A Guide to the Use of Vasopressors and Inotropes for Patients in Shock

Shock is a life-threatening circulatory failure that results in inadequate tissue perfusion and oxygenation. Vasopressors and inotropes are vasoactive medications that are vital in increasing systemic vascular resistance and cardiac contractility, respectively, in patients presenting with shock. To be well versed in using these agents is an important skill to have in the critical care setting where patients can frequently exhibit symptoms of shock. In this review, we will discuss the pathophysiological mechanisms of shock and evaluate the current evidence behind the management of shock with an emphasis on vasopressors and inotropes.

So You Want to Do Trauma Research? A Practical Guide to Creating a Research Program at Your Home Institution

BACKGROUND

There are 3 pillars upon which the foundation of a teaching program in health care is founded: research, education, and clinical care. However, in a busy academic trauma practice, the unfortunate reality is that research is often a low priority in the frenzy of mandates for clinical productivity.

OBJECTIVE

The purpose of this report is to advise hospitals on how to create a modest trauma research program that supports research interests without significantly impacting the overall clinical productivity of the department.

METHODS

Relevant literature related to the development of an academic trauma research department was reviewed. Relevant articles were then compared to this manuscript to assess the novelty of the topic.

RESULTS

There are 4 essential components of a trauma research program: (1) a zealot, (2) institutional commitment and support, (3) a statistician, and (4) registry data access.

CONCLUSION

The creation of a trauma research program may seem like a herculean effort, but this work is necessary for institutions hoping to achieve status as a Level I/II trauma center. Following the steps outlined in this report, trauma providers can create a robust research program at their institution without sacrificing clinical productivity.

Brain Death/Death by Neurologic Criteria: What You Need to Know

ABSTRACT

Since the beginning of time, man has been intrigued with the question of when a person is considered dead. Traditionally, death has been considered the cessation of all cardiorespiratory function. At the end of the last century a new definition was introduced into the lexicon surrounding death in addition to cessation of cardiac and respiratory function: Brain Death/Death by Neurologic Criteria (BD/DNC). There are medical, legal, ethical, and even theological controversies that surround this diagnosis. In addition, there is no small amount of confusion among medical practitioners regarding the diagnosis of BD/DNC. For families enduring the devastating development of BD/DNC in their loved one, it is the duty of the principal caregiver to provide a transparent presentation of the clinical situation and clear definitive explanation of what constitutes BD/DNC. In this report, we present a historical outline of the development of BD/DNC as a clinical entity, specifically how one goes about making a determination of BD/DNC, what steps are taken once a diagnosis of BD/DNC is made, a brief discussion of some of the ethical/moral issues surrounding this diagnosis, and finally the caregiver approach to the family of a patient who had been declared with BD/DNC. It is our humble hope that with a greater understanding of the myriad of complicated issues surrounding the diagnosis of BD/DNC that the bedside caregiver can provide needed closure for both the patient and the family enduring this critical time in their life.

The State of the Union: Trauma System Development in the United States

Injury is both a national and international epidemic that affects people of all age, race, religion, and socioeconomic class. Injury was the fourth leading cause of death in the United States (U.S.) in 2021 and results in an incalculable emotional and financial burden on our society. Despite this, when prevention fails, trauma centers allow communities to prepare to care for the traumatically injured patient. Using lessons learned from the military, trauma care has grown more sophisticated in the last 50 years. In 1966, the first civilian trauma center was established, bringing management of injury into the new age. Now, the American College of Surgeons recognizes 4 levels of trauma centers (I-IV), with select states recognizing Level V trauma centers. The introduction of trauma centers in the U.S. has been proven to reduce morbidity and mortality for the injured patient. However, despite the proven benefits of trauma centers, the U.S. lacks a single, unified, trauma system and instead operates within a "system of systems" creating vast disparities in the level of care that can be received, especially in rural and economically disadvantaged areas. In this review we present the history of trauma system development in the U.S, define the different levels of trauma centers, present evidence that trauma systems and trauma centers improve outcomes, outline the current state of trauma system development in the U.S, and briefly mention some of the current challenges and opportunities in trauma system development in the U.S. today.

American Association for the Surgery of Trauma/American College of Surgeons Committee on Trauma clinical protocol for management of acute respiratory distress syndrome and severe hypoxemia

LEVEL OF EVIDENCE

Therapeutic/Care Management: Level V.

American Trauma Care: A System of Systems

OBJECTIVE

The benefits of organized trauma systems have been well-documented during 50 years of trauma system development in the United States. Unfortunately, despite this evidence, trauma system development has occurred only sporadically in the 50 states.

