Unmasking the Hypovolemic Shock Continuum: The Compensatory Reserve.

Hypovolemic shock exists as a spectrum, with its early stages characterized by subtle pathophysiologic tissue insults and its late stages defined by multi-system organ dysfunction. The importance of timely detection of shock is well known, as early interventions improve mortality, while delays render these same interventions ineffective. However, detection is limited by the monitors, parameters, and vital signs that are traditionally used in the intensive care unit (ICU). Many parameters change minimally during the early stages, and when they finally become abnormal, hypovolemic shock has already occurred. The compensatory reserve (CR) is a parameter that represents a new paradigm for assessing physiologic status, as it comprises the sum total of compensatory mechanisms that maintain adequate perfusion to vital organs during hypovolemia. When these mechanisms are overwhelmed, hemodynamic instability and circulatory collapse will follow. Previous studies involving CR measurements demonstrated their utility in detecting central blood volume loss before hemodynamic parameters and vital signs changed. Measurements of the CR have also been used in clinical studies involving patients with traumatic injuries or bleeding, and the results from these studies have been promising. Moreover, these measurements can be made at the bedside, and they provide a real-time assessment of hemodynamic stability. Given the need for rapid diagnostics when treating critically ill patients, CR measurements would complement parameters that are currently being used. Consequently, the purpose of this article is to introduce a conceptual framework where the CR represents a new approach to monitoring critically ill patients. Within this framework, we present evidence to support the notion that the use of the CR could potentially improve the outcomes of ICU patients by alerting intensivists to impending hypovolemic shock before its onset.

Reducing Lung Injury from Blind Insertion of Small-Bore Feeding Tubes.

ABSTRACT: Using a blind insertion technique to insert small-bore feeding tubes can result in inadvertent placement in the lungs, leading to lung perforation and even mortality. In a Magnet-designated, 500-bed, level 2 trauma center, two serious patient safety events occurred in a four-week period due to nurses blindly inserting a small-bore feeding tube. A patient safety event review team convened and conducted an assessment of reported small-bore feeding tube insertion events that occurred between March 2019 and July 2021. The review revealed six lung perforations over this two-year period. These events prompted the creation of a multidisciplinary team to evaluate alternative small-bore feeding tube insertion practices. The team reviewed the literature and evaluated several evidence-based small-bore feeding tube placement methods, including placement with fluoroscopy, a two-step X-ray, electromagnetic visualization, and capnography. After the evaluation, capnography was selected as the most effective method to mitigate the complications of blind insertion. In this article, the authors describe a quality improvement project involving the implementation of capnography-guided small-bore feeding tube placement to reduce complications and the incidence of lung perforation. Since the completion of the project, which took place from December 13, 2021, through April 18, 2022, no lung injuries or perforations have been reported. Capnography is a relatively simple, noninvasive, and cost-effective technology that provides nurses with a means to safely and effectively insert small-bore feeding tubes, decrease the incidence of adverse events, and improve patient care.

Hemodynamics, survival and neurological function with early versus delayed automated head-up CPR in a porcine model of prolonged cardiac arrest.

AIM: To determine if controlled head and thorax elevation, active compression-decompression cardiopulmonary resuscitation (CPR), and an impedance threshold device combined, termed automated head-up positioning CPR (AHUP-CPR), should be initiated early, as a basic (BLS) intervention, or later, as an advanced (ALS) intervention, in a severe porcine model of cardiac arrest. METHODS: Yorkshire pigs (n = 22) weighing ∼40 kg were anesthetized and ventilated. After 15 minutes of untreated ventricular fibrillation, pigs were randomized to AHUP-CPR for 25 minutes (BLS group) or conventional CPR for 10 minutes, followed by 15 minutes of AHUP-CPR (ALS group). Thereafter, epinephrine, amiodarone, and defibrillation were administered. Neurologic function, the primary endpoint, was assessed 24-hours later with a Neurological Deficit Score (NDS, 0 = normal and 260 = worst deficit score or death). Secondary outcomes included return of spontaneous circulation (ROSC), cumulative survival, hemodynamics and epinephrine responsivity. Data, expressed as mean ± standard deviation, were compared using Fisher's Exact, log-rank, Mann-Whitney U and unpaired t-tests. RESULTS: ROSC was achieved in 10/11 pigs with early AHUP-CPR versus 6/11 with delayed AHUP-CPR (p = 0.14), and cumulative 24-hour survival was 45.5% versus 9.1%, respectively (p < 0.02). The NDS was 203 ± 80 with early AHUP-CPR versus 259 ± 3 with delayed AHUP-CPR (p = 0.035). ETCO2, rSO2, and responsiveness to epinephrine were significantly higher in the early versus delayed AHUP-CPR. CONCLUSION: When delivered early rather than late, AHUP-CPR resulted in significantly increased hemodynamics, 24-hour survival, and improved neurological function in pigs after prolonged cardiac arrest. Based on these findings, AHUP-CPR should be considered a BLS intervention.

