Sex dimorphisms in coagulation: Implications in trauma-induced coagulopathy and trauma resuscitation

Trauma-induced coagulopathy (TIC) is one of the leading causes of preventable death in injured patients. Consequently, it is imperative to understand the mechanisms underlying TIC and how to mitigate this mortality. An opportunity for advancement stems from the awareness that coagulation demonstrates a strong sex-dependent effect. Females exhibit a relative hypercoagulability compared to males, which persists after injury and confers improved outcomes. The mechanisms underlying sex dimorphisms in coagulation and its protective effect after injury have yet to be elucidated. This review explores sex dimorphisms in enzymatic hemostasis, fibrinogen, platelets, and fibrinolysis, with implications for resuscitation of patients with TIC.

Surgical Apgar scores predict complications after emergency general surgery laparotomy

BACKGROUND

The Surgical Apgar Score (SAS) is a 10-point validated score comprised of three intraoperative variables (blood loss, lowest heart rate, and lowest mean arterial pressure). Lower scores are worse and predict major postoperative complications. The SAS has not been applied in emergency general surgery (EGS) but may help guide postoperative disposition. We hypothesize that SAS can predict complications in EGS patients undergoing a laparotomy.

METHODS

We performed a retrospective review of adult patients at a single, quaternary care center who underwent an exploratory laparotomy for EGS conditions within 6 hours of surgical consultation from 2015 to 2019. Patients were grouped by whether they experienced a postoperative complication (systemic, surgical, and/or death). Multivariable regression was performed to predict complications, accounting for SAS and other statistically significant variables between groups. Using this model, predicted probabilities of a complication were generated for each SAS.

RESULTS

The cohort comprised 482 patients: 32.8% (n = 158) experienced a complication, while 67.2% (n = 324) did not. Patients with complications were older, frailer, more often male, had worse SAS (6 vs. 7, p < 0.0001) and American Society of Anesthesiologists scores, and higher rates of perforated hollow viscus ( p = 0.0003) and open abdomens ( p < 0.0001). On multivariable regression, an increasing SAS independently predicted less complications (adjusted odds ratio, 0.85; 95% confidence interval, 0.75-0.96; p = 0.009). An SAS ≤4 was associated with a 49.2% predicted chance of complications, greater rates of septic shock (9.7% vs. 3%, p = 0.01), respiratory failure (20.5% vs. 10.8%, p = 0.02), and death (24.1% vs. 7.5%, p < 0.0001). An SAS ≤ 4 did not correlate with surgical complications ( p = 0.1).

CONCLUSION

The SAS accurately predicts postoperative complications in EGS patients undergoing urgent laparotomy, with an SAS ≤ 4 identifying patients at risk for septic shock, respiratory failure, and mortality. This tool can aid in rapidly determining postoperative disposition and resource allocation.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level IV.

Early Surgical Stabilization of Rib Fractures is Feasible in Patients With Non-Urgent Operative Pelvic Injuries

INTRODUCTION

The feasibility of prioritizing surgical stabilization of rib fractures (SSRF) in patients with other injuries is unknown. The purpose of this study was to evaluate the timing and outcomes of SSRF between patients with and without non-urgent operative pelvic injuries.

PATIENTS AND METHODS

In this retrospective observational study, all patients between 2010 and 2020 who underwent SSRF (SSRF group) and those who underwent SSRF and non-urgent operative management of pelvic fractures (SSRF + P group) were included. Demographics, injury characteristics, operative details, and outcomes were compared between the 2 groups.

RESULTS

Over 11 years, 154 SSRF patients were identified, with 143 patients in the SSRF group (93%) and 11 patients in the SSRF + P group (7%). Median number of rib fractures (7 vs 9, P = .04), total number of fractures (11 vs 15, P < .01), and flail segment (54% vs 91%, P = .02) were higher in SSRF + P group. Median time to SSRF was similar (0 vs 1 day, P = .20) between the 2 groups. Median time to pelvic fixation was 3 days in SSRF + P group and 8 out of 11 patients (73%) underwent SSRF prior to pelvic fixation. Median operative time (137 vs 178 mins, P = .14) and median number of ribs plated (4 vs 5, P = .05) were higher in SSRF + P group. There was no difference in SSRF-related complications, pelvic fracture-related complications from operative positioning, rates of pneumonia, or mortality between the 2 groups.

CONCLUSIONS

SSRF can be performed early in patients with non-urgent operative pelvic injuries without a difference in pelvic fracture-related complications, SSRF-related complications, pneumonia, or mortality.

A metabolomic and proteomic analysis of pathologic hypercoagulability in traumatic brain injury patients after dura violation

BACKGROUND

The coagulopathy of traumatic brain injury (TBI) remains poorly understood. Contradictory descriptions highlight the distinction between systemic and local coagulation, with descriptions of systemic hypercoagulability despite intracranial hypocoagulopathy. This perplexing coagulation profile has been hypothesized to be due to tissue factor release. The objective of this study was to assess the coagulation profile of TBI patients undergoing neurosurgical procedures. We hypothesize that dura violation is associated with higher tissue factor and conversion to a hypercoagulable profile and unique metabolomic and proteomic phenotype.

METHODS

This is a prospective, observational cohort study of all adult TBI patients at an urban, Level I trauma center who underwent a neurosurgical procedure from 2019 to 2021. Whole blood samples were collected before and then 1 hour following dura violation. Citrated rapid and tissue plasminogen activator (tPA) thrombelastography (TEG) were performed, in addition to measurement of tissue factory activity, metabolomics, and proteomics.

RESULTS

Overall, 57 patients were included. The majority (61%) were male, the median age was 52 years, 70% presented after blunt trauma, and the median Glasgow Coma Score was 7. Compared with pre-dura violation, post-dura violation blood demonstrated systemic hypercoagulability, with a significant increase in clot strength (maximum amplitude of 74.4 mm vs. 63.5 mm; p < 0.0001) and a significant decrease in fibrinolysis (LY30 on tPAchallenged TEG of 1.4% vs. 2.6%; p = 0.04). There were no statistically significant differences in tissue factor. Metabolomics revealed notable increases in metabolites involved in late glycolysis, cysteine, and one-carbon metabolites, and metabolites involved in endothelial dysfunction/arginine metabolism/responses to hypoxia. Proteomics revealed notable increase in proteins related to platelet activation and fibrinolysis inhibition.

CONCLUSION

A systemic hypercoagulability is observed in TBI patients, characterized by increased clot strength and decreased fibrinolysis and a unique metabolomic and proteomics phenotype independent of tissue factor levels.

Elucidating the molecular mechanisms of fibrinolytic shutdown after severe injury: The role of thrombin-activatable fibrinolysis inhibitor

BACKGROUND

The mechanisms underlying trauma-induced coagulopathy remain elusive. Hyperfibrinolysis has been linked to increased plasminogen activation and antiprotease consumption; however, the mechanistic players in its counterpart, fibrinolysis shutdown, remain unclear. We hypothesize that thrombin-activatable fibrinolysis inhibitor (TAFI) plays a major role in fibrinolytic shutdown after injury.