METHODS

The relevant literature related to trauma system design and development was reviewed based on relevance to the study. Information from these sources was summarized into a SWOT (strengths, weaknesses, opportunities, and threats) analysis.

RESULTS

Strengths discovered were leadership brought forth by the American College of Surgeons Committee on Trauma and meaningful change generated from The National Academy of Sciences, Engineering, and Medicine report addressing the fractionation of the nation's trauma systems, whereas weaknesses included patient outcome disparities due to the lack of a national governing authority, undertriage, underresourced rural trauma, and underfunded trauma research. Opportunities included the creation of level IV trauma centers; telemedicine; the development of rural trauma management courses; air medical transport to bring high-intensity care to the patient, particularly in rural areas; trauma research; and trauma prevention through outreach and educational programs. The following threats were determined: mass casualty incidents, motor vehicle collisions because of the high rate of motor vehicle collision deaths in the United States relative to other developed countries, and underfunded trauma systems.

CONCLUSION

Much work remains to be done in the development of an American trauma system. Recommendations include implementation of trauma care governance at the federal level; national oversight and support of emergency medical services systems, particularly in rural areas with strict reporting processes for emergency medical services programs; national organization of our mass casualty response; increased federal and state funding allocated to trauma centers; a consistent model for trauma system development; and trauma research.

Surgical Science and the Evolution of Critical Care Medicine

Surgical science has driven innovation and inquiry across adult and pediatric disciplines that provide critical care regardless of location. Surgically originated but broadly applicable knowledge has been globally shared within the pages Critical Care Medicine over the last 50 years.

Paradoxical response to chest wall loading predicts a favorable mechanical response to reduction in tidal volume or PEEP

Background

Chest wall loading has been shown to paradoxically improve respiratory system compliance (CRS) in patients with moderate to severe acute respiratory distress syndrome (ARDS). The most likely, albeit unconfirmed, mechanism is relief of end-tidal overdistension in ‘baby lungs’ of low-capacity. The purpose of this study was to define how small changes of tidal volume (VT) and positive end-expiratory pressure (PEEP) affect CRS (and its associated airway pressures) in patients with ARDS who demonstrate a paradoxical response to chest wall loading. We hypothesized that small reductions of VT or PEEP would alleviate overdistension and favorably affect CRS and conversely, that small increases of VT or PEEP would worsen CRS.

Methods

Prospective, multi-center physiologic study of seventeen patients with moderate to severe ARDS who demonstrated paradoxical responses to chest wall loading. All patients received mechanical ventilation in volume control mode and were passively ventilated. Airway pressures were measured before and after decreasing/increasing VT by 1 ml/kg predicted body weight and decreasing/increasing PEEP by 2.5 cmH2O.

Results

Decreasing either VT or PEEP improved CRS in all patients. Driving pressure (DP) decreased by a mean of 4.9 cmH2O (supine) and by 4.3 cmH2O (prone) after decreasing VT, and by a mean of 2.9 cmH2O (supine) and 2.2 cmH2O (prone) after decreasing PEEP. CRS increased by a mean of 3.1 ml/cmH2O (supine) and by 2.5 ml/cmH2O (prone) after decreasing VT. CRS increased by a mean of 5.2 ml/cmH2O (supine) and 3.6 ml/cmH2O (prone) after decreasing PEEP (P < 0.01 for all). Small increments of either VT or PEEP worsened CRS in the majority of patients.

Conclusion

Patients with a paradoxical response to chest wall loading demonstrate uniform improvement in both DP and CRS following a reduction in either VT or PEEP, findings in keeping with prior evidence suggesting its presence is a sign of end-tidal overdistension. The presence of ‘paradox’ should prompt re-evaluation of modifiable determinants of end-tidal overdistension, including VT, PEEP, and body position.

Paradoxical response to chest wall loading predicts a favorable mechanical response to reduction in tidal volume or PEEP

BACKGROUND

Chest wall loading has been shown to paradoxically improve respiratory system compliance (C_RS) in patients with moderate to severe acute respiratory distress syndrome (ARDS). The most likely, albeit unconfirmed, mechanism is relief of end-tidal overdistension in 'baby lungs' of low-capacity. The purpose of this study was to define how small changes of tidal volume (V_T) and positive end-expiratory pressure (PEEP) affect C_RS (and its associated airway pressures) in patients with ARDS who demonstrate a paradoxical response to chest wall loading. We hypothesized that small reductions of V_T or PEEP would alleviate overdistension and favorably affect C_RS and conversely, that small increases of V_T or PEEP would worsen C_RS.