The association of regional cerebral oximetry and neurologically intact survival in a porcine model of cardiac arrest.

Background: The objective of this study was to determine if regional cerebral oximetry (rSO2) assessed during CPR would be predictive of survival with favorable neurological function in a prolonged model of porcine cardiac arrest. This study also examined the relative predictive value of rSO2 and end-tidal carbon dioxide (ETCO2), separately and together. Methods: This study is a post-hoc analysis of data from a previously published study that compared conventional CPR (C-CPR) and automated head-up positioning CPR (AHUP-CPR). Following 10 min of untreated ventricular fibrillation, 14 pigs were treated with either C-CPR (C-CPR) or AHUP-CPR. rSO2, ETCO2, and other hemodynamic parameters were measured continuously. Pigs were defibrillated after 19 min of CPR. Neurological function was assessed 24 h later. Results: There were 7 pigs in the neurologically intact group and 7 pigs in the poor outcomes group. Within 6 min of starting CPR, the mean difference in rSO2 by 95% confidence intervals between the groups became statistically significant (p < 0.05). The receiver operating curve for rSO2 to predict survival with favorable neurological function reached a maximal area under the curve value after 6 min of CPR (1.0). The correlation coefficient between rSO2 and ETCO2 during CPR increased towards 1.0 over time. The combined predictive value of both parameters was similar to either parameter alone. Conclusion: Significantly higher rSO2 values were observed within less than 6 min after starting CPR in the pigs that survived versus those that died. rSO2 values were highly predictive of survival with favorable neurological function.

Active decompression during automated head-up cardiopulmonary resuscitation.

BACKGROUND: The combination of active compression-decompression cardiopulmonary resuscitation (ACD-CPR) with an impedance threshold device (ITD) and controlled head-up positioning (AHUP-CPR) is associated with improved outcomes compared with conventional CPR (C-CPR). This study focused on the role of active decompression (AD) during AHUP-CPR. METHODS: Farm pigs (n = 10, ∼40 kg) were anesthetized, intubated and ventilated. Physiological parameters and right ventricular pressure-volume loops were recorded continuously. Ventricular fibrillation was induced and left untreated for 10 mins, followed by automated C-CPR (2 min), ACD + ITD CPR in the flat position (2 min), and then AHUP-CPR with 3 cm of lift above the neutral chest position. After 15 min of CPR, AD was discontinued and then restarted incrementally to 4 cm. Data were analyzed with a linear mixed-effects model, using random intercepts for individual pigs. RESULTS: Upon cessation of AD during AHUP-CPR, decompression right atrial pressure (+59%) increased (p < 0.01), whereas multiple hemodynamic parameters positively associated with perfusion, including coronary (-25%) and cerebral perfusion pressures (-11%), end-tidal CO2 (-13%), stroke volume and cardiac output (-26%), decreased immediately and significantly with p < 0.05. Restoration of AD reduced right atrial pressure and increased positive perfusion parameters in an incremental manner. Only with ≥ 3 cm of AD were all hemodynamic parameters restored to ≥ 90% of pre-AD discontinuation levels. CONCLUSION: Full chest wall lift, achieved with ≥ 3 cm of AD, was needed to maintain and optimize hemodynamics during AHUP-CPR in pigs. These findings should be considered when optimizing care with this new approach.

