A systematic review of the relationship between blood loss and clinical signs

Physiologic validation of the Compensatory Reserve Metric obtained from pulse oximetry: A step toward advanced medical monitoring on the battlefield

BACKGROUND

The Compensatory Reserve Metric (CRM) provides a time sensitive indicator of hemodynamic decompensation. However, its in-field utility is limited because of the size and cost-intensive nature of standard vital sign monitors or photoplethysmographic volume-clamp (PPG VC ) devices used to measure arterial waveforms. In this regard, photoplethysmographic measurements obtained from pulse oximetry may serve as a useful, portable alternative. This study aimed to validate CRM values obtained using pulse oximeter (PPG PO ).

METHODS

Forty-nine healthy adults (25 females) underwent a graded lower body negative pressure (LBNP) protocol to simulate hemorrhage. Arterial waveforms were sampled using PPG PO and PPG VC . The CRM was calculated using a one-dimensional convolutional neural network. Cardiac output and stroke volume were measured using PPG VC . A brachial artery catheter was used to measure intra-arterial pressure. A three-lead electrocardiogram was used to measure heart rate. Fixed-effect linear mixed models with repeated measures were used to examine the association between CRM values and physiologic variables. Log-rank analyses were used to examine differences in shock determination during LBNP between monitored hemodynamic parameters.

RESULTS

The median LBNP stage reached was 70 mm Hg (range, 45-100 mm Hg). Relative to baseline, at tolerance, there was a 47% ± 12% reduction in stroke volume, 64% ± 27% increase in heart rate, and 21% ± 7% reduction in systolic blood pressure ( p < 0.001 for all). Compensatory Reserve Metric values obtained with both PPG PO and PPG VC were associated with changes in heart rate ( p < 0.001), stroke volume ( p < 0.001), and pulse pressure ( p < 0.001). Furthermore, they provided an earlier detection of hemodynamic shock relative to the traditional metrics of shock index ( p < 0.001 for both), systolic blood pressure ( p < 0.001 for both), and heart rate ( p = 0.001 for both).

CONCLUSION

The CRM obtained from PPG PO provides a valid, time-sensitized prediction of hemodynamic decompensation, opening the door to provide military medical personnel noninvasive in-field advanced capability for early detection of hemorrhage and imminent onset of shock.

LEVEL OF EVIDENCE

Diagnostic Tests or Criteria; Level III.

Management of Respiratory Failure in Hemorrhagic Shock

Hemorrhagic shock results in acute respiratory failure due to respiratory muscle fatigue and inadequate pulmonary blood flow. Because positive pressure ventilation can reduce venous return and cardiac output, clinicians should use the minimum possible mean airway pressure during assisted or mechanical ventilation, particularly during episodes of severe hypovolemia. Hypoperfusion also worsens dead space fraction. Therefore, clinicians should monitor capnography during mechanical ventilation and recognize that hypercapnia may be treated with fluid resuscitation rather than increasing minute ventilation.

LDSG-Net: an efficient lightweight convolutional neural network for acute hypotensive episode prediction during ICU hospitalization

Objective. Acute hypotension episode (AHE) is one of the most critical complications in intensive care unit (ICU). A timely and precise AHE prediction system can provide clinicians with sufficient time to respond with proper therapeutic measures, playing a crucial role in saving patients' lives. Recent studies have focused on utilizing more complex models to improve predictive performance. However, these models are not suitable for clinical application due to limited computing resources for bedside monitors.Approach. To address this challenge, we propose an efficient lightweight dilated shuffle group network. It effectively incorporates shuffling operations into grouped convolutions on the channel and dilated convolutions on the temporal dimension, enhancing global and local feature extraction while reducing computational load.Main results. Our benchmarking experiments on the MIMIC-III and VitalDB datasets, comprising 6036 samples from 1304 patients and 2958 samples from 1047 patients, respectively, demonstrate that our model outperforms other state-of-the-art lightweight CNNs in terms of balancing parameters and computational complexity. Additionally, we discovered that the utilization of multiple physiological signals significantly improves the performance of AHE prediction. External validation on the MIMIC-IV dataset confirmed our findings, with prediction accuracy for AHE 5 min prior reaching 93.04% and 92.04% on the MIMIC-III and VitalDB datasets, respectively, and 89.47% in external verification.Significance. Our study demonstrates the potential of lightweight CNN architectures in clinical applications, providing a promising solution for real-time AHE prediction under resource constraints in ICU settings, thereby marking a significant step forward in improving patient care.

Abnormal obstetric shock index and associated factors among immediate postpartum women following vaginal delivery at a tertiary hospital in southwestern Uganda

BACKGROUND

Early recognition of haemodynamic instability after birth and prompt interventions are necessary to reduce adverse maternal outcomes due to postpartum haemorrhage. Obstetric shock Index (OSI) has been recommended as a simple, accurate, reliable, and low-cost early diagnostic measure that identifies hemodynamically unstable women.

OBJECTIVES

We determined the prevalence of abnormal obstetric shock index and associated factors among women in the immediate postpartum period following vaginal delivery at Mbarara Regional Referral Hospital (MRRH) in southwestern Uganda.

METHODS

We conducted a cross-sectional study at the labour suite and postnatal ward of MRRH from January 2022 to April 2022. We systematically sampled women who had delivered vaginally, and measured their blood pressures and pulse rates at 1 h postpartum. We excluded mothers with hypertensive disorders of pregnancy. Sociodemographic, medical and obstetric data were obtained through interviewer-administered questionnaires. The prevalence of abnormal OSI was the proportion of participants with an OSI ≥ 0.9 (calculated as the pulse rate divided by the systolic BP). Logistic regression analysis was used to determine associations between abnormal OSI and independent variables.

RESULTS

We enrolled 427 women with a mean age of 25.66 ± 5.30 years. Of these, 83 (19.44%), 95% CI (15.79-23.52) had an abnormal obstetric shock index. Being referred [aPR 1.94, 95% CI (1.31-2.88), p = 0.001], having had antepartum haemorrhage [aPR 2.63, 95% CI (1.26-5.73), p = 0.010] and having a visually estimated blood loss > 200 mls [aPR 1.59, 95% CI (1.08-2.33), p = 0.018] were significantly associated with abnormal OSI.

CONCLUSION

Approximately one in every five women who delivered vaginally at MRRH during the study period had an abnormal OSI. We recommend that clinicians have a high index of suspicion for haemodynamic instability among women in the immediate postpartum period. Mothers who are referred in from other facilities, those that get antepartum haemorrhage and those with estimated blood loss > 200mls should be prioritized for close monitoring. It should be noted that the study was not powered to study the factors associated with AOSI and therefore the analysis for factors associated should be considered exploratory.

Quantification of blood loss for the diagnosis of postpartum hemorrhage: a systematic review and meta-analysis

OBJECTIVE

to compare the effectiveness of different diagnostic methods to estimate postpartum blood volume loss.

METHODS

a systematic review of effectiveness according to PRISMA and JBI Protocol. Searches in PubMed/MEDLINE, LILACS, Scopus, Embase, Web of Science and CINAHL, with descriptor "Postpartum Hemorrhage" associated with keyword "Quantification of Blood Loss". Tabulated extracted data, presented in metasynthesis and meta-analysis was applied to quantitative data. To assess risk of bias, JBI Appraisal Tools were applied.

RESULTS

fourteen studies were included, published between 2006 and 2021. Quantification of loss by any method was superior to visual estimation and is highly recommended, however the studies' high heterogeneity did not allow estimating this association.

CONCLUSION

the studies' high heterogeneity, with a probable margin of error given the uncontrolled factors, indicates the need for further studies, however quantification proved to be effective in relation to visual estimate. PROSPERO registration CRD 42021234486.

Patient blood management to minimize transfusions during the postpartum period

Patient blood management is an evidence-based concept that seeks to minimize blood loss by maintaining adequate hemoglobin levels and optimizing hemostasis during surgery. Since the coronavirus disease 2019 pandemic, patient blood management has gained significance due to fewer blood donations and reduced amounts of blood stored for transfusion. Recently, the prevalence of postpartum hemorrhage (PPH), as well as the frequency of PPH-associated transfusions, has steadily increased. Therefore, proper blood transfusion is required to minimize PPH-associated complications while saving the patient's life. Several guidelines have attempted to apply this concept to minimize anemia during pregnancy and bleeding during delivery, prevent bleeding after delivery, and optimize recovery methods from anemia. This study systematically reviewed various guidelines to determine blood loss management in pregnant women.

