The unstirred, ferroin (Fe(phen)3(2+)) catalyzed Belousov-Zhabotinsky (BZ) reaction is the prototype oscillatory chemical system. Reaction media with added Br(-) appear red (reduced, low [Fe(phen)3(3+)]) during an induction period of several minutes, followed by the "spontaneous" formation of "pacemaker" sites, which oscillate between a blue, oxidized state (high [Fe(phen)3(3+)]) and the red, reduced state and generate target patterns of concentric, outwardly moving waves of oxidation (blue). Auto-oscillatory behavior is also seen in the Oregonator model of Field, Koros and Noyes (FKN), a robust, reduced model that captures qualitative BZ kinetics in the auto-oscillatory regime. However, the Oregonator model predicts a blue (oxidized) induction phase. Here we develop a generalized Oregonator-like model with no explicit bifurcation parameter that yields the observed transition from a red initial state to oscillatory dynamics, and displays a new bifurcation mechanism not seen in the original Oregonator.

Objectives Acute lower extremity ischemia is one of the most common emergencies in vascular surgery and is a cause of considerable morbidity and mortality. The goal of this study was to evaluate outcomes of revascularization for acute lower extremity ischemia and to determine factors associated with perioperative morbidity and mortality. Methods A total of 354 patients underwent urgent revascularization for acute lower extremity ischemia at an academic medical center between 2014 and 2019. A retrospective review of patients’ demographics, comorbidities, etiology and severity of limb ischemia, and procedural characteristics was recorded. Outcomes, including postoperative complications, perioperative limb loss, and mortality, were analyzed. Results The mean patient age was 69 ± 17 years, and 52% were females. 50% of patients presented with Rutherford Class IIb ischemia. Arterial embolization was the most common cause of limb ischemia, seen in 33% of cases. Open surgical revascularization was performed in 241 (68%) patients, while endovascular and hybrid approaches were utilized in 53 (15%) and 60 (17%) cases, respectively. Postoperative adverse events occurred in 44% of patients, including wound complications (11%), cardiac (5%) and pulmonary (16%) complications, strokes (4%), UTIs (10%), renal failure (14%), bleeding (5%), and compartment syndrome (3%). The rate of unplanned return to the operating room was 21%. Major adverse cardiovascular events were seen in 103 (29%) patients and major adverse limb events were seen in 57 (16%) patients. The median length of stay was 10 days (IQR = 4); 49% patients were discharged to skilled nursing facility and 19% were readmitted within 30 days. The rate of amputation during index admission was 10%, and perioperative mortality was 20%. Gender, tibial runoff, and etiology of limb ischemia were independent predictors of limb loss. Women had lower risk of limb loss than men (OR, 0.11; 95% CI, 0.023, 0.38). Poor tibial runoff (one-vessel or absence of flow below the knee) was a significant predictor of limb loss as compared to three-vessel runoff (OR, 14.92; 95% CI, 1.92, 115.88). Aneurysmal disease (OR, 38.35; 95% CI, 3.54, 42.45) and traumatic injuries (OR, 108.08; 95% CI, 8.21, 159.06) were the strongest predictors of amputation as compared to other etiologies of limb ischemia. Multivariate model identified ESRD (OR, 9.2; 95% CI, 1.8–46.3), degree of ischemia (class IIb or higher vs class IIa; OR, 3.5; 95% CI, 1.2–10.6), and age (OR, 1.5; 95% CI 1.1–2.0 for every 10 years) as independent predictors of perioperative mortality. Conclusions Urgent revascularization for management of acute limb ischemia is associated with high morbidity and mortality. Elderly patients with ESRD presenting with severely threatened limbs have especially high risk of perioperative mortality and may not be ideal candidates for limb salvage.

Background: An estimated 33% reduction in cardiovascular events can be achieved when incorporating whole grains, fruits, vegetables, poultry, nuts, and vegetable oils in the diet along with reduced consumption of refined carbohydrates, processed meats, and sugar sweetened beverages. We performed a systematic review to analyze the impact of nutritional intervention on stroke risk, as there is no current consensus concerning dietary recommendation for primary and secondary stroke prevention. Methods: A literature search of the PubMed database from January 2010 to June 2020 was performed using combinations of the following search terms: carotid disease, carotid artery disease, carotid stenosis, carotid intima-media thickness (CIMT), diet, nutrition, micronutrition, embolic stroke, and stroke. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2009 checklist. Results: 28 studies met our inclusion criteria. Multiple studies showed an inverse relationship between consumption of vegetables and fruits and stroke risk. Vitamin B12 or a combination of B Vitamins was the most common supplement studied in stroke prevention. Only one RCT showed the use of B12 (500 micrograms/day) correlated with lower CIMT at follow up in healthy vegetarians. Discussion: The key findings from this systematic review indicate that adopting a diet rich in fruits and vegetables earlier in life may lower stroke risk compared with meats and fat intake. B vitamins also appear to confer some protection against stroke. However, not enough data exists to support the use of multivitamins, calcium, soy products and other supplements for primary or secondary stroke prevention.

Aortoenteric fistulas are an uncommon cause of gastrointestinal bleeding, and iliac-appendiceal fistulas are an even rarer cause. We describe a case of an iliac-appendiceal fistula in a patient who presented several months after aortic reconstruction with gastrointestinal bleeding. An extensive workup revealed that the source of bleeding was localized to the appendiceal orifice. The patient underwent an appendectomy with a two-stage procedure involving the iliac graft for definitive repair and ultimately recovered well. Despite the rarity of aortoenteric and iliac-appendiceal fistulas causing gastrointestinal bleeding, keeping a high index of suspicion in patients with a prior vascular repair can prevent death.