A Deeper Dive Into Combat Medic Training.

The recent article by Knisely et al. provides a comprehensive review and summary of recent literature describing simulation techniques, training strategies, and technologies to teach medics combat casualty care skills. Some of the results reported by Knisely et al. align with the findings of our team's work, and these findings may be helpful to military leadership with their ongoing efforts to maintain medical readiness. Accordingly, we provide some additional contextual understanding to the results of Knisely et al. in this commentary. Our team recently published two papers describing the results of a large survey that examined Army medic pre-deployment training. Combining the findings of Knisely et al. along with some of the contextual information from our work, we provide some recommendations for improving and optimizing the pre-deployment training paradigm for medics.

Initial treatment strategies in new-onset atrial fibrillation in critically ill burn patients.

INTRODUCTION: Atrial fibrillation is associated with increased morbidity and mortality in critically ill patients. Few studies have specifically examined this arrhythmia in burn patients. Given the significant clinical implications of atrial fibrillation, understanding the optimal management strategy of this arrhythmia in burn patients is important. Consequently, the purpose of this study was to examine rate- and rhythm-control strategies in the management of new onset atrial fibrillation (NOAF) and assess their short term outcomes in critically ill burn patients. METHODS: We identified all patients admitted to our institution's burn intensive care unit between January 2007 and May 2018 who developed NOAF. Demographic information and burn injury characteristics were captured. Patients were grouped into two cohorts based on the initial pharmacologic treatment strategy: rate-(metoprolol or diltiazem) or rhythm-control (amiodarone). The primary outcome was conversion to sinus rhythm. Secondary outcomes included relapse or recurrence of atrial fibrillation, drug-related adverse events, and complications and mortality within 30 days of the NOAF episode. RESULTS: There were 68 patients that experienced NOAF, and the episodes occurred on median days 8 and 9 in the rate- and rhythm-control groups, respectively. The length of the episodes was not significantly different between the groups. Conversion to sinus rhythm occurred more often in the rhythm-control group (P = 0.04). There were no differences in the incidences of relapse and recurrence of atrial fibrillation, and the complications and mortality between the groups. Hypotension was the most common drug-related adverse event and occurred more frequently in the rate-control group, though this difference was not significant. CONCLUSIONS: Conversion to sinus rhythm occurred more often in the rhythm-control group. Outcomes were otherwise similar in terms of mortality, complications, and adverse events. Hypotension occurred less frequently in the rhythm-control group, and although this difference was not significant, episodes of hypotension can have important clinical implications. Given these factors, along with burn patients having unique injury characteristics and a hypermetabolic state that may contribute to the development of NOAF, when choosing between rate- and rhythm control strategies, rhythm-control with amiodarone may be a better choice for managing NOAF in burn patients.

Suppression of cautery-induced electromagnetic interference of cardiac implantable electrical devices by closely spaced bipolar sensing.

BACKGROUND: Electromagnetic interference (EMI) induced by electrocautery during surgery in patients with cardiac pacemakers or implanted cardioverter-defibrillators (ICDs) may inhibit pacing and cause inappropriate tachyarrhythmia oversensing. In particular, susceptibility to EMI may be enhanced in ICDs by frequently used wide interelectrode sensing (i.e., integrated bipolar sensing). Consequently, ICD function is usually disabled preoperatively and restored later by noninvasive programming. Because sensing by closely spaced electrodes (i.e., true bipolar) may be less susceptible to EMI, preoperative programming to a true bipolar mode may minimize the need for perioperative programming while preserving device function. METHODS: Our study population consisted of 23 consecutive patients either receiving a new ICD or undergoing ICD pulse generator change. In each patient, electrocautery-induced EMI was initiated with the ICD in the closely spaced sensing configuration and again during widely spaced sensing. RESULTS: In comparing the 2 sensing modes, right ventricular electrogram amplitude was significantly greater and EMI noise amplitude tended to be greater with widely spaced bipolar sensing. Furthermore, widely spaced bipolar sensing was associated with ICD pacing inhibition in 22 of 23 patients and incorrect "ventricular fibrillation" detection in 17 of 23 patients. Conversely, closely spaced bipolar sensing was not accompanied by either pacing inhibition or incorrect ventricular fibrillation sensing. CONCLUSION: Closely spaced bipolar sensing (i.e., true bipolar) appropriately rejects electrocautery-induced EMI. Programming implanted devices to closely spaced bipolar sensing may minimize the need for perioperative reprogramming while preserving intraoperative device operation.