METHODS

Prospective, multi-center physiologic study of seventeen patients with moderate to severe ARDS who demonstrated paradoxical responses to chest wall loading. All patients received mechanical ventilation in volume control mode and were passively ventilated. Airway pressures were measured before and after decreasing/increasing V_T by 1 ml/kg predicted body weight and decreasing/increasing PEEP by 2.5 cmH₂O.

RESULTS

Decreasing either V_T or PEEP improved C_RS in all patients. Driving pressure (DP) decreased by a mean of 4.9 cmH₂O (supine) and by 4.3 cmH₂O (prone) after decreasing V_T, and by a mean of 2.9 cmH₂O (supine) and 2.2 cmH₂O (prone) after decreasing PEEP. C_RS increased by a mean of 3.1 ml/cmH₂O (supine) and by 2.5 ml/cmH₂O (prone) after decreasing V_T. C_RS increased by a mean of 5.2 ml/cmH₂O (supine) and 3.6 ml/cmH₂O (prone) after decreasing PEEP (P < 0.01 for all). Small increments of either V_T or PEEP worsened C_RS in the majority of patients.

CONCLUSION

Patients with a paradoxical response to chest wall loading demonstrate uniform improvement in both DP and C_RS following a reduction in either V_T or PEEP, findings in keeping with prior evidence suggesting its presence is a sign of end-tidal overdistension. The presence of 'paradox' should prompt re-evaluation of modifiable determinants of end-tidal overdistension, including V_T, PEEP, and body position.

A Rationale for Safe Ventilation with Inhalation Injury: An Editorial Review

Lung injury from smoke inhalation manifests as airway and parenchymal damage, at times leading to the acute respiratory distress syndrome. From the beginning of this millennium, the approach to mechanical ventilation in the patient with ARDS was based on reduction of tidal volume to 6 milliliters/kilogram of ideal body weight, maintaining a ceiling of plateau pressure, and titration of driving pressure (plateau pressure minus PEEP). Beyond these broad constraints, there is little specification for the mechanics of ventilator settings, consideration of the metabolic impact of the disease process on the patient, or interaction of patient disease and ventilator settings. Various studies suggest that inhomogeneity of lung injury, which increases the risk of regional lung trauma from mechanical ventilation, may be found in the patient with smoke inhalation. We now appreciate that energy transfer principles may affect optimal ventilator management and come into play in damaged heterogenous lungs. Mechanical ventilation in the patient with inhalation injury should consider various factors. Self-injurious respiratory demand by the patient can be reduced using analgesia and sedation. Dynamic factors beginning with rate management can reduce the incidence of potentially damaging ventilation. Moreover, preclinical study is underway to examine the flow of gas based on the ventilator mode selected, which may also be a factor triggering regional lung injury.

Static and Dynamic Measurements of Compliance and Driving Pressure: A Pilot Study

Rationale

Monitoring tidal cycle mechanics is key to lung protection. For this purpose, compliance and driving pressure of the respiratory system are often measured clinically using the plateau pressure, obtained after imposing an extended end-inspiratory pause, which allows for relaxation of the respiratory system and redistribution of inflation volume (method A). Alternative methods for estimating compliance and driving pressure utilize the measured pressure at the earliest instance of zero flow (method B), the inspiratory slope of the pressure-time tracing during inflation with constant flow (method C), and the expiratory time constant (method D).

Methods

Ten passive mechanically ventilated subjects, at a large tertiary referral center, underwent measurements of compliance and driving pressure using the four different methods. The inspiratory tidal volume, inspiratory to expiratory ratio, and positive end expiratory pressures were then adjusted from baseline and the measurements re-obtained.

Results

Method A yielded consistently higher compliance and lower driving pressure calculations compared to methods B and C. Methods B and C most closely approximated one another. Method D did not yield a consistent reliable pattern.

Conclusion

Static measurements of compliance and driving pressure using the plateau pressure may underestimate the maximum pressure experienced by the most vulnerable lung units during dynamic inflation. Utilizing the pressure at zero flow as a static measurement, or the inspiratory slope as a dynamic measurement, may calculate a truer estimate of the maximum alveolar pressure that generates stress upon compromised lung units.

Reliable Estimates of Power Delivery During Mechanical Ventilation Utilizing Easily Obtained Bedside Parameters

BACKGROUND

Ventilator-induced lung injury (VILI) requires repetitive transfer of energy from the ventilator to the compromised lung. To understand this phenomenon, 2 sets of equations have been developed to partition total inflation energy into harmless and hazardous components using an arbitrary level of alveolar pressure as a threshold beyond which further energy increments may become damaging. One set of equations uses premeasured resistance and compliance as inputs to predict the energy that would be delivered by typical ventilator settings, whereas the other equation set uses observed output values for end-inspiratory peak and plateau pressure of an already completed inflation.