[Postpartum Hemorrhage]

Postpartum hemorrhage (PPH) affects about 4% of all deliveries in high-income countries and continues to rise, a trend attributable to the increase in caesarean section rates and maternal morbidity. Preventive measures such as the precautionary administration of uterotonics effectively reduce the risk of severe bleeding irrespective of birth mode. As a time-critical condition and a significant contributor to adverse maternal outcomes, PPH needs to be diagnosed early by measuring, not estimating, blood losses. Institutional treatment algorithms should be available to guide stage-based interdisciplinary management without delay. The main therapy goals are to identify the etiology and stop the bleeding by using uterotonics and mechanical and surgical interventions, to restore hemodynamic stability by volume and transfusion therapy and to optimize hemostasis by laboratory- and viscoelastic assay-guided factor replacement. This review highlights current recommendations for prevention, diagnosis and treatment of PPH.

Health care provider decision-making and the quality of maternity care: An analysis of postpartum care in Kenyan hospitals

Evidence suggests that health care providers' non-adherence to clinical guidelines is widespread and contributes to poor patient outcomes across low- and middle-income countries. Through observations of maternity care in Kenya, we found limited adherence to guideline-recommended active monitoring of patients for signs of postpartum hemorrhage, the leading cause of maternal mortality, despite providers' having the necessary training and equipment. Using survey vignettes conducted with 144 maternity providers, we documented evidence consistent with subjective risk and perceived uncertainty driving providers' decisions to actively monitor patients. Motivated by these findings, we introduced a simple model of providers' decision-making about whether to monitor a patient, which may depend on their perceptions of risk, diagnostic uncertainty, and the value of new information. The model highlights key trade-offs between gathering diagnostic information through active monitoring versus waiting for signs and symptoms of hemorrhage to manifest. Our work provides a template for understanding provider decision-making and could inform interventions to encourage more proactive obstetric care.

Evaluation During Postpartum Hemorrhage

Postpartum hemorrhage is an obstetric emergency that is the leading and the most preventable cause of maternal death that occurs on the day of birth. The treatment of postpartum hemorrhage in a timely fashion is crucial to prevent morbidity and mortality. The accurate assessment of blood loss during delivery and the postpartum period remains a major challenge. Hence, it is imperative to have a standardized evaluation strategy for accurate assessment of blood loss, adequate classification of hemorrhage, and timely initiated interventions. The multidisciplinary evaluation strategy should be in place regardless of the delivery route.

Coagulation management and transfusion in massive postpartum hemorrhage

PURPOSE OF REVIEW

Excessive bleeding during and following childbirth remains one of the leading causes of maternal mortality.

RECENT FINDINGS

Current guidelines differ in definitions and recommendations on managing transfusion and hemostasis in massive postpartum hemorrhage (PPH). Insights gained from trauma-induced coagulopathy are not directly transferable to the obstetric population due to gestational alterations and a differing pathophysiology.

SUMMARY

Factor deficiency is uncommon at the beginning of most etiologies of PPH but will eventually develop from consumption and depletion in the absence of bleeding control. The sensitivity of point-of-care tests for fibrinolysis is too low and may delay treatment, therefore tranexamic acid should be started early at diagnosis even without signs for hyperfibrinolysis. Transfusion management may be initiated empirically, but is best to be guided by laboratory and viscoelastic assay results as soon as possible. Hypofibrinogenemia is well detected by point-of-care tests, thus substitution may be tailored to individual needs, while reliable thresholds for fresh frozen plasma (FFP) and specific components are yet to be defined. In case of factor deficiency, prothrombin complex concentrate or lyophilized plasma allow for a more rapid restoration of coagulation than FFP. If bleeding and hemostasis are under control, a timely anticoagulation may be necessary.

Blood Product Replacement for Postpartum Hemorrhage

Consideration for blood products replacement in postpartum hemorrhage should be given when blood loss exceeds 1.5 L or when an estimated 25% of blood has been lost. In cases of massive hemorrhage, standardized transfusion protocols have been shown to improve maternal morbidity and mortality. Most protocols recommend a balanced transfusion involving a 1:1:1 ratio of packed red blood cells, platelets, and fresh frozen plasma. Alternatives such as cryoprecipitate, fibrinogen concentrate, and prothrombin complex concentrates can be used in select clinical situations. Although transfusion of blood products can be lifesaving, it does have associated risks.

Review of Current Insights and Therapeutic Approaches for the Treatment of Refractory Postpartum Hemorrhage

Refractory postpartum hemorrhage (PPH) affects 10-20% of patients with PPH when they do not respond adequately to first-line treatments. These patients require second-line interventions, including three or more uterotonics, additional medications, transfusions, non-surgical treatments, and/or surgical intervention. Multiple studies have suggested that patients with refractory PPH have different clinical characteristics and causes of PPH when compared to patients who respond to first-line agents. This review highlights current insights into therapeutic approaches for the management of refractory PPH. Early management of refractory PPH relies on both hypovolemic resuscitation and achievement of hemostasis, with an emphasis on early blood product replacement and massive transfusion protocols. Transfusion needs can be more rapidly and accurately identified through point-of-care tests such as thromboelastography. Medical therapies for the treatment of refractory PPH involve treatment of both uterine atony as well as the underlying coagulopathy, with the use of tranexamic acid and adjunct therapies such as factor replacement. The principles guiding the management of refractory PPH include restoring normal uterine and pelvic anatomy, through the evaluation and management of retained products of conception, uterine inversion, and obstetric lacerations. Intrauterine vacuum-induced hemorrhage control devices are novel methods for the treatment of refractory PPH secondary to uterine atony, in addition to other uterine-sparing surgical procedures that are under investigation. Resuscitative endovascular balloon occlusion of the aorta can be considered for cases of critical refractory PPH, to prevent or decrease ongoing blood loss while definitive surgical interventions are performed. Finally, for patients with critical hemorrhage resulting in hemorrhagic shock, damage control resuscitation (a staged surgical approach focused on restoring normal physiologic recovery and maximizing tissue oxygenation prior to proceeding with definitive surgical management) has been shown to successfully control refractory PPH, with an overall mortality decrease for obstetric patients.

Maternal plasma cytokines and the subsequent risk of uterine atony and postpartum hemorrhage

OBJECTIVES

To determine whether the maternal plasma concentrations of cytokines are higher in pregnant women with postpartum hemorrhage (PPH) compared to pregnant women without PPH.

METHODS

A retrospective case-control study included 36 women with PPH and 72 matched controls. Cases and controls were matched for gestational age at delivery, labor status, delivery route, parity, and year of sample collection. Maternal plasma samples were collected up to 3 days prior to delivery. Comparison of the plasma concentrations of 29 cytokines was performed by using linear mixed-effects models and included adjustment for covariates and multiple testing. A false discovery rate adjusted p-value <0.1 was used to infer significance. Random forest models with evaluation by leave-one-out and 9-fold cross-validation were used to assess the combined value of the proteins in predicting PPH.

RESULTS

Concentrations of interleukin (IL)-16, IL-6, IL-12/IL-23p40, monocyte chemotactic protein 1 (MCP-1), and IL-1β were significantly higher in PPH than in the control group. This difference remained significant after adjustment for maternal age, clinical chorioamnionitis, and preeclampsia. Multi-protein random forest proteomics models had moderate cross-validated accuracy for prediction of PPH [area under the ROC curve, 0.69 (0.58-0.81) by leave-one-out cross validation and 0.73 (0.65-0.81) by 9-fold cross-validation], and the inclusion of clinical and demographic information did not increase the prediction performance.

CONCLUSIONS

Pregnant women with severe PPH had higher median maternal plasma concentrations of IL-16, IL-6, IL-12/IL-23p40, MCP-1, and IL-1β than patients without PPH. These cytokines could serve as biomarkers or their pathways may be therapeutic targets.

Development and validation of a Bayesian belief network predicting the probability of blood transfusion after pediatric injury

BACKGROUND

Early recognition and intervention of hemorrhage are associated with decreased morbidity in children. Triage models have been developed to aid in the recognition of hemorrhagic shock after injury but require complete data and have limited accuracy. To address these limitations, we developed a Bayesian belief network, a machine learning model that represents the joint probability distribution for a set of observed or unobserved independent variables, to predict blood transfusion after injury in children and adolescents.