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.

Characteristics of burn casualties treated at role 2 in Afghanistan.

BACKGROUND: Role 2 medical treatment facilities (MTFs) are frequently located in austere settings and have limited resources. A dedicated assessment of burn casualties treated at this level of care has not been performed. Therefore, the objective of this study was to characterize burn casualties presenting to role 2 MTFs in Afghanistan, along with the procedures they required, complications, and mortality to begin understanding the resources consumed by their care. METHODS: We identified burn casualties from the Department of Defense Trauma Registry (DODTR). The inclusion criteria were (1) experienced burn injuries in Afghanistan between October 2005 and April 2018 and (2) had documentation of treatment at role 2 in the DODTR. We excluded casualties with only first-degree burns, not otherwise specified burns, or only corneal burns. Casualty demographics, injury characteristics, procedures, and outcomes were reported. RESULTS: We identified 453 burn casualties with a median (interquartile range) Injury Severity Score of 10 (4-22) and percent total body surface area burned of 11 (5-30). There were 123 casualties (27.2%) with inhalation injury, and the casualties experienced 3,343 additional traumatic injuries and needed 2,530 procedures. Casualties with documentation of resuscitation information received a median (interquartile range) of 1.9 (0.7-3.7) L of crystalloid fluids. Complications were documented in 53 casualties (11.7%). Final mortality was reported in 36 casualties (8.0%), and mortality at role 2 MTFs was reported in 7 casualties (1.5%). CONCLUSION: Burn casualties had many injuries and needed many procedures, including those related to airway management, resuscitation, and wound care. Given the urgency of these procedures, ensuring that there is enough equipment and supplies will be important in the future. Although infrequent, some casualties experienced complications. Factors that may influence resuscitation include injury severity, concomitant traumatic injuries, and available supplies. Obtaining more contextual information on the patient care environment will be useful going forward. LEVEL OF EVIDENCE: Epidemiological, level III.

An Assessment of Pre-deployment Training for Army Nurses and Medics.

INTRODUCTION: Although military nurses and medics have important roles in caring for combat casualties, no standardized pre-deployment training curriculum exists for those in the Army. A large-scale, survey-based evaluation of pre-deployment training would help to understand its current state and identify areas for improvement. The purpose of this study was to survey Army nurses and medics to describe their pre-deployment training. MATERIALS AND METHODS: Using the Intelink.gov platform, a web-based survey was sent by e-mail to Army nurses and medics from the active and reserve components who deployed since 2001. The survey consisted of questions asking about pre-deployment training from their most recent deployment experience. Descriptive statistics were used to analyze the results, and free text comments were also captured. RESULTS: There were 682 respondents: 246 (36.1%) nurses and 436 (63.9%) medics. Most of the nurses (n = 132, 53.7%) and medics (n = 298, 68.3%) reported that they were evaluated for clinical competency before deployment. Common courses and topics included Tactical Combat Casualty Care, Advanced Cardiac Life Support, cultural awareness, and trauma care. When asked about the quality of their pre-deployment training, most nurses (n = 186; 75.6%) and medics (n = 359; 82.3%) indicated that their training was adequate or better. Nearly all nurses and medics reported being moderately confident or better (nurses n = 225; 91.5% and medics n = 399; 91.5%) and moderately prepared or better (nurses n = 223; 90.7% and medics n = 404; 92.7%) in their ability to provide combat casualty care. When asked if they participated in a team-based evaluation of clinical competence, many nurses (n = 121, 49.2%) and medics (n = 180, 41.3%) reported not attending a team training program. CONCLUSIONS: Most nurse and medic respondents were evaluated for clinical competency before deployment, and they attended a variety of courses that covered many topics. Importantly, most nurses and medics were satisfied with the quality of their training, and they felt confident and prepared to provide care. Although these are encouraging findings, they must be interpreted within the context of self-report, survey-based assessments, and the low response rate. Although these limitations and weaknesses of our study limit the generalizability of our results, this study attempts to address a critical knowledge gap regarding pre-deployment training of military nurses and medics. Our results may be used as a basis for conducting additional studies to gather more information on the state of pre-deployment training for nurses and medics. These studies will hopefully have a higher response rate and better quantify how many individuals received any form of pre-deployment training. Additionally, our recommendations regarding pre-deployment training that we derived from the study results may be helpful to military leadership.

