Mark L. Ryan

Heart rate variability is an independent predictor of morbidity and mortality in hemodynamically stable trauma patients.

BACKGROUND Reduced heart rate variability (HRV) reflects autonomic dysfunction and can triage patients better than routine trauma criteria or vital signs. However, there is questionable specificity and no consensus measurement technique. The purpose of this study was to analyze whether factors that alter autonomic function affect the specificity of HRV for assessing traumatic injury. METHODS We evaluated 216 hemodynamically stable adults (3:1 M:F; 97:3 blunt:penetrating; age 49 years ± 1 year, mean ± standard error) undergoing computed axial tomography (CT) scan to rule out traumatic brain injury (TBI). All were prospectively instrumented with a Mars Holter system (GE Healthcare, Milwaukee, WI). HRV was determined offline using time domain (standard deviation of normal-normal intervals, root-mean-square successive difference) and frequency domain (very low frequency [VLF], LF, wideband frequency, high frequency [HF], low to HF index ratio) calculations from 15-minute electrocardiogram and correlated with routine vital signs, mortality, TBI, morbidity, length of stay (LOS), and comorbidities. Significance (p ≤ 0.05) was determined using nonparametric analysis, Students t test, analysis of variance, or multiple logistic regression. RESULTS VLF alone predicted survival, severity of TBI, intensive care unit LOS, and hospital LOS (all p < 0.05). Beta-blockers or diabetes had no effect, whereas age, sedation, mechanical ventilation, spinal cord injury, and intoxication influenced one or more of the variables with age being the most powerful confounder (all p < 0.05). Except for the Glasgow Coma Scale, no other routine trauma or hemodynamic criteria correlated with any of these outcomes. CONCLUSIONS Decreased VLF is an independent predictor of mortality and morbidity in hemodynamically stable trauma patients. Other time and other frequency domain variables correlated with some, but not all, outcomes. All were heavily influenced by factors that alter autonomic function, especially patient age.

Venous thromboembolism after trauma: A never event?

Objective:Rates of venous thromboembolism as high as 58% have been reported after trauma, but there is no widely accepted screening protocol. If Medicare adds venous thromboembolism to the list of “preventable complications,” they will no longer reimburse for treatment, which could have devastating effects on many urban centers. We hypothesized that prescreening with a risk assessment profile followed by routine surveillance with venous duplex ultrasound that could identify asymptomatic venous thromboembolism in trauma patients. Design:Prospective, observational trial with waiver of consent. Setting:Level I trauma center intensive care unit. Patients:At admission, 534 patients were prescreened with a risk assessment profile. Interventions:Patients (n = 106) with risk assessment profile scores >10 were considered high risk and received routine screening venous duplex ultrasound within 24 hrs and weekly thereafter. Results:In prescreened high-risk patients, 20 asymptomatic deep vein thrombosis were detected with venous duplex ultrasound (19%). An additional ten venous thromboembolisms occurred, including six symptomatic deep vein thrombosis and four pulmonary emboli, resulting in an overall venous thromboembolism rate of 28%. The most common risk factors discriminating venous thromboembolism vs. no venous thromboembolism were femoral central venous catheter (23% vs. 8%), operative intervention >2 hrs (77% vs. 46%), complex lower extremity fracture (53% vs. 32%), and pelvic fracture (70% vs. 47%), respectively (all p < .05). Risk assessment profile scores were higher in patients with venous thromboembolism (19 ± 6 vs. 14 ± 4, p = .001). Risk assessment profile score (odds ratio 1.14) and the combination of pelvic fracture requiring operative intervention >2 hrs (odds ratio 5.75) were independent predictors for development of venous thromboembolism. The rates of venous thromboembolism for no chemical prophylaxis (33%), unfractionated heparin (29%), dalteparin (40%), or inferior vena cava filters (20%) were not statistically different (p = .764). Conclusions:Medicare’s inclusion of venous thromboembolism after trauma as a “never event” should be questioned. In trauma patients, high-risk assessment profile score and pelvic fracture with prolonged operative intervention are independent predictors for venous thromboembolism development, despite thromboprophylaxis. Although routine venous duplex ultrasound screening may not be cost-effective for all trauma patients, prescreening using risk assessment profile yielded a cohort of patients with a high prevalence of venous thromboembolism. In such high-risk patients, routine venous duplex ultrasound and/or more aggressive prophylactic regimens may be beneficial.

