Cloacal Dysgenesis Sequence in a Preterm Neonate

BACKGROUND Cloaca malformations result from a disproportion of apoptosis, cell growth, and maturation. The range of cloacal malformations is extensive and diverse, with a lack of a straightforward classification system. Cloacal dysgenesis sequence (CDS), also known as urorectal septum malformation sequence, is a rare cloaca variant described as the absence of a perineal orifice. Prenatal magnetic resonance imaging and antenatal ultrasounds may reveal a cloacal malformation; however, many patients are not diagnosed with cloacal malformation until birth. CASE REPORT We present a case of a female neonate delivered by a 23-year-old G2P1T1A0L0 mother who had received comprehensive prenatal care. During pregnancy, bilateral multicystic dysplastic kidneys were identified prenatally, leading to the in utero placement of a vesicoamniotic shunt. The physical exam revealed a distended abdomen with reduced abdominal musculature and laxity, ascites, a vesicoamniotic shunt in place, absent urethra, ambiguous genitalia with no vaginal opening, no perineal opening, and clubfoot. Abdominal radiograph showed findings consistent with significant abdominal ascites. An exploratory laparotomy was performed that included diverting colostomy, mucous fistula creation, tube vaginostomy, removal of the vesicoamniotic shunt, and suprapubic tube placement. The patient recovered well from this operation with no complications. CONCLUSIONS CDS is an uncommon condition in pediatric patients, and although sonographic findings can reveal urinary tract abnormalities, prenatal imaging might not always identify CDS. Our case underscores the uniqueness of the case and the significance of early detection and immediate medical and surgical intervention.

Establishment of a successful robotic pediatric general surgery practice

Robotic-assisted surgery (RAS) has a variety of theoretical advantages, including tremor filtration, optimal visualization, and improvement of surgeon ergonomics. Though it has achieved wide application in pediatric urology, the majority of pediatric general surgeons do not employ RAS. This study reports our institution's experience with RAS on a pediatric general surgery team. Following IRB approval, a retrospective review of all pediatric patients at our academic children's hospital who underwent RAS between 2017 and 2022 for pediatric general surgical conditions was performed. Patient demographics, operation performed, operating time, complications, and recovery were evaluated. A total of 159 children underwent RAS, increasing from 10 patients in 2017 to 59 patients in 2022. The median age and weight were 15.3 years and 76.4 kg, and 121 (76.1%) were female. The application of RAS was successful in all cases. There were no intraoperative complications and no conversions to an open approach. Eleven patients (6.9%) had unplanned presentations to the emergency department within 30 days. Five of these patients (3.1%) required admission to the hospital. This study demonstrates that the application of RAS in an academic pediatric general surgery practice is feasible and safe. The application of RAS to pediatric general surgery should continue to increase as operative teams increase their experience and comfort.Level of evidence Level IV.

What animal model should I use to study necrotizing enterocolitis?

Unfortunately, we are all too familiar with the statement: "Necrotizing enterocolitis remains the leading cause of gastrointestinal surgical emergency in preterm neonates". It's been five decades since the first animal models of necrotizing enterocolitis (NEC) were described. There remains much investigative work to be done on identifying various aspects of NEC, ranging from the underlying mechanisms to treatment modalities. Experimental NEC is mainly focused on a rat, mouse, and piglet models. Our aim is to not only highlight the pros and cons of these three main models, but to also present some of the less-used animal models that have contributed to the body of knowledge about NEC. Choosing an appropriate model is essential to conducting effective research and answering the questions asked. As such, this paper reviews some of the variations that come with each model.

Milky pericardial effusion causing tamponade in a neonate after extracorporeal membrane oxygenation cannulation

Cardiac tamponade is a known life-threatening complication of extracorporeal membrane oxygenation (ECMO), often secondary to hemopericardium from major vascular or cardiac perforation. We present the unique case of a neonate with a milky pericardial effusion causing tamponade after ECMO cannulation, managed successfully with pericardial window. Understanding ECMO physiology and its effect on the classic presentation of tamponade is critical and can prevent delays in diagnosis. While hemopericardium is most commonly seen in these cases, findings of a non-bloody, milky effusion should prompt further workup for infection, chylopericardium or total parenteral nutrition-associated pericardial effusion, as the appropriate management can mitigate immediate and potential long-term sequelae.

Multiple Perianal Epidermal Cysts Found in a Case of Lowe Syndrome: A Case Report and Review of the Literature

BACKGROUND Lowe syndrome, also known as oculocerebrorenal syndrome, is a rare genetic condition caused by an X-linked mutation of the OCRL1 gene, with an estimated prevalence in the general population of approximately 1 in 500 000. It is a multisystem disorder most commonly affecting the eyes, central nervous system, and kidneys. These commonly manifest as congenital cataracts, intellectual disability, and proximal renal dysfunction (Fanconi-type). Epidermal lesions are an uncommon manifestation of this condition, and the association is not completely understood. CASE REPORT Here we present a case of a 9-year-old boy with Lowe syndrome who presented with multiple cystic masses found in the perianal region. An excision was then performed to remove the masses and found that the lesions were epidermal cysts, which are infrequently found in Lowe syndrome. After excision, the patient recovered uneventfully without complications. CONCLUSIONS While epidermal cysts are an uncommon manifestation that have been documented, our case remains unique given the location and associated symptoms of the lesions. At presentation, the constellation of pain and perianal masses was concerning for a malignant etiology. However, after diagnostic imaging was performed, these lesions were found to be epidermal cysts, an infrequent manifestation of Lowe syndrome. Few previous case reports described cystic lesions in association with Lowe syndrome, and none, to our knowledge, have described multiple symptomatic perianal lesions. This case is important to consider because epidermal cystic lesions can be found with this presentation and should be considered on differential diagnoses for dermatologic findings in Lowe syndrome patients.

Short-term outcomes of thoracoscopic versus open lobectomy for congenital lung malformations

PURPOSE

Thoracoscopic and open approaches for the management of congenital lung malformations (CLM) has been debated. The aim of this study is to compare 30-day outcomes for non-emergent lobectomies in children.

METHODS

The National Surgical Quality Improvement Program-Pediatric database was queried for patients undergoing CLM resection from 2013 to 2020. Outcomes were compared by operative technique in an intention-to-treat model and then propensity matched.