METHODS

As part of this observational cohort study, whole blood was collected from trauma activation patients at a single, level 1 trauma center. Citrated rapid thrombelastography and the following enzyme-linked immunosorbent assays were conducted: thrombin, antithrombin, thrombin-antithrombin complex, TAFI, plasminogen, antiplasmin, plasmin-antiplasmin (PAP), tissue plasminogen activator, plasminogen activator inhibitor 1, and tissue plasminogen activator-plasminogen activator inhibitor 1 complex. Univariate and cluster analysis were performed.

RESULTS

Overall, 56 patients (median age, 33.5 years; 70% male) were included. The majority (57%) presented after blunt mechanism and with severe injury (median New Injury Severity Score, 27). Two clusters of patients were identified: Group 1 (normal fibrinolysis, n = 21) and Group 2 (fibrinolysis shutdown, n = 35). Group 2 had significantly lower fibrinolysis with a median LY30 of 1.1% (interquartile range [IQR], 0.1-1.9%) versus 2.1% (IQR, 0.5-2.8%) in Group 1; while the median LY30 was within physiologic range, 45% of patients in Group 2 were in shutdown (vs. 24% in Group 1, p = 0.09). Compared with Group 1, Group 2 had significantly higher PAP (median, 4.7 [IQR, 1.7-9.3] vs. 1.4 [1.0-2.1] μg/mL in Group 1; p = 0.002) and higher TAFI (median, 152.5% [IQR, 110.3-190.7%] vs. 121.9% [IQR, 93.2-155.6%]; p = 0.04). There was a strong correlation between PAP and TAFI ( R2 = 0.5, p = 0.0002).

CONCLUSION

The presented data characterize fibrinolytic shutdown, indicating an initial plasmin burst followed by diminished fibrinolysis, which is distinct from hypofibrinolysis (inadequate plasmin burst and fibrinolysis). After an initial thrombin and plasmin burst (increased PAP), fibrinolysis is inhibited, mediated in part by increased TAFI.

Hemorrhagic shock and tissue injury provoke distinct components of trauma-induced coagulopathy in a swine model

INTRODUCTION

Tissue injury (TI) and hemorrhagic shock (HS) are the major contributors to trauma-induced coagulopathy (TIC). However, the individual contributions of these insults are difficult to discern clinically because they typically coexist. TI has been reported to release procoagulants, while HS has been associated with bleeding. We developed a large animal model to isolate TI and HS and characterize their individual mechanistic pathways. We hypothesized that while TI and HS are both drivers of TIC, they provoke different pathways; specifically, TI reduces time to clotting, whereas, HS decreases clot strength stimulates hyperfibrinolysis.

METHODS

After induction of general anesthesia, 50 kg male, Yorkshire swine underwent isolated TI (bilateral muscle cutdown of quadriceps, bilateral femur fractures) or isolated HS (controlled bleeding to a base excess target of - 5 mmol/l) and observed for 240 min. Thrombelastography (TEG), calcium levels, thrombin activatable fibrinolysis inhibitor (TAFI), protein C, plasminogen activator inhibitor 1 (PAI-1), and plasminogen activator inhibitor 1/tissue-type plasminogen activator complex (PAI-1-tPA) were analyzed at pre-selected timepoints. Linear mixed models for repeated measures were used to compare results throughout the model.

RESULTS

TI resulted in elevated histone release which peaked at 120 min (p = 0.02), and this was associated with reduced time to clot formation (R time) by 240 min (p = 0.006). HS decreased clot strength at time 30 min (p = 0.003), with a significant decline in calcium (p = 0.001). At study completion, HS animals had elevated PAI-1 (p = 0.01) and PAI-1-tPA (p = 0.04), showing a trend toward hyperfibrinolysis, while TI animals had suppressed fibrinolysis. Protein C, TAFI and skeletal myosin were not different among the groups.

CONCLUSION

Isolated injury in animal models can help elucidate the mechanistic pathways leading to TIC. Our results suggest that isolated TI leads to early histone release and a hypercoagulable state, with suppressed fibrinolysis. In contrast, HS promotes poor clot strength and hyperfibrinolysis resulting in hypocoagulability.

The Trauma Fellow's Perspective on Grit and Resilience and Its Role in Wellness

Purpose of Review

To describe the unique stressors of surgical training and fellowship and how grit and resilience influence trainee wellness.

Recent Findings

Surgical training is an intense, high-stress experience. For fellows-in-training, unique stressors are associated with this chapter of training, from financial pressors to the stress of job acquisition. Wellness is essential for surgical fellows, not just for the critical need for quality mental health of providers, but also for the patients who are also affected by provider burnout. There are various wellness programs that can be instituted nationally and institutionally to optimize fellow wellness, but one of the most high-yield foci for fellow wellness is focused mentorship, the key to assuring wellness and harnessing grit.

Summary

Surgical residency and fellowship are prodigiously demanding experiences, which mandate grit and resilience. It is imperative that widespread cultural and institutional changes take place to best support surgical trainees.

Beyond uterine atony: characterizing postpartum hemorrhage coagulopathy

BACKGROUND

Postpartum hemorrhage is a leading cause of morbidity and mortality worldwide, yet the associated early coagulopathy is not well defined.

OBJECTIVE

We hypothesized that women who develop postpartum hemorrhage have a distinct derangement of thrombin generation and coagulation factors compared with postpartum women without postpartum hemorrhage.

STUDY DESIGN

This prospective study of pregnant patients with postpartum hemorrhage was completed at a single urban hospital. Blood was drawn on postpartum hemorrhage diagnosis and 2 and 4 hours later. Assays of patients with postpartum hemorrhage included thrombelastography, whole blood thrombin generation, coagulation factor activity, tissue factor levels and activity, and tissue factor pathway inhibitor levels, which were compared with that of patients without postpartum hemorrhage.

RESULTS

A total of 81 patients were included in this study. Of those patients, 66 had postpartum hemorrhage, and 15 served as controls. Compared with patients without PPH, patients with postpartum hemorrhage had lower fibrinogen levels (469.0 mg/dL vs 411.0 mg/dL; P=.02), increased tissue plasminogen activator resistance (fibrinolysis 30 minutes after maximal clot strength: 8.7% vs 4.2%; P=.02), decreased peak thrombin concentration (150.2 nM vs 40.7 nM; P=.01), and decreased maximal rate of thrombin generation (60.1 nM/minute vs 2.8 nM/minute; P=.02). Furthermore, compared with patients without postpartum hemorrhage, patients with postpartum hemorrhage had decreased tissue factor levels (444.3 pg/mL vs 267.1 pg/mL; P=.02) and increased tissue factor pathway inhibitor levels (0.6 U/mL vs 0.8 U/mL; P=.04), with decreased tissue factor pathway inhibitor ratios (624 vs 299; P=.01).

CONCLUSION

PPH is not only an issue of uterine tone and mechanical bleeding but also a distinct coagulopathy that is characterized by decreased fibrinogen level, clot breakdown resistance, and markedly low thrombin generation. This pathology seemed to be driven by low tissue factor and high tissue factor pathway inhibitor levels.