Predeployment training of Army medics assigned to prehospital settings.

BACKGROUND: Medics have numerous responsibilities in the combat theater, which include performing lifesaving interventions, providing basic medical and nursing care, and caring for casualties in a variety of scenarios unique to the battlefield. An evaluation of the medic predeployment training paradigm is important and will help to understand its current state and identify areas for improvement. Therefore, the purpose of this study was to perform a focused assessment of Army medic predeployment training to identify patterns that might inform future medic training. METHODS: A web-based survey was created using the Intelink.gov platform and sent by e-mail to Army medics who deployed since 2001. Medics were asked to reflect upon the predeployment training from their most recent deployment experience. There were multiple choice, Likert-type scale, and free-text response questions. Descriptive statistics were used to analyze the results. RESULTS: There were 254 respondents who met the study inclusion criteria. Most of the respondents had their clinical competency evaluated (68.5%, n = 174). Respondents reported several acute trauma, basic nursing, and battlefield medicine skills as being critical but also felt that many of these same skills would have benefited from additional predeployment training. Most of the respondents felt very or fully confident and prepared to provide combat casualty care (74.8%, n = 190 and 74.8%, n = 190). There were 64 respondents (25.2%) who reported feeling not at all, slightly, or moderately confident, and 54 (84.4%) of these respondents described in a free-text question wanting additional training before deployment. CONCLUSION: Respondents reported many skills as being critical to combat casualty care, but several of these skills would have benefited from additional predeployment training. Respondents with more deployment experience or completion of more predeployment training reported feeling more confident and prepared to provide combat casualty care. A common sentiment was the desire for more training of any form before deployment. LEVEL OF EVIDENCE: Epidemiological, level IV.

CE: Trauma-Related Hemorrhagic Shock: A Clinical Review.

Optimal management of trauma-related hemorrhagic shock begins at the point of injury and continues throughout all hospital settings. Several procedures developed on the battlefield to treat this condition have been adopted by civilian health care systems and are now used in a number of nonmilitary hospitals. Despite the important role nurses play in caring for patients with trauma-related hemorrhagic shock, much of the literature on this condition is directed toward paramedics and physicians. This article discusses the general principles underlying the pathophysiology and clinical management of trauma-related hemorrhagic shock and updates readers on nursing practices used in its management.

Characteristics and outcomes of patients with inhalation injury treated at a military burn center during U.S. combat operations.

BACKGROUND: The purpose of this study was to examine risk factors for mortality in burned patients with inhalation injury (II). We further sought to compare a cohort of burned military service members to civilian patients with II. METHODS: We identified patients treated at our burn center over a 10-year period. Demographics, injury characteristics, and outcomes were compared between patients with and without II. Logistic regression analysis was performed to determine the impact of patient characteristics and II grade on mortality. RESULTS: 3791 patients treated at our burn center met study inclusion criteria. 424 (11.2%) patients were diagnosed with II [II(+)]. Age, % total body surface area (TBSA) burned, % full thickness burned, intensive care unit (ICU) days, hospital days, and mortality were all greater in II(+) patients. Separating the II(+) patients into military and civilian groups, there was a higher incidence of grade 4 II and higher mortality for grades 2-4 II in military patients. Analyses demonstrated that military service was associated with increased mortality in II(+) patients. The bronchoscopic grade of II did not have an association with mortality in this population. CONCLUSIONS: II(+) patients were older, had larger burns, needed more ICU and hospital days, and had higher mortality rates. Among II(+) patients, military affiliation was associated with more severe II and increased mortality. Establishment of an objective grading system for II that is associated with mortality is a meaningful future research endeavor.