Preventable deaths after injury: why are the traditional 'vital' signs poor indicators of blood loss?

The non-haemorrhagic vagal response to trauma: a review of hypotensive and bradycardic responses to injury in the absence of bleeding

PURPOSE

Trauma has the potential to cause haemorrhage, tissue damage, pain, visceral manipulation and psychological distress. Each of these consequences of trauma can cause changes in autonomic outflow, which dictates a patient's vital signs. Patients who are hypotensive and bradycardic due to a vagally mediated parasympathetic response to pain, psychological distress and visceral manipulation may be confused with those who exhibit bradycardia and hypotension following significant blood volume loss.

METHODS

This review summarises literature that describes specific stimuli, patterns of injury and patient characteristics that are associated with a non-haemorrhagic vagal response to trauma.

RESULTS

Twenty-six records described predominantly parasympathetic responses to trauma (both blunt and penetrating) and surgery ("iatrogenic trauma"). Such a non-haemorrhagic vagal response occurs following a wide variety of injury patterns. Patient age and sex are poor predictors of the likelihood of a non-haemorrhagic vagal response. The development and resolution of a non-haemorrhagic vagal response occurs over a heterogenous time period. It is unclear whether speed of onset and resolution is linked to the pattern of injury or other factors causing a predominantly parasympathetic response following non-haemorrhagic trauma.

CONCLUSION

The pattern of injury, patient demographic and speed of onset / resolution associated with the non-haemorrhagic vagal response to trauma may is heterogenous. It is therefore challenging to clinically distinguish between the hypotensive bradycardia due to hypovolaemia secondary to haemorrhage, or a parasympathetic response to trauma in the absence of bleeding.

Critical systolic blood pressure threshold for endovascular aortic occlusion-A multinational analysis to determine when to place a REBOA

BACKGROUND

Systolic blood pressure (SBP) is a potential indicator that could guide when to use a resuscitative endovascular balloon occlusion of the aorta (REBOA) in trauma patients with life-threatening injuries. This study aims to determine the optimal SBP threshold for REBOA placement by analyzing the association between SBP pre-REBOA and 24-hour mortality in severely injured hemodynamically unstable trauma patients.

METHODS

We performed a pooled analysis of the aortic balloon occlusion (ABO) trauma and AORTA registries. These databases record the details related to the use of REBOA and include data from 14 countries worldwide. We included patients who had suffered penetrating and/or blunt trauma. Patients who arrived at the hospital with a SBP pre-REBOA of 0 mm Hg and remained at 0 mm Hg after balloon inflation were excluded. We evaluated the impact that SBP pre-REBOA had on the probability of death in the first 24 hours.

RESULTS

A total of 1,107 patients underwent endovascular aortic occlusion, of these, 848 met inclusion criteria. The median age was 44 years (interquartile range [IQR], 27-59 years) and 643 (76%) were male. The median injury severity score was 34 (IQR, 25-45). The median SBP pre-REBOA was 65 mm Hg (IQR, 49-88 mm Hg). Mortality at 24 hours was reported in 279 (32%) patients. Math modeling shows that predicted probabilities of the primary outcome increased steadily in SBP pre-REBOA below 100 mm Hg. Multivariable mixed-effects analysis shows that when SBP pre-REBOA was lower than 60 mm Hg, the risk of death was more than 50% (relative risk, 1.5; 95% confidence interval, 1.17-1.92; p = 0.001).

DISCUSSION

In patients who do not respond to initial resuscitation, the use of REBOA in SBPs between 60 mm Hg and 80 mm Hg may be a useful tool in resuscitation efforts before further decompensation or complete cardiovascular collapse. The findings from our study are clinically important as a first step in identifying candidates for REBOA.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level IV.

Do we need pre-hospital resuscitative endovascular balloon occlusion of the aorta (REBOA) in the civilian helicopter emergency medical services (HEMS)?

Pre-hospital resuscitative endovascular balloon occlusion of the aorta (REBOA) can be a life-saving procedure for patients with non-compressible torso hemorrhage. We aimed to evaluate the potential eligibility for REBOA in trauma patients of a civilian helicopter emergency medical service (HEMS) using a stepwise approach. A retrospective analysis using the electronic database (HEMSDER) of "DRF Luftrettung" HEMS covering the period from January 2015 to June 2021 was performed. Trauma patients aged ≥ 16 years and with a National Advisory Committee for Aeronautics (NACA) score of ≥ 4 were assessed for potential REBOA eligibility using two different decision trees based on assumed severe bleeding due to injuries of the abdomen, pelvis, and/or lower extremities and different vital signs on the scene and at hospital handover. Non-parametric statistical methods were used for comparison. A total of 22.426 patients met the inclusion criteria for data analysis. Of these, 0.15-2.24% were possible candidates for pre-hospital REBOA. No significant differences between groups on scene and at hospital handover regarding demographics, assumed injuries, and pre-hospital interventions were found. In the on-scene group, 21.1% of the patients remained unstable even at hospital handover despite pre-hospital care. In the handover group, 42.8% of the patients seemed initially stable but then deteriorated during the pre-hospital course. The number of potential pre-hospital REBOA in severely injured patients with a NACA score of ≥ 4 is < 3% or can be even < 1% if more strict criteria are used. There are some patients who may benefit from pre-hospital REBOA as a life-saving procedure. Further research on earlier diagnosis of life-threatening bleeding and proper indications of REBOA in trauma patients is needed.

