Lit Review: REBOA, Whole Blood, and the HVI Score

This episode explores recent medical research and clinical debates concerning the management of severe traumatic injuries and life-threatening bleeding. One study introduces a predictive scoring system to help surgeons accurately identify hollow viscus injuries in patients presenting with an abdominal seatbelt sign. Another major trial evaluates the effectiveness of REBOA, finding that this balloon occlusion technique may actually increase mortality rather than improve outcomes for hemorrhaging patients. Additionally, research on low-titer group O whole blood indicates that while it is generally safe, it specifically provides a survival advantage for patients with a very high risk of death compared to traditional component therapy. Collectively, these articles emphasize a move toward data-driven triage and the critical reassessment of standard emergency interventions. Together, they reflect an ongoing effort to refine resuscitation strategies and surgical decision-making in high-stakes trauma environments.       The Critical Edge is for educational and informational purposes only and is not intended to diagnose, treat, cure, or prevent any disease, nor does it substitute for professional medical advice, diagnosis, or treatment from a qualified healthcare provider—always seek in-person evaluation and care from your physician or trauma team for any health concerns.       REBOA, Whole Blood, and the HVI Score Study Guide This study guide provides a comprehensive review of recent clinical research regarding hollow viscus injury prediction, the efficacy of resuscitative endovascular balloon occlusion of the aorta (REBOA), and the use of whole blood in trauma resuscitation.   I. Hollow Viscus Injury (HVI) Prediction in Abdominal Seatbelt Sign (SBS) The diagnosis of hollow viscus injury following blunt trauma is notoriously difficult. While Computed Tomography (CT) is effective at excluding HVI when findings are entirely absent, it has historically performed poorly in identifying the presence of HVI in at-risk patients.   The Pacific Coast Surgical Association Multicenter Study A prospective observational study (Santos et al.) analyzed 754 adult patients with abdominal seatbelt signs who received a CT scan prior to surgery. The goal was to create a pragmatic scoring system using variables knowable to a triaging surgeon in real-time.   Predictor Variables used in the HVI Score: Physiological Data: Initial Systolic Blood Pressure (SBP) < 110 mmHg. Physical Examination: Abdominal tenderness and guarding. CT Findings: Free fluid, free air, mesenteric hematoma, or mesenteric stranding. The HVI Scoring System and Triage The resulting whole-number scoring system ranges from 0 to 17 points. Higher scores correlate with a higher probability of HVI. The study advocates for a tiered management approach based on these scores: Low Risk (Score 0–5): The risk of HVI is between 0.03% and 5.36%. These patients may typically be managed through observation. Moderate Risk (Score 6–9): The risk of HVI is between 10.6% and 44.1%. Surgical exploration should be strongly considered but is not mandatory. Substantial Risk (Score 10–17): The risk of HVI is between 58.6% and 99.7%. These patients should undergo diagnostic laparoscopy. Clinical Nuances and Limitations Isolated Free Air: Interestingly, the presence of isolated free air on a CT scan confers only a 2.41% risk of HVI. In the study cohort, no patient with isolated free air had a concomitant HVI. This suggests pneumoperitoneum is an imperfect predictor, as mechanisms other than HVI can generate free air. Clinical Judgment: The authors emphasize that the scoring system should support, rather than replace, clinical judgment. Diagnostic Performance: The model demonstrated high predictive performance, with an Area Under the Receiver Operating Curve (AUROC) of 0.94 in the initial analysis and 0.91 in validation sets. II. Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) The UK-REBOA trial was a randomized clinical trial designed to evaluate REBOA as an adjunct to standard care for patients with exsanguinating traumatic hemorrhage.   