Lymph flow depends on both the rate of lymph production by tissues and the extent of passive and active pumping. Here we aim to characterize the passive mechanical properties of a lymphangion in both ...mid-lymphangion and valve segments to assess regional differences along a lymphangion, as well as evaluating its structural composition.
Mesenteric lymphatic vessels were isolated and cannulated in a microchamber for pressure-diameter (P-D) testing. Vessels were inflated from 0 to 20 cmH(2)O at a rate of 4 cmH(2)O/min, and vessel diameter was continuously tracked, using an inverted microscope, video camera, and custom LabVIEW program, at both mid-lymphangion and valve segments. Isolated lymphatic vessels were also pressure-fixed at 2 and 7 cmH(2)O and imaged using a nonlinear optical microscope (NLOM) to obtain collagen and elastin structural information. We observed a highly nonlinear P-D response at low pressures (3-5 cmH(2)O), which was modeled using a three-parameter constitutive equation. No significant difference in the passive P-D response was observed between mid-lymphangion and valve regions. NLOM imaging revealed an inner elastin layer and outer collagen layer at all locations. Lymphatic valve leaflets were predominantly elastin with thick axially oriented collagen bands at the insertion points.
We observed a highly nonlinear P-D response at low pressures (3-5 cmH(2)O) and developed the first constitutive equation to describe the passive P-D response for a lymphangion. The passive P-D response did not vary among regions, in agreement with the composition of elastin and collagen in the lymphatic wall.
Up to 30% of severely injured patients on prophylactic anticoagulation experience venous thromboembolism (VTE). Our previous work shows that acquired antithrombin (AT) deficiency AT<80% occurs in ...approximately 20% of trauma patients upon admission and drives poor responsiveness to enoxaparin. However, changes in AT over time and its association with VTE remain unknown. The aim of this study was to determine the relationship between acquired AT deficiency and VTE in severely injured patients.
A secondary analysis of the Pragmatic, Randomized Optimal Platelet and Plasma Ratios (PROPPR) clinical trial was performed. Patients who died within 24 h of hemorrhage were excluded from analysis. Demographics, mechanism and severity of injury, transfusions volumes, and outcomes were compared between patients who did and did not develop VTE. Non-parametric statistical tests were used to compare patients with and without VTE. Logistic regression analyses were performed to identify predictors of VTE risk, controlling for AT deficiency (over first 72 h), age, gender, race, body mass index, study site, randomization group and injury severity. A Cox proportional hazards model was used to assess the contribution of AT deficiency to the risk of VTE, while censoring for early deaths.
Of the 680 patients enrolled in PROPPR, 101 died of hemorrhage. Of the remaining 579 patients, 86 (14.9%) developed VTE. The median time to VTE was 6 days (IQR 3, 13). No differences in demographics, injuries, or transfusion volumes were identified between VTE cases and controls. AT deficiency at 72 h post-admission was independently associated with VTE. Patients who experienced AT deficiency at 72 h had a 3.3 fold increased risk of VTE p < 0.01; 95% CI 1.56, 6.98. Lastly, patients who developed VTE had worse outcomes as displayed by significantly fewer hospital-free days compared to non-VTE patients 0 (0, 8) vs. 4 (0, 18), p < 0.01, respectively.
Acquired AT deficiency (AT<80%) is an important risk factor for VTE in severely injured patients. These data indicate that intervening, perhaps through AT supplementation, in the first three days after injury could mitigate the risk of VTE and improve patient outcomes.