METHODS

We abstracted patient, injury, and resuscitation characteristics of injured children and adolescents (age 1 to 18 years) from the 2017 to 2019 Trauma Quality Improvement Project database. We trained a Bayesian belief network to predict blood transfusion within 4 hours after arrival to the hospital following injury using data from 2017 and recalibrated the model using data from 2018. We validated our model on a subset of patients from the 2019 Trauma Quality Improvement Project. We evaluated model performance using the area under the receiver operating characteristic curve and calibration curves and compared performance with pediatric age-adjusted shock index (SIPA) and reverse shock index with Glasgow Coma Scale (rSIG) using sensitivity, specificity, accuracy, and Matthew's correlation coefficient (MCC).

RESULTS

The final model included 14 predictor variables and had excellent discrimination and calibration. The model achieved an area under the receiver operating characteristic curve of 0.92 using emergency department data. When used as a binary predictor at an optimal threshold probability, the model had similar sensitivity, specificity, accuracy, and MCC compared with SIPA when only age, systolic blood pressure, and heart rate were observed. With the addition of the Glasgow Coma Scale score, the model has a higher accuracy and MCC than SIPA and rSIG.

CONCLUSION

A Bayesian belief network predicted blood transfusion after injury in children and adolescents better than SIPA and rSIG. This probabilistic model may allow clinicians to stratify hemorrhagic control interventions based upon risk.

LEVEL OF EVIDENCE

Prognostic and Epidemiologic; Level III.

Haemostatic support in postpartum haemorrhage: A review of the literature and expert opinion

Postpartum haemorrhage (PPH) remains the leading cause of pregnancy-related deaths worldwide. Typically, bleeding is controlled by timely obstetric measures in parallel with resuscitation and treatment of coagulopathy. Early recognition of abnormal coagulation is crucial and haemostatic support should be considered simultaneously with other strategies as coagulopathies contribute to the progression to massive haemorrhage. However, there is lack of agreement on important topics in the current guidelines for management of PPH. A clinical definition of PPH is paramount to understand the situation to which the treatment recommendations relate; however, reaching a consensus has previously proven difficult. Traditional definitions are based on volume of blood loss, which is difficult to monitor, can be misleading and leads to treatment delay. A multidisciplinary approach to define PPH considering vital signs, clinical symptoms, coagulation and haemodynamic changes is needed. Moreover, standardised algorithms or massive haemorrhage protocols should be developed to reduce the risk of morbidity and mortality and improve overall clinical outcomes in PPH. If available, point-of-care testing should be used to guide goal-directed haemostatic treatment. Tranexamic acid should be administered as soon as abnormal bleeding is recognised. Fibrinogen concentrate rather than fresh frozen plasma should be administered to restore haemostasis where there is elevated risk of fibrinogen deficiency (e.g., in catastrophic bleeding or in cases of abruption or amniotic fluid embolism) as it is a more concentrated source of fibrinogen. Lastly, organisational considerations are equally as important as clinical interventions in the management of PPH and have the potential to improve patient outcomes.

Echocardiographic indicators of fluid responsiveness in hospitalized dogs with compromised hemodynamics and tissue hypoperfusion

OBJECTIVE

To evaluate the accuracy of selected echocardiographic variables used to predict fluid responsiveness in hospitalized dogs with compromised hemodynamics and tissue hypoperfusion.

DESIGN

Diagnostic test study in a prospective cohort of hospitalized dogs.

SETTING

Veterinary referral clinics.

ANIMALS

Forty-four hospitalized dogs with compromised hemodynamics and tissue hypoperfusion were utilized in this study.

INTERVENTIONS

Echocardiographic examination before and after fluid replacement with 30 ml/kg of lactated Ringer's solution.

MEASUREMENTS AND MAIN RESULTS

Pre-fluid replacement measurements of velocity of transmitral E wave (E-peak), the left ventricular end-diastolic internal diameter normalized to body weight (LVIDdN), and the left ventricular end-systolic internal diameter normalized to body weight (LVIDsN) were significantly lower in fluid-responsive patients compared with nonresponders (P < 0.001). The area under the receiver operating characteristic curve (AUROC) with its 95% confidence interval (CI) for each significant predictor was as follows: E-peak 0.907 (0.776-1.000, P < 0.001) and LVIDdN 0.919 (0.801-1.000, P < 0.001). The predictive capacity of LVIDsN was not significantly better than chance (AUROC, 0.753; 95% CI, 0.472-1.000, P = 0.078). A significant negative linear correlation was observed between the percentage of increase in velocity-time integral after expansion and the echocardiographic variables LVIDdN (r_s  = -0.452, P = 0.023) and E-peak (r_s  = -0.396, P = 0.008) pre-fluid replacement. The intraobserver and interobserver variability was very low (<5 %) for all measurements.

CONCLUSIONS

In this study using critically ill dogs with compromised hemodynamics and tissue hypoperfusion, pre-fluid replacement measurements of LVIDdN and E-peak adequately predict fluid responsiveness. Because a small number of fluid nonresponders were involved in the present study (11.4%), further studies that include larger numbers of fluid-nonresponsive animals are required.

Time is tissue: Barriers to timely transfusion after pediatric injury

ABSTRACT

Strategies to improve outcomes among children and adolescents in hemorrhagic shock have primarily focused on component resuscitation, pharmaceutical coagulation adjuncts, and hemorrhage control techniques. Many of these strategies have been associated with better outcomes in children, but the barriers to their use and the impact of timely use on morbidity and mortality have received little attention. Because transfusion is uncommon in injured children, few studies have identified and described barriers to the processes of using these interventions in bleeding patients, processes that move from the decision to transfuse, to obtaining the necessary blood products and adjuncts, and to delivering them to the patient. In this review, we identify and describe the steps needed to ensure timely blood transfusion and propose practices to minimize barriers in this process. Given the potential impact of time on hemorrhage associated outcomes, ensuring timely intervention may have a similar or greater impact than the interventions themselves.

Maternal body weight and estimated circulating blood volume: a non-linear approach

Postpartum haemorrhage continues to be a leading cause of morbidity and mortality in the obstetric population worldwide, especially in patients at extremes of body weight. Quantification of blood loss has been considered extensively in the literature. However, these volumes must be contextualised to appreciate the consequences of blood loss for individual parturients. Knowledge of a patient's peripartum circulating blood volume is essential to allow accurate interpretation of the significance of haemorrhage and appropriate resuscitation. Greater body weight in obesity can lead to overestimation of blood volume, resulting in inappropriately high thresholds for blood product transfusion and delays in treatment. The most recent Mothers and Babies: Reducing Risk through Audits and Confidential Enquiries across the UK (MBRRACE-UK) surveillance report demonstrated the risk to this population, with more than half of all maternal mortality recorded in parturients who were either overweight or obese. Current linear calculations used to estimate circulating blood volumes based on patients' weights could be contributing to this phenomenon, as blood volume increases at a disproportional rate to body composition. In this review, we summarise the relevant physiology and explore the existing literature on the estimation of circulating blood volume, both during pregnancy and in obesity. Building on key works and principal findings, we present a practical, nonlinear approach to the adjustment of estimated blood volume with increasing body mass. This clinical tool aims to reduce the clinical bias influencing the management of obstetric haemorrhage in a population already at increased risk of morbidity and mortality. Discussion of the limitations of this approach and the call for further research within this field completes this review.

Relationship between tricuspid annular plane systolic excursion, fluid responsiveness and volume status in hospitalised dogs with circulatory abnormalities

AIMS

To evaluate the echocardiographic variable tricuspid annular plane systolic excursion normalised to body weight (TAPSEnorm) as a predictor of fluid responsiveness in hospitalised dogs with haemodynamic and tissue perfusion alterations and to investigate the association of left ventricular internal diameter in diastole normalised to body weight (LVIDdN) and aortic velocity time integral (VTI_Ao) with TAPSEnorm.

METHODS

A single-centre, prospective study was carried out in a cohort of spontaneously breathing dogs, hospitalised for any reason, with severe haemodynamic and tissue perfusion alterations. The echocardiographic variables TAPSEnorm, LVIDdN, and VTI_AO were measured. A bolus of 30 mL/kg of lactated Ringer's solution was administered and then VTI_Ao was subsequently remeasured. Patients were classified as fluid responsive if VTI_Ao increased by ≥15% after fluid expansion, or non-responsive if VTI_Ao increased by <15% after fluid expansion. The area under the receiver operating characteristic (AUROC) curve was generated to evaluate the ability of TAPSE to predict fluid responsiveness. Simple regression models were used to assess the linear relationship between TAPSEnorm and LVIDdN or VTI_AO.

