Hemorrhagic shock: The "physiology approach"

Management of Hemorrhagic Shock: Physiology Approach, Timing and Strategies

Hemorrhagic shock (HS) management is based on a timely, rapid, definitive source control of bleeding/s and on blood loss replacement. Stopping the hemorrhage from progressing from any named and visible vessel is the main stem fundamental praxis of efficacy and effectiveness and an essential, obligatory, life-saving step. Blood loss replacement serves the purpose of preventing ischemia/reperfusion toxemia and optimizing tissue oxygenation and microcirculation dynamics. The "physiological classification of HS" dictates the timely management and suits the 'titrated hypotensive resuscitation' tactics and the 'damage control surgery' strategy. In any hypotensive but not yet critical shock, the body's response to a fluid load test determines the cut-off point between compensation and progression between the time for adopting conservative treatment and preparing for surgery or rushing to the theater for rapid bleeding source control. Up to 20% of the total blood volume is given to refill the unstressed venous return volume. In any critical level of shock where, ab initio, the patient manifests signs indicating critical physiology and impending cardiac arrest or cardiovascular accident, the balance between the life-saving reflexes stretched to the maximum and the insufficient distal perfusion (blood, oxygen, and substrates) remains in a liable and delicate equilibrium, susceptible to any minimal change or interfering variable. In a cardiac arrest by exsanguination, the core of the physiological issue remains the rapid restoration of a sufficient venous return, allowing the heart to pump it back into systemic circulation either by open massage via sternotomy or anterolateral thoracotomy or spontaneously after aorta clamping in the chest or in the abdomen at the epigastrium under extracorporeal resuscitation and induced hypothermia. This is the only way to prevent ischemic damage to the brain and the heart. This is accomplishable rapidly and efficiently only by a direct approach, which is a crush laparotomy if the bleeding is coming from an abdominal +/- lower limb site or rapid sternotomy/anterolateral thoracotomy if the bleeding is coming from a chest +/- upper limbs site. Without first stopping the bleeding and refilling the heart, any further exercise is doomed to failure. Direct source control via laparotomy/thoracotomy, with the concomitant or soon following venous refilling, are the two essential, initial life-saving steps.

The effect of subdiaphragmatic vagotomy on heart rate variability and lung inflammation in rats with severe hemorrhagic shock

Background

The influence of cutting the sub-diaphragmatic branch of the vagus nerve on heart rate variability (HRV) and inflammatory reaction to severe hemorrhagic shock has not been determined prior to this study.

Methods

Male Sprague–Dawley rats were divided into four groups of Sham, sub-diaphragmatic vagotomized (Vag), subacute (135 ± 2 min) hemorrhagic shock (SHS), and sub-diaphragmatic vagotomized with SHS (Vag + SHS). Hemodynamic parameters were recorded and HRV calculated during multiple phases in a conscious model of hemorrhagic shock. The expressions of TNF-α and iNOS were measured in the spleen and lung tissues at the conclusion of the protocol.

Results

Decreases in blood pressure during blood withdrawal were identical in the SHS and Vag + SHS groups. However, heart rate only decreased in the Nadir-1 phase of the SHS group. HRV indicated increased power in the very-low, low, and high (VLF, LF, and HF) frequency bands during the Nadir-1 phase of the SHS and Vag + SHS groups, albeit the values were higher in the SHS group. In the recovery phase, the HF bands were only lower in the SHS group. After hemorrhagic shock followed by resuscitation, the expression of TNF-α and iNOS increased in the spleen and lung of the SHS group, and the expression of these genes was significantly lower in the Vag + SHS group than in the SHS group.

Conclusion

Parasympathetic activity increases during the hypotensive phase of hemorrhagic shock, whereas the cardiac vagal tone decreases in the recovery phase. Sub-diapragmatic vagotomy blunts the cardiac vagal tone during hemorrhagic shock, but its effect is reversed in the recovery phase. The vagus nerve plays a role in proinflammatory responses in the lungs and spleen in subacute hemorrhagic shock followed by resuscitation.

