Evaluation of platelet function in dogs with cardiac disease using the PFA‐100 platelet function analyzer

Background: Cardiac disease has the potential to alter platelet function in dogs. Evaluation of platelet function using the PFA‐100 analyzer in dogs of multiple breeds and with a broad range of cardiac conditions would help clarify the effect of cardiac disease on platelets. Objectives: The objective of this study was to assess differences in closure time (CT) in dogs with cardiac disease associated with murmurs, when compared with that of healthy dogs. Methods: Thirty‐nine dogs with cardiac murmurs and turbulent blood flow as determined echocardiographically were included in the study. The dogs represented 23 different breeds. Dogs with murmurs were further divided into those with atrioventricular valvular insufficiency (n=23) and subaortic stenosis (n=9). Fifty‐eight clinically healthy dogs were used as controls. CTs were determined in duplicate on a PFA‐100 analyzer using collagen/ADP cartridges. Results: Compared with CTs in the control group (mean±SD, 57.6±5.9 seconds; median, 56.5 seconds; reference interval, 48.0–77.0 seconds), dogs with valvular insufficiency (mean±SD, 81.9±26.3 seconds; median, 78.0 seconds; range, 52.5–187 seconds), subaortic stenosis (71.4±16.5 seconds; median, 66.0 seconds; range, 51.5–95.0 seconds), and all dogs with murmurs combined (79.6±24.1 seconds; median, 74.0 seconds; range, 48.0–187 seconds) had significantly prolonged CTs (P<.01). Conclusions: The PFA‐100 analyzer is useful in detecting platelet function defects in dogs with cardiac murmurs, most notably those caused by mitral and/or tricuspid valvular insufficiency or subaortic stenosis. The form of turbulent blood flow does not appear to be an important factor in platelet hypofunction in these forms of cardiac disease.     

Multiple organ dysfunction syndrome in humans and dogs

Objective: To describe the clinical appearance and theories on the pathogenesis of multiple organ dysfunction syndrome (MODS) in humans, and to review the evidence suggesting that a similar syndrome occurs in critically ill dogs. Human‐based studies: Currently, there are a multitude of publications describing the pathogenesis and clinical course of MODS in humans. Providing much of the basis for on‐going research and the development of clinical applications, a consensus statement made by the American College of Chest Physicians and Society of Critical Care Medicine defined parameters that had guided and shaped much of what is known about MODS. Veterinary‐based studies: To date, there are few publications describing MODS in dogs and much of what is known has been derived from case reports and reviews of various critical illnesses in dogs. While a similar syndrome of multiple organ dysfunction likely exists in dogs, a consensus statement defining clinical parameters has not been made. Data sources: Veterinary and human literature review. Conclusions: The development of MODS in human critical illness is widely recognized and major strides have been made in the understanding of this complex syndrome. Scoring schemes applied to human MODS patients have established that with increasing numbers of failing organs, there is a worse prognosis. As a similar finding likely exists in dogs, an awareness of MODS is vital to veterinary critical care clinicians and a consensus definition of MODS in dogs is warranted.     

Evaluation of platelet function screening tests to detect platelet procoagulant deficiency in dogs with Scott syndrome