Predictive value of tachycardia for mortality in trauma-related haemorrhagic shock: a systematic review and meta-regression

OBJECTIVES

Heart rate (HR) is one of the physiological variables in the early assessment of trauma-related haemorrhagic shock, according to Advanced Trauma Life Support (ATLS). However, its efficiency as predictor of mortality is contradicted by several studies. Furthermore, the linear association between HR and the severity of shock and blood loss presented by ATLS is doubtful. This systematic review aims to update current knowledge on the role of HR in the initial haemodynamic assessment of patients who had a trauma.

DESIGN

This study is a systematic review and meta-regression that follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations.

DATA SOURCES

EMBASE, MEDLINE, CENTRAL and Web of Science databases were systematically searched through on 1 September 2020.

ELIGIBILITY CRITERIA

Papers providing early HR and mortality data on bleeding patients who had a trauma were included. Patient cohorts were considered haemorrhagic if the inclusion criteria of the studies contained transfusion and/or positive focused assessment with sonography for trauma and/or postinjury haemodynamical instability and/or abdominal gunshot injury. Studies on burns, traumatic spinal or brain injuries were excluded. Papers published before January 2010 were not considered.

DATA EXTRACTION AND SYNTHESIS

Data extraction and risk of bias were assessed by two independent investigators. The association between HR and mortality of patients who had a trauma was assessed using meta-regression analysis. As subgroup analysis, meta-regression was performed on patients who received blood products.

RESULTS

From a total of 2017 papers, 19 studies met our eligibility criteria. Our primary meta-regression did not find a significant relation (p=0.847) between HR and mortality in patients who had a trauma with haemorrhage. Our subgroup analysis included 10 studies, and it could not reveal a linear association between HR and mortality rate.

CONCLUSIONS

In accordance with the literature demonstrating the multiphasic response of HR to bleeding, our study presents the lack of linear association between postinjury HR and mortality. Modifying the pattern of HR derangements in the ATLS shock classification may result in a more precise teaching tool for young clinicians.

The role of tricuspite annular plane systolic excursion as a marker of hypovolemia in healthy blood donor volunteers

AIM

The aim of this study is to compare the diameter of the inferior vena cava with tricuspid annular plane systolic excursion (TAPSE) measurement in order to determine the volume loss before and after blood donation in healthy volunteers.

METHODS

This Institutional Review Board-approved single center, prospective, cross-sectional study included 60 healthy blood donors donating in a tertiary care hospital's blood bank. After obtaining written consent, systolic, diastolic, and mean arterial blood pressures along with pulse rate of the donors were measured in sitting and supine positions by the attending physician, then, inferior vena cava (IVC) and TAPSE measurements were made before and after blood donation.

RESULTS

Statistically significant differences was found between standing systolic blood pressure and pulse rate, lying systolic blood pressure and pulse rate, IVC and TAPSE values before and after blood donation (p < 0.05). There was no difference between the other variables before and after blood donation.

CONCLUSION

Our study revealed that, low IVC and TAPSE values correlated in determining blood loss after blood donation. TAPSE may be useful to predict blood loss in early stages of hypovolemic shock.

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.

Physiology of Human Hemorrhage and Compensation

Hemorrhage is a leading cause of death following traumatic injuries in the United States. Much of the previous work in assessing the physiology and pathophysiology underlying blood loss has focused on descriptive measures of hemodynamic responses such as blood pressure, cardiac output, stroke volume, heart rate, and vascular resistance as indicators of changes in organ perfusion. More recent work has shifted the focus toward understanding mechanisms of compensation for reduced systemic delivery and cellular utilization of oxygen as a more comprehensive approach to understanding the complex physiologic changes that occur following and during blood loss. In this article, we begin with applying dimensional analysis for comparison of animal models, and progress to descriptions of various physiological consequences of hemorrhage. We then introduce the complementary side of compensation by detailing the complexity and integration of various compensatory mechanisms that are activated from the initiation of hemorrhage and serve to maintain adequate vital organ perfusion and hemodynamic stability in the scenario of reduced systemic delivery of oxygen until the onset of hemodynamic decompensation. New data are introduced that challenge legacy concepts related to mechanisms that underlie baroreflex functions and provide novel insights into the measurement of the integrated response of compensation to central hypovolemia known as the compensatory reserve. The impact of demographic and environmental factors on tolerance to hemorrhage is also reviewed. Finally, we describe how understanding the physiology of compensation can be translated to applications for early assessment of the clinical status and accurate triage of hypovolemic and hypotensive patients. © 2021 American Physiological Society. Compr Physiol 11:1531-1574, 2021.

Internal Jugular Vein Waveform; A New Insight to Detect Early Stage of Hemorrhagic Shock

OBJECTIVE

To evaluate the accuracy of internal jugular vein waveform to detect early stage of hemorrhagic shock.

METHODS

Forty-three volunteers enrolled in our study between November and December 2018. After blood donation of 450cc, the blood donors in the case group underwent color Doppler sonography of internal Jugular Vein. Besides, the clinical and laboratory indicators of shock were evaluated. The same clinical, laboratory and sonographic data was also obtained from the volunteers in the control group, then Chi-square and Student t-test were applied to make comparison between mentioned groups.