Multidisciplinary Programed Learning Simulation to Improve Visual Blood Loss Estimation for Obstetric Trauma Scenarios

INTRODUCTION

We designed and implemented a Programmed Learning Simulation (PLS) exercise depicting obstetric scenarios of hemorrhage to train anesthesiologists, ancillary staff, and surgeons to accurately estimate blood loss visually. We then measured the efficacy of this exercise in a clinical setting.

METHODS

We conducted a prospective study to assess the effect of implementing a PLS exercise on quantification of blood loss in an operative setting. The PLS exercise consisted of 13 simulation stations of varying quantities of simulated blood loss paired with standardized objects of known volume. Eighty-eight individuals participated including attending physicians, residents, medical students, and ancillary staff participated in this study. The PLS was part of regularly scheduled continuing medical education activities; thus, the sampling used was non-randomized convenience method. The percent error was calculated for each of the 13 stations. A subgroup analysis was performed to assess the effect of the years of experience, size of hemorrhage, and occupation on accuracy. Univariate analyses for continuous variables were compared using a one-way ANOVA test. For the comparison of the three groups (years of experience and size of hemorrhage), a p-value of <0.02 was considered statistically significant and for 5-way comparison (professional grouping) a p <0.01 was considered significant after application of the Bonferroni correction (α=0.05). (Part A). To determine the effect of PLS in a clinical setting, the percent error of blood loss estimation for cesarean deliveries during the two-month period after the PLS exercise was compared to the two-month period immediately prior to using the student's t-test with p<0.05 as significant (Part B). Statistical analysis was performed using International Business Machine, Statistical Package for the Social Sciences, Version 26.0 (IBM SPSS).

RESULTS

During Part A, the baseline performance of the participants was evaluated during the PLS activity. The PLS data showed no significant difference in absolute value of mean percent error estimation (standard deviation) across professions: student 63.61% (69.74), ob/gyn 56.91% (47.72), ancillary 62.15% (77.90), general/trauma surgeon 66.70% (65.06), anesthesia 61.51% (63.12). (p = 0.681), or levels of experience 0-5: 62.21% (60.06), 6-10 years: 56.22% (52.66), greater than 10 years: 61.89% (71.89) (p = 0.831). However, mean percent error of estimation was higher when participants estimated smaller samples 77.7% (104.73) compared to either medium 56.8% (49.06) or large 57.9% (46.19) samples (p<0.001). For Part B, 179 cesarean deliveries occurred during the pre-intervention period and 193 occurred during the post-intervention period. Mean error in provider estimation of blood loss significantly improved from 47% (68.51) pre-intervention to 31% (32.70) post-intervention (p=0.009).

CONCLUSION

We believe our described PLS activity was effective in teaching techniques for visual blood loss estimation. This was reflected by improved competency in a clinical setting, demonstrated by more accurate visually estimated blood loss during the period immediately following simulation activity compared to a prior time frame. Further research is needed to assess the impact of simulation activities on patient outcomes, such as utilization of blood products and patient morbidity.

Comparison of the Previous and Current Trauma-Related Shock Classifications: A Retrospective Cohort Study from a Level I Trauma Center

PURPOSE

The aim was to examine the predictive value of the hypovolemic shock classification currently accepted by the Advanced Trauma Life Support (ATLS) program over the previous one, which used only vital signs (VS) for patient allocation. The primary outcome was 30-day mortality; as secondary outcome, heart rate (HR), systolic blood pressure (SBP), Glasgow Coma Scale (GCS) and base deficit (BD) data were compared and investigated in terms of mortality prediction.

METHODS

Retrospective analysis at a level I trauma center between 2014 and 2019. Adult patients treated by trauma teams were allocated into severity classes (I-IV) based on the criteria of the current and previous ATLS classifications, respectively. The prognostic values for the classifications were determined with Fisher's exact test and χ2 test for independence, and compared with the 2-proportion Z test. The individual variables were analyzed with receiver-operating characteristic (ROC) analyses.