Estradiol provokes hypercoagulability and affects fibrin biology: A mechanistic exploration of sex dimorphisms in coagulation

BACKGROUND

Sex dimorphisms in coagulation are well established, with female-specific hypercoagulability conferring a survival benefit in the setting of trauma-induced coagulopathy (TIC). The mechanism behind these phenomena remains to be elucidated. We hypothesize that estradiol provokes a hypercoagulable profile and alters clot proteomics and fibrin crosslinking.

METHODS

Whole blood was collected from healthy adult volunteers (n = 30). A battery of thrombelastography (TEG) assays (native, kaolin, platelet-mapping, functional fibrinogen), whole blood thrombin generation, proteomics, and clot structure architecture (via analysis of fibrin crosslinks and fluorescent fibrinogen-visualized clots) were performed after pre-treatment of the blood with physiologic concentrations of beta-estradiol. In addition, a prospective study of coagulation through the menstrual cycle was conducted by collecting blood from women on peak and nadir estrogen days in the standard 28-day menstrual cycle.

RESULTS

On TEG, in females, estradiol provoked a hypercoagulable phenotype, specifically a shorter time to clot formation and greater thrombin generation, greater rate of clot propagation and functional fibrinogen, higher clot strength, and diminished clot fibrinolysis. In both males and females, estradiol increased platelet hyperactivity. Similar changes were seen in time to clot formation and clot strength in vivo during peak estrus of the menstrual cycle. On proteomic analysis, in both males and females, estradiol was associated with increases in abundance of several procoagulant and antifibrinolytic proteins. Crosslinking mass spectrometry analysis showed addition of estradiol increased the abundance of several FXIII crosslinks within the FIBA alpha chain in both sexes. Fluorescent fibrinogen analysis revealed a trend toward increased fiber resolvability index after addition of estradiol.

CONCLUSION

Estradiol provokes a hypercoagulable phenotype, affecting time to clot formation, clot propagation, clot strength, clot fibrinolysis, and clot structure. In sum, these data highlight the role of estradiol is driving female-specific hypercoagulability and highlights its potential role as a therapeutic adjunct in resuscitation of TIC.

Patient characteristics and diagnostic tests associated with syncopal falls: A Southwestern surgical congress multicenter study

BACKGROUND

Patients suspected of syncope frequently undergo laboratory and imaging studies to determine the etiology of the syncope. Variability exists in these workups across institutions. The purpose of this study was to evaluate the utilization and diagnostic yield of these workups and the patient characteristics associated with syncopal falls.

METHODS

A multi-institutional retrospective review was performed on adult patients admitted after a fall between 1/2017-12/2018. Syncopal falls were compared to non-syncopal falls.

RESULTS

4478 patients were included. There were 795 (18%) patients with a syncopal fall. Electrocardiogram, troponin, echocardiogram, CT angiography (CTA), and carotid ultrasound were more frequently tested in syncope patients compared to non-syncope patients. Syncope patients had higher rates of positive telemetry/Holter monitoring, CTAs, and electroencephalograms.

CONCLUSION

Patients who sustain syncopal falls frequently undergo diagnostic testing without a higher yield to determine the etiology of syncope.

Apolipoprotein A-I, elevated in trauma patients, inhibits platelet activation and decreases clot strength

Apolipoprotein A-I (ApoA-I) is elevated in the plasma of a subgroup of trauma patients with systemic hyperfibrinolysis. We hypothesize that apoA-I inhibits platelet activation and clot formation. The effects of apoA-I on human platelet activation and clot formation were assessed by whole blood thrombelastography (TEG), platelet aggregometry, P-selectin surface expression, microfluidic adhesion, and Akt phosphorylation. Mouse models of carotid artery thrombosis and pulmonary embolism were used to assess the effects of apoA-I in vivo. The ApoA-1 receptor was investigated with transgenic mice knockouts (KO) for the scavenger receptor class B member 1 (SR-BI). Compared to controls, exogenous human apoA-I inhibited arachidonic acid and collagen-mediated human and mouse platelet aggregation, decreased P-selectin surface expression and Akt activation, resulting in diminished clot strength and increased clot lysis by TEG. ApoA-I also decreased platelet aggregate size formed on a collagen surface under flow. In vivo, apoA-I delayed vessel occlusion in an arterial thrombosis model and conferred a survival advantage in a pulmonary embolism model. SR-BI KO mice significantly reduced apoA-I inhibition of platelet aggregation versus wild-type platelets. Exogenous human apoA-I inhibits platelet activation, decreases clot strength and stability, and protects mice from arterial and venous thrombosis via the SR-BI receptor.

Inflate and pack! Pelvic packing combined with REBOA deployment prevents hemorrhage related deaths in unstable pelvic fractures

INTRODUCTION

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is advocated for hemorrhage control in pelvic fracture patients in shock. We evaluated REBOA in patients undergoing preperitoneal pelvic packing (PPP) for pelvic fracture-related hemorrhage.

METHODS

Retrospective, single-institution study of unstable pelvic fractures (hemodynamic instability despite 2 units of red blood cells (RBCs) and fracture identified on x-ray). Management included the placement of a Zone III REBOA in the emergency department (ED) for systolic blood pressure <80 mmHg. All PPP patients were included and analyzed for injury characteristics, transfusion requirements, outcomes and complications. Additionally, patients who received REBOA (REBOA+) were compared to those that did not (REBOA-).

RESULTS

During the study period (January 2015 - January 2019), 652 pelvic fracture patients were admitted; 78 consecutive patients underwent PPP. Median RBCs at PPP completion compared to 24 h post-packing were 11 versus 3 units (p<0.05). Median time to operation was 45 min. After PPP, 7 (9%) patients underwent angioembolization. Mortality was 14%. No mortalities were due to ongoing pelvic fracture hemorrhage or physiologic exhaustion; all were a withdrawal of life sustaining support, most commonly due to neurologic insults (TBI/fat emboli = 6, stroke/spinal cord injury = 3). REBOA+ patients (n = 31) had a significantly higher injury severity score (45 vs 38, p<0.01) and higher heart rate (130 vs 118 beats per minute, p = 0.04) than REBOA-. The systolic blood pressure, base deficit, and number of RBCs transfused in the ED, and time spent in the ED were similar between groups. REBOA+ had a higher median transfusion of RBCs at PPP completion (11 units vs 5 units, p<0.01) but similar RBC transfusion in the 24 h after PPP (2 vs 1 units, p = 0.27). Mortality, pelvic infection, and ICU length of stay was not different between these cohorts.

CONCLUSION

PPP with REBOA was utilized in more severely injured patients with greater physiologic derangements. Although REBOA patients required greater transfusion requirements, there were no deaths due to acute pelvic hemorrhage. This suggests the combination of REBOA with PPP provides life-saving hemorrhage control in otherwise devastating injuries.

Hormones, age, and sex affect platelet responsiveness in vitro

BACKGROUND

Female sex confers a survival advantage following severe injury in the setting of trauma-induced coagulopathy, with female platelets having heightened responsiveness likely due to estrogen. The effects of testosterone on platelet biology are unknown, and platelets express both estradiol and androgen receptors on the plasma membrane. We hypothesize testosterone decreases platelet responses in vitro, and there are baseline differences in platelet function and metabolism stratified by sex/age.