Background: The endothelial glycocalyx layer (EGL) is a complex meshwork of glycosaminoglycans and proteoglycans that protect the vascular endothelium. Cleavage or shedding of EGL-specific ...biomarkers, such as hyaluronic acid (HA) and syndecan-1 (SDC-1, CD138) in plasma, have been shown to be associated with poor clinical outcomes. However, it is unclear whether levels of circulating EGL biomarkers are representative of the EGL injury within the tissues. The objective of the present feasibility study was to describe a pathway for plasma and tissue procurement to quantify EGL components in a cohort of surgical patients with intra-abdominal sepsis. We sought to compare differences between tissue and plasma EGL biomarkers and to determine whether EGL shedding within the circulation and/or tissues correlated with clinical outcomes. Methods: This was a prospective, observational, single-center feasibility study of adult patients (N = 15) with intra-abdominal sepsis, conducted under an approved institutional review boards. Blood and resected tissue (pathologic specimen and unaffected peritoneum) samples were collected from consented subjects at the time of operation and 24-48 hours after surgery. Endothelial glycocalyx layer biomarkers (i.e., HA and SDC-1) were quantified in both tissue and plasma samples using a CD138 stain and ELISA kit, respectively. Pairwise comparisons were made between plasma and tissue levels. In addition, we tested the relationships between measured EGL biomarkers and clinical status and patient outcomes. Results: Fifteen patients with intra-abdominal sepsis were enrolled in the study. Elevations in EGL-specific circulating biomarkers (HA, SDC-1) were positively correlated with postoperative SOFA scores and weakly associated with resuscitative volumes at 24 hours. Syndecan-1 levels from resected pathologic tissue significantly correlated with SOFA scores at all time points ( R = 0.69 and P < 0.0001) and positively correlated with resuscitation volumes at 24 hours ( R = 0.41 and P = 0.15 for t = 24 hours). Tissue and circulating HA and SDC-1 positively correlated with SOFA >6. Conclusions: Elevations in both circulating and tissue EGL biomarkers were positively correlated with postoperative SOFA scores at 24 hours, with resected pathologic tissue EGL levels displaying significant correlations with SOFA scores at all time points. Tissue and circulating EGL biomarkers were positively correlated at higher SOFA scores (SOFA > 6) and could be used as indicators of resuscitative needs within 24 hours of surgery. The present study demonstrates the feasibility of tissue and plasma procurement in the operating room, although larger studies are needed to evaluate the predictive value of these EGL biomarkers for patients with intra-abdominal sepsis.
Clinicians intuitively recognize that faster time to hemostasis is important in bleeding trauma patients, but these times are rarely reported.
Prospectively collected data from the Pragmatic ...Randomized Optimal Platelet and Plasma Ratios trial were analyzed. Hemostasis was predefined as no intraoperative bleeding requiring intervention in the surgical field or resolution of contrast blush on interventional radiology (IR). Patients who underwent an emergent (within 90 minutes) operating room (OR) or IR procedure were included. Mixed-effects Poisson regression with robust error variance (controlling for age, Injury Severity Score, treatment arm, injury mechanism, base excess on admission missing values estimated by multiple imputation, and time to OR/IR as fixed effects and study site as a random effect) with modified Bonferroni corrections tested the hypothesis that decreased time to hemostasis was associated with decreased mortality and decreased incidence of acute kidney injury (AKI), acute respiratory distress syndrome (ARDS), multiple-organ failure (MOF), sepsis, and venous thromboembolism.
Of 680 enrolled patients, 468 (69%) underwent an emergent procedure. Patients with decreased time to hemostasis were less severely injured, had less deranged base excess on admission, and lower incidence of blunt trauma (all p < 0.05). In 408 (87%) patients in whom hemostasis was achieved, every 15-minute decrease in time to hemostasis was associated with decreased 30-day mortality (RR, 0.97; 95% confidence interval CI, 0.94-0.99), AKI (RR, 0.97; 95% CI, 0.96-0.98), ARDS (RR, 0.98; 95% CI, 0.97-0.99), MOF (RR, 0.94; 95% CI, 0.91-0.97), and sepsis (RR, 0.98; 95% CI, 0.96-0.99), but not venous thromboembolism (RR, 0.99; 95% CI, 0.96-1.03).
Earlier time to hemostasis was independently associated with decreased incidence of 30-day mortality, AKI, ARDS, MOF, and sepsis in bleeding trauma patients. Time to hemostasis should be considered as an endpoint in trauma studies and as a potential quality indicator.
Therapeutic/care management, level III.
Nutritional support in the intensive care unit (ICU) is a vital element of patient care. Polyunsaturated fatty acids (PUFAs) like γ‐linolenic acid (GLA), eicosapentaenoic acid (EPA) and ...docosahexaenoic acid (DHA) have been recommended in immunomodulatory diets because of their anti‐inflammatory effects. However, clinical trials have failed to show unanimous benefit with PUFA‐rich diets. Metabolic conversion of these PUFAs are dependent on fatty acid desaturase (FADS) and elongase (ELOVL) enzymes, which are unequal across humans. In fact, several genetic variants within FADS and ELOVL genes have been shown to impact PUFA metabolism. Select variants are also differentially expressed in African Americans. We hypothesize that these genetic variants may help explain the differential responses to PUFA‐rich diets. In this study, we aimed to investigate gene‐diet interactions in patients with acute lung injury (ALI).