RESULTS

A total of 156 patients met the inclusion criteria. Mortality was effectively predicted by both classifications, and there was no statistically significant difference between the predictive performances. According to ROC analyses, GCS, BD and SBP had significant prognostic values while HR change was ineffective in this regard.

CONCLUSIONS

The currently used ATLS shock classification does not appear to be superior to the VS-based previous classification. GCS, BD and SBP are useful parameters to predict the prognosis. Changes in HR do not reflect the clinical course accurately; thus, further studies will be needed to determine the value of this parameter in trauma-associated hypovolemic-hemorrhagic shock conditions.

Rotational Thromboelastometry-Guided Transfusion Protocol to Reduce Allogeneic Blood Transfusion in Proximal Aortic Surgery With Deep Hypothermic Circulatory Arrest

OBJECTIVES

To determine the impact of a rotational thromboelastometry (ROTEM)-guided transfusion protocol on the use of blood products, patient outcomes, coagulation factor concentrates, and costs.

DESIGN

A single-center retrospective cohort study.

SETTING

A tertiary university hospital.

PATIENTS

Adults undergoing proximal aortic surgery with deep hypothermic circulatory arrest.

INTERVENTION

ROTEM-guided transfusion protocol compared with clinically-guided transfusion.

MEASUREMENTS AND MAIN RESULTS

Two hundred seventeen patients were included; seventy-one elective and 24 emergency patients in the clinically-guided group, and 59 elective and 63 emergency patients in the ROTEM-guided transfusion protocol group. In the ROTEM-guided transfusion protocol group, a significant reduction in transfusion of red blood cells (5 [3-8] v 2 [0-4], p < 0.001), platelet concentrate (2 [2-3] v 1 [1-2], p < 0.001), and plasma (1,980 mL [1,320-3,300] v 800 mL [0-1,000], p < 0.001) was seen in elective surgery. Emergency patients received fewer red blood cells (7 [5-10] v 5 [2-10], p = 0.040), platelet concentrate (3 [2-4] v 2 [2-3], p = 0.023), and plasma (3,140 mL [1,980-3,960] v 1,000 mL [0-1,400], p < 0.001). Prothrombin complex concentrate and fibrinogen concentrate were increased significantly in elective and emergency patients. The surgical reexploration for bleeding rate was decreased in elective patients 33.8% v 5.1%.

CONCLUSION

The implementation of a ROTEM-guided transfusion protocol might have the potential to decrease blood product transfusion and may improve patient outcomes.

Therapeutic cardiac arrest as an adjunct to resuscitative endovascular balloon occlusion of the aorta: Bridging the gap from fatal hemorrhage to definitive surgical control in swine

BACKGROUND

Uncontrolled hemorrhage is the leading cause of potentially survivable combat casualty mortality, with 86.5% of cases resulting from noncompressible torso hemorrhage. Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a minimally invasive technique used to stabilize patients with noncompressible torso hemorrhage; however, its application can take an average of 8 minutes to place. One therapeutic capable of bridging this gap is adenosine-lidocaine-magnesium (ALM), which at high doses induces a reversible cardioplegia. We hypothesize by using ALM as an adjunct to REBOA, the ALM-induced cardiac arrest will temporarily halt exsanguination and reduce blood loss, allowing for REBOA placement and control of bleeding.

METHODS

Male Yorkshire swine (60-80 kg) were randomly assigned to REBOA only or ALM-REBOA (n = 8/group). At baseline, uncontrolled hemorrhage was induced via a 1.5-cm right femoral arteriotomy, and hemorrhaged blood was quantified. One minute after injury (S1), ALM was administered, and 7 minutes later (T0), zone 1 REBOA inflation occurred. If cardiac arrest ensued, cardiac function either recovered spontaneously or advanced life support was initiated. At T30, surgical hemostasis was obtained, and REBOA was deflated. Animals were resuscitated until they were humanely euthanized at T90.