Trial Outcomes and Findings The trial, which included 90 patients across 16 major trauma centers, was stopped early due to evidence of harm. Mortality: All-cause mortality at 90 days was 54% in the REBOA group compared to 42% in the standard care group. Hemorrhage-Related Death: There were more deaths due to bleeding in the REBOA group (32%) than in the standard care group (17%), with most occurring within the first 24 hours. Conclusion: The researchers concluded that REBOA does not reduce, and may actually increase, mortality in this patient population. Critical Limitations and Contextual Factors Despite the trial's conclusions, several factors may have influenced the outcomes: Baseline Severity: Patients in the REBOA arm were more hypotensive on arrival and had higher median Abbreviated Injury Scale (AIS) scores for the head, suggesting more severe traumatic brain injuries (TBI) that might have been unsalvageable. Low Intervention Rates: Only 41% of patients in the REBOA arm actually received the intervention (balloon inflation). This resulted in only 19 patients receiving the actual REBOA procedure across 16 centers over five years. Experience and Volume: Many centers had never used REBOA prior to the study, and low individual center volume may have impacted outcomes. Time to Control: The median prehospital time was 90 minutes. Furthermore, the time to definitive hemorrhage control was significantly longer in the REBOA group (83 minutes) than in the standard care group (64 minutes). Sub-optimal Usage: The median inflation time was 29 minutes. Clinical guidelines generally suggest REBOA should only be used if hemorrhage control can be achieved within 15 minutes, as ischemia time exceeding 30 minutes increases mortality risk. III. Whole Blood Resuscitation in Hemorrhagic Shock The SWAT (Shock, Whole Blood, and Assessment of Traumatic Brain Injury) study explored the safety and efficacy of Low-Titer Group O Whole Blood (LTOWB) compared to traditional blood component therapy. General Findings   In the overall cohort of 1,051 patients in hemorrhagic shock, LTOWB was found to be safe but did not show a statistically significant difference in 4-hour, 24-hour, or 28-day mortality when compared to component therapy.   High-Risk Subset Analysis The most significant findings emerged when analyzing patients with an elevated prehospital probability of mortality (determined by mechanism of injury and vital signs): Mortality Reduction: For patients with a 50% predicted risk of mortality, receiving LTOWB was associated with an almost 40% decreased risk of mortality compared to those receiving components. Survival Correlation: In the component group, actual mortality directly correlated with predicted mortality. In the LTOWB group, the mortality rate "plateaued," remaining lower than predicted for the most severely injured. Long-term Association: Among high-risk patients, LTOWB was independently associated with a 48% lower risk of 4-hour mortality and a 30% lower risk of 28-day mortality. Study Limitations Pragmatic Design: Institutions were allowed discretion regarding leukoreduction, titer levels, and specific indications for use. Crossover: Only 66% of patients at LTOWB sites actually received whole blood, and many patients in the whole blood group also received components during their resuscitation. IV. Glossary of Key Terms Abbreviated Injury Scale (AIS): An anatomical-based coding system to classify and describe the severity of specific individual injuries. Area Under the Receiver Operating Curve (AUROC): A performance metric for predictive models; a score of 1.0 represents a perfect model, while 0.5 represents a model no better than chance. Blood Component Therapy: The practice of transfusing specific parts of blood (e.g., packed red blood cells, plasma, platelets) rather than whole blood. Exsanguinating Hemorrhage: Severe, life-threatening bleeding that leads to the loss of a significant portion of a patient's total blood volume. Hollow Viscus Injury (HVI): Injury to the hollow organs of the body, such as the stomach, intestines, or bladder. Injury Severity Score (ISS): An anatomical scoring system that provides an overall score for patients with multiple injuries. Low-Titer Group O Whole Blood (LTOWB): Whole blood from a group O donor that has been tested to ensure it contains low levels of anti-A and anti-B antibodies, making it safer for emergency transfusion to patients of any blood type. Pneumoperitoneum: The presence of air or gas in the abdominal (peritoneal) cavity. Pragmatic Trial: A clinical trial designed to show the real-world effectiveness of the intervention in broad clinical practice. REBOA (Resuscitative Endovascular Balloon Occlusion of the aorta): A procedure involving the placement of a balloon catheter in the aorta to control bleeding and maintain blood pressure in the upper body during severe hemorrhage. Seatbelt Sign (SBS): A physical finding of bruising or abrasions on the abdomen or chest in the distribution of a seatbelt following a motor vehicle accident.