RESULTS

After excluding five volunteers, eighteen subjects were included in the blood donor group (mean of age: 35.81±8.05) and 20 healthy volunteers enrolled in the control group (mean of age: 34.95± 6.86). The Jugular pulsatility index was significantly smaller in the case group (0.47 ± 0.27 vs. 0.77 ± 0.52). The jugular pulsatility index above 0.91 excluded blood loss (sensitivity=100%). The combination of clinical, laboratory and sonographic data were also represented as two other indices; Jugular Pulsatility-Shock index and Jugular Pulsatility-Shock-Base Deficit index (JPSBDI). These indices were also accurate enough to detect early blood loss (p=0.011 and <0.001, respectively). JPSBDI below 0.38 was highly accurate to rule out blood loss. (Area under the curve: 0.868, sensitivity=95% and specificity=76.47%).

CONCLUSION

The internal Jugular vein waveform is accurate to detect early stages of shock. The combination of clinical, laboratory and sonographic data is more promising than each of them, separately.

Role of nurses and nurse practitioners in the recognition, diagnosis, and management of neurogenic orthostatic hypotension: a narrative review

Neurogenic orthostatic hypotension (nOH) is a sustained reduction in blood pressure (BP) upon standing that is caused by autonomic dysfunction and is common among patients with a variety of neurodegenerative disorders (eg, Parkinson's disease, multiple system atrophy, pure autonomic failure). A systolic BP drop of ≥20 mmHg (or ≥10 mmHg diastolic) upon standing with little or no compensatory increase in heart rate is consistent with nOH. Symptoms of nOH include light-headedness, dizziness, presyncope, and syncope; these symptoms can severely impact patients' activities of daily living and increase the likelihood of potentially dangerous falls. Because of their patient contact, nurses and nurse practitioners can play a key role in identifying and evaluating patients at risk for nOH. It is advisable to screen for nOH in patients presenting with one or more of the following characteristics: those who have disorders associated with autonomic failure, those with episodes of falls or syncope, those with symptoms upon standing, those who are elderly or frail, or those taking multiple medications. Initial evaluations should include questions about postural symptoms and measurement of orthostatic BP and heart rate. A review of medications for potential agents that can have hypotensive effects should be performed before initiating treatment. Treatment for nOH may include non-pharmacologic measures and pharmacologic therapy. Droxidopa and midodrine are approved by the US Food and Drug Administration for the treatment of symptomatic nOH and symptomatic OH, respectively. nOH is associated with the coexistence of supine hypertension, and the two disorders must be carefully managed. In conclusion, timely screening and diagnosis of patients with nOH can streamline the path to disease management and treatment, potentially improving patient outcomes.

Lower Body Negative Pressure: Physiological Effects, Applications, and Implementation

This review presents lower body negative pressure (LBNP) as a unique tool to investigate the physiology of integrated systemic compensatory responses to altered hemodynamic patterns during conditions of central hypovolemia in humans. An early review published in Physiological Reviews over 40 yr ago (Wolthuis et al. Physiol Rev 54: 566-595, 1974) focused on the use of LBNP as a tool to study effects of central hypovolemia, while more than a decade ago a review appeared that focused on LBNP as a model of hemorrhagic shock (Cooke et al. J Appl Physiol (1985) 96: 1249-1261, 2004). Since then there has been a great deal of new research that has applied LBNP to investigate complex physiological responses to a variety of challenges including orthostasis, hemorrhage, and other important stressors seen in humans such as microgravity encountered during spaceflight. The LBNP stimulus has provided novel insights into the physiology underlying areas such as intolerance to reduced central blood volume, sex differences concerning blood pressure regulation, autonomic dysfunctions, adaptations to exercise training, and effects of space flight. Furthermore, approaching cardiovascular assessment using prediction models for orthostatic capacity in healthy populations, derived from LBNP tolerance protocols, has provided important insights into the mechanisms of orthostatic hypotension and central hypovolemia, especially in some patient populations as well as in healthy subjects. This review also presents a concise discussion of mathematical modeling regarding compensatory responses induced by LBNP. Given the diverse applications of LBNP, it is to be expected that new and innovative applications of LBNP will be developed to explore the complex physiological mechanisms that underline health and disease.

Postpartum hemorrhage: new insights for definition and diagnosis

The current definition of is inadequate for early recognition of this important cause of maternal death that is responsible for >80,000 deaths worldwide in 2015. A stronger definition of postpartum hemorrhage should include both blood loss and clinical signs of cardiovascular changes after delivery, which would help providers to identify postpartum hemorrhage more promptly and accurately. Along with the amount of blood loss, clinical signs, and specifically the shock index (heart rate divided by systolic blood pressure) appear to aid in more accurate diagnosis of postpartum hemorrhage.

Improvement of blood loss volume estimation by paramedics using a pictorial nomogram: A developmental study

INTRODUCTION

To propose and evaluate a nomogram to assist paramedics to visually estimate the external blood loss on a non-absorbent surface and to identify whether the nomogram improves visual estimation.