RESULTS

TAPSEnorm was lower in fluid responsive dog (mean 0.57 (95% CI=0.50-0.64) cm/kg) compared to non-responders (mean 0.76 (95% CI=0.62-0.90) cm/kg). The AUROC for TAPSEnorm was 0.827 (95% CI=0.65-1.00). The optimal cut-off point was 0.76 with sensitivity of 80 (95% CI=28.4-99.5)% and specificity of 86.7 (95% CI=69.3-99.2)%, positive predictive value of 50 (95% CI=15.7-84.3)% and negative predictive value of 96.3 (95% CI=81-99.9)%. A monotonic linear relationship was observed between TAPSEnorm and LVIDdN (p<0.001) and between TAPSEnorm and VTI_Ao (p=0.001).

CONCLUSIONS AND CLINICAL RELEVANCE

TAPSEnorm could be useful in determining those dogs that are likely to respond to a fluid bolus from those that are likely to be non-responsive. Additionally, a positive linear association between the LVIDdN and the TAPSEnorm suggests that TAPSEnorm decreases at lower preload values. The present study results suggest that TAPSEnorm could be a valuable tool for evaluating blood volume status and fluid responsiveness in hospitalised dogs.

Predictive accuracy of adding shock index to the American College of Surgeons' minimum criteria for full trauma team activation

BACKGROUND

The American College of Surgeons requires trauma centers to use six minimum criteria (ACS-6) for full trauma team activation: hypotension, gunshot wound to the neck or torso, Glasgow Coma Scale (GCS) score < 9, respiratory compromise, transfers receiving blood transfusion, or physician discretion. Our goal was to evaluate the effect of adding varying shock index (SI) thresholds to the ACS-6 in an adult trauma population with the hypothesis that SI would significantly improve sensitivity at the expense of an acceptable decrease in specificity.

METHODS

We performed a secondary analysis of EMS and trauma registry data from an urban Level I trauma center. Consecutive patients > 15 years of age were included from 1993 through 2006. SI at thresholds of ≥0.8, ≥0.85, ≥0.9, and ≥1 were evaluated. Primary outcome was emergency operative (within 1 h of arrival) or procedural (cricothyrotomy or thoracotomy) intervention (EOPI); secondary outcomes were Injury Severity Score (ISS) > 15, ISS > 24, a composite of EOPI or ISS > 15, and urgent operative intervention (within 4 h).

RESULTS

A total of 20,872 patients were included, 27% with an ISS > 15 and 5% who underwent EOPI. Sensitivity and specificity of the ACS-6 alone for EOPI were 86% (95% confidence interval [CI] = 84% to 88%) and 81% (95% CI = 80% to 81%), respectively. Inclusion of SI thresholds of 0.8, 0.85, 0.9, and 1 resulted in sensitivities of 95% (95% CI = 93% to 96%), 93% (CI = 91% to 94%), 92% (95% CI = 90% to 93%), and 90% (95% CI = 88% to 92%), respectively, and specificities of 52% (95% CI = 51% to 52%), 59% (95% CI = 58% to 59%), 64% (95% CI = 64% to 65%), and 72% (95% CI = 71% to 73%), respectively. Similar trends were found for each secondary outcome.

CONCLUSION

The addition of SI to the ACS-6 for trauma team activation increased sensitivity for EOPI with a larger decrease in specificity across all thresholds. Inclusion of a SI threshold of ≥0.9 closely aligns with under- and overtriage benchmarks in this trauma registry cohort using a strict definition of trauma team activation need.

Shock index as a predictor for mortality in trauma patients: a systematic review and meta-analysis

PURPOSE

The primary aim was to determine whether a shock index (SI) ≥ 1 in adult trauma patients was associated with increased in-hospital mortality compared to an SI < 1.

METHODS

This systematic review including a meta-analysis was performed in accordance with the PRISMA guidelines. EMBASE, MEDLINE, and Cochrane Library were searched, and two authors independently screened articles, performed the data extraction, and assessed risk of bias. Studies were included if they reported in-hospital, 30-day, or 48-h mortality, length of stay, massive blood transfusion or ICU admission in trauma patients with SI recorded at arrival in the emergency department or trauma center. Risk of bias was assessed using the Newcastle-Ottawa Scale, and the strength and quality of the body of evidence according to GRADE. Data were pooled using a random effects model. Inter-rater reliability was assessed with Cohen's kappa.

RESULTS

We screened 1350 citations with an inter-rater reliability of 0.90. Thirty-eight cohort studies were included of which 14 reported the primary outcome. All studies reported a significant higher in-hospital mortality in adult trauma patients with an SI ≥ 1 compared to those having an SI < 1. Twelve studies involving a total of 348,687 participants were included in the meta-analysis. The pooled risk ratio (RR) of in-hospital mortality was 4.15 (95% CI 2.96-5.83). The overall quality of evidence was low.

CONCLUSIONS

This systematic review found a fourfold increased risk of in-hospital mortality in adult trauma patients with an initial SI ≥ 1 in the emergency department or trauma center.

A comprehensive digital phenotype for postpartum hemorrhage

OBJECTIVE

We aimed to establish a comprehensive digital phenotype for postpartum hemorrhage (PPH). Current guidelines rely primarily on estimates of blood loss, which can be inaccurate and biased and ignore complementary information readily available in electronic medical records (EMR). Inaccurate and incomplete phenotyping contributes to ongoing challenges in tracking PPH outcomes, developing more accurate risk assessments, and identifying novel interventions.

MATERIALS AND METHODS

We constructed a cohort of 71 944 deliveries from the Mount Sinai Health System. Estimates of postpartum blood loss, shifts in hematocrit, administration of uterotonics, surgical interventions, and diagnostic codes were combined to identify PPH, retrospectively. Clinical features were extracted from EMRs and mapped to common data models for maximum interoperability across hospitals. Blinded chart review was done by a physician on a subset of PPH and non-PPH patients and performance was compared to alternate PPH phenotypes. PPH was defined as clinical diagnosis of postpartum hemorrhage documented in the patient's chart upon chart review.

RESULTS

We identified 6639 PPH deliveries (9% prevalence) using our phenotype-more than 3 times as many as using blood loss alone (N = 1,747), supporting the need to incorporate other diagnostic and intervention data. Chart review revealed our phenotype had 89% accuracy and an F1-score of 0.92. Alternate phenotypes were less accurate, including a common blood loss-based definition (67%) and a previously published digital phenotype (74%).

CONCLUSION

We have developed a scalable, accurate, and valid digital phenotype that may be of significant use for tracking outcomes and ongoing clinical research to deliver better preventative interventions for PPH.

Improving postpartum hemorrhage risk prediction using longitudinal electronic medical records

OBJECTIVE

Postpartum hemorrhage (PPH) remains a leading cause of preventable maternal mortality in the United States. We sought to develop a novel risk assessment tool and compare its accuracy to tools used in current practice.

MATERIALS AND METHODS

We used a PPH digital phenotype that we developed and validated previously to identify 6639 PPH deliveries from our delivery cohort (N = 70 948). Using a vast array of known and potential risk factors extracted from electronic medical records available prior to delivery, we trained a gradient boosting model in a subset of our cohort. In a held-out test sample, we compared performance of our model with 3 clinical risk-assessment tools and 1 previously published model.

RESULTS

Our 24-feature model achieved an area under the receiver-operating characteristic curve (AUROC) of 0.71 (95% confidence interval [CI], 0.69-0.72), higher than all other tools (research-based AUROC, 0.67 [95% CI, 0.66-0.69]; clinical AUROCs, 0.55 [95% CI, 0.54-0.56] to 0.61 [95% CI, 0.59-0.62]). Five features were novel, including red blood cell indices and infection markers measured upon admission. Additionally, we identified inflection points for vital signs and labs where risk rose substantially. Most notably, patients with median intrapartum systolic blood pressure above 132 mm Hg had an 11% (95% CI, 8%-13%) median increase in relative risk for PPH.

CONCLUSIONS

We developed a novel approach for predicting PPH and identified clinical feature thresholds that can guide intrapartum monitoring for PPH risk. These results suggest that our model is an excellent candidate for prospective evaluation and could ultimately reduce PPH morbidity and mortality through early detection and prevention.

Quantification of stroke volume in a simulated healthy volunteer model of traumatic haemorrhage; a comparison of two non-invasive monitoring devices using error grid analysis alongside traditional measures of agreement

Introduction

Haemorrhage is a leading cause of death following traumatic injury and the early detection of hypovolaemia is critical to effective management. However, accurate assessment of circulating blood volume is challenging when using traditional vital signs such as blood pressure. We conducted a study to compare the stroke volume (SV) recorded using two devices, trans-thoracic electrical bioimpedance (TEB) and supra-sternal Doppler (SSD), against a reference standard using trans- thoracic echocardiography (TTE).