STUDY DESIGN AND METHODS

Apheresis platelets were collected from: older males (OM) ≥45 years, younger males (YM) <45 years, older females (OF) ≥54 years, and younger females (YF) <54 years, and testosterone and estradiol were measured. Platelets were incubated with testosterone (5.31 ng/ml), estradiol (105 pg/ml) or vehicle and stimulated with buffer, adenosine diphosphate (20 μM), platelet activating factor (2 μM), or thrombin (0.3 U/ml). Aggregation, CD62P surface expression, fibrinogen receptor surface expression, and platelet mitochondrial metabolism were measured.

RESULTS

Testosterone significantly inhibited aggregation in OF and OM (p < .05), inhibited CD41a expression in YF, YM, and OM (p < .05), and affected a few of the baseline amounts of CD62P surface expression but not platelet activation to platelet-activating factor and adenosine diphosphate, and variably changed platelet metabolism.

DISCUSSION

Platelets have sex- and age-specific aggregation, receptor expression, and metabolism. Testosterone decreases platelet function dependent on the stimulus, age, and sex. Similarly, platelet metabolism has varying responses to sex hormones with baseline metabolic differences dependent upon sex and age.

Full-length plasma skeletal muscle myosin isoform deficiency is associated with coagulopathy in acutely injured patients

BACKGROUND

Skeletal muscle myosin (SkM) molecules are procoagulant both in vitro and in vivo. The association of plasma SkM isoforms with blood coagulability and hemostatic capacity has not been defined.

OBJECTIVES

We hypothesized that coagulopathy in acutely injured patients is associated with procoagulant plasma SkM heavy chain levels.

METHODS

To test this hypothesis, citrated whole blood and plasma from 104 trauma patients were collected and studied to obtain data for rapid thrombelastography, international normalized ratios, and plasma SkM levels. Coagulability parameters were dichotomized by the threshold for the hypercoagulable trauma-induced coagulopathy.

RESULTS

Lower plasma full-length SkM heavy chain (full-SkM) levels were associated with higher international normalized ratio values (>1.3) (p = .03). The full-SkM levels were also associated with a lower rate of clot propagation (thrombelastography angle <65°) (p = .004), and plasma full-SkM levels were positively correlated with the thrombelastography angle (r2  = .32, p = .0007). The trauma patient group with the lower plasma full-SkM levels showed an association with lower clot strength (maximum amplitude <55 mm) (p = .002), and plasma full-SkM levels positively correlated with maximum amplitude (r2  = .27, p = .005). Hyperfibrinolysis was associated with significantly decreased full-SkM levels (p = .03). Trauma patients who required red blood cells and fresh frozen plasma transfusions had lower plasma full-SkM levels compared with those without transfusions (p = .04 and .02, respectively).

CONCLUSIONS

In acutely injured trauma patients, lower levels of plasma full-SkM levels are linked to hypocoagulability in trauma-induced coagulopathy, implying that SkM plays a role in the hemostatic capacity in trauma patients and may contribute to trauma-induced coagulopathy.

Lived Experiences of Surgical Residents During the COVID-19 Pandemic: A Qualitative Assessment

OBJECTIVE

As the COVID-19 pandemic dynamically changes our society, it is important to consider how the pandemic has affected the training and wellness of surgical residents. Using a qualitative study of national focus groups with general surgery residents, we aim to identify common themes surrounding their personal, clinical, and educational experiences that could be used to inform practice and policy for future pandemics and disasters.

DESIGN

Six 90-minute focus groups were conducted by a trained qualitative researcher who elicited responses on six predetermined topics. De-identified transcripts and audio recordings were later analyzed by two independent researchers who organized responses to each topic into themes.

SETTING

Focus groups were conducted virtually and anonymously.

PARTICIPANTS

General surgery residents were recruited from across the country. Demographic information of potential participants was coded, and subjects were randomly selected to ensure a diverse group of participants.

RESULTS

The impact of the COVID-19 pandemic on residents' clinical, educational, and personal experiences varied depending on the institutional response of the program and the burden of COVID-19 cases geographically. Many successes were identified: the use of telehealth and virtual didactics, an increased sense of camaraderie amongst residents, and flexibility in scheduling. Many challenges were also identified: uncertainty at work regarding personal protective equipment and scheduling, decreased case volume and educational opportunities, and emotional trauma and burnout associated with the pandemic.

CONCLUSIONS

These data gathered from our qualitative study highlight a clear, urgent need for thoughtful institutional planning and policies for the remainder of this and future pandemics. Residency programs must ensure a balanced training program for surgical residents as they attempt to master the skills of their craft while also serving as employed health care providers in a pandemic. Furthermore, a focus on wellness, in addition to clinical competency and education, is vital to resident resilience and success in a pandemic setting.

Current Surgical Trainee Perceptions and Experiences in Telehealth

Introduction: Broad expansion of telehealth technologies has been implemented during the coronavirus disease 2019 (COVID-19) pandemic to allow for physical distancing and limitation of viral transmission within health care facilities. Although telehealth has been studied for its impact on patients, payors, and practitioners, its educational impact is largely unstudied. To better understand the trainee experience and perception of telehealth during the COVID-19 pandemic, we conducted a survey of the membership of the American College of Surgeons Resident and Associate Society (RAS). Methods: An anonymous survey was sent to members of RAS. Descriptive analysis was used to report experiences and perceptions. Chi-square analysis was used to compare cohorts with and without exposure to telehealth. Results: Of the 465 RAS respondents, 292 (62.8%) reported knowledge of telehealth technologies at their institutions. The majority of these respondents experienced a decrease in in-person clinic volume (94.4%) and an associated increase in virtual clinic volume (95.7%) related to the COVID-19 pandemic. Trainee integration into telehealth workflows increased drastically from prepandemic levels (11% vs. 54.5%, p < 0.001). Likelihood of trainee exposure to telehealth was associated with university-based training programs or larger program size. Trainees demonstrated a desire for more integration and development of curricula. Conclusions: These data serve as the first description of surgical trainee experience with, and opinion of, telehealth. Trainees recognize the importance of their integration and training in telehealth. These results should be used to guide the development of workflows and curricula that integrate trainees into telemedicine clinics.

Strategies for successful implementation of resuscitative endovascular balloon occlusion of the aorta in an urban Level I trauma center

BACKGROUND

The rationale for resuscitative endovascular balloon occlusion of the aorta (REBOA) is to control life-threatening subdiaphragmatic bleeding and facilitate resuscitation; however, incorporating this into the resuscitative practices of a trauma service remains challenging. The objective of this study is to describe the process of successful implementation of REBOA use in an academic urban Level I trauma center. All REBOA procedures from April 2014 through December 2019 were evaluated; REBOA was implemented after surgical faculty attended a required and internally developed Advanced Endovascular Strategies for Trauma Surgeons course. Success was defined by sustained early adoption rates.

METHODS

An institutional protocol was published, and a REBOA supply cart was placed in the emergency department with posters attached to depict technical and procedural details. A focused professional practice evaluation was utilized for the first three REBOA procedures performed by each faculty member, leading to internal privileging.