METHODS

The study was a prospective, paired-control design (pre-training control group & post-training group), utilizing Emergency Medical Assistant (EMA) I and II trainees from the Hong Kong Fire Services Ambulance Command Training School. A nomogram (blood loss volume to area on a non-absorbent surface) was prepared to aid blood loss estimation. All participants estimated four scenarios of blood pools twice (A: 180mL; B: 470mL;C: 940mL; D: 1550mL) before and after using the nomogram. Every participant received two-minute training on how to use the nomogram correctly. The difference between the estimations and the actual volume in each scenario was calculated. The absolute percentage errors were used for direct comparison and identification of improvement between visual estimation and the use of the nomogram.

RESULTS

Sixty-one participants with an average of 3-year paramedic field experience were recruited by convenience sampling. In combining all scenarios, the median of absolute percentage error of 61 participants was 43% (95%CI 38.0-50.9%) in visual estimation, while it was 23% (95%CI 17.4-27.0%) when using the nomogram. There was a significant reduction in absolute percentage error between visual estimation and the use of the nomogram (p<0.0001).

CONCLUSION

The nomogram significantly improved the estimation of external blood loss volume.

Damage Control Resuscitation for Catastrophic Bleeding

The timely recognition of shock secondary to hemorrhage from severe facial trauma or as a complication of complex oral and maxillofacial surgery presents formidable challenges. Specific hemostatic disorders are induced by hemorrhage and several extreme homeostatic imbalances may appear during or after resuscitation. Damage control resuscitation has evolved from massive transfusion to a more complex therapeutic paradigm that includes hemodynamic resuscitation, hemostatic resuscitation, and homeostatic resuscitation. Definitive control of bleeding is the principal objective of any comprehensive resuscitation scheme for hemorrhagic shock.

The physiology of blood loss and shock: New insights from a human laboratory model of hemorrhage

The ability to quickly diagnose hemorrhagic shock is critical for favorable patient outcomes. Therefore, it is important to understand the time course and involvement of the various physiological mechanisms that are active during volume loss and that have the ability to stave off hemodynamic collapse. This review provides new insights about the physiology that underlies blood loss and shock in humans through the development of a simulated model of hemorrhage using lower body negative pressure. In this review, we present controlled experimental results through utilization of the lower body negative pressure human hemorrhage model that provide novel insights on the integration of physiological mechanisms critical to the compensation for volume loss. We provide data obtained from more than 250 human experiments to classify human subjects into two distinct groups: those who have a high tolerance and can compensate well for reduced central blood volume (e.g. hemorrhage) and those with low tolerance with poor capacity to compensate.We include the conceptual introduction of arterial pressure and cerebral blood flow oscillations, reflex-mediated autonomic and neuroendocrine responses, and respiration that function to protect adequate tissue oxygenation through adjustments in cardiac output and peripheral vascular resistance. Finally, unique time course data are presented that describe mechanistic events associated with the rapid onset of hemodynamic failure (i.e. decompensatory shock). Impact Statement Hemorrhage is the leading cause of death in both civilian and military trauma. The work submitted in this review is important because it advances the understanding of mechanisms that contribute to the total integrated physiological compensations for inadequate tissue oxygenation (i.e. shock) that arise from hemorrhage. Unlike an animal model, we introduce the utilization of lower body negative pressure as a noninvasive model that allows for the study of progressive reductions in central blood volume similar to those reported during actual hemorrhage in conscious humans to the onset of hemodynamic decompensation (i.e. early phase of decompensatory shock), and is repeatable in the same subject. Understanding the fundamental underlying physiology of human hemorrhage helps to test paradigms of critical care medicine, and identify and develop novel clinical practices and technologies for advanced diagnostics and therapeutics in patients with life-threatening blood loss.

On-admission blood pressure and pulse rate in trauma patients and their correlation with mortality: Cushing's phenomenon revisited

BACKGROUND

Injury-induced alteration in initial physiological responses such as hypertension and heart rate (HR) has a significant effect on mortality. Research on such associations from our country-India is limited. The present study investigates the injury-induced early blood pressure (BP) and HR changes and their association with mortality.

MATERIALS AND METHODS

The data were selected from Towards Improved Trauma Care Outcomes collected from October 1, 2013, to July 24, 2014. Patients above 18 years of age with documented systolic BP (SBP) and HR were selected. BP was categorized into hypotension (SBP <90 mmHg), hypertension (SBP >140 mmHg), and normal (SBP 90-140 mmHg). HR was categorized into bradycardia (HR <60 beats/min [bpm]), tachycardia (HR >100 bpm), and normal (HR 60-100 bpm). These categories were compared with mortality.

RESULTS

A total of 10,200 patients were considered for the study. Mortality rate was 24%. Mortality among females was more than males. Patients with normal BP and HR had 20% of mortality. Mortality in patients with abnormal BP and HR findings was 36%. Mortality was higher among hypotension-bradycardia patients (80%) followed by hypertension-bradycardia patients (58%) and tachycardia hypotension patients (48%). Elderly patients were at higher risk of deaths with an overall mortality of 35% compared to 23% of adults.

CONCLUSION

The study reports that initial combination of hypotension-bradycardia had higher mortality rate. Specific precautions in prehospital care should be given to trauma patients with these findings. Further prospective study in detail should be considered for exploring this abnormality.

