Monica M. Dua

Hyperglycemia limits experimental aortic aneurysm progression.

OBJECTIVE Diabetes mellitus (DM) is associated with reduced progression of abdominal aortic aneurysm (AAA) disease. Mechanisms responsible for this negative association remain unknown. We created AAAs in hyperglycemic mice to examine the influence of serum glucose concentration on experimental aneurysm progression. METHODS Aortic aneurysms were induced in hyperglycemic (DM) and normoglycemic models by using intra-aortic porcine pancreatic elastase (PPE) infusion in C57BL/6 mice or by systemic infusion of angiotensin II (ANG) in apolipoprotein E-deficient (ApoE(-/-)) mice, respectively. In an additional DM cohort, insulin therapy was initiated after aneurysm induction. Aneurysmal aortic enlargement progression was monitored with serial transabdominal ultrasound measurements. At sacrifice, AAA cellularity and proteolytic activity were evaluated by immunohistochemistry and substrate zymography, respectively. Influences of serum glucose levels on macrophage migration were examined in separate models of thioglycollate-induced murine peritonitis. RESULTS At 14 days after PPE infusion, AAA enlargement in hyperglycemic mice (serum glucose ≥ 300 mg/dL) was less than that in euglycemic mice (PPE-DM: 54% ± 19% vs PPE: 84% ± 24%, P < .0001). PPE-DM mice also demonstrated reduced aortic mural macrophage infiltration (145 ± 87 vs 253 ± 119 cells/cross-sectional area, P = .0325), elastolysis (% residual elastin: 20% ± 7% vs 12% ± 6%, P = .0209), and neovascularization (12 ± 8 vs 20 ± 6 vessels/high powered field, P = .0229) compared with PPE mice. Hyperglycemia limited AAA enlargement after ANG infusion in ApoE(-/-) mice (ANG-DM: 38% ± 12% vs ANG: 61% ± 37% at day 28). Peritoneal macrophage production was reduced in response to thioglycollate stimulation in hyperglycemic mice, with limited augmentation noted in response to vascular endothelial growth factor administration. Insulin therapy reduced serum glucose levels and was associated with AAA enlargement rates intermediate between euglycemic and hyperglycemic mice (PPE: 1.21 ± 0.14 mm vs PPE-DM: 1.00 ± 0.04 mm vs PPE-DM + insulin: 1.14 ± 0.05 mm). CONCLUSIONS Hyperglycemia reduces progression of experimental AAA disease; lowering of serum glucose levels with insulin treatment diminishes this protective effect. Identifying mechanisms of hyperglycemic aneurysm inhibition may accelerate development of novel clinical therapies for AAA disease.

Live transference of surgical subspecialty skills using telerobotic proctoring to remote general surgeons

BACKGROUND Certain clinical environments, including military field hospitals or rural medical centers, lack readily available surgical subspecialists. We hypothesized that telementoring by a surgical subspecialist using a robotic platform is feasible and can convey subspecialty knowledge and skill to a remotely located general surgeon. STUDY DESIGN Eight general surgery residents evaluated the effect of remote surgical telementoring by performing 3 operative procedures, first unproctored and then again when teleproctored by a surgical subspecialist. The clinical scenarios consisted of a penetrating right ventricular injury requiring suture repair, an open tibial fracture requiring external fixation, and a traumatic subdural hematoma requiring craniectomy. A robotic platform consisting of a pan-and-tilt camera with laser pointer attached to an overhead surgical light with integrated audio allowed surgical subspecialists the ability to remotely teleproctor residents. Performance was evaluated using an Operative Performance Scale. Satisfaction surveys were given after performing the scenario unproctored and again after proctoring. RESULTS Overall mean performance scores were superior in all scenarios when residents were proctored than when they were not (4.30 +/- 0.25 versus 2.43 +/- 0.20; p < 0.001). Mean performance scores for individual metrics, including tissue handling, instrument handling, speed of completion, and knowledge of anatomy, were all superior when residents were proctored (p < 0.001). Satisfaction surveys showed greater satisfaction and comfort among residents when proctored. Proctored residents believed the robotic platform facilitated learning and would be feasible if used clinically. CONCLUSIONS This study supports the use of surgical teleproctoring in guiding remote general surgeons by a surgical subspecialist in the care of a wounded patient in need of an emergency subspecialty operation.

Hyperglycemia modulates plasminogen activator inhibitor-1 expression and aortic diameter in experimental aortic aneurysm disease.