RESULTS

Resuscitative endovascular balloon occlusion of the aorta was performed in 97 patients by nine trauma surgeons, which is 1% of the total trauma admissions during this time. Each surgeon performed a median of 12 REBOAs (interquartile range, 5-14). Blunt (77/97, 81%) or penetrating abdominopelvic injuries (15/97, 15%) comprised the main injury mechanisms; 4% were placed for other reasons (4/97), including ruptured abdominal aortic aneurysms (n = 3) and preoperatively for a surgical oncologic resection (n = 1). Overall survival was 65% (63/97) with a steady early adoption trend that resulted in participation in a Department of Defense multicenter trial.

CONCLUSION

Strategies for how departments adopt new procedures require clinical guidelines, a training program focused on competence, and a hospital education and privileging process for those acquiring new skills.

LEVEL OF EVIDENCE

Therapeutic, level V.

Surgeons Underestimate the Importance of Surgical Topics for Non-Surgeons: Results of a National Survey

OBJECTIVE

To determine if surgeons and non-surgeons agree on the importance of surgical topics covered in the surgical clerkship to the daily practice of non-surgeons.

DESIGN

An IRB-approved anonymous survey ranking the relative importance of 35 topics drawn from surgical clerkship curricula asking physicians to rank the relative importance of each topic, using a five-point Likert scale, to the daily practice of non-surgeons.

SETTING

Online anonymous survey.

PARTICIPANTS

Convenience sample of practicing physicians and trainees. The survey was offered to physicians in all specialties via social media and professional connections, responders identified their practice specialty.

RESULTS

295 physicians completed the survey. Two hundred thirty-one (85%) were from non-surgical specialties: emergency medicine (EM, n = 100); primary care (PC, n = 71 - included internal medicine, family medicine, and pediatrics); a variety of others (n = 60).  Surgeons and non-surgeons agreed on the relative importance of the acute abdomen, breast disease, inguinal hernias, inflammatory bowel disease, morbid obesity, sinusitis, thyroid and parathyroid disease, and wound care; surgeons believed colorectal cancer and diverticulitis to be more important. Surgeons rated all other topics as less important to non-surgeons than non-surgeons. EM rated most acute problems more important that PC; both groups ranked most topics higher importance to the practice of a non-surgeon than surgeons (p < 0.05).

CONCLUSIONS

Surgeons consistently underestimate the importance non-surgeons place on surgical topics in their practice.  These results reinforce the perceived importance of a wide exposure to surgery in the surgical clerkship to all medical students - but topics could be focused differently depending on acute or non-acute non-surgical care career plans.

"Death Diamond" Tracing on Thromboelastography as a Marker of Poor Survival After Trauma

BACKGROUND

Improvements in health care innovations have resulted in an enhanced ability to extend patient viability. As a consequence, resources are being increasingly utilized at an unsustainable level. As we implement novel treatments, identifying futility should be a focus. The "death diamond" (DD) is a unique thrombelastography (TEG) tracing that is indicative of failure of the coagulation system, with a mortality rate exceeding 90%. The purpose of this study was to determine if the DD was a consistent marker of poor survival in a multicenter study population. We hypothesize that the DD, while an infrequent occurrence, predicts poor survival and can be used to stratify patients in whom resuscitation efforts are futile.

METHODS

A retrospective multi-institutional study of trauma patients presenting with TEG DDs between 8/2008 and 12/2018 at four American College of Surgeons trauma centers was completed. Demographics, injury mechanisms, TEG results, management, and survival were examined.

RESULTS

A total of 50 trauma patients presented with DD tracings, with a 94% (n = 47) mortality rate. Twenty-six (52%) patients received a repeat TEG with 10 patients re-demonstrating the DD tracing. There was 100% mortality in patients with serial DD tracings. The median use of total blood products was 18 units (interquartile range 6, 34.25) per patient.

DISCUSSION

The DD is highly predictive of trauma-associated mortality. This multicenter study highlights that serial DDs may represent a possible biomarker of futility.

Whole Blood Thrombin Generation in Severely Injured Patients Requiring Massive Transfusion

BACKGROUND

Despite the prevalence of hypocoagulability after injury, the majority of trauma patients paradoxically present with elevated thrombin generation (TG). Although several studies have examined plasma TG post injury, this has not been assessed in whole blood. We hypothesize that whole blood TG is lower in hypocoagulopathy, and TG effectively predicts massive transfusion (MT).

STUDY DESIGN

Blood was collected from trauma activation patients at an urban Level I trauma center. Whole blood TG was performed with a prototype point-of-care device. Whole blood TG values in healthy volunteers were compared with trauma patients, and TG values were examined in trauma patients with shock and MT requirement.

RESULTS

Overall, 118 patients were included. Compared with healthy volunteers, trauma patients overall presented with more robust TG; however, those arriving in shock (n = 23) had a depressed TG, with significantly lower peak thrombin (88.3 vs 133.0 nM; p = 0.01) and slower maximum rate of TG (27.4 vs 48.3 nM/min; p = 0.04). Patients who required MT (n = 26) had significantly decreased TG, with a longer lag time (median 4.8 vs 3.9 minutes, p = 0.04), decreased peak thrombin (median 71.4 vs 124.2 nM; p = 0.0003), and lower maximum rate of TG (median 15.8 vs 39.4 nM/min; p = 0.01). Area under the receiver operating characteristics (AUROC) analysis revealed lag time (AUROC 0.6), peak thrombin (AUROC 0.7), and maximum rate of TG (AUROC 0.7) predict early MT.

CONCLUSIONS

These data challenge the prevailing bias that all trauma patients present with elevated TG and highlight that deficient thrombin contributes to the hypocoagulopathic phenotype of trauma-induced coagulopathy. In addition, whole blood TG predicts MT, suggesting point-of-care whole blood TG can be a useful tool for diagnostic and therapeutic strategies in trauma.

COVID-19 Pandemic and the Lived Experience of Surgical Residents, Fellows, and Early-Career Surgeons in the American College of Surgeons

BACKGROUND

To better understand how the COVID-19 pandemic has affected surgical trainees' and early-career surgeons' professional and personal experiences, a survey of the membership of the American College of Surgeons (ACS) Resident and Associate Society (RAS) and Young Fellows Association (YFA) was performed.

STUDY DESIGN

An anonymous online survey was disseminated to members of RAS and YFA. Descriptive analyses were performed and factors associated with depression and burnout were examined with univariate and multivariable stepwise logistic regression.

RESULTS

Of the RAS/YFA membership of 21,385, there were 1,160 respondents. The majority of respondents (96%) reported the COVID-19 pandemic having a negative impact on their clinical experience, with 84% of residents reporting a > 50% reduction in operative volume and inability to meet minimum case requirements. Respondents also reported negative impacts on personal wellness. Nearly one-third reported inadequate access to personal protective equipment, and depression and burnout were pervasive (≥21% of respondents reported yes to every screening symptom). On multivariable analysis, female sex (odds ratio [OR] 1.54 for depression, OR 1.47 for burnout) and lack of wellness resources (OR 1.55 for depression, OR 1.44 for burnout) predicted depression and burnout. Access to adequate personal protective equipment was protective against burnout (OR 0.52).

CONCLUSIONS

These data demonstrate a significant impact of the COVID-19 pandemic on the lives of residents and early-career surgeons. Actionable items from these data include mitigation of burnout and depression through increasing personal protective equipment access and provision of wellness programs, with a particular focus on high-risk groups.