Definition of hemodynamic stability in blunt trauma patients: a systematic review and assessment amongst Dutch trauma team members

INTRODUCTION

Trauma is a great contributor to mortality worldwide. One of the challenges in trauma care is early identification and management of bleeding. The circulatory status of blunt trauma patients in the emergency room is evaluated using hemodynamic (HD) parameters. However, there is no consensus on which parameters to use. In this study, we evaluate the used terms and definitions in the literature for HD stability and compare those to the opinion of Dutch trauma team members.

METHOD

A systematic review was performed to collect the definitions used for HD stability. Studies describing the assessment and/or treatment of blunt trauma patients in the emergency room were included. In addition, an online survey was conducted amongst Dutch trauma team members.

RESULTS

Out of a total of 222, 67 articles were found to be eligible for inclusion. HD stability was defined in 70% of these articles. The most used parameters were systolic blood pressure and heart rate. Besides the variety of parameters, a broad range of corresponding cut-off points is noted. Despite some common ground, high inter- and intra-variability is seen for the physicians that are part of the Dutch trauma teams.

CONCLUSION

All authors acknowledge HD stability as the most important factor in the assessment and management of blunt trauma patients. There is, however, no consensus in the literature as well as none-to-fair consensus amongst Dutch trauma team members in the definition of HD stability. A trauma team ready to co-operate with consensus-based opinions together with a valid scoring system is in our opinion the best method to assess and treat seriously injured trauma patients.

[Fluid resuscitation in hemorrhage]

How fluid resuscitation has to be performed for acute hemorrhage situations is still controversially discussed. Although the forced administration of crystalloids and colloids has been and still is practiced, nowadays there are good arguments that a cautious infusion of crystalloids may be initially sufficient. Saline should no longer be used for fluid resuscitation. The main argument for cautious fluid resuscitation is that no large prospective randomized clinical trials exist which have provided evidence of improved survival when fluid resuscitation is applied in an aggressive manner. The explanation that no positive effect has so far been observed is that fluid resuscitation is thought to boost bleeding by increasing blood pressure and dilutional coagulopathy. Nevertheless, national and international guidelines recommend that fluid resuscitation should be applied at the latest when hemorrhage causes hemodynamic instability. Consideration should be given to the fact that damage control resuscitation per se will neither improve already reduced tissue perfusion nor hemostasis. In acute and possibly rapidly progressing hypovolemic shock, colloids can be used. The third and fourth generations of hydroxyethyl starch (HES) are safe and effective if used correctly and within prescribed limits. If fluid resuscitation is applied with ongoing re-evaluation of the parameters which determine oxygen supply, it should be possible to keep fluid resuscitation restricted without causing undesirable side effects and also to administer a sufficient quantity so that survival of patients is ensured.

Shock index and prediction of traumatic hemorrhagic shock 28-day mortality: data from the DCLHb resuscitation clinical trials

INTRODUCTION

To assess the ability of the shock index (SI) to predict 28-day mortality in traumatic hemorrhagic shock patients treated in the diaspirin cross-linked hemoglobin (DCLHb) resuscitation clinical trials.

METHODS

We used data from two parallel DCLHb traumatic hemorrhagic shock efficacy trials, one in U.S. emergency departments, and one in the European Union prehospital setting to assess the relationship between SI values and 28-day mortality.

RESULTS

In the 219 patients, the mean age was 37 years, 64% sustained a blunt injury, 48% received DCLHb, 36% died, and 88% had an SI≥1.0 at study entry. The percentage of patients with an SI≥1.0 dropped by 57% (88 to 38%) from the time of study entry to 120 minutes after study resuscitation (p<0.001). Patients with a SI≥1.0, 1.4, and 1.8 at any time point were 2.3, 2.7, and 3.1 times, respectively, more likely to die by 28 days than were patients with SI values below these cutoffs (p<0.001). Similarly, after 120 minutes of resuscitation, patients with a SI≥1.0 were 3.9× times more likely to die by 28 days (40 vs. 15%, p<0.001). Although the distribution of SI values differed based on treatment group, the receiver operator characeristics data showed no difference in SI predictive ability for 28-day mortality in patients treated with DCLHb.

CONCLUSION

In these traumatic hemorrhagic shock patients, the shock index correlates with 28-day mortality, with higher SI values indicating greater mortality risk. Although DCLHb treatment did alter the distribution of SI values, it did not influence the ability of the SI to predict 28-day mortality.

The Shock Index revisited - a fast guide to transfusion requirement? A retrospective analysis on 21,853 patients derived from the TraumaRegister DGU

INTRODUCTION

Isolated vital signs (for example, heart rate or systolic blood pressure) have been shown unreliable in the assessment of hypovolemic shock. In contrast, the Shock Index (SI), defined by the ratio of heart rate to systolic blood pressure, has been advocated to better risk-stratify patients for increased transfusion requirements and early mortality. Recently, our group has developed a novel and clinical reliable classification of hypovolemic shock based upon four classes of worsening base deficit (BD). The objective of this study was to correlate this classification to corresponding strata of SI for the rapid assessment of trauma patients in the absence of laboratory parameters.

METHODS

Between 2002 and 2011, data for 21,853 adult trauma patients were retrieved from the TraumaRegister DGU database and divided into four strata of worsening SI at emergency department arrival (group I, SI <0.6; group II, SI ≥0.6 to <1.0; group III, SI ≥1.0 to <1.4; and group IV, SI ≥1.4) and were assessed for demographics, injury characteristics, transfusion requirements, fluid resuscitation and outcomes. The four strata of worsening SI were compared with our recently suggested BD-based classification of hypovolemic shock.