BACKGROUND Extracellular matrix degradation is a sentinel pathologic feature of abdominal aortic aneurysm (AAA) disease. Diabetes mellitus, a negative risk factor for AAA, may impair aneurysm progression through its influence on the fibrinolytic system. We hypothesize that hyperglycemia limits AAA progression through effects on endogenous plasminogen activator inhibitor-1 (PAI-1) levels and subsequent reductions in plasmin generation. METHODS Experimental AAAs were induced in diabetic and control mice via the intra-aortic elastase infusion method. Serial transabdominal high-frequency ultrasound examinations were performed to monitor aortic diameter following elastase infusion. Circulating PAI-1 and plasmin alpha2-antiplasmin (PAP) complex concentrations were determined by ELISA and local expression of PAI-1 levels was examined by RT-PCR and immunohistochemistry. RESULTS Hyperglycemia was associated with reduced AAA diameter, increased plasma PAI-1 concentration and reduced plasmin generation. Aneurysmal aortic PAI-1 gene expression increased in parallel with plasma concentration, with peak expression occurring early after aneurysm initiation. CONCLUSION Hyperglycemia increases PAI-1 expression and attenuates AAA diameter in experimental AAA disease. These results emphasize the role of the fibrinolytic pathway in AAA pathophysiology, and suggest a candidate mechanism for hyperglycemic inhibition of AAA disease.

RGD-conjugated human ferritin nanoparticles for imaging vascular inflammation and angiogenesis in experimental carotid and aortic disease

PurposeInflammation and angiogenesis are important contributors to vascular disease. We evaluated imaging both of these biological processes, using Arg–Gly–Asp (RGD)-conjugated human ferritin nanoparticles (HFn), in experimental carotid and abdominal aortic aneurysm (AAA) disease.ProceduresMacrophage-rich carotid lesions were induced by ligation in hyperlipidemic and diabetic FVB mice (n = 16). AAAs were induced by angiotensin II infusion in apoE−/− mice (n=10). HFn, with or without RGD peptide, was labeled with Cy5.5 and injected intravenously for near-infrared fluorescence imaging.ResultsRGD-HFn showed significantly higher signal than HFn in diseased carotids and AAAs relative to non-diseased regions, both in situ (carotid: 1.88 ± 0.30 vs. 1.17 ± 0.10, p = 0.04; AAA: 2.59 ± 0.24 vs. 1.82 ± 0.16, p = 0.03) and ex vivo. Histology showed RGD-HFn colocalized with macrophages in carotids and both macrophages and neoangiogenesis in AAA lesions.ConclusionsRGD-HFn enhances vascular molecular imaging by targeting both vascular inflammation and angiogenesis, and allows more comprehensive detection of high-risk atherosclerotic and aneurysmal vascular diseases.

Lipoxin A4 Attenuates Microvascular Fluid Leak During Inflammation

BACKGROUND The release of proinflammatory cytokines during inflammation disturbs the endothelial barrier and can initiate significant intravascular volume loss. Proinflammatory cytokines also induce the expression of anti-inflammatory mediators, such as lipoxin, which promote the resolution of inflammation. Our hypothesis is that lipoxin A(4) (LXA(4)) reverses the increased microvascular fluid leak observed during inflammatory conditions. MATERIALS AND METHODS Microvascular fluid leak (L(p)) was measured in rat mesenteric venules using a micro-cannulation technique. L(p) was measured under the following conditions: (1) LXA(4) (100 nM) alone (n = 5), (2) LXA(4) (100 nM) administered after endothelial hyperpermeability induced by a continuous perfusion of 10 nM platelet activating factor (PAF) (n = 5), (3) LXA(4) (100 nM) perfused after inflammation induced by a systemic bolus of 10 mg/kg lipopolysaccharide (LPS) (n = 5), and (4) LXA(4) (100 nM) perfused after LPS-induced inflammation during inhibition of c-Jun N-terminal kinase (n = 4). RESULTS LXA(4) alone slightly increased L(p) from baseline (L(p)-baseline = 1.05 +/- 0.03, L(p)-LXA(4) = 1.55 +/- 0.04; P < 0.0001). PAF increased L(p) 4-fold (L(p)-baseline = 1.20 +/- 0.10, L(p)-PAF = 4.49 +/- 0.95; P < 0.0001). LXA(4) administration after PAF decreased L(p) 66% versus PAF alone (from 4.49 +/- 0.95 to 1.54 +/- 0.13; P = 0.0004). LPS-induced inflammation increased L(p) over 2-fold (L(p)-baseline = 1.05 +/- 0.03, L(p)-LPS = 2.27 +/- 0.13; P < 0.0001). LXA(4) administration after LPS decreased L(p) 42% versus LPS alone (from 2.27 +/- 0.13 to 1.31 +/- 0.05; P < 0.0001). The effect of c-Jun N-terminal kinase inhibition during LPS-induced inflammation attenuated the decrease in leak cause by LXA(4) by 51% (P = 0.0002). CONCLUSION After either LPS or PAF, LXA(4) attenuated the intravascular volume loss caused by these inflammatory mediators. The activity of LXA(4) may be partly mediated by the c-Jun N-terminal kinase signaling pathway. These data support an anti-inflammatory role for LXA(4) and suggests a potential pharmacologic role for LXA(4) during inflammation.