A Stitch in Time Saves Clots: Venous Thromboembolism Chemoprophylaxis in Traumatic Brain Injury

BACKGROUND

Venous thromboembolism chemoprophylaxis (VTE-CHEMO) is often delayed in patients with traumatic brain injury because of the concern for intracranial hemorrhage (ICH) progression. We hypothesize that (1) late time to VTE-CHEMO (≥48 h) is associated with higher incidence of VTE, and (2) VTE-CHEMO use does not correlate with ICH progression.

MATERIALS AND METHODS

This is a multiinstitutional retrospective study of patients with traumatic brain injury admitted between 2014 and 2016. Inclusion criteria were head Abbreviated Injury Code ≥2, ICH present on initial head computed tomography, and two or more head computed tomography scans after admission. The primary outcome was VTE, and the secondary outcome was ICH progression. Patients were classified as receiving VTE-CHEMO early (<48 h) or late (≥48 h). Multivariable analysis with Cox proportional hazards regression was performed.

RESULTS

Overall, 1803 patients were included. Patients with VTE (n = 137) were more likely to have spinal cord injury, blunt cerebrovascular injury, pelvic or femur fractures, and missed VTE-CHEMO doses. After multivariable regression, body mass index >30 (hazard ratio [HR], 1.05; P = 0.002), Injury Severity Score (HR, 1.004; P < 0.001), pelvic or femur fractures (HR, 1.05; P < 0.0001), spinal cord injury (HR, 1.28; P = 0.02), and missed VTE-CHEMO doses (HR, 1.08; P = 0.01) were significant predictors of VTE. In those who required neurosurgery, late VTE-CHEMO predicted VTE (HR, 1.21; P = 0.0001). Overall, 32% patients experienced ICH progression, which did not correlate with VTE-CHEMO use or timing.

CONCLUSIONS

This multicenter study highlights benefits from early VTE-CHEMO and identifies high-risk groups who may benefit from more aggressive prophylaxis. These data also emphasize risk to patients by withholding VTE-CHEMO.

28-day thawed plasma maintains α2 -antiplasmin levels and inhibits tPA-induced fibrinolysis

INTRODUCTION

Evidence supports the use of plasma-first resuscitation in the treatment of trauma-induced coagulopathy (TIC). While thawed plasma (TP) has logistical benefits, the ability of plasma proteins to attenuate fibrinolysis and correct TIC remain unknown. We hypothesize that TP retains the ability to inhibit tissue plasminogen activator(tPA)-induced fibrinolysis at 28-day storage.

METHODS

Healthy volunteers underwent blood draws followed by 50% dilution of whole blood (WB) with TP at 28-, 21-, 14-, 7-, 5-, and, 0-day storage, normal saline (NS), and WB control. Samples underwent citrated tPA-challenge (75 ng/ml) thromboelastography (TEG). Plasminogen activator inhibitor-1 (PAI-1) and α₂ -antiplasmin (α₂ -AP) concentrations in thawed or stored plasma were determined.

RESULTS

In the presence of tPA, 28-day TP inhibited tPA-induced coagulopathy as effectively as WB. 28-day TP had a similar R-time, MA, and fibrinolysis (P > 0·05 for all) compared to WB, while angle was enhanced (P = 0·02) compared to WB. Significant correlations were present between storage time and clot strength (P = 0·04) and storage time and fibrinolysis (P = 0·0029). Active PAI-1 levels in thawed plasma were 1·10 ± 0·54 ng/mL while total PAI-1 levels were 4·79 ± 1·41 ng/mL. There was no difference of α₂ -AP levels in FFP (40·45 ± 3·5 μg/mL) compared to plasma thawed for 14 (36·78 ± 5·39 μg/mL, P = 0·65) or 28 days (45·16 ± 5·61 μg/mL, P = 0·51).

DISCUSSION

Thawed plasma retained the ability to inhibit tPA-induced fibrinolysis over 28-day storage at 1-4°C. α₂ -AP levels were maintained in plasma thawed for 28 days and FFP. These in vitro results suggest consideration should be made to increasing the storage life of TP.

"Bedside Anatomy": A Tool to Contextualize Learning and Introduce Surgical Careers

BACKGROUND

Many medical students cite an unwelcoming culture in surgery and perceive surgeons as arrogant or unfriendly. These perceptions have been reported as factors discouraging medical students from applying to surgical residency programs. This highlights an opportunity early in medical education to address these negative stereotypes and create opportunities for positive interactions with surgeons. We hypothesize that positive experiences with surgical residents and introduction to representative surgical cases early in the medical school curriculum can provide a real-world context for learning anatomy and encourage students to consider a surgical career.

METHODS

We developed and implemented a series of structured, one-hour, cadaver-based sessions cofacilitated by anatomists and surgical residents for medical students during their anatomy didactics. Sessions included common surgical cases and focused on critical thinking and problem-solving skills, while offering opportunities to review cadaver anatomy. Students completed a postcourse survey.

RESULTS

Nine sessions were implemented with involvement of eight surgical residents and 185 students; 83 students completed a postcourse survey (response rate of 45%). A majority of students rated the sessions "very helpful" in terms of highlighting the importance of anatomy in medical education (n = 52, 63%) and providing clinical context (n = 59, 71%). 54% (n = 45) indicated interest in a surgical career and 64% (n = 53) agreed that session participation had increased their interest in surgery.

CONCLUSIONS

Overall, students agreed that sessions provided clinical context for their learning and increased interest in a surgical career. Surgical faculty and residents should engage in preclinical medical education to bridge the basic science and clinical years and introduce positive surgical role models early during medical training.

Association between Young-Burgess pelvic ring injury classification and concomitant injuries requiring urgent intervention

BACKGROUND

Young-Burgess classification (YB) is a mechanistic system which classifies pelvic ring injuries into anterior-posterior compression (APC), lateral compression (LC), vertical shear (VS) injuries, and combined mechanism (CM). The objective of this study was to identify associated injuries which require urgent operative intervention by YB classification. We hypothesize that YB classification is associated with 1) need for urgent intervention for pelvic fracture-related hemorrhage and 2) patterns of injury complexes requiring surgery.

METHODS

This is a retrospective study of severely injured trauma patients with pelvic ring injuries who presented to an urban Level-1 trauma center from 2007 to 2017. Associated injuries and procedures were determined by Abbreviated Injury Scale (AIS) and ICD-9/10 codes. YB classes were compared, followed by a cluster analysis to identify injury patterns and association with YB classifications.

RESULTS

Overall, 135 patients were included. 98 (72%) of patients presented with LC, 16 (12%) with APC, 8 (6%) with VS, and 13 (10%) with CM. VS and APC groups had higher rates of REBOA use compared to LC and CM groups (38% and 31% versus 11% and 0%, respectively, p = 0.01). The CM group, compared to LC, APC, and VS, had higher rates of urgent operative intervention for bleeding control (69% versus 32%, 50% and 43%, respectively, p = 0.01). 39 (29%) patients had a concomitant injury which was identified by CT scan in initial trauma work up and altered management, 46% which merited urgent intervention. On cluster analysis, there were no distinct injury complexes which required urgent operative intervention by YB class.