Banked DNA and plasma samples from the OMEGA randomized clinical trial (NCT00609180) were used to conduct a secondary analysis on genetic variants within FADS and ELOVL regions; 43 SNPs were genotyped. Plasma PUFA levels were quantified using gas chromatography. Of the 272 enrolled, 143 received omega‐rich vs. 129 placebo diets. All statistical analyses were stratified by race and adjusted for age and gender.
Several SNPs were associated with PUFA levels. Notably, SNP rs174537 had a significant impact on arachidonic acid (ARA). Caucasian T allele carriers on the omega‐rich diet had lower ARA levels (p=0.022, Fig. 1). Interestingly, this SNP had a major impact on PUFAs within African Americans on both placebo and omega‐rich diets. ARA levels were significantly higher and DHA levels were low (p=0.0007) in African Americans. Genotype at rs174537 was associated with patient outcomes; Caucasians with the T allele had significantly more VENT‐free and ICU‐free days (~>12%) than GGs, but this was not observed within African Americans. Instead, a significant interaction between gender and diet was seen, with African American women on placebo diet having 40% fewer VENT‐free (p=0.009) and ICU‐free days (p=0.022) than African American men. Mortality was highest in GGs receiving omega‐rich diets in both races, however this was not statistically significant. These data suggest strong ethnic, gender and genetic factors influencing the response to omega‐rich diets. Further investigation on other gene‐gene interactions (e.g. between FADS and ELOVL variants), and epigenetic modifications are needed to understand the underlying mechanisms regulating PUFA metabolism and biosynthesis in critically injured and ill patients.
Support or Funding Information
NIH K25 HL133611
This is from the Experimental Biology 2019 Meeting. There is no full text article associated with this published in The FASEB Journal.
Thrombelastography (TEG) fibrinolysis shutdown after trauma is associated with increased mortality due to hypercoagulability-associated organ failure. However, a lack of mechanistic data has ...precluded the development of novel interventions to treat shutdown.
To define the pathophysiology of TEG shutdown in severely injured, bleeding patients through secondary analysis of the PROPPR trial.
Fibrinolysis was characterized in PROPPR subjects using admission TEG lysis at 30 min (LY30) or plasmin-antiplasmin (PAP) levels. LY30 categories were low (<0.9%), moderate (0.9-2.9%), or high (≥ 3%). PAP was classified as low (<1,500 μg/L), moderate (1,500-20,000 μg/L), or high (>20,000 μg/L). Demographics, outcomes, admission TEG values, platelet count and function, standard coagulation tests, and coagulation proteins were compared.
Five hundred forty-seven patients had TEG data and 549 patients had PAP data available. Low LY30 was associated with reduced platelet count and aggregation, poorer TEG clot formation, prolonged clotting times, and reduced fibrinogen and alpha2 antiplasmin. Compared to moderate PAP, low PAP subjects had similar platelet parameters, TEG values, fibrinogen, and alpha2 antiplasmin, but reduced tPA, and elevated PAI-1. D-Dimer values increased as PAP increased, however patients with low LY30 had elevated D-Dimer compared with moderate LY30 patients. Most low LY30 deaths were due to TBI (45%) and hemorrhage (42%) versus one of each cause (TBI, hemorrhage, MOF) in low PAP patients.
Low TEG LY30 does not reflect shutdown of enzymatic fibrinolysis with hypercoagulability, but rather a coagulopathic state of moderate fibrinolysis with fibrinogen consumption and platelet dysfunction that is associated with poor outcomes.
The glycosaminoglycan hyaluronan (HA) plays important roles in diverse physiological functions where the distribution of its molecular weight (MW) can influence its behavior and is known to change in ...response to disease conditions. During inflammation, HA undergoes a covalent modification in which heavy chain subunits of the inter-alpha-inhibitor family of proteins are transferred to its structure, forming heavy chain-HA (HC•HA) complexes. While limited assessments of HC•HA have been performed previously, determining the size distribution of its HA component remains a challenge. Here, we describe a selective method for extracting HC•HA from mixtures that yields material amenable to MW analysis with a solid-state nanopore sensor. After demonstrating the approach in vitro, we validate extraction of HC•HA from osteoarthritic human synovial fluid as a model complex biological matrix. Finally, we apply our technique to pathophysiology by measuring the size distributions of HC•HA and total HA in an equine model of synovitis.
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