively measured blood loss may prompt earlier provider action during excessive blood loss compared with visual assessment. However, the rate of PPH was not lower in cases that used calibrated V-drapes compared to visual EBL. This negative finding may be explained by incomplete compliance and/or incorrect use of the collector bag in the intervention group. However, it also may be that QBL in isolation, without an associated treatment protocol, may not be sufficient to change PPH management or morbidity [ ].

In a review of methods for blood loss estimation after vaginal birth, Diaz et al. compared direct measurement using calibrated drapes versus visual estimation and gravimetric techniques [ ]. There was unsatisfactory evidence to support any one method for estimating vaginal delivery blood loss [ ]. Ambardekar et al. compared the calibrated V-drape method to gravimetry in 900 parturients undergoing vaginal delivery [ ]. The mean blood loss in the calibrated V-drape group was significantly higher compared to the gravimetric group. Amniotic fluid contamination may have led to an overestimation of blood loss in the calibrated V-drape group, while inability to weigh all sanguineous items may have led to an underestimation in the gravimetric group. This study illustrated the various limitations of measurement techniques that need to be taken into account when performing QBL in obstetrics [ ].

• c.
  

  Colorimetric technologies

Colorimetric methods for QBL account for and exclude non-sanguineous contamination to reduce the overestimation of blood loss that can occur with the gravimetric method. The Triton system with Feature Extraction Technology (FET; Stryker, Kalamazoo, MI, USA) uses tablet-based computer vision algorithms to measure blood loss [ ]. The system uses fine-grained detection and color density‐based algorithmic calculations to remove the effects of non-sanguineous fluids, resulting in a cumulative measured hemoglobin value [ , ].

Holmes et al. compared gravimetry and colorimetry to the gold standard of manual rinsing of laparotomy sponges to determine hemoglobin content [ ]. The Triton system provided a more accurate measure of hemoglobin content on laparotomy sponges compared to the gravimetric method, based on a strong positive linear correlation (r = 0.93; P < 0.0001) and the Bland-Altman analysis bias of 9.0 g [95% confidence interval (CI): 6.5–11.5 g] of hemoglobin [ ]. Bland-Altman analysis of blood loss on sponges using the gravimetric method showed a significant positive bias of 466 mL (overestimation) with corresponding upper and lower limits of agreement of −171 ml and 1103 ml, respectively [ ]. Ongoing refinement of colorimetric techniques will allow for continued improvement in QBL accuracy.

• d.
  

  Practical Application

Our institution uses a combination of QBL methods to provide a comprehensive assessment that is context-appropriate. For both vaginal and cesarean delivery, automated systems are used that incorporate a combination of gravimetry, calibrated receptacles, or colorimetry. Each labor and delivery room is equipped with a gravimetric scale linked to an iPad. After every vaginal delivery, the nursing staff weighs saturated sponges for gravimetric QBL. Blood collected in a calibrated V-drape beneath the patient is added to the gravimetric QBL for total QBL. Team members are vigilant in assessing the contribution of amniotic fluid and subtracting it such that it does not factor into the overall QBL. For cesarean delivery, QBL is achieved with the following: 1) use of FET to assess blood saturation of sponges based on hemoglobin mass 2) use of FET to assess the density of blood contained in the suction canister (this excludes other fluids in the canister such as amniotic fluid) 3) visual assessment of the quantity of blood contained within surgical drapes or within V-drapes (for hysterectomy cases).

Improved provider awareness of QBL is essential to elicit a quick response to PPH. Our hemorrhage protocol includes an automated hemorrhage alert system via phone and watch systems that notify the obstetric anesthesiology team when blood loss is greater than 500 mL after vaginal delivery. The 500 mL threshold to trigger response was chosen after a pilot study demonstrated that anesthesia interventions were provided for 50% of such triggered alerts [ ]. An anesthesia provider responds to each of these alerts with a PPH kit containing secondary uterotonics, the antifibrinolytic agent tranexamic acid (TXA), vasopressors, intravenous access supplies, and blood collection tubes. The provider assesses the patient’s clinical status, helps dictate resuscitation goals, initiates transfusions, administers medications, and gains additional labs and intravenous access as needed. This practice allows for rapid treatment and response to hemorrhage with timely, multidisciplinary escalation of care.

2.3

Future directions

• 
  

  Further research is required to evaluate whether use of QBL impacts PPH-related maternal morbidity and mortality. Quality improvement studies to refine QBL methodology and devices for better accuracy are also warranted. Failure to account for irrigation on sponges may lead to overestimation of gravimetric QBL, and unnecessary interventions for PPH. Conversely, late entry of sponge weights in a vaginal delivery system may preclude timely activation of response to hemorrhage, even with automated alerts programmed. A system that incorporates abnormal vital signs and clinical presentation with QBL systems may expedite assessment and management of PPH, and timely escalation of care.