CONCLUSIONS

These data failed to identify unique injury complexes which merit urgent operative intervention by YB class. Nearly one in four patients had injuries identified by initial CT imaging which altered initial management, demonstrating the importance of early, full body CT imaging in severely injured patients with pelvic ring injuries.

Cardiac and Skeletal Muscle Myosin Exert Procoagulant Effects

INTRODUCTION

Trauma-induced coagulopathy (TIC) and the tissue injury-provoked procoagulant profile are prevalent in severely injured patients, but their mechanisms remain unclear. Myosin, exposed by or released from tissue injury, may play a role in promoting thrombin generation and attenuating fibrinolysis. The objective of the study is to examine the effects of cardiac and skeletal muscle myosins on coagulation in whole blood using thrombelastography (TEG).

MATERIALS AND METHODS

Whole blood was collected from healthy adult volunteers (n=8) and native TEGs were performed to evaluate the global coagulation response in the presence of cardiac or skeletal muscle myosin by measuring reaction (R) time (minutes), clot angle (), and maximum amplitude (MA, mm). TEG measurements were compared using paired t tests.

RESULTS

Cardiac and skeletal muscle myosins decreased R, from 10.8 min to 8.0 min (P<0.0001) and 6.9 min (P =0.0007), respectively. There were no effects observed on clot propagation (angle) or clot strength (MA) with myosin addition. In the presence of tPA, both cardiac and skeletal muscle myosins shortened R from 11.1 min to 8.62 min (P=0.0245) and 7.75 min (P =0.0027), respectively), with no changes on angle or MA.

CONCLUSIONS

Cardiac and skeletal muscle myosins exhibit procoagulant effects in TEG assays. These whole blood TEG results support the hypothesis that cardiac and skeletal muscle myosins may be either pro-hemostatic or prothrombotic depending on context.

Whole blood thrombin generation is distinct from plasma thrombin generation in healthy volunteers and after severe injury

BACKGROUND

Plasma thrombin generation has been used to characterize trauma-induced coagulopathy, but description of whole blood thrombin generation is lacking. This study aimed to evaluate plasma and whole blood thrombin generation in healthy volunteers and trauma patients. We hypothesized that (1) plasma and whole blood thrombin generation are distinct, (2) whole blood thrombin generation is more pronounced in trauma patients than in healthy volunteers, and (3) thrombin generation correlates with clinical coagulation assays.

METHODS

Blood was collected from healthy volunteers and trauma patients at a single, level-1 trauma center. Whole blood thrombin generation was assessed with a prototype point-of-care whole blood thrombin generation device, and plasma thrombin generation was measured with a calibrated automated thrombogram analogue. Plasma and whole blood thrombin generation were compared and correlated with international normalized ratio and thrombelastography.

RESULTS

Overall, 10 healthy volunteers (average age 30, 50% men) were included and 58 trauma patients (average age 34, 76% men, 55% blunt mechanism, and with a median new injury severity score of 17) were included. Plasma and whole blood thrombin generation differed with more robust thrombin generation in plasma. Trauma patients had a significantly increased whole blood thrombin generation compared with healthy volunteers]. Plasma thrombin generation correlated with international normalized ratio, whereas whole blood thrombin generation did not correlate with thrombelastography.

CONCLUSION

Plasma and whole blood thrombin generation are distinct, highlighting the need to perform standardized assays to better understand their correlation and to assess how whole blood thrombin generation confers differential outcomes in trauma.

A Cadaver-Based Course for Humanitarian Surgery Improves Manual Skill in Powerless External Fixation

BACKGROUND

General surgery residents interested in humanitarian careers may benefit from supplemental training beyond modern residency. The Colorado Humanitarian Surgical Skills Workshop is a 2-d cadaver-based course for senior surgical residents, teaching low-resource skills across multiple specialties, including orthopedics. We assessed the course's ability to transmit manual competence in a critical humanitarian surgical skill, powerless lower extremity external fixation.

MATERIALS AND METHODS

We created a novel standardized manual skills test of powerless lower extremity external fixation. Course participants had no prior experience with this technique. At course initiation, paired participants attempted to stabilize a proximal tibia-fibula fracture in a cadaver. Subsequently, participants received didactics from orthopedic surgeons followed by hands-on practice. At course completion, paired participants repeated the exercise. Fixator constructs were scored using standardized criteria. Precourse and postcourse surveys measured participants' level of confidence in performing external fixation.

RESULTS

Twelve senior surgical residents were included. Average scores of external fixator constructs improved significantly (23% pre versus 75% post, P < 0.01). On pretesting, none of the participants completed the exercise within 15 min. Only one of six constructs was marginally stable, and none were aligned. On post-testing, five of six teams completed the exercise in an average of 12.4 min. Four of six constructs were stable and two of six were also well aligned. Confidence with external fixation also improved significantly.

CONCLUSIONS

Participants in a short cadaver-based workshop demonstrated significant improvements in manual skill and confidence related to powerless external fixation. However, additional training is likely required to achieve clinical competence.

Trauma Resuscitation Consideration: Sex Matters

BACKGROUND

Sex dimorphisms in coagulation have been recognized, but whole blood assessment of these dimorphisms and their relationship to outcomes in trauma have not been investigated. This study characterizes the viscoelastic hemostatic profile of severely injured patients by sex, and examines how sex-specific coagulation differences affect clinical outcomes, specifically, massive transfusion (MT) and death. We hypothesized that severely injured females are more hypercoagulable and therefore, have lower rates of MT and mortality.

STUDY DESIGN

Hemostatic profiles and clinical outcomes from all trauma activation patients from 2 level I trauma centers were examined, with sex as an experimental variable. As part of a prospective study, whole blood was collected and thrombelastography (TEG) was performed. Coagulation profiles were compared between sexes, and association with MT and mortality were examined. Poisson regression with robust standard errors was performed.

RESULTS

Overall, 464 patients (23% female) were included. By TEG, females had a more hypercoagulable profile, with a higher angle (clot propagation) and maximum amplitude (MA, clot strength). Females were less likely to present with hyperfibrinolysis or prolonged activating clotting time than males. In the setting of depressed clot strength (abnormal MA), female sex conferred a survival benefit, and hyperfibrinolysis was associated with higher case-fatality rate in males.

CONCLUSIONS

Severely injured females have a more hypercoagulable profile than males. This hypercoagulable status conferred a protective effect against mortality in the setting of diminished clot strength. The mechanism behind these dimorphisms needs to be elucidated and may have treatment implications for sex-specific trauma resuscitation.

Locating, quantifying and characterising radiation hazards in contaminated nuclear facilities using a novel passive non-electrical polymer based radiation imaging device

This paper provides a summary of recent trials which took place at the US Department of Energy Oak Ridge National Laboratory (ORNL) during December 2010. The overall objective for the trials was to demonstrate that a newly developed technology could be used to locate, quantify and characterise the radiological hazards within two separate ORNL hot cells (B and C). The technology used, known as RadBall(®), is a novel, passive, non-electrical polymer based radiation detection device which provides a 3D visualisation of radiation from areas where effective measurements have not been previously possible due to lack of access. This is particularly useful in the nuclear industry prior to the decommissioning of facilities where the quantity, location and type of contamination are often unknown. For hot cell B, the primary objective of demonstrating that the technology could be used to locate, quantify and characterise three radiological sources was met with 100% success. Despite more challenging conditions in hot cell C, two sources were detected and accurately located. To summarise, the technology performed extremely well with regards to detecting and locating radiation sources and, despite the challenging conditions, moderately well when assessing the relative energy and intensity of those sources. Due to the technology's unique deployability, non-electrical nature and its directional awareness the technology shows significant promise for the future characterisation of radiation hazards prior to and during the decommissioning of contaminated nuclear facilities.