METHODS

Our aim for this study was to compare the relative accuracy of these equation sets against the performance of a physical one-compartment model of the respiratory system, programmed with information readily available at the bedside and ventilated using both constant and decelerating flow profiles. Accordingly, equations of each set were compared against the corresponding energy areas measured by digital planimetry of pressure-volume curves for 76 ventilator and patient parameter combinations and over 500 power calculations.

RESULTS

With few exceptions, all equations strongly correlated with their corresponding measurements by planimetry.

CONCLUSIONS

This validation of threshold-partitioned energy equations suggests their potential utility for implementing practical strategies for VILI avoidance.

Intracycle power and ventilation mode as potential contributors to ventilator-induced lung injury

Background

High rates of inflation energy delivery coupled with transpulmonary tidal pressures of sufficient magnitude may augment the risk of damage to vulnerable, stress-focused units within a mechanically heterogeneous lung. Apart from flow amplitude, the clinician-selected flow waveform, a relatively neglected dimension of inflation power, may distribute inflation energy of each inflation cycle non-uniformly among alveoli with different mechanical properties over the domains of time and space. In this initial step in modeling intracycle power distribution, our primary objective was to develop a mathematical model of global intracycle inflation power that uses clinician-measurable inputs to allow comparisons of instantaneous ICP profiles among the flow modes commonly encountered in clinical practice: constant, linearly decelerating, exponentially decelerating (pressure control), and spontaneous (sinusoidal).

Methods

We first tested the predictions of our mathematical model of passive inflation with the actual physical performance of a mechanical ventilator–lung system that simulated ventilation to three types of patients: normal, severe ARDS, and severe airflow obstruction. After verification, model predictions were then generated for 5000 ‘virtual ARDS patients’. Holding constant the tidal volume and inflation time between modes, the validated model then varied the flow profile and quantitated the resulting intensity and timing of potentially damaging ‘elastic’ energy and intracycle power (pressure–flow product) developed in response to random combinations of machine settings and severity levels for ARDS.

Results

Our modeling indicates that while the varied flow patterns ultimately deliver similar total amounts of alveolar energy during each breath, they differ profoundly regarding the potentially damaging pattern with which that energy distributes over time during inflation. Pressure control imposed relatively high maximal intracycle power.

Conclusions

Flow amplitude and waveform may be relatively neglected and modifiable determinants of VILI risk when ventilating ARDS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40635-021-00420-9.

Variation in Early Management Practices in Moderate-to-Severe ARDS in the United States: The Severe ARDS: Generating Evidence Study

BACKGROUND

Although specific interventions previously demonstrated benefit in patients with ARDS, use of these interventions is inconsistent, and patient mortality remains high. The impact of variability in center management practices on ARDS mortality rates remains unknown.

RESEARCH QUESTION

What is the impact of treatment variability on mortality in patients with moderate to severe ARDS in the United States?

STUDY DESIGN AND METHODS

We conducted a multicenter, observational cohort study of mechanically ventilated adults with ARDS and Pao2 to Fio2 ratio of ≤ 150 with positive end-expiratory pressure of ≥ 5 cm H2O, who were admitted to 29 US centers between October 1, 2016, and April 30, 2017. The primary outcome was 28-day in-hospital mortality. Center variation in ventilator management, adjunctive therapy use, and mortality also were assessed.

RESULTS

A total of 2,466 patients were enrolled. Median baseline Pao2 to Fio2 ratio was 105 (interquartile range, 78.0-129.0). In-hospital 28-day mortality was 40.7%. Initial adherence to lung protective ventilation (LPV; tidal volume, ≤ 6.5 mL/kg predicted body weight; plateau pressure, or when unavailable, peak inspiratory pressure, ≤ 30 mm H2O) was 31.4% and varied between centers (0%-65%), as did rates of adjunctive therapy use (27.1%-96.4%), methods used (neuromuscular blockade, prone positioning, systemic steroids, pulmonary vasodilators, and extracorporeal support), and mortality (16.7%-73.3%). Center standardized mortality ratios (SMRs), calculated using baseline patient-level characteristics to derive expected mortality rate, ranged from 0.33 to 1.98. Of the treatment-level factors explored, only center adherence to early LPV was correlated with SMR.

INTERPRETATION

Substantial center-to-center variability exists in ARDS management, suggesting that further opportunities for improving ARDS outcomes exist. Early adherence to LPV was associated with lower center mortality and may be a surrogate for overall quality of care processes. Future collaboration is needed to identify additional treatment-level factors influencing center-level outcomes.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT03021824; URL: www.clinicaltrials.gov.