3.1

Overview

During periods of severe hemorrhage, bleeding may surpass the ability to prepare cross-matched blood products and require activation of a massive transfusion protocol (MTP), another key component of the NPMS hemorrhage bundle [ ]. A traditional MTP has a predefined ratio of pRBCs, fresh frozen plasma (FFP), and platelets per pack, allowing for blood to be delivered in a rapid and timely manner to aid in resuscitation. This allows for more streamlined communication between providers and the blood bank and efficient delivery of products for an unstable bleeding patient. Importantly, MTPs do not serve as therapies but, critically, as organizational tools to bring blood bank products to the patient in a standardized and efficient manner, allowing for the clinical team to have all necessary blood product resources readily available.

Obstetric-specific MTPs are warranted because obstetric and trauma-induced bleeding differ in pathophysiology [ ]. The timing and mechanism of coagulopathy differ depending on the etiology of the obstetric hemorrhage and duration of resuscitation [ ]. In cases of uterine atony and surgical trauma-induced bleeding, coagulopathy is rare [ ]. When bleeding is uncontrolled and large-volume replacement occurs, dilutional coagulopathy can evolve [ , ]. Acquired coagulopathy can also ensue due to loss of clotting factors [ ]. In the setting of placental abruption and amniotic fluid embolism, a consumptive coagulopathy occurs and can ultimately lead to disseminated intravascular coagulation (DIC) [ , ]. Recent studies have shown that acquired coagulation abnormalities such as fibrinogen deficiency can also be associated with obstetric hemorrhage [ ].

Trauma-based MTPs frequently use high pRBC to FFP ratios (1:1), which are designed to mimic whole blood transfusion. In the obstetric population, unless rapid and profound blood loss occurs, most patients do not benefit from such transfusion ratios due to the low likelihood of coagulopathy and an intrinsically higher serum fibrinogen than plasma fibrinogen content (see below). At our institution, we utilize an obstetric-specific emergency hemorrhage transfusion algorithm ( Fig. 1 ) that specifies release of fibrinogen concentrate or cryoprecipitate as fibrinogen-rich sources, as well as focused laboratory testing to identify coagulopathy and hypofibrinogenemia [ ].

Transfusion algorithm for obstetric hemorrhage. Used with permission, R.M. Kaufman, A.D. Miller, and S.M. Seifert.

3.2

Role of fibrinogen in obstetric hemorrhage

Acquired hypofibrinogenemia occurs in the setting of imbalanced transfusion of blood products and loss or consumption of coagulation factors during PPH. Fibrinogen plays a critical role in hemostasis during obstetric hemorrhage; Charbit et al. found that a serum fibrinogen of < 200 mg/dL after the onset of PPH had a positive predictive value of 100% for progression to severe PPH (decrease of hemoglobin > 4 g/dL, transfusion of at least four pRBC units, hemostatic intervention (angiographic embolization, surgical arterial ligation, hysterectomy), or death [ ]. For every 100 mg/dL decrease in fibrinogen, there was a 2.63-fold higher risk of severe PPH (95% CI: 1.66–4.16; P < 0.0001) [ ].

When acquired hypofibrinogenemia occurs during PPH, FFP is not the preferred method for fibrinogen replacement due to its low fibrinogen concentration and the large volume required for fibrinogen repletion [ , ]. Administration of FFP in early PPH can paradoxically lower fibrinogen levels, as the fibrinogen concentration in FFP is lower than the maternal serum fibrinogen level at term gestation [ ]. Similarly, the high volume of FFP required to raise the fibrinogen level exacerbates dilutional anemia to the point of increasing pRBC transfusion requirement [ , ]. Large volumes of FFP place the patient at increased risk for transfusion-related acute lung injury (TRALI) (7 to 8-fold increase compared to RBCs) and transfusion-associated circulatory overload (TACO) [ , , , ]. Superior sources for fibrinogen replacement are cryoprecipitate and fibrinogen concentrate. Cryoprecipitate requires a smaller transfusion volume but is pooled from multiple donors. Fibrinogen concentrate reduces the risk of infectious transmission and immunologic reaction from exposure to multiple donors required for cryoprecipitate [ ]. Two examples of fibrinogen concentrate are Fibryga® (Octapharma AG) and RiaSTAP® (CSL Behring GmbH) [ , ].