RESULTS

During field care phase, heart rate and end-tidal CO2 of the ALM-REBOA group were significantly lower than the REBOA only group. While mean arterial pressure significantly decreased from baseline, no significant differences between groups were observed throughout the field care phase. There was no significant difference in survival between the two groups (ALM-REBOA = 89% vs. REBOA only = 100%). Total blood loss was significantly decreased in the ALM-REBOA group (REBOA only = 24.32 ± 1.89 mL/kg vs. ALM-REBOA = 17.75 ± 2.04 mL/kg, p = 0.0499).

CONCLUSION

Adenosine-lidocaine-magnesium is a novel therapeutic, which, when used with REBOA, can significantly decrease the amount of blood loss at initial presentation, without compromising survival. This study provides proof of concept for ALM and its ability to bridge the gap between patient presentation and REBOA placement.

The Need for a Physiological Classification of Hemorrhagic Shock

Classifications mean to conceptualize in a cluster and rapidly summarize the assessment and management of a clinical scenario. In the specific case of a hemorrhagic shock (HS), a classification should serve the purpose of allowing a rapid clinical assessment of the shock level and the earliest or right timing of source control, possibly also on whether to apply damage control surgery (DCS) strategy or not. ATLS^® classification of HS is not sensitive and specific enough to help decision-making in reference to the timing of management, based only on the amount of blood loss that may be or may not rightly estimated, for example, blood loss on the floor in penetrating injuries before theatre. Moreover, it focuses also on other parameters, which are taken singularly, instead of the individual generalized physiological response to hemorrhage, which is the core by definition of the derangement we call "shock." It is unhelpful, difficult, and impractical to apply as well. A new classification, which may well be called as the "physiological HS classification" or "therapeutic HS classification," was proposed since 2010, following the new developments on microcirculation and an already going-on sensible praxis among some trauma surgeons. It bases on some physiological considerations such as the significance of fluid-blood resistant hypotension, body natural hemostatic mechanisms, the right definition of shock, and the relevance that hemorrhage-triggered ischemia-reperfusion toxemia and systemic inflammatory response have in critical illness scenarios as secondary insults from ischemia, which is what we mean to prevented with DCS. The key factor remains the persistence of hypotension, following fluid challenge.

Comparison of the trometamol-balanced solution with two other crystalloid solutions for fluid resuscitation of a rat hemorrhagic model

Currently, the optimal resuscitation fluid remains debatable. Therefore, in the present study, we designed a trometamol-balanced solution (TBS) for use as a resuscitation fluid for hemorrhagic shock. Hemorrhagic shock was induced in 18 male Wistar-Kyoto rats, which were assigned to normal saline (NS), Ringer's solution (RS), and TBS groups. During the hemorrhagic state, their hemodynamic parameters were recorded using an Abbott i-STAT analyzer with the CG4+ cartridge (for pH, pressure of carbon dioxide, pressure of oxygen, total carbon dioxide, bicarbonate, base excess, oxygen saturation, and lactate), the CG6+ cartridge (for sodium, potassium, chloride, blood glucose, blood urea nitrogen, hematocrit, and hemoglobin), and enzyme-linked immunosorbent assay kits (calcium, magnesium, creatinine, aspartate aminotransferase, alanine aminotransferase, bilirubin, and albumin). Similar trends were found for the parameters of biochemistries, electrolytes, and blood gas, and they revealed no significant changes after blood withdrawal-induced hemorrhagic shock. However, the TBS group showed more effective ability to correct metabolic acidosis than the NS and RS groups. TBS was a feasible and safe resuscitation solution in this study and may be an alternative to NS and RS for resuscitation in hemorrhagic shock patients without liver damage.

Practicing Military Medicine in Truly Austere Environments: What to Expect, How to Prepare, When to Improvise

Introduction

The majority of the published literature on contemporary military medicine contradicts the concept of austere. Operational medicine is part of every armed conflict around the world, while armed forces of most countries internationally have limited medical resources especially in the front line. The aim of this review is to identify the particularities of a truly austere environment and present a short guide of preparation and action for military medical personnel internationally.