Cyst Fluid Glucose is Rapidly Feasible and Accurate in Diagnosing Mucinous Pancreatic Cysts

OBJECTIVES:Better diagnostic tools are needed to differentiate pancreatic cyst subtypes. A previous metabolomic study showed cyst fluid glucose as a potential marker to differentiate mucinous from non-mucinous pancreatic cysts. This study seeks to validate these earlier findings using a standard laboratory glucose assay, a glucometer, and a glucose reagent strip.METHODS:Using an IRB-approved prospectively collected bio-repository, 65 pancreatic cyst fluid samples (42 mucinous and 23 non-mucinous) with histological correlation were analyzed.RESULTS:Median laboratory glucose, glucometer glucose, and percent reagent strip positive were lower in mucinous vs. non-mucinous cysts (P<0.0001 for all comparisons). Laboratory glucose<50 mg/dl had a sensitivity of 95% and a specificity of 57% (LR+ 2.19, LR− 0.08). Glucometer glucose<50 mg/dl had a sensitivity of 88% and a specificity of 78% (LR+ 4.05, LR− 0.15). Reagent strip glucose had a sensitivity of 81% and a specificity of 74% (LR+ 3.10, LR− 0.26). CEA had a sensitivity of 77% and a specificity of 83% (LR+ 4.67, LR− 0.27). The combination of having either a glucometer glucose<50 mg/dl or a CEA level>192 had a sensitivity of 100% but a low specificity of 33% (LR+ 1.50, LR− 0.00).CONCLUSIONS:Glucose, whether measured by a laboratory assay, a glucometer, or a reagent strip, is significantly lower in mucinous cysts compared with non-mucinous pancreatic cysts.

Laparoscopic Transgastric Necrosectomy for the Management of Pancreatic Necrosis

BACKGROUND Traditional open necrosectomy for pancreatic necrosis is associated with significant morbidity and mortality. Although minimally invasive techniques have been described and offer some promise, each has considerable limitations. This study assesses the safety and effectiveness of laparoscopic transgastric necrosectomy (LTN), a novel technique for the management of necrotizing pancreatitis. STUDY DESIGN Between 2009 and 2013, patients with retrogastric pancreatic necrosis requiring debridement were evaluated for LTN. Debridement was performed via a laparoscopic transgastric approach using 2 to 3 ports and the wide cystgastrostomy left open. Patient demographics, disease severity, operative characteristics, and outcomes were collected and analyzed. RESULTS Twenty-one patients (13 men, median age 54 years; interquartile range [IQR] 46 to 62 years) underwent LTN during the study period. The duration between pancreatitis onset and debridement was 65 days (IQR 53 to 124 years). Indications for operation included infection (7 patients) and persistent unwellness (14 patients). Median duration of LTN was 170 minutes (IQR 136 to 199 minutes); there were no conversions. Control of the necrosis was achieved via the single procedure in 19 of 21 patients. Median postoperative hospital stay was 5 days (IQR 3 to 14 days) and the majority (71%) of patients experienced no (n = 9) or only minor postoperative complications (n = 6) by Clavien-Dindo grade. Complications of Clavien-Dindo grade 3 or higher developed in 6 patients, including 1 death (5%). With a median follow-up of 11 months (IQR 7 to 22 months), none of the patients required additional operative debridement or had pancreatic/enteric fistulae or wound complications develop. CONCLUSIONS Laparoscopic transgastric necrosectomy is a novel, minimally invasive technique for the management of pancreatic necrosis that allows for debridement in a single operation. When feasible, LTN can reduce the morbidity associated with traditional open necrosectomy and avoid the limitations of other minimally invasive approaches.

Usability of robotic platforms for remote surgical teleproctoring.