RESULTS

Worsening of SI was associated with increasing injury severity scores from 19.3 (± 12) in group I to 37.3 (± 16.8) in group IV, while mortality increased from 10.9% to 39.8%. Increments in SI paralleled increasing fluid resuscitation, vasopressor use and decreasing hemoglobin, platelet counts and Quick's values. The number of blood units transfused increased from 1.0 (± 4.8) in group I to 21.4 (± 26.2) in group IV patients. Of patients, 31% in group III and 57% in group IV required ≥10 blood units until ICU admission. The four strata of SI discriminated transfusion requirements and massive transfusion rates equally with our recently introduced BD-based classification of hypovolemic shock.

CONCLUSION

SI upon emergency department arrival may be considered a clinical indicator of hypovolemic shock in respect to transfusion requirements, hemostatic resuscitation and mortality. The four SI groups have been shown to equal our recently suggested BD-based classification. In daily clinical practice, SI may be used to assess the presence of hypovolemic shock if point-of-care testing technology is not available.

UK triage--an improved tool for an evolving threat

INTRODUCTION

A key challenge at a major incident is to quickly identify those casualties most urgently needing treatment in order to survive - triage. The UK Triage Sieve (TS) advocated by the Major Incident Medical Management (MIMMS) Course categorises casualties by ability to walk, respiratory rate (RR) and heart rate (HR) or capillary refill time. The military version (MS) includes assessment of consciousness. We tested whether the MS better predicts need for life-saving intervention in a military trauma population. Ideal HR, RR and Glasgow Coma Score (GCS) thresholds were calculated.

METHODS

A gold standard Priority 1 casualty was defined using resource-based criteria. Pre-hospital data from a military trauma database allowed calculation of triage category, which was compared with this standard, and presented as 2×2 tables. Sensitivity and specificity of each physiological parameter was calculated over a range of values to identify the ideal cut-offs.

RESULTS

A gold standard could be ascribed in 1657 cases. In 1213 both the MS and TS could ascribe a category. MS was significantly more sensitive than TS (59% vs 53%, p<0.001) with similar specificity (89 vs 88%). Varying the limits for each parameter allowed some improvements in sensitivity (70-80%) but specificity dropped rapidly.

DISCUSSION

Previous studies support the inclusion of GCS assessment for blunt as well as penetrating trauma. Optimising the physiological cut-offs increased sensitivity in this sample to only 71% - a Sieve based purely on physiological parameters may not be capable of an acceptable level of sensitivity.

CONCLUSIONS

The MS is more sensitive than the TS. Major incident planners utilising the Sieve should consider adopting the military version as their first line triage tool. If validated, altering the HR and RR thresholds may further improve the tool.

Vital signs and estimated blood loss in patients with major trauma: testing the validity of the ATLS classification of hypovolaemic shock

AIM

The Advanced Trauma Life Support (ATLS) system classifies the severity of shock. The aim of this study is to test the validity of this classification.

METHODS

Admission physiology, injury and outcome variables from adult injured patients presenting to hospitals in England and Wales between 1989 and 2007 and stored on the Trauma Audit and Research Network (TARN) database, were studied. For each patient, the blood loss was estimated and patients were divided into four groups based on the estimated blood loss corresponding to the ATLS classes of shock. The median and interquartile ranges (IQR) of the heart rate (HR) systolic blood pressure (SBP), respiratory rate (RR) and Glasgow Coma Score (GCS) were calculated for each group.

RESULTS

The median HR rose from 82 beats per minute (BPM) in estimated class 1 shock to 95 BPM in estimated class 4 shock. The median SBP fell from 135 mm Hg to 120 mm Hg. There was no significant change in RR or GCS.

CONCLUSION

With increasing estimated blood loss there is a trend to increasing heart rate and a reduction in SBP but not to the degree suggested by the ATLS classification of shock.

Paradoxical bradycardia in a patient with haemorrhagic shock secondary to blunt abdominal trauma

A 47-year-old woman, with no previous medical problems, presented to the Accident and Emergency department with left shoulder pain following a fall onto her left side from a horse. Physical examination was unremarkable and she was discharged with simple analgesia. However, 2 h later, she re-presented with worsening left shoulder pain, dizziness and mild epigastric discomfort. A new examination revealed blood pressure of 100/60 mm Hg, which dropped to 95/65 mm Hg on standing, a Glasgow Coma Scale score of 15 and pulse of 62 beats/min. She was resuscitated with 2 litres of Hartmann's fluid. A focused assessment with sonography for trauma (FAST) scan of her abdomen was negative. Then, 1 h later she experienced generalised abdominal pain and developed postural hypotension. However she remained bradycardic (heart rate 45-60 beats/min). Repeat examination revealed peritonitis. A further FAST scan showed free fluid in the left hypochondrium. A CT scan demonstrated a complex tear of the spleen, for which she underwent an emergency total splenectomy. Her postoperative recovery was uncomplicated.

Comparing the systolic blood pressure (SBP) and pulse rate (PR) in injured children with and without traumatic brain injury

AIMS

Following evidence that injured children have higher systolic blood pressures (SBP) than similar-aged resting uninjured children, we investigate whether the initial cardiovascular physiology differs between forms of injury.