Fibrinogen concentrate is a human plasma-derived, pasteurized concentrate powder. Each vial contains approximately 1 g of fibrinogen concentrate. Fibryga® can be stored at room temperature (of 2–25 °C) while RiaSTAP® is stored at refrigerated temperatures of 2–8 °C; neither require thawing or cross-matching [ , ]. Fibrinogen concentrate is reconstituted with 50 mL of sterile water and can be rapidly administered over 10 min during hemorrhage. The study used to develop the dosing equation for fibrinogen concentrate was performed in 12 non-pregnant patients with hypofibrinogenemia [ ]. Further studies are needed to determine the appropriate fibrinogen dose-response equation in the obstetric population. In massive hemorrhage, repletion with fibrinogen concentrate may not be optimal, as it lacks von Willebrand factor and, depending on the formulation, factor XIII, which is necessary for clot stabilization.

The role of pre-emptive treatment with fibrinogen concentrate in decreasing the need for pRBC transfusion in patients with PPH has been assessed. No benefit was found for the use of pre-emptive treatment of PPH with fibrinogen concentrate (2 g) [ ]. The impact of fibrinogen replacement guided by rotational thromboelastometry (ROTEM) point-of-care (POC) coagulation testing was evaluated by Collins et al. who randomized 55 women with PPH and FIBTEM A5 ≤ 15 mm to receive either fibrinogen concentrate or placebo [ ]. Fibrinogen concentrate replacement at this threshold did not influence the number of blood products transfused, and a threshold of ≤ 12 mm has been proposed based on a subgroup analysis [ ].

3.3

Role of POC testing to guide transfusion

The etiology of PPH, co-morbid conditions, and type of coagulopathy influence PPH transfusion goals, demonstrating that a standard, universal approach (i.e., MTP) may not be as successful as POC-guided transfusion approaches. There is growing clinical evidence to support the use of POC viscoelastic hemostatic assays (VHA), including thromboelastography and ROTEM, in place of fixed ratio blood product administration during PPH. POC VHAs offer valuable, rapid information on coagulation status for tailored product transfusion to specifically replete fibrinogen or other clotting factors and platelets, and detect and treat hyperfibrinolysis.

De Lloyd et al. demonstrated that coagulation factors were diluted when blood loss exceeded 3 L, suggesting that fixed-ratio transfusion methods during PPH, particularly with FFP, may lead to excessive transfusion of blood products and undertreatment of women with coagulopathy [ ]. In addition, a subgroup of patients developed severe early coagulopathy due to hyperfibrinolysis and hypofibrinogenemia (1/1000 cases), in whom focused treatment with antifibrinolytic agents and fibrinogen replacement would be beneficial [ ].

POC testing may lower overall transfusion rate and associated transfusion-related complications and morbidity [ ]. Mallaiah et al. compared transfusion requirements during obstetric hemorrhage before and after the introduction of fibrinogen concentrate repletion that was guided by ROTEM FIBTEM A5 results [ ]. Compared to the fixed transfusion approach using 1:1:1 (pRBCs:FFP:platelets), the introduction of the FIBTEM-guided fibrinogen repletion was associated with decreased transfusion requirement and the concomitant risk of TACO [ ]. A larger 4-year observational study by the same center found a decrease in the number of units transfused and total volume of blood products transfused when a “shock pack” method was replaced by a FIBTEM-based algorithm for treatment of obstetric hemorrhage [ ]. Specifically, there was a statistically significant decrease in FFP , cryoprecipitate, platelets, and fibrinogen concentrate administration, and a reduction in TACO [ ]. In another 2-year prospective cohort study, Bell et al. implemented POC VHA to guide transfusion goals as part of a Wales national quality improvement initiative [ ]. This targeted approach to transfusion resulted in an increase in use of VHA, a decrease in FFP administration, and an increase in fibrinogen administration [ ]. Taken together, these data support moving away from fixed ratio transfusion methods in PPH and use of POC VHA-guided therapy to enable individualized, targeted hemostatic treatment and avoid unnecessary transfusion and associated transfusion morbidity.

4.1

Rationale: Tranexamic acid for postpartum hemorrhage treatment

The World Maternal ANtifibrinolytic trial (WOMAN trial), an international, multicenter placebo-controlled study, investigated the effect of TXA compared to placebo in 20,060 patients who experienced PPH after vaginal or cesarean delivery in predominantly low- and middle-income countries [ ]. The study found that TXA reduced the risk of death from PPH compared to placebo (mortality rate, 1.5% vs 1.9%; relative risk (RR) = 0.81; 95% CI: 0.65–1.00; P = 0.045), when administered within 3 h of birth (RR = 0.69; 95% CI: 0.52–0.9). There was no difference in morbidity outcomes of transfusion or hysterectomy.