RESULTS

2157 patients met inclusion criteria and underwent non-emergent pulmonary lobectomy for CLM. The intended operative approach was thoracoscopic in 57.7% of patients. Patients in the open group compared to the thoracoscopic were more likely to be born premature, have chronic lung disease, require preoperative oxygen support, and be ventilator dependent. After propensity matching, there was no statistically significant difference in 30-day mortality, unplanned readmission, and other complications between the thoracoscopic and open groups. Thoracoscopic approach was associated with a shorter length of stay. The proportion of cases approached via thoracoscopy increased over time from 48.8% in 2013 to 69.9% in 2020.

CONCLUSIONS

This large multicenter retrospective matched analysis demonstrates thoracoscopic lobectomy in children has similar favorable 30-day outcomes and shorter length of stay for the non-emergent management of CLM, compared to open thoracotomy.

LEVEL OF EVIDENCE

Level III.

A 12-Year-Old Girl with Juvenile Granulosa Cell Tumor of the Ovary, Presenting with Adolescent Hyperprolactinemia, Galactorrhea, and Amenorrhea

BACKGROUND Juvenile-type granulosa cell tumors (JGCTs) are a rare subtype of sex cord stromal tumor with a characteristic histology that is commonly found in the first 3 decades of life. It most commonly presents with symptoms of hyperestrogenism, which may present as precocious pseudopuberty or as menstruation-related symptoms, allowing for early detection of the tumor. CASE REPORT We present the case of a 12-year-old girl who presented to her primary care provider (PCP) with secondary amenorrhea with intermittent abdominal pain, who underwent an ultrasound for further evaluation, which revealed a large incidental pelvic mass. She was admitted to the Emergency Department (ED) and had findings of galactorrhea and hyperprolactinemia on examination. Imaging studies demonstrated a large ovarian mass measuring 15.0×9.0×18.8 cm that was resected, and subsequent pathology results showed JGCT stage 1A. CONCLUSIONS Prognosis of granulosa cell tumors (GCT) largely depends on its initial size, stage at diagnosis, residual tumors after surgery, and the subtype of GCT. If the patient is of reproductive age, fertility-sparing surgical options must be considered and patients must be regularly monitored for recurrence. JGCTs can present with minimal to no symptoms of precocious puberty in young girls but may present with amenorrhea, which may be considered normal for their developmental age. Although JGCTs are rare, they are important to include in differential diagnoses of younger female patients with abdominal pain, especially if accompanied by hormonal irregularities.

Analysis of Outcomes in Adolescents and Young Adults With Pilonidal Disease

Purpose: Numerous definitive surgical techniques exist for the treatment of pilonidal disease with varied recurrence rates and wound complications. Due to the wide array of techniques and lack of consensus on the best approach, we proposed to study our experience treating pilonidal disease in adolescents and young adults.

Methods: A retrospective analysis was conducted of patients 10–24 years old treated at a tertiary medical center from 2011 to 2016. Data including demographics, management, and outcomes were collected and analyzed. Primary outcome was recurrence of disease.

Results: One hundred and thirty three patients with pilonidal disease underwent operative management. Fifty one percent underwent primary closure and 49% healed by secondary intention with no significant difference in recurrence rates (primary 18%, secondary 11%; p = 0.3245). Secondary healing patients had significantly lower wound complication rates (primary 51%, secondary 23%; p = 0.0012). After accounting for sex, race, weight, and operative technique, age was predictive of disease recurrence with an adjusted odds ratio (OR) of 0.706 (0.560–0.888; p = 0.003). Age and sex were both predictive of wound complications. Older patients had decreased risk of wound complication (adjusted OR 0.806, 95% CI 0.684–0.951; p = 0.0105), and male patients had increased risk of wound complication (adjusted OR 2.902, 95% CI 1.001–8.409; p = 0.0497).

Conclusion: In summary, there is no significant difference in the recurrence rates between operative techniques for pilonidal disease. Older patients have decreased risk of recurrence following intervention. Wound complication rates are lower in patients undergoing secondary healing, though this may be better explained by differences in age and sex. Additional research investigating newer, minimally-invasive techniques needs to be pursued.

Immediate versus silo closure for gastroschisis: Results of a large multicenter study

BACKGROUND/PURPOSE

The optimal method to repair gastroschisis defects continues to be debated. The two primary methods are immediate closure (IC) or silo placement (SP). The purpose of this study was to compare outcomes between each approach using a multicenter retrospective analysis. We hypothesized that patients undergoing SP for ≤5 days would have largely equivalent outcomes compared to IC patients.

METHODS

Gastroschisis patient data were collected over a 7-year period. The cohort was separated into IC and SP groups. The SP group was further stratified based on time to closure (≤5 days, 6-10 days, >10 days). Characteristics and outcomes were compared between groups. Multivariate logistic regression was also performed.

RESULTS

566 neonates with gastroschisis were identified including 224 patients in the IC group and 337 patients in the SP group. Among SP patients, 130 were closed within 5 days, 140 in 6-10 days, and 57 in >10 days. There were no significant differences in mortality, sepsis, readmission, or days to full enteral feeds between IC patients and SP patients who had a silo ≤5 days. IC patients had a significantly higher incidence of ventral hernias. Multivariate analysis revealed time to closure as a significant independent predictor of length of stay, ventilator duration, time to full enteral feeds, and TPN duration.

CONCLUSIONS

Our data show largely equivalent outcomes between patients who undergo immediate closure and those who have silos ≤5 days. We propose that closure within 5 days avoids many of the risks commonly attributed to delay in closure.

LEVEL OF EVIDENCE

Level II retrospective study.

Cell-free nuclear, but not mitochondrial, DNA concentrations correlate with the early host inflammatory response after severe trauma

Severe blunt trauma is associated with an early ‘genomic storm’ which causes simultaneous up- and down-regulation of host protective immunity. Excessive inflammation can lead to organ injury. In the absence of infection, the inflammatory response is presumably driven by release of endogenous alarmins called danger-associated molecular patterns (DAMPs), which initiate immune responses through pattern-recognition receptors (PRR). Here we examined the relationship between concentrations of cell-free (cf) nuclear DNA (ncDNA) and mitochondrial DNA (mtDNA) within 24 hours post trauma with circulating leukocyte transcriptomics and plasma IL-6 concentrations, as well as the patients’ clinical trajectories. In 104 patients enrolled from two level-1 trauma centers, ncDNA and mtDNA concentrations were increased within 24 hours of severe trauma, but only ncDNA concentrations correlated with leukocyte gene expression and outcomes. Surprisingly, ncDNA, not mtDNA concentrations, were significantly elevated in trauma patients who developed chronic critical illness versus rapid clinical recovery. Plasma IL-6 and leukocyte transcriptomics were better predictors of outcomes than cfDNA levels. Although mtDNA and ncDNA are significantly increased in the immediate post-trauma period, the dramatic inflammatory and gene expression changes seen after severe trauma are only weakly correlated with ncDNA concentrations, and more importantly, mtDNA concentrations are not associated with adverse clinical trajectories.