METHODS

Analysis of prospectively recorded data from the Trauma Audit and Research Network (TARN) database of injured children aged <or=15, presenting with blunt trauma from March 1988 to February 2009. We compared the ED arrival SBP and pulse rate (PR) in children with and without TBI. The analysis was stratified by age and injury severity (ISS<or=8=mild, ISS 9-14=moderate, ISS>or=15=severe) through medians, graphs and compared through analysis of covariance.

RESULTS

Data for 18,135 children were analysed. Those with TBI had a higher mortality rate (17.2%) and were more severely injured. No difference was seen between the two groups in the SBP of severely injured children (p=0.09) who were almost all hypertensive compared to APLS "norms". Further analysis revealed a significant difference in the PR of severely injured children (p<0.001), attributed to children <9 years of age with brain injuries showing lower heart rates than those with extracranial injuries, though all still within the normal range for their age.

CONCLUSIONS

Although injured children remain hypertensive as compared to resting norms, we have seen no difference in the initial systolic blood pressure of moderately and severely injured children with and without traumatic brain injury. The relative bradycardia in the younger children appears to be an early sign of a severe traumatic brain injury.

Estimation of external blood loss by paramedics: is there any point?

OBJECTIVES

There are many patient assessment challenges in the prehospital setting, especially the estimation of external blood loss. Previous studies of experienced paramedics have demonstrated that external blood loss estimation is highly inaccurate. The objective of this study was to determine if undergraduate paramedic students could accurately estimate external blood loss on four surfaces commonly found in the prehospital environment.

METHODS

This prospective, observational, blinded study used a convenience sample of undergraduate students studying at Monash University during 2006. Students were provided with four clinical vignettes using four different surfaces and varying simulated blood amounts.

RESULTS

Accurate estimation occurred with the vinyl simulation (100 ml), with a mean value of the estimations of 98 ml (95% Confidence Interval (CI) 84-113 ml). Carpet and concrete surfaces were both associated with large under-estimations. The carpet simulation (1,000 ml) had a mean value for the estimations of 347 ml (95% CI 320-429 ml). The concrete simulation (1,500 ml) had a mean value for the estimations of 885ml (95% CI 771-999 ml). Conversely, the clothing simulation (500 ml) emphasized over-estimation, with a mean value for the estimations of 1,253 ml (95% CI 1,093-1,414 ml). There was no relationship between increased accuracy and clinical experience, exposure, educational qualifications, or age of students.

CONCLUSIONS

External blood loss estimation by undergraduate paramedic students generally is too inaccurate to be of any clinical benefit. Particularly, absorbent and impermeable surfaces precipitated inaccuracies by undergraduate paramedic students.

Clinicians' responses to abnormal vital signs in an emergency department

The importance of observing patient vital signs in emergency department (ED) practice has been stressed in the literature. Failure of clinicians to respond to abnormal vital signs (AVS) has been described as a potential reason for delayed management in ED practice, with a likelihood of increased morbidity. This study aimed to explore and describe clinicians' responses to AVS in a busy ED. A qualitative descriptive approach was used with three focus groups being conducted with 18 volunteer registered nurses (RNs) and medical officers (MOs) who worked in the ED of an area health service in Western Sydney. Transcribed focus group interviews were analysed using a process of constant comparison and contrast and a description of clinicians' responses to AVS written. An analysis of text from focus groups revealed three main categories of clinicians' responses to AVS: identification, reporting and implementing action. Clinicians in this study recognised, reported and acted on AVS. However, delays in responding to AVS occurred due to a variety of reasons. The main reasons identified were issues with documentation and the ability to seek advice of appropriate staff, ineffective communication, fear of reprimand, inexperience of working in EDs, workload, distractions and interruptions. In conclusion, environmental and human factors contribute to inappropriate delays regarding AVS in the ED. These factors can be acted on by initiating appropriate education programmes and establishing improved communication networks. Better use of the existing medical emergency team (MET) in the ED can act to alleviate situations associated with delays in managing AVS.

The accuracy of external blood loss estimation by ambulance and hospital personnel

OBJECTIVE

To determine if emergency personnel, either ambulance or hospital based, can estimate the volume of external blood loss accurately enough to be of potential clinical use in guiding fluid resuscitation.

METHODS

A total of 61 ambulance and 35 hospital personnel viewed nine scenarios consisting of volumes of blood (100 mL, 400 mL and 700 mL) spilt onto three surfaces--carpet, vinyl and a clothed manikin. They were asked to estimate the blood loss in each case.

RESULTS

Estimates of volumes of blood loss on all surfaces were generally inaccurate. Both ambulance and hospital groups were comparable in this regard. Hospital personnel had higher mean estimates than those of ambulance personnel. Of particular clinical relevance were the findings that blood loss on carpet was underestimated and small volumes on a clothed manikin were overestimated.

CONCLUSION

External blood loss estimation by ambulance and hospital personnel is generally too inaccurate to be of clinical use.

Systolic hypertension and the response to blunt trauma in infants and children

OBJECTIVES

To describe age-related systolic blood pressures and pulse rates in children following blunt injury. To compare these variables with standard reference values for uninjured children at rest and with reference ranges from the Advanced Paediatric Life Support (APLS) guidelines.