Clinical Applications of Heart Rate Variability in the Triage and Assessment of Traumatically Injured Patients

Heart rate variability (HRV) is a method of physiologic assessment which uses fluctuations in the RR intervals to evaluate modulation of the heart rate by the autonomic nervous system (ANS). Decreased variability has been studied as a marker of increased pathology and a predictor of morbidity and mortality in multiple medical disciplines. HRV is potentially useful in trauma as a tool for prehospital triage, initial patient assessment, and continuous monitoring of critically injured patients. However, several technical limitations and a lack of standardized values have inhibited its clinical implementation in trauma. The purpose of this paper is to describe the three analytical methods (time domain, frequency domain, and entropy) and specific clinical populations that have been evaluated in trauma patients and to identify key issues regarding HRV that must be explored if it is to be widely adopted for the assessment of trauma patients.

Military trauma training at civilian centers: a decade of advancements.

Abstract In the late 1990s, a Department of Defense subcommittee screened more than 100 civilian trauma centers according to the number of admissions, percentage of penetrating trauma, and institutional interest in relation to the specific training missions of each of the three service branches. By the end of 2001, the Army started a program at University of Miami/Ryder Trauma Center, the Navy began a similar program at University of Southern California/Los Angeles County Medical Center, and the Air Force initiated three Centers for the Sustainment of Trauma and Readiness Skills (C-STARS) at busy academic medical centers: R. Adams Cowley Shock Trauma Center at the University of Maryland (C-STARS Baltimore), Saint Louis University (C-STARS St. Louis), and The University Hospital/University of Cincinnati (C-STARS Cincinnati). Each center focuses on three key areas, didactic training, state-of-the-art simulation and expeditionary equipment training, as well as actual clinical experience in the acute management of trauma patients. Each is integral to delivering lifesaving combat casualty care in theater. Initially, there were growing pains and the struggle to develop an effective curriculum in a short period. With the foresight of each trauma training center director and a dynamic exchange of information with civilian trauma leaders and frontline war fighters, there has been a continuous evolution and improvement of each center’s curriculum. Now, it is clear that the longest military conflict in US history and the first of the 21st century has led to numerous innovations in cutting edge trauma training on a comprehensive array of topics. This report provides an overview of the decade-long evolutionary process in providing the highest-quality medical care for our injured heroes.

Operating room or angiography suite for hemodynamically unstable pelvic fractures

Background: Few patients require angiography and therapeutic embolization for bleeding pelvic fractures, but they are risk for significant morbidity and mortality. In hemodynamically unstable trauma patients with pelvic fractures, the decision to proceed to the operating room (OR) to address intraabdominal bleeding, or angiography to address pelvic bleeding (ANGIO), is rarely straightforward. This study tested the hypothesis that outcomes are similar regardless if the sequence was OR-ANGIO or ANGIO-OR. Methods: All pelvic fractures between 1999 and 2011 were retrospectively reviewed and stratified by initial management with ANGIO or OR. Results: Of 2,922 patients with pelvic fractures, only 183 (6%) required angiography for suspected bleeding. For OR-ANGIO (n = 49) versus ANGIO (n = 134), injury severity score was similar (40 ± 15 vs. 35 ± 16), but systolic blood pressure (97 ± 28 vs. 108 ± 32 mmHg, p = 0.038) and base excess were both lower (−9 ± 5 vs. −5 ± 5 mEq/L, p < 0.001). During initial resuscitation and in the first 24 hours, crystalloid, blood product usage and total fluid requirements were all increased 50% to 100% (all p < 0.001). Despite these differences, lengths of stay (32 ± 32 vs. 26 ± 28 days) and mortality (33% vs. 31%) were similar. The same trends in fluid requirements remained in the subset of patients with unstable pelvic fractures, with an increased mortality (67% vs. 20%, p = 0.011) in those requiring ANGIO-OR versus OR-ANGIO. Conclusion: These data support current management algorithms. In hemodynamically unstable trauma patients with pelvic fractures, those who proceeded immediately to the OR to address intraabdominal bleeding tended to be sicker but had outcomes that were the same or better compared with those who received angiography to address pelvic bleeding. Level of Evidence: III, retrospective review.