Methods

A lower body negative pressure (LBNP) model was used to simulate hypovolaemia and in half of the study sessions lower limb tourniquets were applied as these are common in military practice and can potentially affect some haemodynamic monitoring systems. In order to provide a clinically relevant comparison we constructed an error grid alongside more traditional measures of agreement.

Results

21 healthy volunteers aged 18–40 were enrolled and underwent 2 sessions of LBNP, with and without lower limb tourniquets. With respect to absolute SV values Bland Altman analysis showed significant bias in both non-tourniquet and tourniquet strands for TEB (-42.5 / -49.6 ml), rendering further analysis impossible. For SSD bias was minimal but percentage error was unacceptably high (35% / 48%). Degree of agreement for dynamic change in SV, assessed using 4 quadrant plots showed a seemingly acceptable concordance rate for both TEB (86% / 93%) and SSD (90% / 91%). However, when results were plotted on an error grid, constructed based on expert clinical opinion, a significant minority of measurement errors were identified that had potential to lead to moderate or severe patient harm.

Conclusion

Thoracic bioimpedance and suprasternal Doppler both demonstrated measurement errors that had the potential to lead to clinical harm and caution should be applied in interpreting the results in the detection of early hypovolaemia following traumatic injury.

Effects of blood loss on organ attenuation on postmortem CT and organ weight at autopsy

BACKGROUND

Cases of external hemorrhage are difficult to recognize on postmortem computed tomography (PMCT).

PURPOSE

To investigate the effects of blood loss on CT attenuation of the spleen, liver, kidneys, and lungs on PMCT and to assess the relationship between blood loss and organ weight.

METHODS

A total of 125 cases with blood loss were sex- and age-matched to 125 control cases without blood loss. Individual organ attenuation was measured on transverse CT images. Organ weights of the liver, spleen, kidneys, and lung were extracted from the autopsy protocols.

RESULTS

Organ weight was significantly lower in cases with blood loss (lung 30%, spleen 28%, kidneys 14%, liver 18%) than in controls. CT attenuation of the lungs was significantly lower (30%) in cases with blood loss than in controls. CT attenuation of the spleen and kidneys did not significantly differ between cases and controls. CT attenuation of the liver was significantly higher (25%) in cases with blood loss than in controls.

CONCLUSION

Blood loss decreases organ weight and CT attenuation of the lungs but appears to have no significant effect on CT attenuation of the spleen and kidneys. The increased liver attenuation in cases with blood loss compared to controls was an unexpected finding and remains challenging to explain. One probable interpretation refers to different levels of hepatic glycogen; however, further work is warranted to substantiate this hypothesis.

Splenomegaly development and disseminated intravascular coagulation syndrome in acute canine babesiosis

Disseminated intravascular coagulation (DIC) syndrome is the main defining process in the pathogenetic axis of complications in canine babesiosis. The involvement of the spleen with further irreversible changes in the organ largely determines the severity of the animal’s condition after spontaneous babesiosis. The work presented here aimed to determine the role of the DIC syndrome as a triggering factor for lesions of the spleen. Clinical and laboratory studies (haematological, biochemical, hemodynamic) have been carried out. Pathological studies of the removed spleen were carried out by histological methods using universal and specific staining. After suffering acute spontaneous babesiosis, the development of hypersplenism and splenomegaly was found in dogs. The diagnosis was confirmed haematologically by the detected cytopenia, normochromic type anaemia. An additional parameter was a significantly increased erythrocyte sedimentation rate. The biochemical profile indicated the development of bilirubinaemia due to the conjugated fraction, hyperfermentation of transaminases, hypoalbuminemia, which reflected the development of hepatitis and liver failure. Markers of DIC syndrome in laboratory studies are represented by reliable hypofibrinogenemia, increased level of fibrinogen/fibrin degradation products, including D-dimer, and soluble fibrin monomer complexes. The multidirectional indices of coagulation tests (activated partial thromboplastin and prothrombin time) made it possible to classify the stage of “consumption coagulopathy” of the DIC syndrome. The haemodynamic parameters of the sick dogs were characterized by a significant deficit in the circulating blood volume. Together with the indicators of the “consumption coagulopathy” stage of the DIC syndrome, the hemodynamic indexes indicate a moderate degree of shock stage II – the stable reversibility, but the magnitude of the circulating blood volume deficit determines the tendency towards shock irreversibility. Histological studies have established a significant proliferation of the stromal elements of the organ, the formation of specific complexes of vessels with sinuses, clogging with blood clots, and the organ's parenchyma dystrophy. Such changes characterize complete splenomegaly, which is based on the organo-pathology of the DIC syndrome. The deposition of “old” fibrin in the connective tissue structures of the spleen indicates that DIC syndrome continues throughout the entire period of hyperplastic changes in the organ. The presence of hyalinosis in blood vessel walls of the spleen parenchyma determines irreversible changes in them. Thus, DIC syndrome is the basis for splenomegaly development in dogs after acute spontaneous babesiosis. It is confirmed by laboratory blood tests and histologically by the presence of fibrin thrombi in the structures of the organ, which determine the organopathology of the syndrome. The information obtained serves to expand the concepts of the pathogenesis of blood protozoal disease, define the high risk of complications that can become fatal for the health and life of animals.

A mathematical model of cardiovascular dynamics for the diagnosis and prognosis of hemorrhagic shock

A variety of mathematical models of the cardiovascular system have been suggested over several years in order to describe the time-course of a series of physiological variables (i.e. heart rate, cardiac output, arterial pressure) relevant for the compensation mechanisms to perturbations, such as severe haemorrhage. The current study provides a simple but realistic mathematical description of cardiovascular dynamics that may be useful in the assessment and prognosis of hemorrhagic shock. The present work proposes a first version of a differential-algebraic equations model, the model dynamical ODE model for haemorrhage (dODEg). The model consists of 10 differential and 14 algebraic equations, incorporating 61 model parameters. This model is capable of replicating the changes in heart rate, mean arterial pressure and cardiac output after the onset of bleeding observed in four experimental animal preparations and fits well to the experimental data. By predicting the time-course of the physiological response after haemorrhage, the dODEg model presented here may be of significant value for the quantitative assessment of conventional or novel therapeutic regimens. The model may be applied to the prediction of survivability and to the determination of the urgency of evacuation towards definitive surgical treatment in the operational setting.

Prehospital Hemorrhage Assessment Criteria: A Concise Review

OBJECTIVE

Early assessment of the clinical status of trauma patients is crucial for guiding the treatment strategy, and it requires a rapid and systematic approach. The aim of this report is to critically review the assessment parameters currently used in the prehospital setting to quantify blood loss in trauma.

DATA SOURCES

Studies regarding hemorrhagic shock in trauma were pooled from PubMed, EMBASE, and Cochrane databases using key words such as "hemorrhagic shock," "vital signs evaluation," "trauma," "blood loss," and "emergency medical service," alone or combined.

STUDY SELECTION

Articles published since 2009 in English and Italian were considered eligible if containing data on assessment parameters in blood loss in adults.

DATA EXTRACTION

Sixteen articles matching the inclusion criteria were considered in our study.

DATA SYNTHESIS

Current prehospital assessment measures lack precise correlation with blood loss.

CONCLUSIONS

Traditional assessment parameters such as heart rate, systolic blood pressure, shock index, and Glasgow Coma Scale score often lag in providing accurate blood loss assessment. The current literature supports the need for a noninvasive, continuously monitored assessment parameter to identify early shock in the prehospital setting.

Unifying the Estimation of Blood Volume Decompensation Status in a Porcine Model of Relative and Absolute Hypovolemia Via Wearable Sensing

Hypovolemia remains the leading cause of preventable death in trauma cases. Recent research has demonstrated that using noninvasive continuous waveforms rather than traditional vital signs improves accuracy in early detection of hypovolemia to assist in triage and resuscitation. This work evaluates random forest models trained on different subsets of data from a pig model (n = 6) of absolute (bleeding) and relative (nitroglycerin-induced vasodilation) progressive hypovolemia (to 20% decrease in mean arterial pressure) and resuscitation. Features for the models were derived from a multi-modal set of wearable sensors, comprised of the electrocardiogram (ECG), seismocardiogram (SCG) and reflective photoplethysmogram (RPPG) and were normalized to each subject.s baseline. The median RMSE between predicted and actual percent progression towards cardiovascular decompensation for the best model was 30.5% during the relative period, 16.8% during absolute and 22.1% during resuscitation. The least squares best fit line over the mean aggregated predictions had a slope of 0.65 and intercept of 12.3, with an R² value of 0.93. When transitioned to a binary classification problem to identify decompensation, this model achieved an AUROC of 0.80. This study: a) developed a global model incorporating ECG, SCG and RPPG features for estimating individual-specific decompensation from progressive relative and absolute hypovolemia and resuscitation; b) demonstrated SCG as the most important modality to predict decompensation; c) demonstrated efficacy of random forest models trained on different data subsets; and d) demonstrated adding training data from two discrete forms of hypovolemia increases prediction accuracy for the other form of hypovolemia and resuscitation.