Military field hospitals and rural medical centers may lack surgical subspecialists. Robotic technology can enable proctoring of remotely located general surgeons by subspecialists. Our objective compared three proctoring platforms: (1) 6-degree-of-freedom (DOF) computer input devices controlling a camera and laser pointer mounted on robotic arms, (2) a computer mouse controlling a pan-tilt-zoom (PTZ) camera and robotic laser scanner, and (3) a computer pen/tablet controlling a PTZ-camera and robotic laser scanner. Our hypothesis was that a pen/tablet or mouse platform would be superior to the 6-DOF-input device platform. Five surgeons used each platform by simulating the creation of operative incisions. Qualitative (instrument handling, time, motion, spatial awareness) and quantitative performance (accuracy, speed) was assessed on a five-point scale. Each surgeon completed a satisfaction survey. Both mouse and pen/tablet had higher mean performance scores than the 6-DOF-input device in all quantitative (6-DOF = 1.7 +/- 0.8, mouse = 4.3 +/- 0.2, pen = 4.1 +/- 0.6; p < 0.001) and qualitative measures (6-DOF = 1.7 +/- 0.2, mouse = 4.8 +/- 0.0, pen = 4.6 +/- 0.1; p < 0.001). Handling, motion, and instrument awareness were superior with the mouse and pen/tablet versus 6-DOF-input devices (p < 0.0001). Speed and accuracy were also superior using the mouse or pen/tablet versus 6-DOF-input devices (p < 0.0001). Surgeons completed tasks faster using the mouse versus pen/tablet (p = 0.02). Satisfaction surveys revealed a preference for the mouse. This study demonstrates the superiority of a mouse or pen/tablet controlling a PTZ-camera and robotic laser scanner for remote surgical teleproctoring versus 6-DOF-input devices controlling a camera and laser pointer. Either a mouse or pen/tablet platform allows subspecialists to proctor remotely located surgeons.

Pancreatectomy with vein reconstruction: technique matters

BACKGROUND A variety of techniques have been described for portal vein (PV) and/or superior mesenteric vein (SMV) resection/reconstruction during a pancreatectomy. The ideal strategy remains unclear. METHODS Patients who underwent PV/SMV resection/reconstruction during a pancreatectomy from 2005 to 2014 were identified. Medical records and imaging were retrospectively reviewed for operative details and outcomes, with particular emphasis on patency. RESULTS Ninety patients underwent vein resection/reconstruction with one of five techniques: (i) longitudinal venorrhaphy (LV, n = 17); (ii) transverse venorrhaphy (TV, n = 9); (iii) primary end-to-end (n = 28); (iv) patch venoplasty (PV, n = 17); and (v) interposition graft (IG, n = 19). With a median follow-up of 316 days, thrombosis was observed in 16/90 (18%). The rate of thrombosis varied according to technique. All patients with primary end-to-end or TV remained patent. LV, PV and IG were all associated with significant rates of thrombosis (P = 0.001 versus no thrombosis). Comparing thrombosed to patent, there were no differences with respect to pancreatectomy type, pre-operative knowledge of vein involvement and neoadjuvant therapy. Prophylactic aspirin was used in 69% of the total cohort (66% of patent, 81% of thrombosed) and showed no protective benefit. CONCLUSIONS Primary end-to-end and TV have superior patency than the alternatives after PV/SMV resection and should be the preferred techniques for short (<3 cm) reconstructions.

Bioluminescence and Magnetic Resonance Imaging of Macrophage Homing to Experimental Abdominal Aortic Aneurysms

Macrophage infiltration is a prominent feature of abdominal aortic aneurysm (AAA) progression. We used a combined imaging approach with bioluminescence (BLI) and magnetic resonance imaging (MRI) to study macrophage homing and accumulation in experimental AAA disease. Murine AAAs were created via intra-aortic infusion of porcine pancreatic elastase. Mice were imaged over 14 days after injection of prepared peritoneal macrophages. For BLI, macrophages were from transgenic mice expressing luciferase. For MRI, macrophages were labeled with iron oxide particles. Macrophage accumulation during aneurysm progression was observed by in situ BLI and by in vivo 7T MRI. Mice were sacrificed after imaging for histologic analysis. In situ BLI (n = 32) demonstrated high signal in the AAA by days 7 and 14, which correlated significantly with macrophage number and aortic diameter. In vivo 7T MRI (n = 13) at day 14 demonstrated T2* signal loss in the AAA and not in sham mice. Immunohistochemistry and Prussian blue staining confirmed the presence of injected macrophages in the AAA. BLI and MRI provide complementary approaches to track macrophage homing and accumulation in experimental AAAs. Similar dual imaging strategies may aid the study of AAA biology and the evaluation of novel therapies.