Materials and Methods

An exhaustive search of the existing English literature on operational and military medicine in austere environments was carried out in EMBASE and PubMed databases.

Results

This review included seminal and contemporary papers on the subject and synthesized a multiperspective short guide for operational medical personnel.

Discussion

Experience from forward surgical teams of the U.S. Army and humanitarian teams of physicians in war zones who work under precarious and austere circumstances has shown that the management of casualties requires different strategies than in higher levels of combat casualty care and in a civilian setting. A number of factors that must be controlled can be categorized into human, environmental, equipment-related, and socioeconomic. Surgeons and other medical personnel should have knowledge of these aspects beforehand and be adequately trained in peacetime. Physicians must master a number of essential skills and drugs, and be familiar with dosage regimens and side effects.

Conclusion

The military surgeon must be specially trained and prepared to use a wide range of skills in truly austere environments in contemporary conflicts.

Digital postpartum hemorrhage management device (DPHMD)

Background

Primary postpartum hemorrhage (PPH) is an obstetric emergency caused by excessive blood loss that occurs most commonly after the placenta is delivered. PPH can lead to volume depletion, hypovolemic shock, anemia, and it is the leading cause of maternal mortality worldwide. With 470 deaths per 100,000 live births, the maternal mortality ratio in Ethiopia is one of the highest in the world. It is estimated that 94% of births occur at home in Ethiopia and that 10% of maternal deaths are attributed to PPH. Currently, physicians use visual estimation to calculate blood loss and provide fluid during delivery. This traditional method is subjective and generally inaccurate.

Method

In this project, after delivery blood loss measurement system integrated with fluid delivery and vital sign monitoring method is proposed. The collection and measurement system collects blood loss after delivery and measures the amount of blood loss. The management system continuously monitors the mother’s heart rate and blood pressure. These vital sign values are integrated with the measured blood loss to estimate the amount of IV fluid required to be delivered for the mother. The rate of IV fluid delivery is regulated by a flow rate sensor and solenoid valve.

Results

The prototype was built and undergone through different tests and iterations. The proposed device was tested for accuracy, cost effectiveness and ease to use. 91.28% accuracy has been achieved and the prototype was built with less than 210 USD.

Conclusion

The proposed design allows physicians, especially those in low resource setting, to estimate blood loss and deliver fluid accurately. This helps to reduce maternal mortality rate that may occur due to postpartum hemorrhage.

Dissociation between macro- and microvascular parameters in the early phase of hemorrhagic shock

Hemorrhagic shock (HS) therapy is based on macrohemodynamic improvement, but it is not clear if this therapy correlates directly with increases in tissue perfusion. Aiming to clarify this point, we compared norepinephrine (NE, a vasoconstrictor), sodium nitroprusside (NP, a vasodilator) and levosimendan (LEV, an inodilator) treatments on macro and microvascular parameters using the hamster dorsal skinfold chamber preparation. One hour after HS, animals received Ringer's lactate (RL) solution within 10 min, then animals received RL, NP, NE and LEV during 90 min via jugular vein. Macrovascular variables: mean arterial pressure (MAP), heart rate (HR), maximal ventricle pressure (MVP), change in ventricular pressure over time (dP/dt) and microvascular variables: arteriolar and venular diameters, functional capillary density (FCD) and red blood cell velocity (RBCV) were evaluated at baseline, 60 min after HS, 60 and 90 min after treatments. Lactate blood concentrations were evaluated at baseline, 60 min after HS and 90 min after treatments. Hematocrit (Hct), cardiac output (CO), stroke volume (SV) and number of rolling and adhered leukocytes were assessed at 90 min after treatments. Data were considered significant when p < 0.05. NE increased significantly all macrohemodynamic variables compared to baseline (except MAP), and it was the only treatment that increased Hct, CO and SV significantly. NE decreased significantly all microvascular variables in comparison to baseline. NP increased HR, FCD and RBCV and reduced MVP and dP/dt significantly. LEV decreased MVP and dP/dt, arteriolar diameter and FCD and augmented RBCV significantly in comparison to baseline. Blood concentration of lactate increased significantly 60 min after HS. Leukocyte rolling and adhesion were not different between groups. We concluded that, early, during hemorrhagic shock, norepinephrine associated to fluid therapy improved macrohemodynamic parameters but failed to improved microvascular flow. Conversely, sodium nitroprusside association had the opposite effect. Despite its inodilator properties, levosimendan did not improve macro or microhemodynamic parameters when combined to fluid therapy.