The role of internal jugular vein Doppler ultrasonography in predicting hypovolemic shock in polytrauma patients

PURPOSE

The aim of this study was to evaluate the accuracy of internal jugular vein (IJV) Doppler ultrasonography in predicting hypovolemic shock in polytrauma patients.

METHODS

This prospective observational study was conducted on 75 multiple trauma patients (injury severity score >15) with a mean age of 33.00±9.57 years. IJV Doppler ultrasonography was performed in all patients with stable vital signs and a negative extended focused assessment with sonography for trauma. Jugular pulsatility index (JPI) values were calculated using the equation (Vmax-Vmin)/Vmax. Clinical and laboratory indices of hypovolemic shock were recorded at the time of admission. Patients were subsequently divided into those with hemorrhagic shock (n=36) and those without (n=39) based on the occurrence of hemorrhagic shock within 6 hours after admission. The results were compared between these groups.

RESULTS

IJV Doppler ultrasound parameters (JPI, Vmin, and Vmax-Vmin) showed significant differences between the two groups. The JPI values of patients with hemorrhagic shock were significantly lower than those in the control group (0.43±0.21 vs. 0.78±0.24, P<0.001). The sensitivity, specificity, and discriminant ability (area under the curve) of JPI in detecting hemorrhagic shock were 86.11%, 82.05%, and 0.853 (P<0.001), respectively.

CONCLUSION

IJV Doppler ultrasonography can reliably predict hemorrhagic shock in polytrauma patients with stable vital signs. Ultrasonography can be used in combination with clinical signs and laboratory findings to diagnose patients at risk of hypovolemic shock.

Comparing Hemorrhage in Human Physiology Simulation Tools: How They Compare With Expected Human Physiology and Each Other

INTRODUCTION

Several different whole-body physiology simulation tools (PST) using modeling techniques are now available with potential use for healthcare simulation, but these novel technologies lack objective analysis from an independent organization.

METHODS

We identified BioGears, HumMod, and Muse as 3 PSTs that met our requirements for testing. We ran mild, moderate, and severe hemorrhage scenarios on each PST and collected outputs for comparison with each other and published human physiology data.

RESULTS

All PSTs tested followed the expected tachycardic and hypotensive response to hemorrhage for all levels of severity with variable qualitative patterns. Complete data for analysis were not available in all PSTs for urine output, stroke volume, blood volume, hemoglobin, and serum epinephrine concentration, but the partial findings are discussed in detail. We determined the predicted time to reach hemorrhage shock based on the hemorrhage guidelines and compared this with time to cardiovascular collapse from each PST. Overall, the differences from known human physiology were much larger than expected before testing and trends show HumMod with the smallest difference for severe (-6.25%) and moderate (-1.42%) and Muse with the smallest difference for mild hemorrhage (27.9%). BioGears demonstrated the largest differences in all classifications of severity.

CONCLUSIONS

Our analysis of currently available whole-body PSTs provides insight into the novel, evolving field. We hope our efforts shed light to a wider audience to the exciting developments and uses of mathematical modeling for whole-body simulation and the potential for integration into healthcare simulation for medical education.

The golden hour for postpartum hemorrhage: Results from a prospective cohort study

OBJECTIVE

To evaluate the predictive capacity of vital signs for the diagnosis of postpartum hemorrhage (PPH).

METHODS

A prospective cohort study performed at the University of Campinas, Brazil, between February 2015 and March 2016 with women who delivered vaginally. Vital signs and postpartum bleeding were collected over 24 h. Exploratory data analysis was performed plus receiver operating characteristic curve analysis where the areas under the curve was used to determine the best cutoff points for sensitivity, specificity, likelihood ratio, and diagnostic odds ratio.

RESULTS

For the 270 women recruited, mean blood loss after 120 min was 427.49 ± 335.57 ml, while 84 (31.1%) and 22 (8.1%) women had blood loss ≥500 and ≥1000 ml, respectively. Heart rate cutoff point of 105 bpm measured between 21-40 min after birth identified blood loss ≥1000 ml with 90% specificity. A shock index (SI) of 0.965 at 41-60 min after birth identified blood loss ≥500 and ≥1000 ml within 2 h with approximately 95% specificity.

CONCLUSION

Shock index and heart rate measured after birth showed high specificity with low sensitivity to identify PPH. In clinical practice, "The rule of 1s" should receive special attention: SI ≥1, or heart rate >100 bpm, or estimated blood loss ≥1 L.

The utility of shock index and heart rate in the management of postpartum blood loss in pregnant women complicated with hypertensive disorders in pregnancy

BACKGROUND

Although the shock index (SI) (heart rate/systolic blood pressure) and heart rate (HR) are a helpful indicator in the management of postpartum blood loss, there are few reports of SI in pregnant women complicated with hypertensive disorders in pregnancy (HDP). The purpose of this study was to examine whether SI and HR would be a clinically helpful indicator, and to detect the cutoff value for judging abnormal obstetric bleeding.

METHODS

This was a retrospective case-control study in 107 patients with HDP in a singleton tertiary perinatal medical facility. The values of postpartum highest SI (peak SI) and highest HR (peak HR), and the amount of bleeding until peak SI and peak HR were retrospectively examined and analyzed. We used the receiver operating characteristic analysis to assess the diagnostic value of peak SI and peak HR for judging abnormal obstetric bleeding.

RESULTS

Peak SI and peak HR were significantly related to the amount of bleeding up to peak SI and up to peak HR. The cutoff values of peak SI with blood loss volumes above 500 ml, 1000 ml, and 1500 ml were 0.77, 0.76, and 0.99, respectively. The cutoff values of peak HR with blood loss volumes above 500 ml, 1000 ml, and 1500 ml were 97, 98, and 103, respectively.

CONCLUSION

In cases of pregnant women complicated with HDP, both SI and HR were probably useful indicators in the management of postpartum blood loss. Further prospective trials are warranted to confirm these results.

Development and validation of a prediction model for postpartum hemorrhage at a single safety net tertiary care center

BACKGROUND

Postpartum hemorrhage is a leading cause of pregnancy-related morbidity and mortality; however, there is limited ability to identify women at risk of this obstetrical complication.

OBJECTIVE

This study aimed to develop and validate a prediction model for postpartum hemorrhage based on antenatal and intrapartum risk factors.

STUDY DESIGN

This was a retrospective cohort study of women who delivered between April 2016 and March 2019 at a single safety net hospital. The prevalence of postpartum hemorrhage, defined as blood loss of ≥1000 mL at the time of delivery, was determined, and characteristics were compared between women with and without postpartum hemorrhage. Women were randomly assigned to a prediction or a validation cohort. The selection of predictors to be included in the model was based on known antenatal and intrapartum risk factors for postpartum hemorrhage. A multivariable logistic regression with a backward stepwise approach was used to create a prediction model. Area under the receiver operating characteristic curve and 95% bootstrap confidence intervals were calculated. Using the final model, a single threshold for classifying postpartum hemorrhage was chosen, and the resulting sensitivity, specificity, and false-negative and false-positive rates were explored.

RESULTS

The prevalence rates of postpartum hemorrhage in the prediction and validation cohorts were 6.3% (377 of 6000 cases) and 6.4% (241 of 3774 cases), respectively (P=.83). The following predictors were selected for the final model: maternal body mass index (kg/m²), number of fetuses, history of postpartum hemorrhage, admission platelets of <100,000/µL, chorioamnionitis, arrest of descent, placental abruption, and active labor duration. The predictive model had an area under the receiver operating characteristic curve of 0.82 (95% confidence interval, 0.81-0.84). When applied to the validation cohort, the model had an area under the receiver operating characteristic curve of 0.81 (95% confidence interval, 0.78-0.83), a sensitivity of 86.9%, a specificity of 74.2%, a positive predictive value of 18.6%, a negative predictive value of 98.8%, a false-negative rate of 13.1%, and a false-positive rate of 25.9%.

CONCLUSION

The model performed reasonably well in identifying women at risk of postpartum hemorrhage. Further studies are necessary to evaluate the model in clinical practice and its effect on decreasing the prevalence of postpartum hemorrhage and associated maternal morbidity.