Predicting Morbidity and Mortality in Neonates Born With Gastroschisis

BACKGROUND

Gastroschisis is an increasingly common congenital abdominal wall defect. Due to advances in neonatal critical care and early surgical management, mortality from gastroschisis and associated complications has decreased to less than 10% in most series. However, it has been recognized that the outcome of gastroschisis has a spectrum and that the disorder affects a heterogeneous cohort of neonates. The goal of this study is to predict morbidity and mortality in neonates with gastroschisis using clinically relevant variables.

METHODS

A multicenter, retrospective observational study of neonates born with gastroschisis was conducted. Neonatal characteristics and outcomes were collected and compared. Prediction of morbidity and mortality was performed using multivariate clinical models.

RESULTS

Five hundred and sixty-six neonates with gastroschisis were identified. Overall survival was 95%. Median hospital length of stay was 37 d. Sepsis was diagnosed in 107 neonates. Days on parenteral nutrition and mechanical ventilation were considerable with a median of 27 and 5 d, respectively. Complex gastroschisis (atresia, perforation, volvulus), preterm delivery (<37 wk), and very low birth weight (<1500 g) were associated with worse clinical outcomes including increased sepsis, short bowel syndrome, parenteral nutrition days, and length of stay. The composite metric of birth weight, Apgar score at 5 min, and complex gastroschisis was able to successfully predict mortality (area under the curve, 0.81).

CONCLUSIONS

Clinical variables can be used in gastroschisis to distinguish those who will survive from nonsurvivors. Although these findings need to be validated in other large multicenter data sets, this prognostic score may aid practitioners in the identification and management of at-risk neonates.

Outcomes in omphalocele correlate with size of defect

BACKGROUND

Omphaloceles can be some of the more challenging cases managed by pediatric surgeons. Single center studies have not been meaningful in delineating outcomes due to the length of time required to accumulate a large enough series with historical changes in management negating the results. The purpose of this study was to evaluate factors impacting the morbidity and mortality of neonates with omphaloceles.

METHODS

A multicenter, retrospective observational study was performed for live born neonates with omphalocele between 2005 and 2013 at nine centers in the United States. Maternal and neonatal data were collected for each case. In-hospital management and outcomes were also reported and compared between neonates with small and large omphaloceles.

RESULTS

Two hundred seventy-four neonates with omphalocele were identified. The majority were delivered by cesarean section with a median gestational age of 37 weeks. Overall survival to hospital discharge was 81%. The presence of an associated anomaly was common, with cardiac abnormalities being the most frequent. Large omphaloceles had a significantly longer hospital and ICU length of stay, time on ventilator, number of tracheostomies, time on total parenteral nutrition, and time to full feeds, compared to small omphaloceles. Birth weight and defect size were independent predictors of survival.

CONCLUSION

This is the largest contemporary study of neonates with omphalocele. Increased defect size is an independent predictor of neonatal morbidity and mortality.

LEVEL OF EVIDENCE

Level II.

Sepsis is associated with reduced spontaneous neutrophil migration velocity in human adults

Sepsis is a common and deadly complication among trauma and surgical patients. Neutrophils must mobilize to the site of infection to initiate an immediate immune response. To quantify the velocity of spontaneous migrating blood neutrophils, we utilized novel microfluidic approaches on whole blood samples from septic and healthy individuals. A prospective study at a level 1 trauma and tertiary care center was performed with peripheral blood samples collected at <12 hours, 4 days, and/or 14 days relative to study initiation. Blood samples were also collected from healthy subjects. Ex vivo spontaneous neutrophil migration was measured on 2 μl of whole blood using microfluidic devices and time-lapse imaging. For each sample, individual neutrophils were tracked to calculate mean instantaneous velocity. Forty blood samples were collected from 33 patients with sepsis, and 15 blood samples were collected from age- and gender-matched healthy, control subjects. Average age was 61 years for septic patients with a male predominance (67%). Overall, average spontaneous neutrophil migration velocity in septic samples was 16.9 μm/min, significantly lower than controls samples at 21.1 μm/min (p = 0.0135). Neutrophil velocity was reduced the greatest at <12 hours after sepsis (14.5 μm/min). Regression analysis demonstrated a significant, positive correlation between neutrophil velocity and days after sepsis (p = 0.0059). There was no significant association between neutrophil velocity and age, gender, APACHE II score, SOFA score, sepsis severity, total white blood cell count, or percentage of neutrophils. Circulating levels of the cytokines IL-6, IL-8, IL-10, MCP-1, IP-10, and TNF were additionally measured using bead-based multiplex assay and found to peak at <12 hours and be significantly increased in patients with sepsis at all three time points (<12 hours, 4 days, and 14 days after sepsis) compared to healthy subjects. In conclusion, these findings may demonstrate an impaired ability of neutrophils to respond to sites of infection during the proinflammatory phase of sepsis.

Initial primary spontaneous pneumothorax in children and adolescents: Operate or wait?

PURPOSE

The management of primary spontaneous pneumothorax (PSP) in the pediatric population is not standardized. The purpose of this study was to understand the management options for a first episode of PSP in children and adolescents, and their associated outcomes.

METHODS

A retrospective study was conducted for patients 5-20 years old with a diagnosis of PSP at a large academic children's hospital between 2002 and 2014. Patient data were reviewed for each case. Management and outcomes were analyzed and compared between groups.

RESULTS

Eighty patients met all inclusion criteria. Overall recurrence rate was 40% with 86% occurring within 12 months of the initial PSP. Patients with recurrent PSP were significantly taller. Size of pneumothorax based on initial chest x-ray was comparable between recurrent and nonrecurrent groups. A negative CT scan for subpleural blebs did not predict recurrence. Patients undergoing thoracoscopic blebectomy and mechanical pleurodesis at initial presentation had significantly lower recurrence rate compared to patients who underwent nonoperative management (operative group 14%, nonoperative group 45%; p=0.0373).

CONCLUSIONS

Recurrence following nonoperative management was high with the majority occurring within a year and requiring readmission. These findings support offering surgery to families as a potential initial management option.

LEVEL OF EVIDENCE

3b/4 - retrospective series or case control study, single institution, very limited population.