Effect of Out-of-Hospital Tranexamic Acid vs Placebo on 6-Month Functional Neurologic Outcomes in Patients With Moderate or Severe Traumatic Brain Injury

IMPORTANCE

Traumatic brain injury (TBI) is the leading cause of death and disability due to trauma. Early administration of tranexamic acid may benefit patients with TBI.

OBJECTIVE

To determine whether tranexamic acid treatment initiated in the out-of-hospital setting within 2 hours of injury improves neurologic outcome in patients with moderate or severe TBI.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, double-blinded, randomized clinical trial at 20 trauma centers and 39 emergency medical services agencies in the US and Canada from May 2015 to November 2017. Eligible participants (N = 1280) included out-of-hospital patients with TBI aged 15 years or older with Glasgow Coma Scale score of 12 or less and systolic blood pressure of 90 mm Hg or higher.

INTERVENTIONS

Three interventions were evaluated, with treatment initiated within 2 hours of TBI: out-of-hospital tranexamic acid (1 g) bolus and in-hospital tranexamic acid (1 g) 8-hour infusion (bolus maintenance group; n = 312), out-of-hospital tranexamic acid (2 g) bolus and in-hospital placebo 8-hour infusion (bolus only group; n = 345), and out-of-hospital placebo bolus and in-hospital placebo 8-hour infusion (placebo group; n = 309).

MAIN OUTCOMES AND MEASURES

The primary outcome was favorable neurologic function at 6 months (Glasgow Outcome Scale-Extended score >4 [moderate disability or good recovery]) in the combined tranexamic acid group vs the placebo group. Asymmetric significance thresholds were set at 0.1 for benefit and 0.025 for harm. There were 18 secondary end points, of which 5 are reported in this article: 28-day mortality, 6-month Disability Rating Scale score (range, 0 [no disability] to 30 [death]), progression of intracranial hemorrhage, incidence of seizures, and incidence of thromboembolic events.

RESULTS

Among 1063 participants, a study drug was not administered to 96 randomized participants and 1 participant was excluded, resulting in 966 participants in the analysis population (mean age, 42 years; 255 [74%] male participants; mean Glasgow Coma Scale score, 8). Of these participants, 819 (84.8%) were available for primary outcome analysis at 6-month follow-up. The primary outcome occurred in 65% of patients in the tranexamic acid groups vs 62% in the placebo group (difference, 3.5%; [90% 1-sided confidence limit for benefit, -0.9%]; P = .16; [97.5% 1-sided confidence limit for harm, 10.2%]; P = .84). There was no statistically significant difference in 28-day mortality between the tranexamic acid groups vs the placebo group (14% vs 17%; difference, -2.9% [95% CI, -7.9% to 2.1%]; P = .26), 6-month Disability Rating Scale score (6.8 vs 7.6; difference, -0.9 [95% CI, -2.5 to 0.7]; P = .29), or progression of intracranial hemorrhage (16% vs 20%; difference, -5.4% [95% CI, -12.8% to 2.1%]; P = .16).

CONCLUSIONS AND RELEVANCE

Among patients with moderate to severe TBI, out-of-hospital tranexamic acid administration within 2 hours of injury compared with placebo did not significantly improve 6-month neurologic outcome as measured by the Glasgow Outcome Scale-Extended.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01990768.

Increasing Numbers of Rib Fractures Do Not Worsen Outcome: An Analysis of the National Trauma Data Bank

Increasing age and number of rib fractures are thought to portend a worse outcome with blunt chest trauma, although this is not clearly substantiated in the literature. We hypothesized that these parameters have a significant and synergistic effect, worsening patient outcome. Using the National Trauma Data Bank, we evaluated patients from 2002 to 2006. Patients with a rib fracture International Classification of Diseases, 9th Revision code were included; those with sternal fractures were excluded. Data on demographics, injury, comorbidity, complications, intensive care unit duration, ventilator duration, length of stay, and death were collected. Significant univariate predictors were included in the multivariate logistic regression analysis to adjust for any potential confounders. We identified 35,467 patients who met the inclusion. The mean age was 45.5 years with a mean Injury Severity Score of 19.3. There were 2.1 per cent open rib fractures. Using univariate analysis, rib fracture number was significant. However, once multivariate analyses were applied, the number of rib fractures was not found to be an independent predictor of outcome. The number of rib fractures is not an independent predictor of outcome. Age and overall trauma burden are more powerful predictors of poor outcomes. Treatment focus should shift from the chest to the broader scope of injuries and comorbidities.