In vivo assessment of dual-function submicron textured nitric oxide releasing catheters in a 7-day rabbit model.

Catheter-induced thrombosis is a major contributor to infectious and mechanical complications of biomaterials that lead to device failure. Herein, a dualfunction submicron textured nitric oxide (NO)-releasing catheter was developed. The hemocompatibility and antithrombotic activity of vascular catheters were evaluated in both 20 h in vitro blood loop and 7 d in vivo rabbit model. Surface characterization assessments via atomic force microscopy show the durability of the submicron pattern after incorporation of NO donor S-nitroso-N-acetylpenicillamine (SNAP). The SNAP-doped catheters exhibited prolonged and controlled NO release mimicking the levels released by endothelium. Fabricated catheters showed cytocompatibility when evaluated against BJ human fibroblast cell lines. After 20h in vitro evaluation of catheters in a blood loop, textured-NO catheters exhibited a 13-times reduction in surface thrombus formation compared to the control catheters, which had 83% of the total area covered by clots. After the 7 d in vivo rabbit model, analysis on the catheter surface was examined via scanning electron microscopy, where significant reduction of platelet adhesion, fibrin mesh, and thrombi can be observed on the NO-releasing textured surfaces. Moreover, compared to relative controls, a 63% reduction in the degree of thrombus formation within the jugular vein was observed. Decreased levels of fibrotic tissue decomposition on the jugular vein and reduced platelet adhesion and thrombus formation on the texture of the NO-releasing catheter surface are indications of mitigated foreign body response. This study demonstrated a biocompatible and robust dual-functioning textured NO PU catheter in limiting fouling-induced complications for longer-term blood-contacting device applications. STATEMENT OF SIGNIFICANCE: Catheter-induced thrombosis is a major contributor to infectious and mechanical complications of biomaterials that lead to device failure. This study demonstrated a robust, biocompatible, dual-functioning textured nitric oxide (NO) polyurethane catheter in limiting fouling-induced complications for longer-term blood-contacting device applications. The fabricated catheters exhibited prolonged and controlled NO release that mimics endothelium levels. After the 7 d in vivo model, a significant reduction in platelet adhesion, fibrin mesh, and thrombi was observed on the NO-releasing textured catheters, along with decreased levels of fibrotic tissue decomposition on the jugular vein. Results illustrate that NO-textured catheter surface mitigates foreign body response.

Assessment of Acute Kidney Injury and Renal Fibrosis after Renal Ischemia Protocols in Cats.

In an attempt to identify a feline model of acute or chronic kidney disease, this study was designed to evaluate the effects of 15 or 30 min of bilateral renal ischemia (RI) and 60 min of unilateral RI with delayed contralateral nephrectomy as models of acute kidney injury and chronic interstitial fibrosis in cats. Adult, purpose-bred, USDA Class A cats (n = 14) were randomly assigned to receive bilateral RI for 15 min (n = 3) or 30 min (n = 3), unilateral RI for 60 min with a delayed (2 wk) contralateral nephrectomy (n = 5), or sham unilateral RI with a delayed contralateral nephrectomy (n = 3). Serum creatinine concentration, urine specific gravity, and plasma clearance of iohexol were assessed at several time points throughout the study. Renal interstitial inflammatory cell counts and descriptive histopathology were acquired in all cats. Histomorphometry was used to quantify renal interstitial fibrosis and collagen at 120 d after RI in cats undergoing unilateral RI. Renal histopathology was evaluated at 21 and 120 d after bilateral and unilateral RI, respectively. Neither duration of bilateral RI resulted in appreciable histologic renal damage at 21 d after ischemia. At 120 d after ischemia, variable amounts of renal fibrosis were noted after 60 min of unilateral RI with delayed contralateral nephrectomy. Neither of the tested methods is a suitable model of consistent renal interstitial fibrosis in cats. Healthy cats appear able to sustain bilateral RI for as long as 30 min with no apparent effects on renal morphology or function at 21 d after ischemia.

FOCUSED ASSESSMENT WITH SONOGRAPHY AS AN AID FOR THE DIAGNOSIS OF GASTROINTESTINAL PERFORATION IN A BOBCAT ( FELIS RUFUS ).