Review: The Perioperative Use of Thromboelastography for Liver Transplant Patients

Thromboelastography (TEG) is a viscoelastic test that allows rapid evaluation of clot formation and fibrinolysis from a sample of whole blood. TEG is increasingly utilized to guide blood product resuscitation in surgical patients and transfusions for liver transplant patients. Patients with severe liver failure have significant derangement of their clotting function due to impaired production of procoagulant and anticoagulant factors. Traditional coagulation studies are limited by the short time needed for the result and provide little information about the dynamics and strength of clot formation. In addition, traditional coagulation studies do not correlate well with bleeding episodes and may lead to over-transfusion of various blood products. Evidence is less robust regarding the use of TEG for transfusion management decisions in severe liver failure patients awaiting, undergoing, or immediately after liver transplant surgery. However, the available evidence suggests that systematic implementation of TEG rather than traditional coagulation studies results in the administration of fewer blood products without increased mortality or complications. The purpose of this study is to review the literature regarding the use of TEG in liver failure patients prior to liver transplant, intraoperatively, and postoperatively. Additional high-quality randomized controlled studies should be performed to evaluate the use of TEG to guide transfusion decisions, particularly in the postoperative period following liver transplantation.

Chronic Critical Illness and the Persistent Inflammation, Immunosuppression, and Catabolism Syndrome

Dysregulated host immune responses to infection often occur, leading to sepsis, multiple organ failure, and death. Some patients rapidly recover from sepsis, but many develop chronic critical illness (CCI), a debilitating condition that impacts functional outcomes and long-term survival. The “Persistent Inflammation, Immunosuppression, and Catabolism Syndrome” (PICS) has been postulated as the underlying pathophysiology of CCI. We propose that PICS is initiated by an early genomic and cytokine storm in response to microbial invasion during the early phase of sepsis. However, once source control, antimicrobial coverage, and supportive therapies have been initiated, we propose that the persistent inflammation in patients developing CCI is a result of ongoing endogenous alarmin release from damaged organs and loss of muscle mass. This ongoing alarmin and danger-associated molecular pattern signaling causes chronic inflammation and a shift in bone marrow stem cell production toward myeloid cells, contributing to chronic anemia and lymphopenia. We propose that therapeutic interventions must target the chronic organ injury and lean tissue wasting that contribute to the release of endogenous alarmins and the expansion and deposition of myeloid progenitors that are responsible for the propagation and persistence of CCI.

Impact of toll-like receptor 4 stimulation on human neonatal neutrophil spontaneous migration, transcriptomics, and cytokine production

Neonates rely on their innate immune system, and neutrophils in particular, to recognize and combat life-threatening bacterial infections. Pretreatment with lipopolysaccharide (LPS), a toll-like receptor (TLR) 4 agonist, improves survival to polymicrobial sepsis in neonatal mice by enhancing neutrophil recruitment. To understand the response of human neonatal neutrophils to TLR4 stimulation, ex vivo spontaneous neutrophil migration, neutrophil transcriptomics, and cytokine production in the presence and absence of LPS were measured directly from whole blood of adults, term neonates, and preterm neonates. Spontaneous neutrophil migration was measured on novel microfluidic devices with time-lapse imaging for 10 h. Genome-wide neutrophil transcriptomics and plasma cytokine concentrations were also determined. Preterm neonates had significantly fewer spontaneously migrating neutrophils at baseline, and both term and preterm neonates had decreased neutrophil velocity, compared to adults. In the presence of LPS stimulation, the number of spontaneously migrating neutrophils was reduced in preterm neonates compared to term neonates and adults. Neutrophil velocity was not significantly different among groups with LPS stimulation. Preterm neonates upregulated expression of genes associated with the recruitment and response of neutrophils following LPS stimulation, but failed to upregulate the expression of genes associated with antimicrobial and antiviral responses. Plasma levels of IL-1β, IL-6, IL-8, MIP-1α, and TNF-α increased in response to LPS stimulation in all groups, but IL-10 was increased only in term and preterm neonates. In conclusion, age-specific changes in spontaneous neutrophil migration counts are not affected by LPS despite changes in gene expression and cytokine production.

KEY MESSAGES

Preterm neonates have reduced spontaneous neutrophil migration compared to term neonates and adults in the absence and presence of TLR4 stimulation. Preterm and term neonates have reduced neutrophil velocities compared to adults in the absence of TLR4 stimulation but no difference in the presence of TLR4 stimulation. Unique transcriptomic response to TLR4 stimulation is observed in neutrophils from preterm neonates, term neonates, and adults. TLR4 stimulation produces an age-specific cytokine response.

Delayed Healing Associated with Silver Sulfadiazine Use for Partial Thickness Scald Burns in Children

Burns are a leading cause of injury in children. Management principles vary widely, with no consensus about the best treatment. The purpose of this study was to compare outcomes of three different dressings for pediatric partial-thickness scald burns. A retrospective, single-center study was conducted for patients 0-16 years old with a diagnosis of acute partial-thickness scald burn between July 2007 and December 2012. Data regarding prehospital, inpatient, and outpatient course were collected. Cohort was stratified into topical antimicrobial (TA) ointment, silver sulfadiazine (SS), and biosynthetic dressing (BD) groups for analysis. The primary outcome of interest was time to full healing. One hundred and seventy-seven patients met all study criteria. Overall, mean total body surface area burned was 8.3 per cent. TA was used in 24 per cent cases, SS in 32 per cent, and BD in 44 per cent. The groups were comparable in terms of presenting burn characteristics and hospital course with the exception of the BD group being associated with greater extent of injury. Patients treated with SS had a significantly longer time to full healing and increased requirement of compression garments for scar therapy. Based on these data, the authors have amended their practice and presently use BD or TA dressings to improve healing.

Delayed Healing Associated with Silver Sulfadiazine Use for Partial Thickness Scald Burns in Children

Burns are a leading cause of injury in children. Management principles vary widely, with no consensus about the best treatment. The purpose of this study was to compare outcomes of three different dressings for pediatric partial-thickness scald burns. A retrospective, single-center study was conducted for patients 0–16 years old with a diagnosis of acute partial-thickness scald burn between July 2007 and December 2012. Data regarding prehospital, inpatient, and outpatient course were collected. Cohort was stratified into topical antimicrobial (TA) ointment, silver sulfadiazine (SS), and biosynthetic dressing (BD) groups for analysis. The primary outcome of interest was time to full healing. One hundred and seventy-seven patients met all study criteria. Overall, mean total body surface area burned was 8.3 per cent. TAwas used in 24 per cent cases, SS in 32 per cent, and BD in 44 per cent. The groups were comparable in terms of presenting burn characteristics and hospital course with the exception of the BD group being associated with greater extent of injury. Patients treated with SS had a significantly longer time to full healing and increased requirement of compression garments for scar therapy. Based on these data, the authors have amended their practice and presently use BD or TA dressings to improve healing.