A systematic review of large animal models of combined traumatic brain injury and hemorrhagic shock

Traumatic brain injury (TBI) and severe blood loss (SBL) frequently co-occur in human trauma, resulting in high levels of mortality and morbidity. Importantly, each of the individual post-injury cascades is characterized by complex and potentially opposing pathophysiological responses, complicating optimal resuscitation and therapeutic approaches. Large animal models of poly-neurotrauma closely mimic human physiology, but a systematic literature review of published models has been lacking. The current review suggests a relative paucity of large animal poly-neurotrauma studies (N = 52), with meta-statistics revealing trends for animal species (exclusively swine), characteristics (use of single biological sex, use of juveniles) and TBI models. Although most studies have targeted blood loss volumes of 35-45%, the associated mortality rates are much lower relative to Class III/IV human trauma. This discrepancy may result from potentially mitigating experimental factors (e.g., mechanical ventilation prior to or during injury, pausing/resuming blood loss based on physiological parameters, administration of small volume fluid resuscitation) that are rarely associated with human trauma, highlighting the need for additional work in this area.

Thromboelastometry-guided hemostatic therapy for hemorrhagic shock in the postoperative period of vascular surgery: a case report

Background

Hemorrhagic shock is a medical emergency that often complicates vascular surgery and can lead to death. Hemorrhagic shock is characterized by hypoperfusion and hemodynamic abnormalities leading to the collapse of homeostasis due to massive blood loss. Early diagnosis is critical for a favorable outcome. Thromboelastometry has been considered an effective tool for bleeding management in critically ill patients. Thromboelastometry can guide transfusion therapy quickly, reducing the need for blood products. Therefore, it could be an alternative test to guide hemostatic therapy in complex cases of hemorrhagic shock as a result of vascular surgeries. We report our successful experience with a case of hemorrhagic shock in postoperative care in vascular surgery, in which bleeding management was guided by thromboelastometry and bleeding control was achieved with hemostatic drugs and coagulation factor concentrates.

Case presentation

We report a case of an 82-year-old Afro-Brazilian man who presented to the intensive care unit with hemorrhagic shock in the postoperative period of vascular surgery. He underwent surgery for correction of iliac artery aneurysm with endoleak. His laboratory tests revealed severe anemia (hemoglobin 7.4 mg/dL), metabolic acidosis (bicarbonate 10 mEq/L, pH 7.11), acute kidney injury (creatinine 3.1 mg/dL), thrombocytopenia (platelets count 83 × 10³/mm³), hypofibrinogenemia (70 mg/dL), international nationalized ratio 1.95, activated partial thromboplastin time 64.5 seconds, and lactate 87 mmol/L. There was active bleeding in surgical site. Bleeding management was guided by thromboelastometry. The first test showed fulminant hyperfibrinolysis, which was corrected with the administration of tranexamic acid. The second thromboelastometry test showed improvement of hyperfibrinolysis but severe hypocoagulability. Fibrinogen concentrate, platelet apheresis, cryoprecipitate, and prothrombin complex concentrate were sequentially administrated. Thromboelastometry was completely corrected after 2 hours. Arteriography to evaluate mechanical cause of bleeding was normal. No more bleeding was identified, and neither was any further transfusion needed. He was discharged from the intensive care unit from the ward 3 days after admission.