Assessing the accuracy of visual blood loss estimation in postpartum hemorrhage in Shanghai hospitals: A web-based survey for nurses and midwives

Aims and objectives

This study aimed at evaluating the accuracy of visual estimated blood loss in postpartum haemorrhage by midwives and nurses, as well as exploring its influencing factors.

Background

Timely recognition of postpartum haemorrhage is critical in saving maternal lives. Yet midwives and nurses can barely distinguish whether the blood loss has reached a life‐threatening amount without precise measurement. Understanding their ability to accurately estimate the amount of blood loss and the influencing factors can help improve this ability with effective measures.

Design

This research was a multicenter cross‐sectional survey with convenient sampling.

Material and Methods

Using a modified online visual estimation questionnaire of blood loss, the QR code of this survey was sent to midwives and obstetrical nurses engaged in clinical practice in secondary and tertiary hospitals in Shanghai. A descriptive analysis was performed with demographics and the responses of visual estimated blood loss of each volume. The difference and consistency of the responses of each volume were evaluated. The relationship between each demographic characteristic and accuracy was explored. STROBE statement checklist was chosen for reporting the study process.

Results

A total of 361 midwives and nurses participated in the survey. The finding showed an overall accuracy of 30.52% (1763/5776), with 25.3% and 18.0% subjects distinguishing postpartum haemorrhage (500 ml) and severe postpartum haemorrhage (1000 ml), respectively. The Kappa coefficients were slight to moderate (0.037–0.590). There were no differences among the categories of gender, age, academic degree, position, title, working experience in years, working department and reported methods of blood loss estimation with regard to accuracy. However, having institutional guidance for blood loss calculation showed a significant relationship with higher accuracy.

Relevance to clinical practice

While representing a relatively well‐developed area in China, the accuracy of visual estimated blood loss was not satisfactory, as suggested in other developed countries around the world. Training and institutional guidance on blood loss quantification should be provided in midwifery settings, regardless of how the level of medical development is advanced.

Conclusions

The accuracy of VEBL was low even with a visual aid, especially when the volume exceeds 500 ml. To improve accuracy, institutions should make standardadized assessment guidance and provide regular training for blood loss quantification.

Current Challenges in the Peripartum Management of Women with von Willebrand Disease

For many women, pregnancy and childbirth represent their first major hemostatic challenges. Despite advancements in obstetric care, up to 2 to 5% of all deliveries are complicated by postpartum hemorrhage (PPH). To mitigate bleeding risk, physiological changes occur in pregnancy, including increases in plasma von Willebrand factor (VWF) and factor VIII levels. For women with von Willebrand disease (VWD), these physiological alterations are blunted or absent. As a result, women with VWD have a heightened risk of PPH, both primary (in the first 24 hours) and secondary (>24 hours to 6 to 12 weeks postpartum). Pregnancy and delivery management for women with VWD should therefore be carefully coordinated as part of a multidisciplinary team approach. In the absence of large-scale clinical trials, the management of women with VWD during pregnancy is guided by expert consensus guidelines. Clinical practices internationally are not uniform, and areas of considerable clinical uncertainty exist. Traditional peripartum plasma VWF thresholds for hemostatic cover and therapeutic targets are currently under scrutiny, as PPH is not eliminated in women with VWD who receive replacement therapy. The benefit and optimal duration of postpartum tranexamic acid have yet to be defined, and standardized methods of quantification of blood loss at the time of delivery are currently lacking. In this article, we review the evidence base to date and explore the current clinical challenges in the management of pregnant women with VWD.

A review of postpartum hemorrhage in low-income countries and implications for strengthening health systems

Postpartum hemorrhage (PPH) is the leading cause of maternal morbidity and mortality worldwide. Disparities in PPH-associated survival between high and low-/middle-income countries reflect an imperative for low-resource countries to improve strategies for rapid diagnosis and treatment. A review of current PPH diagnosis, prevention, treatment, and access to care in low-income countries has been used to understand, extract, and report the challenges that public health systems face in trying to solve the marked global disparity in PPH outcomes. Improvement in PPH survival begins with holistic strengthening of each step along the continuum of care in health systems and should include performance feedback measures and quality-of-care research.

Hospital transfer for patients with postpartum hemorrhage in Yokohama, Japan: a single‐center descriptive study

Aim

To describe the transport time and timing of transfer of patients with postpartum hemorrhage to a tertiary care institution in an urban area.

Methods

We included patients with postpartum hemorrhage transferred to our hospital from a perinatal care facility. We defined transfer time as the time between the referring physician's request for transfer and the patient's arrival at our hospital. We examined transfer time and its breakdown, the shock index before and after transfer, and the prognosis.

Results

Overall, 79 patients with postpartum hemorrhage were transported to our hospital within a median (interquartile range) of 53 min (47–63 min). In 70 cases (89%), the request for transport was made before the shock index reached 1.5, and two cases had cardiac arrest during transport.

Conclusions

Most patients who were transferred to our hospital were transferred according to the criteria recommended by the guideline. However, the occurrence of cardiac arrest during transport indicates the need to shorten the time from transfer requests to emergency calls by strengthening cooperation with regional perinatal care facilities.

A Simple Cardiovascular Model for the Study of Hemorrhagic Shock

Hemorrhagic shock is the number one cause of death on the battlefield and in civilian trauma as well. Mathematical modeling has been applied in this context for decades; however, the formulation of a satisfactory model that is both practical and effective has yet to be achieved. This paper introduces an upgraded version of the 2007 Zenker model for hemorrhagic shock termed the ZenCur model that allows for a better description of the time course of relevant observations. Our study provides a simple but realistic mathematical description of cardiovascular dynamics that may be useful in the assessment and prognosis of hemorrhagic shock. This model is capable of replicating the changes in mean arterial pressure, heart rate, and cardiac output after the onset of bleeding (as observed in four experimental laboratory animals) and achieves a reasonable compromise between an overly detailed depiction of relevant mechanisms, on the one hand, and model simplicity, on the other. The former would require considerable simulations and entail burdensome interpretations. From a clinical standpoint, the goals of the new model are to predict survival and optimize the timing of therapy, in both civilian and military scenarios.

The association of shock index and haemoglobin variation with postpartum haemorrhage after vaginal delivery: a prospective cohort pilot study

INTRODUCTION

Shock index and continuous non-invasive haemoglobin monitoring (SpHb) have both been proposed for the timely recognition of postpartum haemorrhage (PPH). We sought to determine, in parallel, the association of each of shock index and SpHb with blood loss after vaginal delivery.

METHODS

Sixty-six women were recruited to this prospective observational study. Shock index and SpHb were recorded postpartum for 120 min. The association between each of shock index and SpHb with quantitative blood loss (QBL) at 30, 60 and 120 min postpartum was determined using linear mixed models. Area-under-the-receiver-operator-characteristic (AUROC) curves were constructed to evaluate the diagnostic ability of shock index and SpHb to detect PPH (defined as QBL ≥1000 mL).

RESULTS

Shock index trend was associated with QBL over the first 30 min (r=0.37, P=0.002), but not over 60 or 120 min. There was an association of SpHb trend with QBL over the first 30 min (P=0.06), but not over 60 min (r=-0.32, P=0.009) or 120 min (r=-0.26, P=0.03). Maximum shock index within 60 min correlated with QBL (r=0.54, P <0.001) and was a predictor of PPH (P=0.0012, AUROC 0.796). Maximum change in SpHb within 60 min negatively correlated with QBL (r=-0.4, P <0.001) and was a predictor of PPH (P=0.048, AUROC 0.761).

CONCLUSIONS

The trend of shock index and its peak values are associated with blood loss after vaginal delivery and are early indicators of PPH. Negative trend of SpHb is a late sign of PPH and has a weaker association with blood loss than shock index.

Physiology and clinical utility of the peripheral venous waveform

The peripheral venous system serves as a volume reservoir due to its high compliance and can yield information on intravascular volume status. Peripheral venous waveforms can be captured by direct transduction through a peripheral catheter, non-invasive piezoelectric transduction, or gleaned from other waveforms such as the plethysmograph. Older analysis techniques relied upon pressure waveforms such as peripheral venous pressure and central venous pressure as a means of evaluating fluid responsiveness. Newer peripheral venous waveform analysis techniques exist in both the time and frequency domains, and have been applied to various clinical scenarios including hypovolemia (i.e. hemorrhage, dehydration) and volume overload.