Innate Immunity in the Persistent Inflammation, Immunosuppression, and Catabolism Syndrome and Its Implications for Therapy

Clinical and technological advances promoting early hemorrhage control and physiologic resuscitation as well as early diagnosis and optimal treatment of sepsis have significantly decreased in-hospital mortality for many critically ill patient populations. However, a substantial proportion of severe trauma and sepsis survivors will develop protracted organ dysfunction termed chronic critical illness (CCI), defined as ≥14 days requiring intensive care unit (ICU) resources with ongoing organ dysfunction. A subset of CCI patients will develop the persistent inflammation, immunosuppression, and catabolism syndrome (PICS), and these individuals are predisposed to a poor quality of life and indolent death. We propose that CCI and PICS after trauma or sepsis are the result of an inappropriate bone marrow response characterized by the generation of dysfunctional myeloid populations at the expense of lympho- and erythropoiesis. This review describes similarities among CCI/PICS phenotypes in sepsis, cancer, and aging and reviews the role of aberrant myelopoiesis in the pathophysiology of CCI and PICS. In addition, we characterize pathogen recognition, the interface between innate and adaptive immune systems, and therapeutic approaches including immune modulators, gut microbiota support, and nutritional and exercise therapy. Finally, we discuss the future of diagnostic and prognostic approaches guided by machine and deep-learning models trained and validated on big data to identify patients for whom these approaches will yield the greatest benefits. A deeper understanding of the pathophysiology of CCI and PICS and continued investigation into novel therapies harbor the potential to improve the current dismal long-term outcomes for critically ill post-injury and post-infection patients.

Neutrophil chemotaxis and transcriptomics in term and preterm neonates

Neutrophils play a crucial role in combating life-threatening bacterial infections in neonates. Previous studies investigating neonatal cell function have been limited because of restricted volume sampling. Here, using novel microfluidic approaches, we provide the first description of neutrophil chemotaxis and transcriptomics from whole blood of human term and preterm neonates, as well as young adults. Ex vivo percent cell migration, neutrophil velocity, and directionality to N-formylmethionyl-leucyl-phenylalanine were measured from whole blood using time-lapse imaging of microfluidic chemotaxis. Genome-wide expression was also evaluated in CD66b⁺ cells using microfluidic capture devices. Neutrophils from preterm neonates migrated in fewer numbers compared to term neonates (preterm 12.3%, term 30.5%, P = 0.008) and at a reduced velocity compared to young adults (preterm 10.1 μm/min, adult 12.7 μm/min, P = 0.003). Despite fewer neutrophils migrating at slower velocities, neutrophil directionality from preterm neonates was comparable to adults and term neonates. 3607 genes were differentially expressed among the 3 groups (P < 0.001). Differences in gene expression between neutrophils from preterm and term neonates were consistent with reduced pathogen recognition and antimicrobial activity but not neutrophil migration, by preterm neonates. In summary, preterm neonates have significant disturbances in neutrophil chemotaxis compared to term neonates and adults, and these differences in phenotype appear at the transcriptional level to target inflammatory pathways in general, rather than in neutrophil migration and chemotaxis.

Adjuvant pretreatment with alum protects neonatal mice in sepsis through myeloid cell activation

The high mortality in neonatal sepsis has been related to both quantitative and qualitative differences in host protective immunity. Pretreatment strategies to prevent sepsis have received inadequate consideration, especially in the premature neonate, where outcomes from sepsis are so dismal. Aluminium salts-based adjuvants (alum) are used currently in many paediatric vaccines, but their use as an innate immune stimulant alone has not been well studied. We asked whether pretreatment with alum adjuvant alone could improve outcome and host innate immunity in neonatal mice given polymicrobial sepsis. Subcutaneous alum pretreatment improves survival to polymicrobial sepsis in both wild-type and T and B cell-deficient neonatal mice, but not in caspase-1/11 null mice. Moreover, alum increases peritoneal macrophage and neutrophil phagocytosis, and decreases bacterial colonization in the peritoneum. Bone marrow-derived neutrophils from alum-pretreated neonates produce more neutrophil extracellular traps (NETs) and exhibit increased expression of neutrophil elastase (NE) after in-vitro stimulation with phorbol esters. In addition, alum pretreatment increases bone marrow and splenic haematopoietic stem cell expansion following sepsis. Pretreatment of neonatal mice with an alum-based adjuvant can stimulate multiple innate immune cell functions and improve survival. These novel findings suggest a therapeutic pathway for the use of existing alum-based adjuvants for preventing sepsis in premature infants.

Microbial recognition and danger signals in sepsis and trauma

Early host recognition of microbial invasion or damaged host tissues provides an effective warning system by which protective immune and inflammatory processes are initiated. Host tissues responsible for continuous sampling of their local environment employ cell surface and cytosolic pattern recognition receptors (PRRs) that provide redundant and overlapping identification of both microbial and host alarmins. Microbial products containing pathogen-associated molecular patterns (PAMPs), as well as damage-associated molecular patterns (DAMPs) serve as principle ligands for recognition by these PRRs. It is this interaction which plays both an essential survival role in response to infection and injury, as well as the pathologic role in tissue and organ injury associated with severe sepsis and trauma. Elucidating the interaction between ligands and their respective PRRs can provide both a better understanding of the host response, as well as a rational basis for therapeutic intervention. This article is part of a Special Issue entitled: Immune and Metabolic Alterations in Trauma and Sepsis edited by Dr. Raghavan Raju.

Murine Models of Sepsis and Trauma: Can We Bridge the Gap?

Sepsis and trauma are both leading causes of death in the United States and represent major public health challenges. Murine models have largely been used in sepsis and trauma research to better understand the pathophysiological changes that occur after an insult and to develop potential life-saving therapeutic agents. Mice are favorable subjects for this type of research given the variety of readily available strains including inbred, outbred, and transgenic strains. In addition, they are relatively easy to maintain and have a high fecundity. However, pharmacological therapies demonstrating promise in preclinical mouse models of sepsis and trauma often fail to demonstrate similar efficacy in human clinical trials, prompting considerable criticism surrounding the capacity of murine models to recapitulate complex human diseases like sepsis and traumatic injury. Fundamental differences between the two species include, but are not limited to, the divergence of the transcriptomic response, the mismatch of temporal response patterns, differences in both innate and adaptive immunity, and heterogeneity within the human population in comparison to the homogeneity of highly inbred mouse strains. Given the ongoing controversy, this narrative review aims to not only highlight the historical importance of the mouse as an animal research model but also highlight the current benefits and limitations of the model as it pertains to sepsis and trauma. Lastly, this review will propose future directions that may promote further use of the model.