A 10-yr-old female spayed bobcat (Felis rufus) presented with a 3-day history of lethargy, anorexia, and two episodes of vomiting. An emergency field visit was scheduled to perform abdominal radiography and ultrasonography. The bobcat was assessed to be approximately 5-10% dehydrated, on the basis of decreased skin turgor and tacky mucous membranes. Free peritoneal gas, reduced abdominal serosal detail, and an abnormal-appearing right-sided intestinal segment were identified in the abdominal radiographs. However, the emergency field clinicians were not knowledgeable of these abnormalities, because the radiographs could not be processed in the field. During an initial complete abdominal ultrasound evaluation, a nondependent hyperechoic interface with reverberation artifact suggestive of intestinal or free gas and focal intestinal changes indicative of marked enteritis or peritonitis were identified. Free peritoneal fluid was not present on initial examination. In a focused abdominal sonography for trauma (FAST) scan, made after subcutaneous fluid administration, a small volume of anechoic free fluid was present in the peritoneal space. With ultrasound guidance, the fluid was aspirated and appeared grossly turbid. This fluid was subsequently confirmed as septic suppurative effusion, secondary to a foreign body-associated intestinal perforation. The use of a FAST scan is well described in human medicine, and to a limited degree in veterinary literature. This case represents a novel application of FAST scanning in an emergency field setting in a nontraumatized patient. This case report illustrates the utility of the FAST scan in yielding critical clinical information after fluid resuscitation in a zoological setting.

Learning confounds algometric assessment of mechanical thresholds in normal dogs.

OBJECTIVE: To perform algometric readings in normal dogs in a design that would assess possible confounding factors. STUDY DESIGN: Prospective study. ANIMALS: Skeletally mature spayed female, intact male and castrated male retriever or retriever mix dogs without orthopedic or neurologic disease (n = 19). METHODS: Twelve common surgical sites were selected for algometric pressure testing. Threshold response was defined as a conscious recognition of the stimulus, and recorded in Newtons. Sites were tested in the same order, and the testing sequence repeated 3 times on each side of the dog. Dogs were tested in the morning and evening of the same day and was repeated 10-14 days later, allowing 4 separate data collections for each dog. RESULTS: Data were analyzed using ANOVA or ANCOVA. When all the data were included in the analysis, dog (P < .0001), order (P < .0001), site (P < .0001), site order (P = .0217), time (P < .0001), day (P < .0001) and repetition (P < .0001) all significantly affected the algometer readings. When only the first reading for each site was included in the analysis, dog (P < .0001), site (P < .0001) and sex (P < .0001) all significantly affected algometer readings. CONCLUSION: These results suggest that learning occurred over repeated collection time points, with dogs anticipating the stimulus and reacting at lower thresholds.

Assessment of plasma uracil-to-dihydrouracil concentration ratio as an indicator of dihydropyrimidine dehydrogenase activity in clinically normal dogs and dogs with neoplasia or renal insufficiency.

OBJECTIVE: To determine and compare the ratio of uracil (U) to dihydrouracil (UH(2)) concentrations in plasma as an indicator of dihydropyrimidine dehydrogenase activity in clinically normal dogs and dogs with neoplasia or renal insufficiency. ANIMALS: 101 client- and shelter-owned dogs. PROCEDURES: Study dogs included 74 clinically normal dogs, 17 dogs with neoplasia, and 10 dogs with renal insufficiency. For each dog, a blood sample was collected into an EDTA-containing tube; plasma U and UH(2) concentrations were determined via UV high-performance liquid chromatography, and the U:UH(2) concentration ratio was calculated. Data were compared among dogs grouped on the basis of sex, clinical group assignment, reproductive status (sexually intact, spayed, or castrated), and age. RESULTS: Mean ± SEM U:UH(2) concentration ratio for all dogs was 1.55 ± 0.08 (median, 1.38; range, 0.4 to 7.14). In 14 (13.9%) dogs, the U:UH(2) concentration ratio was considered abnormal (ie, > 2). Overall, mean ratio for sexually intact dogs was significantly higher than that for neutered dogs; a similar difference was apparent among males but not females. Dogs with ratios > 2 and dogs with ratios ≤ 2 did not differ significantly with regard to sex, clinical group, reproductive status, or age. CONCLUSIONS AND CLINICAL RELEVANCE: Determination of the U:UH(2) concentration ratio was easy to perform. Ratios were variable among dogs, possibly suggesting differences in dihydropyrimidine dehydrogenase activity. However, studies correlating U:UH(2) concentration ratio and fluoropyrimidine antimetabolite drug tolerability are required to further evaluate the test's validity and its appropriate use in dogs.