Toward interprofessional team training for surgeons and anesthesiologists using virtual reality

Purpose

In this work, a virtual environment for interprofessional team training in laparoscopic surgery is proposed. Our objective is to provide a tool to train and improve intraoperative communication between anesthesiologists and surgeons during laparoscopic procedures.

Methods

An anesthesia simulation software and laparoscopic simulation software are combined within a multi-user virtual reality (VR) environment. Furthermore, two medical training scenarios for communication training between anesthesiologists and surgeons are proposed and evaluated. Testing was conducted and social presence was measured. In addition, clinical feedback from experts was collected by following a think-aloud protocol and through structured interviews.

Results

Our prototype is assessed as a reasonable basis for training and extensive clinical evaluation. Furthermore, the results of testing revealed a high degree of exhilaration and social presence of the involved physicians. Valuable insights were gained from the interviews and the think-aloud protocol with the experts of anesthesia and surgery that showed the feasibility of team training in VR, the usefulness of the system for medical training, and current limitations.

Conclusion

The proposed VR prototype provides a new basis for interprofessional team training in surgery. It engages the training of problem-based communication during surgery and might open new directions for operating room training.

Electronic supplementary material

The online version of this article (10.1007/s11548-020-02276-y) contains supplementary material, which is available to authorized users.

Caudal vena cava collapsibility index as a tool to predict fluid responsiveness in dogs

OBJECTIVE

To evaluate the use of the caudal vena cava collapsibility index (CVCCI) as a predictor of fluid responsiveness in hospitalized, critically ill dogs with hemodynamic or tissue perfusion abnormalities.

DESIGN

Retrospective observational study.

SETTING

Private referral center.

ANIMALS

Twenty-seven critically ill, spontaneously breathing dogs with compromised hemodynamics or tissue hypoperfusion.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The electronic medical records were searched for dogs admitted for any cause, from August 2016 to December 2017. We included dogs with ultrasound measurements of: CVCCI, performed at baseline; and velocity time integral (VTI) of the subaortic blood flow, carried out before and after a fluid load. CVCCI was estimated as: (maximum diameter-minimum diameter/maximum diameter) × 100. Dogs in which VTI increased ≥15% were considered fluid responders. The CVCCI accurately predicted fluid responsiveness with an area under the receiver operating characteristic curve of 0.96 (95% CI, 0.88 to 1.00). The optimal cut-off of CVCCI that better discriminated between fluid responders and nonresponders was 27%, with 100.0% sensitivity and 83.3% specificity. At baseline, fluid responders had lower VTI (5.48 [4.26 to 7.40] vs 10.61 [7.38 to 13.23] cm, P = 0.004) than nonresponders. The basal maximum diameter of the caudal vena cava adjusted to body weight was not different between responders and nonresponders (0.050 [0.030 to 0.100] vs 0.079 [0.067 to 0.140] cm/kg, P = 0.339). The increase in VTI was related to basal CVCCI (R = 0.60, P = 0.001). Bland-Altman analysis showed narrow 95% limits of agreement between measurements of CVCCI and VTI performed by different observers or by the same observer.

CONCLUSIONS

The results of this small cohort study suggest that CVCCI can accurately predict fluid responsiveness in critically ill dogs with perfusion abnormalities. Further research is necessary to extrapolate these results to larger populations of hospitalized dogs.

Disseminated Intravascular Coagulation Syndrome as a Complication in Acute Spontaneous Canine Babesiosis

The polyetiological syndrome of disseminated intravascular coagulation (DIC) is characterized by changes in patients’ hemostasis. The aim of the current research was to elucidate the main factors for the development of DIC syndrome during canine babesiosis, and to assess their correlation level. Dogs included in this study were of various breeds and sex, weighing 10-40 kg and aged 2-7 years. They were separated in two groups (n=50) according to their diagnosis to babesiosis. Oscillometry (blood pressure, pulse rate), vascular-platelet hemostasis, coagulogram, hematological, biochemical (fibrinogen, fibrin degradation product, soluble fibrin-monomer complex) and hemodynamic (circulating blood volume) assessment methods were used. The group of dogs positive on Babesia spp., had clear manifestation of DIC with 5-7% of the erythrocyte population being affected. DIC was manifested by a significant increase in soluble fibrin-monomer complex and fibrin degradation product (p<0.001), hypofibrinogenemia (p<0.001), thrombocytopenia (p<0.001), and an increase in indicators of spontaneous aggregation ability of platelets and red blood cells (p<0.001). Significant hemodynamic disorders were observed: a decrease in circulating blood volume, circulating erythrocytes volume (p<0.05), specific circulating blood volume and hematocrit value (p<0.001). The average blood pressure was reduced (p<0.001), and the Allgöwer’s shock index was increased 2 times (p<0.05). A shock of II degree (medium, subcompensated) was confirmed. Therefore, it can be concluded that acute spontaneous dogs’ babesiosis can be characterized by the occurrence of DIC in a consumption coagulopathy form, and shock of II degree. This condition renders the patients for emergency admission.

Machine Learning and Statistical Models to Predict Postpartum Hemorrhage

OBJECTIVE

To predict a woman's risk of postpartum hemorrhage at labor admission using machine learning and statistical models.

METHODS

Predictive models were constructed and compared using data from 10 of 12 sites in the U.S. Consortium for Safe Labor Study (2002-2008) that consistently reported estimated blood loss at delivery. The outcome was postpartum hemorrhage, defined as an estimated blood loss at least 1,000 mL. Fifty-five candidate risk factors routinely available on labor admission were considered. We used logistic regression with and without lasso regularization (lasso regression) as the two statistical models, and random forest and extreme gradient boosting as the two machine learning models to predict postpartum hemorrhage. Model performance was measured by C statistics (ie, concordance index), calibration, and decision curves. Models were constructed from the first phase (2002-2006) and externally validated (ie, temporally) in the second phase (2007-2008). Further validation was performed combining both temporal and site-specific validation.

RESULTS

Of the 152,279 assessed births, 7,279 (4.8%, 95% CI 4.7-4.9) had postpartum hemorrhage. All models had good-to-excellent discrimination. The extreme gradient boosting model had the best discriminative ability to predict postpartum hemorrhage (C statistic: 0.93; 95% CI 0.92-0.93), followed by random forest (C statistic: 0.92; 95% CI 0.91-0.92). The lasso regression model (C statistic: 0.87; 95% CI 0.86-0.88) and logistic regression (C statistic: 0.87; 95% CI 0.86-0.87) had lower-but-good discriminative ability. The above results held with validation across both time and sites. Decision curve analysis demonstrated that, although all models provided superior net benefit when clinical decision thresholds were between 0% and 80% predicted risk, the extreme gradient boosting model provided the greatest net benefit.

CONCLUSION

Postpartum hemorrhage on labor admission can be predicted with excellent discriminative ability using machine learning and statistical models. Further clinical application is needed, which may assist health care providers to be prepared and triage at-risk women.

Shock Index and Postpartum Hemorrhage in Vaginal Deliveries: A Multicenter Retrospective Study

INTRODUCTION

Shock index (SI), calculated by dividing heart rate by systolic blood pressure, is used to detect hemodynamic instability and hypovolemia. In obstetric practice, limited evidence is available regarding its usefulness in detecting postpartum hemorrhage (PPH). We aimed to evaluate the usefulness of SI in detecting PPH in vaginal deliveries using clinical data from 12 primary maternity care units in Japan.

MATERIAL AND METHODS

In this multicenter retrospective study, a total of 30,820 women who delivered vaginally at term at 12 primary maternity care units from January 2012 to December 2018 were included. Systolic and diastolic blood pressures and heart rate were measured at five different time points from admission to postpartum 2 h, and postpartum blood loss was measured. We evaluated the trend of average SI and the performance of each vital sign for detection of PPH.

RESULTS

The trend of average SI during labor and the immediate postpartum period was approximately 0.7 in women with blood loss of <500 mL. SI from the time of delivery of the placenta increased with an increase in blood loss. SI had the highest area under the receiver operating characteristic curve of 0.699 [95% confidence interval (CI), 0.682-0.716] and 0.758 (95% CI, 0.729-0.788) for PPH of ≥1,000 and ≥1,500 mL, respectively. However, both sensitivity of SI (1.0) for PPH (≥1,000 mL; 29.9%, and ≥1,500 mL; 40.5%, respectively) and correlation between maximum SI and blood loss (coefficient of correlation, 0.263) were low.

CONCLUSIONS

SI is a better parameter for PPH detection in vaginal deliveries than other vital signs. However, clinical judgment must incorporate other vital signs and symptoms associated with hypovolemic shock due to the low sensitivity of SI.