Impact of Early-Life Exposures to Infections, Antibiotics, and Vaccines on Perinatal and Long-term Health and Disease

Essentially, all neonates are exposed to infections, antibiotics, or vaccines early in their lives. This is especially true for those neonates born underweight or premature. In contrast to septic adults and children who are at an increased risk for subsequent infections, exposure to infection during the neonatal period is not associated with an increased risk of subsequent infection and may be paradoxically associated with reductions in late-onset sepsis (LOS) in the most premature infants. Perinatal inflammation is also associated with a decreased incidence of asthma and atopy later in life. Conversely, septic neonates are at increased risk of impaired long-term neurodevelopment. While the positive effects of antibiotics in the setting of infection are irrefutable, prolonged administration of broad-spectrum, empiric antibiotics in neonates without documented infection is associated with increased risk of LOS, necrotizing enterocolitis, or death. Vaccines provide a unique opportunity to prevent infection-associated disease; unfortunately, vaccinations have been largely unsuccessful when administered in the first month of life with the exception of vaccines against hepatitis B and tuberculosis. Future vaccines will require the use of novel adjuvants to overcome this challenge. This review describes the influence of infections, antibiotics, and vaccines during the first days of life, as well as the influence on future health and disease. We will also discuss potential immunomodulating therapies, which may serve to train the preterm immune system and reduce subsequent infectious burden without subjecting neonates to the risks accompanied by virulent pathogens.

Immunological Defects in Neonatal Sepsis and Potential Therapeutic Approaches

Despite advances in critical care medicine, neonatal sepsis remains a major cause of morbidity and mortality worldwide, with the greatest risk affecting very low birth weight, preterm neonates. The presentation of neonatal sepsis varies markedly from its presentation in adults, and there is no clear consensus definition of neonatal sepsis. Previous work has demonstrated that when neonates become septic, death can occur rapidly over a matter of hours or days and is generally associated with inflammation, organ injury, and respiratory failure. Studies of the transcriptomic response by neonates to infection and sepsis have led to unique insights into the early proinflammatory and host protective responses to sepsis. Paradoxically, this early inflammatory response in neonates, although lethal, is clearly less robust relative to children and adults. Similarly, the expression of genes involved in host protective immunity, particularly neutrophil function, is also markedly deficient. As a result, neonates have both a diminished inflammatory and protective immune response to infection which may explain their increased risk to infection, and their reduced ability to clear infections. Such studies imply that novel approaches unique to the neonate will be required for the development of both diagnostics and therapeutics in this high at-risk population.

Physiological and pharmacological characterizations of the larval Anopheles albimanus rectum support a change in protein distribution and/or function in varying salinities

Ion regulation is a biological process crucial to the survival of mosquito larvae and a major organ responsible for this regulation is the rectum. The recta of anopheline larvae are distinct from other subfamilies of mosquitoes in several ways, yet have not yet been characterized extensively. Here we characterize the two major cell types of the anopheline rectum, DAR and non-DAR cells, using histological, physiological, and pharmacological analyses. Proton flux was measured at the basal membrane of 2%- and 50%-artificial sea water-reared An. albimanus larvae using self-referencing ion-selective microelectrodes, and the two cell types were found to differ in basal membrane proton flux. Additionally, differences in the response of that flux to pharmacological inhibitors in larvae reared in 2% versus 50% ASW indicate changes in protein function between the two rearing conditions. Finally, histological analyses suggest that the non-DAR cells are structurally suited for mediating ion transport. These data support a model of rectal ion regulation in which the non-DAR cells have a resorptive function in freshwater-reared larvae and a secretive function in saline water-reared larvae. In this way, anopheline larvae may adapt to varying salinities.

Effects of feeding a blend of grains naturally contaminated with Fusarium mycotoxins on feed intake, metabolism, and indices of athletic performance of exercised horses

An experiment was conducted to determine the effect of feeding blends of grains naturally contaminated with Fusarium mycotoxins to mature, exercised horses, and to test the efficacy of a polymeric glucomannan mycotoxin adsorbent (GM polymer) in preventing Fusarium mycotoxicoses. Six mature, mixed-breed mares with an average BW of 530 kg were assigned to one of three dietary treatments for 21 d in a replicated 3 x 3 Latin square design. Feed consumed each day was a combination of up to 3.5 kg of concentrates and 5.0 kg of mixed timothy/alfalfa hay (as-fed basis). The concentrates fed included 1) manage; 2) blend of contaminated grains; and 3) contaminated grains + 0.2% GM polymer (MTB-100, Alltech Inc., Nicholasville, KY). Concentrates containing contaminated grains averaged 11.0 ppm deoxynivalenol, 0.7 ppm 15-acetyldeoxynivalenol, and 0.8 ppm zearalenone (as-fed basis). Feed intake and BW were monitored over a 21-d period. Horses were maintained on a fixed exercise schedule throughout the experiment. At the end of the experiment, each horse completed a time-to-fatigue treadmill step test. Variables measured during pretest, each step of the test, and 5 and 10 min posttest were as follows: 1) time-to-fatigue, 2) heart rate, 3) hematological variables, and 4) serum lactate concentration. Each step consisted of 2 min of fast trot with a 2% increase in incline after each 2 min. Feed intake by horses fed contaminated grains was decreased compared with controls throughout the experiment (P < 0.05). Supplementation of 0.2% GM polymer to the contaminated diet did not alter feed intake by horses compared with those fed the unsupplemented contaminated diet. All hay was consumed regardless of concentrate fed. Weight loss from 0 to 21 d was observed in horses fed contaminated grains compared with controls (P < 0.05). No effect of diet was seen on variables used to measure athletic ability, although the results showed an expected response to exercise for a fit horse. We conclude that exercised horses are susceptible to Fusarium mycotoxicoses as indicated by appetite suppression and weight loss.