Biosynthesis of carbonic anhydrase in Chlamydomonas reinhardtii during adaptation to low CO(2)

The unicellular green alga Chlamydomonas reinhardtii synthesizes carbonic anhydrase in response to low levels of CO(2) (i.e., air levels of CO(2)). This enzyme, localized predominantly in the periplasmic space of the alga (or associated with the cell wall), is an important component of the machinery required for the active accumulation of inorganic carbon by C. reinhardtii and the saturation of ribulose-1,5-bisphosphate carboxylase at low extracellular carbon concentrations. We have begun to examine the synthesis and compartmentalization of carbonic anhydrase in C. reinhardtii. The monomeric species associated with carbonic anhydrase activity is synthesized as a precursor on 80S cytoplasmic ribosomes. This precursor can be detected immunologically in the profiles of translation products when a reticulocyte lysate, cell-free system is primed with poly(A)-RNA from either air-grown C. reinhardtii or cells shifted from growth on 5% CO(2) to air for 12 hr. It is not synthesized when the in vitro system is primed with poly(A)-RNA from CO(2)-grown algae. Since translatable RNA for the polypeptide responsible for carbonic anhydrase activity was only present in cells that experienced low levels of CO(2), the adaptation process either involves the regulation of transcription of the carbonic anhydrase gene (and perhaps other genes involved in adaptation) or the post-transcriptional processing of the messenger RNA. Furthermore, the appearance of the mature polypeptide associated with carbonic anhydrase activity in the periplasmic space of C. reinhardtii is inhibited by tunicamycin, an antibiotic that prevents core glycosylation of polypeptides on the endoplasmic reticulum. Together, these results suggest that the biosynthesis of this extracellular algal enzyme involves the translation of mRNA for the carbonic anhydrase monomer on ribosomes bound to the endoplasmic reticulum, the cleavage of a signal sequence during transport of the nascent polypeptide into the lumen of the endoplasmic reticulum, and subsequent glycosylation events prior to export across the plasmalemma.

Permeability measurement of macromolecules and assessment of mucosal antigen sampling using in vitro converted M cells

INTRODUCTION

M cells are located in the epithelial layer covering the gut-associated lymphoid tissue and are responsible for delivery of macromolecules and microorganisms to the underlying lymphoid cells. It has been shown that the human colonic cell line Caco-2 can be converted to M cells in vitro following coculture with isolated lymphocytes from murine Peyer's patches. Studies were undertaken to evaluate and characterize the transepithelial transport of select macromolecules across these in vitro derived M cells.

METHODS

Caco-2 cells were converted to M cells as reported previously. The morphology of Caco-2 cells and M cells was compared by transmission electron microscopy (TEM). The transport properties of macromolecules such as horseradish peroxidase, FITC-conjugated polystyrene beads, and radiolabeled dextrans were examined. The activation of murine antigen-specific T cells following transport of the antigen ovalbumin across the M-cell barrier was assessed by measuring cytokine production.

RESULTS

M cells were shown to be irregular in shape and have fewer and shorter microvilli compared to the Caco-2 cell progenitors. These cells were still able to form tight junctions and monolayers on polycarbonate membranes. Time-course studies demonstrated that the transport of polystyrene beads and large-molecular-weight dextrans at physiological temperature across M-cell-containing monolayers was size dependent and more rapid than across Caco-2 cell monolayers. The transport of dextrans was also shown to be temperature and concentration dependent. Befitting the role of the M cell in mucosal defense, protein antigen could be delivered by these cells in order to be processed and presented to antigen-specific CD4+ T lymphocytes.

DISCUSSION

The M-cell permeability model is a functional and practical system for evaluating the transport properties of macromolecules and assessing the potential for intestinal mucosal antigen sampling to elicit immunological responses.

Using continuous quality improvement techniques to determine the causes of hospital readmission

This 6-month retrospective study provided our medical center with a profile of the population of patients readmitted within 31 days of discharge. We found that chronic illness and age greater than 65 years were the high risk factors related to patient readmissions. These 2 attributes are common in critical care patients. In addition, the study indicated that data input and collection procedures must be correctly followed in order to have accurate information on admission and readmission. Accurate information is important to management and external agencies. Accuracy is also important so that future problems with continuous quality improvement can be recognized and resources properly assigned. Recommendations for improving the data collection and reporting procedures and for improving the readmission rates were made to management, to the quality improvement coordinator, and to the quality improvement/risk management director.

Anti-epileptiform effects of audiogenic seizure priming on in vitro kindling in rat hippocampus

The effect of priming for audiogenic seizures (AGS) on the development of epileptiform activity in the hippocampus was studied using in vitro kindling (IVK) in Long-Evans rats. AGS priming consists of intense auditory stimulation during a critical period of auditory development, resulting in sound-induced clonic convulsions upon subsequent testing. Between postnatal day (PND) 28 and 50, slices from subjects primed and sham-primed for AGS on PND 18 were used for recording responses in area CA1 of hippocampus following Schaffer collateral stimulation from stratum radiatum of area CA2/CA3. The developmental priming procedure, which enhances auditory brainstem excitability, resulted in fewer afterdischarges in slices from primed subjects across initial IVK stimulation sequences. These results suggest that changes in excitability that occur with acoustic priming can initially diminish selective epileptiform response characteristics in forebrain areas such as the hippocampus.

The embryology, classification, epidemiology, and genetics of facial clefting

Facial clefting results from a variety of genetic and environmental causes. It occurs when developing facial processes fail to fuse, merge, or interact; the clefts range from mild to severe. The embryology and classification of these clefts have been characterized. Moreover, the epidemiology has been determined from population data. Unfortunately, complete understanding of the genetics of facial clefting has not been completely uncovered. Facial clefts exist within more than 300 syndromes with only a few being commented on in this article. As the human genome project continues, the understanding of facial clefting and its syndromes may continue to improve. Such knowledge could advance diagnosis and treatment of the patient and counseling of the affected family. Other articles within this issue address the management of these clefts.

Effects of low atmospheric CO(2) on plants: more than a thing of the past

In recent geological time, atmospheric CO(2) concentrations were 25-50% below the current level. Photosynthetic productivity of C(3) plants is substantially reduced at these low CO(2) levels, particularly at higher temperatures and during stress. Acclimation of photosynthesis to reduced CO(2) levels might compensate for some of this inhibition, but plants have a limited capacity to modulate Rubisco and other photosynthetic proteins following CO(2) reduction. Because of this, low CO(2) probably acted as a significant evolutionary agent, selecting plants adapted to CO(2) deficiency. Adaptations to low CO(2) might still exist in plants and might constrain responses to a rising CO(2) concentration.