Conclusions

Thromboelastometry may be considered a useful, feasible and safe tool to monitor and manage coagulopathy in patients with hemorrhagic shock. Moreover, it has the potential benefit of allowing rapid diagnosis,  goal-directed therapy with hemostatic drugs and coagulation factor concentrates and thus, avoiding unnecessary blood component transfusion.

Vital Sign Prediction of Adverse Maternal Outcomes in Women with Hypovolemic Shock: The Role of Shock Index

OBJECTIVE

To determine the optimal vital sign predictor of adverse maternal outcomes in women with hypovolemic shock secondary to obstetric hemorrhage and to develop thresholds for referral/intensive monitoring and need for urgent intervention to inform a vital sign alert device for low-resource settings.

STUDY DESIGN

We conducted secondary analyses of a dataset of pregnant/postpartum women with hypovolemic shock in low-resource settings (n = 958). Using receiver-operating curve analysis, we evaluated the predictive ability of pulse, systolic blood pressure, diastolic blood pressure, shock index, mean arterial pressure, and pulse pressure for three adverse maternal outcomes: (1) death, (2) severe maternal outcome (death or severe end organ dysfunction morbidity); and (3) a combined severe maternal and critical interventions outcome comprising death, severe end organ dysfunction morbidity, intensive care admission, blood transfusion ≥ 5 units, or emergency hysterectomy. Two threshold parameters with optimal rule-in and rule-out characteristics were selected based on sensitivities, specificities, and positive and negative predictive values.

RESULTS

Shock index was consistently among the top two predictors across adverse maternal outcomes. Its discriminatory ability was significantly better than pulse and pulse pressure for maternal death (p<0.05 and p<0.01, respectively), diastolic blood pressure and pulse pressure for severe maternal outcome (p<0.01), and systolic and diastolic blood pressure, mean arterial pressure and pulse pressure for severe maternal outcome and critical interventions (p<0.01). A shock index threshold of ≥ 0.9 maintained high sensitivity (100.0) with clinical practicality, ≥ 1.4 balanced specificity (range 70.0-74.8) with negative predictive value (range 93.2-99.2), and ≥ 1.7 further improved specificity (range 80.7-90.8) without compromising negative predictive value (range 88.8-98.5).

CONCLUSIONS

For women with hypovolemic shock from obstetric hemorrhage, shock index was consistently a strong predictor of all adverse outcomes. In lower-level facilities in low resource settings, we recommend a shock index threshold of ≥ 0.9 indicating need for referral, ≥ 1.4 indicating urgent need for intervention in tertiary facilities and ≥ 1.7 indicating high chance of adverse outcome. The vital sign alert device incorporated values 0.9 and 1.7; however, all thresholds will be prospectively validated and clinical pathways for action appropriate to setting established prior to clinical implementation.

Vasopressin in hemorrhagic shock: a systematic review and meta-analysis of randomized animal trials

Objective. The latest European guidelines for the management of hemorrhagic shock suggest the use of vasopressors (norepinephrine) in order to restore an adequate mean arterial pressure when fluid resuscitation therapy fails to restore blood pressure. The administration of arginine vasopressin (AVP), or its analogue terlipressin, has been proposed as an alternative treatment in the early stages of hypovolemic shock. Design. A meta-analysis of randomized controlled animal trials. Participants. A total of 433 animals from 15 studies were included. Interventions. The ability of AVP and terlipressin to reduce mortality when compared with fluid resuscitation therapy, other vasopressors (norepinephrine or epinephrine), or placebo was investigated. Measurements and Main Results. Pooled estimates showed that AVP and terlipressin consistently and significantly improve survival in hemorrhagic shock (mortality: 26/174 (15%) in the AVP group versus 164/259 (63%) in the control arms; OR = 0.09; 95% CI 0.05 to 0.15; P for effect < 0.001; P for heterogeneity = 0.30; I₂ = 14%). Conclusions. Results suggest that AVP and terlipressin improve survival in the early phases of animal models of hemorrhagic shock. Vasopressin seems to be more effective than all other treatments, including other vasopressor drugs. These results need to be confirmed by human clinical trials.