Effects of feeding a blend of grains naturally contaminated with Fusarium mycotoxins on feed intake, serum chemistry, and hematology of horses, and the efficacy of a polymeric glucomannan mycotoxin adsorbent

The feeding of Fusarium mycotoxin-contaminated grains adversely affects the performance of swine and poultry. Very little information is available, however, on adverse effects associated with feeding these mycotoxin-contaminated grains on the performance of horses. An experiment was conducted to investigate the effects of feeding a blend of grains naturally contaminated with Fusarium mycotoxins on feed intake, serum immunoglobulin (Ig) concentrations, serum chemistry, and hematology of horses. A polymeric glucomannan mycotoxin adsorbent (GM polymer) was also tested for efficacy in preventing Fusarium mycotoxicoses. Nine mature, nonexercising, light, mixed-breed mares were assigned randomly to one of three dietary treatments for 21 d. The horses were randomly reassigned and the experiment was subsequently replicated in time following a 14-d washout interval. Feed consumed each day was a combination of up to 2.8 kg of concentrates and 5 kg of mixed timothy/alfalfa hay. The concentrates fed included the following: 1) control, 2) blend of contaminated grains (36% contaminated wheat and 53% contaminated corn), and 3) blend of contaminated grains + 0.2% GM polymer. Diets containing contaminated grains averaged 15.0 ppm of deoxynivalenol, 0.8 ppm of 15-acetyldeoxynivalenol, 9.7 ppm of fusaric acid, and 2.0 ppm of zearalenone. Feed intake by all horses fed contaminated grains was reduced (P < 0.001) compared with controls throughout the experiment. Supplementation of 0.2% GM polymer to the contaminated diet increased (P = 0.004) feed intake of horses compared with those fed the unsupplemented contaminated diet. Serum activities of gamma-glutamyltransferase were higher (P = 0.047 and 0.027) in horses fed the diet containing contaminated grain compared with those fed the control diet on d 7 and 14, but not on d 21 (P = 0.273). Supplementation of GM polymer to the contaminated diet decreased (P < 0.05) serum gamma-glutamyltransferase activities of horses compared with those fed unsupplemented contaminated diet on d 7 and 14. Other hematology and serum chemistry measurements including serum IgM, IgG, and IgA, were not affected by diet. It was concluded that the feeding of grains naturally contaminated with Fusarium mycotoxins caused a decrease in feed intake and altered serum gamma glutamyltransferase activities. The supplementation of GM polymer prevented these mycotoxin-induced adverse effects.

Epidemiologic features of von Willebrand's disease in Doberman pinschers, Scottish terriers, and Shetland sheepdogs: 260 cases (1984-1988)

During a study period from 1985 through 1988, plasma von Willebrand's factor antigen (vWF:Ag) concentration was measured as a marker for prevalence of the von Willebrand's disease (vWD) trait in Doberman Pinschers (doberman, n = 5,554), Scottish Terriers (scottie, n = 1,363), and Shetland Sheepdogs (sheltie, n = 4,279). Significant increase in prevalence of the trait was seen in scotties and shelties during this period. In 1988, 73% of dobermans, 30% of scotties, and 28% of shelties tested had abnormal vWF:Ag concentration (less than 50% vWF:Ag). We found significant differences between breeds with respect to age and vWF:Ag concentration of clinically affected dogs at time of diagnosis. The affected dobermans were older (doberman mean age, 4.6 years; scottie mean age, 1.7 years; sheltie mean age, 1.9 years) and had higher concentration of plasma vWF:Ag (doberman mean vWF:Ag, 15%; scottie mean vWF:Ag, 0%; sheltie mean vWF:Ag, 8%). Bleeding in affected dogs of all 3 breeds was observed predominantly from mucosal surfaces and from cutaneous sites of surgery or trauma. The most common site of mucosal bleeding in scotties and shelties was oral or nasal cavity, and in dobermans was the urogenital tract. Differences in clinical manifestations of vWD in purebred dogs may reflect heterogeneous defects within the vWF gene, causing a variety of abnormalities in production, structure, and function of vWF protein. Analogous to vWD in human beings, acquired deficiencies of vWF may also contribute to the clinical variability of vWD in dogs.

Clinical and laboratory features of a severe form of von Willebrand disease in Shetland sheepdogs

Ten clinically affected Shetland Sheepdogs were evaluated to define their severe bleeding diathesis and were determined to have von Willebrand factor antigen (vWF:Ag) values less than 0.1% by ELISA assay. The virtual absence of vWF protein by ELISA assay and on multimeric analysis was diagnostic of either homozygosity or probable double heterozygosity for the canine von Willebrand disease (vWD) gene. Clinically affected dogs have type-III vWD and are the offspring of 2 heterozygous parents carrying type-I vWD. Twenty-three percent (1,428 dogs) of the more than 6,000 Shetland Sheepdogs screened for vWD at our facility since 1982 tested within the heterozygous carrier range for the common type-I form of this inherited disorder. Veterinarians and breeders should be aware of the potential for bleeding associated with elective and medical procedures in Shetland Sheepdogs and should use caution when breeding carriers of vWD because of the risk of producing clinically affected offspring with severe type-III vWD.

Defective platelet-fibrinogen interaction in hereditary canine thrombopathia

A unique, intrinsic, hereditary canine platelet disorder attributable to abnormal fibrinogen receptor availability is described. Thrombopathic platelets from 13 severely affected basset hounds failed to aggregate in response to all agonists tested except thrombin. Normal platelet interaction with the various stimuli was inferred on the basis of their ability to elicit unimpaired shape change in thrombopathic platelets. No quantitative differences in major platelet membrane glycoproteins, intraplatelet fibrinogen, adenine nucleotides, or serotonin uptake were detected. Dense granule secretion was impaired. The ultrastructural appearance of thrombopathic platelets was normal. Fibrinogen-platelet interaction was evaluated by reacting platelet-rich plasma (PRP) with fibrinogen coupled to polymeric acrylonitrile beads and scoring the extent of stimulus-induced agglutination. The aggregatory responses of normal and thrombopathic platelets were closely correlated with fibrinogen receptor availability. In contrast to human platelets, epinephrine-stimulated canine platelets did not interact with immobilized fibrinogen, and arachidonate generally induced only weak agglutination. Thrombopathic platelets agglutinated fibrinogen beads at reduced rates when stimulated with physiologic doses of thrombin and high-dose calcium ionophore, A23187. Our data suggest that thrombin-mediated induction of canine platelet fibrinogen receptors may proceed by pathway(s) alternate to those shared by other platelet agonists, and/or that secreted granule constituents may act synergistically with thrombin to overcome inhibition of signal-response-coupled reactions mediating the interaction of fibrinogen with its receptor. This congenital platelet defect provides further evidence, in a species other than human, for the pivotal role of fibrinogen receptor induction in platelet aggregation.