DESIGN

Secondary analysis of a prospective cohort.

SETTING

Emergency departments throughout England and Wales.

PARTICIPANTS

12906 children presenting with acute blunt traumatic injury from August 1989 to September 1998.

MAIN OUTCOME MEASURES

Systolic blood pressure and pulse rate on arrival.

RESULTS

Injured children had higher systolic blood pressures than the standard quoted 'norms'. Standard reference values of systolic blood pressure for children at rest always appeared below the 50th percentile for our cohort of injured children (range 7th-27th percentiles). Pulse rates for children at rest were always towards the mid-range for injured children (range 41st-54th percentiles). These results appeared unrelated to injury severity. Age related APLS reference ranges for systolic blood pressure and pulse rate resembled the standard reference values for uninjured children at rest.

CONCLUSIONS

Injured children have a relative systolic hypertension compared with children at rest. Pulse rates in the two groups are comparable. Following injury, children with apparently 'normal' age-specific systolic blood pressures on arrival in the Emergency Department are relatively hypotensive and should be carefully assessed.

The reliability of vital sign measurements

STUDY OBJECTIVE

Vital sign measurements, specifically heart rate, respiratory rate, and blood pressure, play a fundamental role in many medical evaluations, yet little is known about the reliability of noninvasive vital sign measurements. We sought to determine whether trained observers can reproducibly assess vital signs in the clinical setting.

METHODS

Two trained observers independently measured vital signs on 140 patients presenting to an urban emergency department with acute medical complaints. Heart rate and respiratory rate were each measured by auscultation of heart and breath sounds for 1 minute. Systolic and diastolic blood pressures were determined by auscultating Korotkoff sounds while viewing pressure measurements from a standard cuff and mercury manometer. The mean value of each vital sign and Bland-Altman statistics (mean difference between observers [MDO], expected range of agreement [ERA]) were used to provide absolute and relative indices of reliability.

RESULTS

The observers found a mean heart rate of 78.5 beats/min, with an MDO of 0.02 beats/min (0.03%), and an ERA of +/- 10.6 beats/min (+/- 13.5%). Respiratory rate exhibited a mean of 17.5 breaths/min, an MDO of 0.04 breaths/min (0.2%), and an ERA of +/- 6.2 breaths/min (+/- 35.5%). The mean systolic blood pressure of 127.1 mm Hg was associated with an MDO of 1.3 mm Hg (1.0%), and an ERA of +/- 24.2 mm Hg (+/- 19.0%). Diastolic blood pressure exhibited a mean of 77.4 mm Hg, an MDO of 0.3 mm Hg (0.4%) with an ERA of +/- 19.9 mm Hg (+/- 25.7%).

CONCLUSION

The reproducibility of vital sign measurements may be limited by significant interobserver variability. Clinicians should recognize this inherent variability and interpret vital signs with caution.

Non-invasive assessment of cardiac output in children

BACKGROUND

Stroke distance, the systolic velocity integral of aortic blood flow, is a linear analogue of stroke volume; its product with heart rate is minute distance, analogous to cardiac output.

OBJECTIVE

To investigate the feasibility of assessing cardiac output in children with a simple non-invasive Doppler ultrasound technique, and to determine the normal range of values.

METHODS

Peak aortic blood velocity, stroke distance, and minute distance were measured through the suprasternal window in 166 children (mean age 9.6 years, range 2-14) using a portable non-imaging Doppler ultrasound instrument.

RESULTS

The technique was well tolerated by all the children participating. Mean peak aortic blood velocity was 138 cm/s and was independent of age. Mean stroke distance was 31.8 cm and showed a small but significant increase with age; mean minute distance was 2490 cm and fell with age, as did heart rate.

CONCLUSIONS

Suprasternal Doppler ultrasound measurement of stroke distance is a convenient, well tolerated, non-invasive technique for the assessment of cardiac output in children. The normal range of values during childhood has been established. The technique has great potential for assessing hypovolaemia in children.

Acute metabolic and endocrine effects of induced hypothermia in hemorrhagic shock: an experimental study in the pig

BACKGROUND

Hypothermia is considered harmful in trauma patients. In surgery, hypothermia is occasionally used to reduce metabolism and protect the brain. Recent studies in animals have also shown protective effects of hypothermia in hemorrhagic shock. The aim of this study was to evaluate the metabolic and endocrine effects of induced hypothermia in hemorrhagic shock.

METHODS

Half of the individually calculated blood volume was removed from 17 anesthetized piglets. They were then randomized to normothermia or hypothermia and followed for 4 hours after hemorrhage.

RESULTS

In the hypothermic pigs, arterial PO2 increased from 10.3 +/- 0.7 to 16.4 +/- 0.9 kPa, but it remained unchanged in the normothermic group. The serum levels of potassium increased from 3.9 +/- 0.2 to 5.0 +/- 0.2 mmol/L in the normothermic group. In the hypothermic pigs, the potassium levels temporarily decreased from 3.8 +/- 0.1 to 3.0 +/- 0.1 mmol/L but then returned to baseline levels. The levels of serum catecholamines surged in both groups during hemorrhage. They remained elevated in normothermic pigs but declined in the hypothermic group.

CONCLUSION

In porcine hemorrhagic shock, induced hypothermia increases arterial oxygen tension and stabilizes serum levels of potassium and catecholamines.