The external validity of the WOMAN trial in high-resource settings has been questioned [ ]. The study’s secondary analysis highlighted that no deaths occurred in high-resource settings [ ]. In a nationwide cohort study of 1260 patients with PPH in the Netherlands, there was no reduced risk of morbidity (classified as hysterectomy, vessel ligation, B-lynch suture, arterial embolization, or ICU admission) or death in patients exposed to early TXA compared with those who had no TXA or late TXA exposure (adjusted odds ratio (aOR) = 0.92; 95% CI: 0.66–1.27) [ ].

4.2

Tranexamic acid prophylaxis for vaginal delivery

A multicenter randomized placebo-controlled trial (TRAAP) evaluated the effect of prophylactic TXA on PPH prevention after vaginal delivery [ ]. In this study, 4079 patients were randomized to receive 1 g TXA or placebo after vaginal delivery and umbilical cord clamping. The PPH rate was not different between the TXA and placebo groups (8.1% vs 9.8%; RR = 0.83; 95% CI: 0.68–1.01; P = 0.07), nor were there differences in peripartum hemoglobin change or transfusion requirement. Meta-analyses combining data from multiple trials have shown conflicting results regarding TXA’s efficacy in preventing PPH after vaginal delivery [ , ].

4.3

Tranexamic acid prophylaxis for cesarean delivery

Another multicenter randomized placebo-controlled trial (TRAAP2) evaluated the effect of prophylactic TXA on PPH prevention after cesarean delivery [ ]. In this study, 4551 patients were randomized to receive either 1 g TXA or placebo after umbilical cord clamping. The primary outcome of PPH when using calculated (hemoglobin assayed) blood loss was 16% lower for the TXA group compared to the placebo group (26.7% vs 31.6%; aRR = 0.84; 95% CI: 0.75–0.94; P = 0.003). However, no between-group differences were reported for clinical PPH outcomes of mean gravimetric QBL, PPH classified by a QBL > 1000 mL, or postpartum transfusion requirement. In the largest study to date, the US Maternal-Fetal Medicine Units Network performed a multicenter placebo-controlled trial enrolling 11,000 patients to receive TXA versus placebo during cesarean delivery [ ]. There was no difference in the composite outcome of either death or transfusion (TXA: 3.6% vs placebo: 4.3%; aRR = 0.89; 95.26% CI: 0.74–1.07; P = 0.19). Similar to the TRAAP2 findings, there were no significant between-group differences in rates of PPH, surgical or radiologic intervention, or blood transfusion. While meta-analyses of TXA prophylaxis for cesarean delivery studies have suggested benefit [ ], such analyses have been criticized for including substandard trials with unreliable data, selective reporting bias, and poor overall quality [ ]. The lack of benefit demonstrated in these two high-quality, large RCTs is compelling to suggest that TXA prophylaxis for PPH after cesarean delivery is unwarranted. Studies to further identify higher-risk groups that may benefit from TXA prophylaxis are needed.

4.4

Mechanism of action

The minimum serum level of TXA to achieve antifibrinolytic effect is thought to be 10–20 mcg/mL. Seifert et al. demonstrated that administration of 1g IV TXA to patients at high risk for PPH having cesarean delivery yielded a peak serum level of 59.8 mcg/mL 3 min after administration, with serum levels sustained higher than 10 mcg/mL for more than 1 h during surgery [ ]. In patients having cesarean delivery randomized to receive TXA 1 g, TXA 0.5 g, or placebo, d-dimer as a surrogate for hyperfibrinolysis were increased in placebo, and lowered with superior dose response to 1 g TXA [ ]. Taken together, these and other studies are reassuring to suggest that 1 g TXA causes adequate hyperfibrinolysis while avoiding serum levels for thrombosis risk.

4.5

Safety

Safety considerations for TXA must be prioritized given its ubiquitous administration to patients with PPH. Vigilance when dosing neuraxial medications is of paramount importance to eliminate the risk of accidental intrathecal or epidural injection of TXA. Numerous reports of this catastrophic drug error continue to be published, and the associated mortality in obstetric patients is up to 86% [ ]. The US Food and Drug Administration (FDA) issued an alert recommending proper handling, labeling, and storage of TXA on labor and delivery units to eliminate this iatrogenic source of maternal morbidity and mortality.

5.1

Overview

The pathophysiology of placenta accrete spectrum (PAS) involves abnormal anchoring of placental villi to the uterine myometrium (accreta), invasion into the myometrium (increta), or invasion through the myometrium to the uterine serosa or adjacent tissues (percreta), rather than the decidua [ ]. The International Federation of Gynecology and Obstetrics (FIGO) consensus panel classification system is the most widely accepted pathologic classification of PAS ( Table 2 ) [ ].

Table 2

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