Age-related renal, hematologic, and hemostatic abnormalities in FH/Wjd rats

This longitudinal study compared the renal morphologic changes and hemostatic defects of FH/Wjd rats at different ages. A second aim was to determine whether the bleeding tendency becomes intensified in older animals by the concomitant renal disease. Results indicated that reduced capacity for platelet 14C-serotonin release (P less than 0.01) was found for each age group studied in comparison with Wistar controls. The nephropathy of old FH/Wjd male rats was more severe than that in either FH/Wjd females or age-matched Wistars of both sexes. The mesangial lesions showed abundant deposits of factor VIII-related antigen, fibronectin, and immunoglobulins, but not C3, along with tightly packed or loose electron-dense material. Polyethylene glycol precipitation and platelet aggregation tests detected small amounts of circulating immune complex-like material. Old FH/Wjd rats did not develop edema, and the glomerular filtration rate remained normal despite the persistent proteinuria, hematuria, and arterial hypertension characteristic of this strain. Our data indicated that the congenital platelet dysfunction does not become more severe in older animals and that the nephropathy seems unrelated, does not appear to be mediated by immune complexes, and, in contrast to the focal segmental glomerulosclerosis of persons, the lesions progress without a parallel impairment of renal function.

Platelet adhesion to noncovalently immobilized collagen

Affinity chromatography with collagen covalently immobilized to agarose is frequently used to measure platelet adhesion. A simpler, equally sensitive affinity chromatographic assay for quantitation of platelet adhesion to noncovalently immobilized type I collagen has been developed. In the presence of EDTA, human and canine platelet adhesion increased linearly with increasing collagen up to 0.3 mg/ml of packed resin and attained a maximum of 90% adhesion above 1 mg/ml. No temperature dependence was observed. When collagen fibrils were immobilized with periodate-oxidized or CNBr-activated agarose, platelets from both species were rarely observed adhering to fibrils in close association with the agarose surface. Increased divalent cation levels resulted in increased platelet adhesion. In citrated platelet-rich plasma, where aggregation may occur, experiments with thrombopathic canine platelets which fail to aggregate or secrete in response to collagen suggest that up to 84% of the maximal "adhesion" observed in citrated systems is adhesion to collagen per se. In contrast to adhesion to glass bead surfaces, in vitro platelet adhesion to collagen was only marginally affected in the absence of aggregation and secretion. Normal platelet interaction with fibrinogen is not essential for platelet adhesion to collagen. Formalin fixation had no effect on platelet adhesion to collagen. Fixed platelets were quantitatively recovered after elution with 1M NaCl. Our results suggest that in vitro adhesion of canine platelets to collagen is similar to that observed for human platelets and that collagen fibril-fibril associations may be essential for platelet adhesion whereas active platelet metabolism and membrane fluidity are not. Initial adhesion of platelets to collagen in vitro appears to be predominantly ionic in nature.

Platelet membrane glycoproteins in normal dogs and dogs with hemostatic defects

Glycoproteins solubilized from membrane-enriched fractions of platelets from dogs with TT or VWD and from normal controls were compared by SDS-PAGE. The results were similar to those for the analogous human disorders. Both normal and VWD canine platelet MPs contained three major glycoproteins as well as four smaller-molecular-weight proteins that stained for carbohydrate with the PAS reagent. In contrast, MPs from dogs with TT had a higher concentration of GP I, a varied expression of GP II, and a lower concentration of GP III. The findings re-emphasize the value of comparative studies of these models of human hemostatic defects.

Spontaneous atrial thrombosis in aged Syrian hamsters. II. Hemostasis

Coagulation and fibrinolysis were studied in a colony of aged Syrian hamsters with spontaneous atrial thrombosis, and the results are consistent with concomitant consumption coagulopathy. In comparison to age- and sex-matched hamsters from the same colony, those with atrial thrombi had significantly prolonged prothrombin and partial thromboplastin times, reduced levels of factors II, VII, VIII and X activities and plasminogen; and concentrations of fibrinogen-fibrin split products in excess of 80 microgram/ml. Hematocrits of the thrombosed animals were significantly decreased, total plasma proteins were increased, leukocyte counts were within normal limits, and platelet counts were about half those of the controls. Thrombosed hamsters had significantly reduced plasma albumin content, increased alpha1-, beta-, and gamma-globulins, and reduced A/G ratios. Aged sick hamsters demonstrable thrombi also had reduced coagulation and fibrinolytic activities and platelet counts, but their fibrinogen levels were markedly elevated, and fibrinogen-fibrin split products were either absent or present in trace amounts. This suggests an earlier and/or less acute form of the thrombotic process.

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Evaluation of platelet cryopreservation techniques by isolated kidney perfusion

The isolated perfused rabbit kidney, a model system used previously to assess platelet function, was adapted for evaluation of human platelet cryopreservation techniques. A new, simple, efficient device for controlling cooling rates before, during, and after freezing was used. Platelet concentrates frozen with 5 per cent dimethyl sulfoxide (DMSO) under different conditions were the most effective of those tried in maintaining the hemostatic function and vascular integrity of perfused kidneys. Our studies indicate that the isolated, perfused rabbit kidney can be used to evaluate platelet cryopreservation techniques and is potentially adaptable for studies of organ cryopreservation.

Characterization of the fawn-hooded rat as a model for hemostatic studies

A large colony of fawn-hooded (FH) rats, comprising five original families and six generations of their progeny, was developed for genetic and comparative studies of their bleeding tendency. The characteristics of the bleeding diathesis in these rats are similar to those originally reported in related rats by Tschopp and Zucker. FH rats have normal clot retraction, ADP-induced platelet aggregation and platelet ADP; variable aggregation with collagen; minimal aggregation with adrenaline and cobra venom factor; and reduced platelet ATP, ATP/ADP ratio, serotonin content and -14C-serotonin release. In comparison to age- and sex-matched Wistar rats, FH rats have significantly prolonged partial thromboplastin time, shortened Russell's viper venom time and increased factor X and XI levels. Other coagulation screening tests and specific assays for fibrinogen, plasminogen and factors VII, VIII and IX were normal. Some age- and sex-related differences in coagulation and other parameters were observed within each rat strain. Plasma proteins, glycoproteins and ceruloplasmin (copper oxidase activity) showed no abnormalities, nor did initial studies of immunoglobulins and complement. However, FH rats have significantly lower glucose and higher cholesterol levels than comparable Wistar rats.