Predeployment Mass Casualty and Clinical Trauma Training for Us Army Forward Surgical Teams

Since the beginning of the program in 2002, 84 Forward Surgical Teams (FSTs) have rotated through the Army Trauma Training Center (ATTC) at the University of Miami/Ryder Trauma Center including all those deployed to Iraq and Afghanistan. The purpose of this study was to provide the latest updates of our experience with FSTs at the ATTC. Before deployment, each FST participates in a 2-week training rotation at the ATTC. The rotation is divided into 3 phases. Phase 1 is to refresh FST knowledge regarding the initial evaluation and management of the trauma patient. Phase 2 is the clinical phase and is conducted entirely at the Ryder Trauma Center. The training rotation culminates in phase 3, the Capstone exercise. During the Capstone portion of their training, the entire 20-person FST remains at the Ryder Trauma Center and is primarily responsible for the evaluation and resuscitation of all patients arriving over a 24-hour period. Subject awareness concerning their role within the team improved from 71% to 95%, indicating that functioning as a team in the context of the mass casualty training exercise along with clinical codes was beneficial. The clinical component of the rotation was considered by 47% to be the most valuable aspect of the training. Our experience strongly suggests that a multimodality approach is beneficial for preparing a team of individuals with minimal combat (or trauma) experience for the rigors of medical care and triage on the battlefield. The data provided by participants rotating through the ATTC show that through clinical exposure and simulation over a 2-week period, FST performance is optimized by defining provider roles and improving communication. The mass casualty training exercise is a vital component of predeployment training that participants feel is valuable in preparing them for the challenges that lay ahead.

Pre-existing hypercoagulability in patients undergoing potentially curative cancer resection

BACKGROUND Rotational thromboelastometry (ROTEM) is a new point-of-care test that allows a rapid and comprehensive evaluation of coagulation. We were among the first to show that ROTEM identifies baseline hypercoagulability in 40% of patients with intra-abdominal malignancies and that hypercoagulability persists for ≥1 month after resection. The purpose of this follow-up study was to confirm and extend these observations to a larger population in outpatient preoperative clinics. The hypothesis is that pre-existing hypercoagulability is present in patients undergoing surgery for malignant disease and that coagulation status varies by tumor type. METHODS After informed consent, preoperative blood samples were drawn from patients undergoing exploratory laparotomies for intra-abdominal malignancies and analyzed with ROTEM. RESULTS Eighty-two patients were enrolled, including 72 with a confirmed pathologic diagnosis and 10 age-matched controls with benign disease. The most common cancers involved the pancreas (n = 23; 32%), esophagus (n = 19; 26%), liver (n = 12; 17%), stomach (n = 7; 10%), and bile ducts (n = 5; 7%). Preoperative hypercoagulability was detected in 31% (n = 22); these patients were more likely to have lymphovascular invasion (88% vs 50%; P = .011), perineural invasion (77% vs 36%; P = .007), and stage III/IV disease (80% vs 62%; P = .039). More patients with pancreatic tumors (9/23, 39%) were hypercoagulable than with esophageal (3/19, 16%) or liver (2/13, 15%, P = .034) tumors. When only resectable malignancies were considered, clot formation was more rapid (low clot formation time, high alpha) with enhanced maximum clot strength (high maximum clot firmness) in pancreatic versus esophageal or liver cancers and in all cancers versus those with benign disease. CONCLUSION Preoperative hypercoagulability can be identified with ROTEM and is associated with lymphovascular/perineural invasion and advanced-staged disease in cancer. Compared with other tumor types, pancreatic adenocarcinomas have the greatest risk for hypercoagulability.

Persistence of hypercoagulable state after resection of intra-abdominal malignancies

