The Daily Dose • Sunday, April 16, 2023

A Mother’s Blood…You Can’t Manage What You Don’t Measure

Adaora M. Chima, MBBS, MPH

Postpartum hemorrhage (PPH) remains a significant contributor to obstetric maternity and morbidity and the panelists of the session, “Postpartum Hemorrhage: Novel Assessments to Guide Perioperative Management and Improve Outcomes,” expertly highlighted the crisis as well as novel approaches to assessing obstetric hemorrhage, a key step to safe and efficient PPH management on Saturday, April 15, at the IARS Annual Meeting.

Co-sponsored by the Society for Obstetric Anesthesia and Perinatology (SOAP), this engaging session was moderated by Jaime Daly, MD, Assistant Professor in Anesthesiology and Obstetric Anesthesiologist at University of Colorado.

Trained in cardiac and obstetric anesthesia, Clemens Ortner, MD, MS, DESA, a Clinical Associate Professor at Stanford School of Medicine, was the first speaker to take the podium. With a presentation on the use of Transthoracic Echocardiography (TTE) in PPH, he described two clinical cases where TTE facilitated appropriate evaluation and resuscitation management in maternal deliveries complicated by severe PPH. In one instance, the presence of B-lines in a patient responding poorly to treatment informed a halt in further volume resuscitation as this sign could be indicative of pulmonary edema. He highlighted the usability of TTE for novice users. Dr. Ortner referenced study findings that demonstrated the ability of novice TTE users to obtain at least one viable and relevant TTE image following an educational workshop that included didactics, simulation and performance of a stipulated number of TTE scans.

TTE features of hypovolemia such as the kissing heart sign can be distinguished from distributive shock by measuring the left ventricular end diastolic area and challenges with image acquisition improve following resuscitation in the case of hypovolemia. He also stated the importance of performing FAST scans in the presence of hemodynamic instability, looking at bilateral upper quadrants for signs of intraabdominal bleeding. Quantifying blood in Morrison’s pouch in different patient positions during FAST exams can facilitate decisions to return to the operating room. He cautioned that implants like breast implants have been known to obfuscate TTE views. Inferior vena cava diameter can be used to assess CVP but has limitations in evaluating fluid responsiveness and should be used with other clinical information. Maneuvers such as passive leg raising can improve fluid responsiveness evaluation.

Cristina Wood, MD, Associate Professor and obstetric anesthesiologist at University of Colorado School of Medicine, followed with a presentation on a novel FDA approved technology to assess compensatory reserve index (CRI) in patients undergoing delivery. The CRI device resembles a pulse oximeter and is similarly strapped to a digit. It is based off algorithms from Department of Defense projects designed for battlefield assessments of injury and hemodynamic status, and has diverse clinical applications. It is an earlier detection system than vital signs (can be delayed by physiologic compensation), and demonstrates higher negative predictive value than systolic blood pressure. It is easy to use and provides real time updates, thus can be used to assess the effectiveness of interventions.

A prospective observational study on non-emergent cesarean sections showed a decrease in CRI in all patients over the perioperative period, worse in patients with hemorrhage. Placental auto transfusion was associated with CRI stabilization, which declined with subsequent bleeding. Low risk patients were noted to have higher CRI levels than high risk patients and patients who experienced PPH had a decreased CRI from the outset. This raises the possibility of using CRI as a PPH predictive tool and begs further investigation as does the cause of lower CRIs in high-risk patients. Dr. Wood concluded by stating that CRI promises to be a useful tool in managing PPH, in conjunction with other tools like TTE.

Michaela Farber, MD, MS, an Associate Professor and Chief of Obstetric Anesthesiology at Brigham and Women’s Hospital, continued the session with a presentation on, “Systems to Assist in Assessment of Quantitative Blood Loss (QBL)” in obstetrics. She expounded on the gross inaccuracy of visual estimation of obstetric blood loss, potentially causing unnecessary or delayed interventions, both dangerous scenarios. Underestimation can be as high as 16-41% in the absence of calibrated drapes. Existing research shows that approximately 75% of maternal mortality/morbidity from PPH is preventable. The importance of the role of PPH management in decreasing this statistic is underscored by national and international consensus bundles on hemorrhage management and accurate measurement of QBL is a crucial step in ensuring appropriate treatment.

Dr. Farber introduced methods of quantitative blood loss assessment including calibrated drapes, gravimetry systems (direct blood collection and weight of blood-soaked materials), and colorimetry. The latter is very accurate but can be impractical in the perioperative setting.

Multiple salient studies demonstrate that QBL improves detection of PPH, lowers transfusion rates and decreases associated morbidity. However, a challenge to evaluating its impact is the difficulty in isolating its effect from other items in the PPH bundle. QBL should be used with other clinical data for a complete assessment. Dr. Wood encouraged performing audits of pre- and post-hemoglobin to compare with documented QBL.

She concluded by explaining that successful implementation requires teamwork amongst obstetric personnel, the necessary education can be intensive and needs to be continuous to bridge gaps in the event of high personnel turnover.

Alexander Butwick, MBBS, FRCA, MS, obstetric anesthesiologist and Professor of Anesthesiology, Perioperative and Pain Medicine at Stanford School of Medicine, shared insights on the use of Rotational Thromboelastometry (ROTEM) and Thromboelastography (TEG) in PPH. ROTEM and TEG are both modalities that measure viscoelastic characteristics of clot formation and lysis, used to identify multiple coagulation defects for targeted treatment. Evaluation of clinical data has shown that 31% of examined obstetric transfusions did not have identified triggers for transfusion, likely due to long wait times for lab results. Both American and European Societies of Anesthesia have featured TEG and ROTEM as useful tools in obstetric hemorrhage management. They both provide real time physiologic data at the bedside that can guide diagnosis and treatment in obstetric hemorrhage.

Retrospective studies have shown that viscoelastic hemostatic assay (VHA) algorithms lead to faster clinical management and improve outcomes. Randomized control trials (RCTs) are hindered by problems with patient recruitment. Potential challenges to implementation include cost, education of staff and logistical issues with storing the devices.

Next generation devices such as TEG 6S, and ROTEM sigma are cartridge based and have 70% sensitivity and 90% specificity for hypofibrinogenemia. Fibrinogen less than 200mg/dl has a 100% PPV for progression to severe PPH and a 2.7-12-fold increased risk, with a 100% PPV for transfusion. Fibrin based clot formation is an early and rapid biomarker that can be used to make early diagnosis and prompt treatment. Dr. Butwick reminded the audience of the importance of rechecking levels following treatment.

PPH remains a significant contributor to maternal morbidity and mortality. In addition to clinical evaluations, the use of technologies such as TTE, CRI, viscoelastic profile tests and appropriate quantification of obstetric blood loss can effectively improve timely diagnosis and management of obstetric hemorrhage with concomitant reduction in maternal mortality due to PPH.