Background: Clinical diagnosis of platelet dysfunction is complex and technically challenging. The wide repertoire of platelet responses requires a test panel to assess different parameters of platelet reactivity. While “global” hemostasis analyzers and whole blood assays have potential for testing platelet function, their ability to evaluate platelet procoagulant activity is ill‐defined. Objectives: The aim of this study was to determine whether platelet procoagulant deficiency, the pathophysiologic defect of Scott syndrome, could be detected in point‐of‐care and whole blood assays. Methods: Study subjects were 4 Scott syndrome‐affected German Shepherds and 8 control dogs. We evaluated 2 point‐of‐care instruments: the platelet function analyzer (PFA‐100) and thromboelastograph (TEG). TEG analysis was performed on recalcified citrated whole blood with and without tissue‐factor activation. A whole blood flow cytometric assay was configured to detect thrombin‐induced platelet P‐selectin expression and platelet‐derived microparticle release. Cytometric samples were analyzed after 1 hour and 1 day of storage. Results: We found no significant differences between Scott and control dogs in PFA‐100 COL/ADP closure times or in any TEG parameter in tissue‐factor–activated samples. In nonactivated samples, mean clotting time (K) and time to maximal rate of thrombus generation were significantly prolonged in Scott dogs; however, values overlapped with those of control dogs. Cytometric analysis of samples from Scott dogs showed significantly diminished platelet‐derived microparticle release. Samples from all dogs reanalyzed after 1 day of storage had nonspecific increases in basal P‐selectin expression and vesiculation. Conclusion: A whole blood cytometric assay to detect stimulated platelet microparticle release can be used to screen for Scott syndrome. However, platelet activation artifacts preclude overnight storage for next‐day analysis.     

Evaluation of platelet additive solution for prolonging storage of functional canine platelet concentrate

Objective

To assess storage lesion development, platelet function, and bacterial growth in canine platelet concentrates (PCs) stored in a platelet additive solution (PAS) or a plasma control at 4°C for 21 days.

Design

Prospective, ex vivo, experimental controlled study.

Setting

University veterinary teaching hospital.

Animals

Ten units of canine PCs collected from blood bank donations.

Interventions

The PCs were separated into 2 bags, 1 containing 100% plasma and the other containing 35% plasma and 65% of a PAS (Plasma-Lyte A), and stored at 4°C for 21 days. At days 0, 7, 14, and 21, PCs were analyzed for the presence of swirling, aggregate formation, platelet counts, platelet indices, glucose, lactate, lactate dehydrogenase, Pvco ₂, Pvo ₂, aggregation via light aggregometry, activation percentages using flow cytometry, and bacterial growth.

Measurements and main results

Cold-stored PCs in both PAS and plasma control maintained mean pH >6.8 and mean lactate <9.0 mmol/L over 21 days, with no difference in glucose utilization. Swirl was maintained in both solutions for most days (76/80 combined total samples), with no difference in aggregate formation between solutions. The Pvco ₂ was higher in plasma on all days (P < 0.001), with no difference in Pvo ₂. Platelet indices did not reflect significant storage lesion development in either solution. Lactate dehydrogenase did not differ between solutions but did increase from day 7 to day 21. Mean maximal aggregation percentage was reduced overall but with no significant difference between solutions. The only observed difference in mean activation percentage between solutions was in PAS on day 7, which was significantly higher than plasma (P < 0.05). No bacterial growth occurred during storage.

Conclusions

Cold storage in PAS and plasma allowed PCs to be stored for up to 21 days with minimal storage lesion development, maintenance of platelet function, limited platelet activation, and no bacterial growth within stored bags.     

Uveitis associated with septic peritonitis in a cat

Objective – To report a case of bilateral uveitis believed to be a consequence of septic peritonitis in a 19‐month‐old cat. Case Summary – Bilateral anterior uveitis with suspicion of extension to the posterior segment was documented in a previously healthy young cat during hospitalization for severe septic peritonitis. Based on medical history and other findings uveitis was believed to result from concurrent abdominal sepsis, due either to metastatic seeding of bacterial organisms or to effects of bacterial toxins and inflammatory mediators on the blood‐aqueous barrier. The cat was surgically and medically managed, and made a full recovery with respect to both his ocular and his abdominal disease. New or Unique Information Provided – Ocular complications secondary to systemic sepsis are well documented in people but seldom reported in the veterinary literature. To the authors' knowledge this is the first report of uveitis linked to septic peritonitis in any veterinary species and the first to report sepsis‐related uveitis in a cat. Ocular inflammatory disease in the context of critical illness deserves attention as a potential significant source of morbidity. The development of ocular inflammatory disease may serve as a sentinel lesion for systemic sepsis and other life‐threatening conditions.