BACKGROUND The hypercoagulable state associated with cancer imparts considerable risk for venous thromboembolism. Surgical resection of malignancies should theoretically reverse tumor-induced hypercoagulability. However, coagulation changes in cancer patients postresection have not been described thoroughly. Conventional coagulation tests are unable to detect hypercoagulable states. In contrast, rotational thromboelastography (ROTEM) can detect hypo- or hypercoagulable conditions. We hypothesized that the cancer-induced hypercoagulable state would improve after surgical resection. METHODS After informed consent, blood samples of patients undergoing surgical resection for curative intent were analyzed with serial ROTEM. RESULTS Thirty-five patients (mean ± SD age 66 ± 17 years; 67% male) had cancers involving the pancreas (n = 12 [34%]), esophagus (n = 10 [29%]), stomach (n = 7 [20%]), bile ducts (n = 3 [9%]), and duodenum (n = 3 [9%]). Preoperative ROTEM identified 14 (40%) who were hypercoagulable. After surgical resection, patients became progressively hypercoagulable with more rapid clot formation time (low clot formation time, high alpha) and higher maximum clot firmness. By week one, 86% (n = 30) had abnormal ROTEM values, including 17 of 21 (81%) who had normal coagulation profiles preoperatively. Most (n = 30 [86%]) remained hypercoagulable at 3 to 4 weeks. CONCLUSIONS Rotational thromboelastography identifies baseline hypercoagulability in more than one third of patients with intra-abdominal malignancies. This is among the first studies to demonstrate progressive hypercoagulability that persists for at least 1 month after resection. These data support postdischarge thromboprophylaxis regimens in high-risk cancer patients.

Initial hematocrit in trauma: a paradigm shift?

Background: After severe trauma and hemorrhage, it is generally assumed that the rate of fluid shift from the interstitial space into the vasculature is relatively slow and that initial hematocrit (Hct) does not reflect estimated blood loss. This study challenges that idea and tests the hypothesis that initial Hct correlates with signs of shock and hemorrhage in trauma patients. Methods: Data were retrospectively reviewed from 198 trauma patients requiring emergency surgery at a Level I center from July 2009 to April 2010. Patients were divided into quartiles based on the initial Hct measured within 10 minutes of arrival. Categorical data were compared using &khgr;2 test or Fishers exact test, as appropriate. Normally distributed data were compared using Students t test or analysis of variance. Nonparametric data were compared with a Mann-Whitney U test or Kruskal-Wallis test. Post hoc analysis was conducted using the Bonferroni correction or paired Mann-Whitney U tests. Results: The study population was 83% male, aged 35 ± 1 years (mean ± SE), with 71% penetrating injuries. Lower initial Hct correlated with hypotension (p < 0.001), acidosis (p = 0.003), altered mental status (p < 0.001), Injury Severity Score (p < 0.001), Revised Trauma Score (p < 0.001), estimated blood loss (p < 0.001), and usage of packed red blood cells (p < 0.001), fresh frozen plasma (p = 0.003), crystalloid (p = 0.021), and vasopressors (p < 0.001). Conclusion: Admission Hct correlates with signs of shock and hemorrhage in trauma patients requiring emergency surgery because fluid shifts rapidly from the interstitial space into the vasculature. This finding of a rapid Hct change contradicts the current teaching in most trauma textbooks. Level of evidence: II, diagnostic study.

Bispectral index to monitor propofol sedation in trauma patients

BACKGROUND This study tested the hypothesis that the bispectral index (BIS) is reliable relative to clinical judgment for estimating sedation level during daily propofol spontaneous awakening trials (SATs) in trauma patients. METHODS This was a prospective observational trial with waiver of consent conducted in the intensive care unit of Level I trauma center in 94 mechanically ventilated trauma patients sedated with propofol alone or in combination with midazolam. BIS, Richmond Agitation Sedation Scale (RASS), electromyography, and heart rate variability, as a test of autonomic function, were measured for 45 minutes during daily SATs. Data were evaluated with analysis of variance, linear regression, and nonparametric tests. RESULTS The BIS wave form coincided almost exactly with propofol on/off. Steady-state BIS correlated with RASS (p < 0.0001) and with propofol dose (p < 0.0001), but the strengths of association were relatively low (all r(2) < 0.5). BIS wave form was not altered by age, heart rate, or heart rate variability and was similar with propofol alone or propofol plus midazolam, but the presence of brain injury or the use of paralytics shifted the curve downward (both p < 0.001). The overall test characteristics for BIS versus RASS without neuromuscular blockade were sensitivity: 90% versus 77% (p = 0.034); specificity: 90% versus 75% (p = 0.021); positive predictive value: 90% versus 76% (p = 0.021), and negative predictive value: 90% versus 76% (p = 0.021). CONCLUSIONS In the first trial in trauma patients and largest trial in any surgical population, the (1) BIS was reliable and has advantages over RASS of being continuous and objective, at least during a propofol SAT; (2) BIS interpretation remains somewhat subjective in patients receiving paralytic agents or with traumatic brain injury.