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OBJECTIVE: To describe patient characteristics, underlying disease processes, clinical outcomes, transfusion dose and type (therapeutic or prophylactic), platelet count changes, and adverse events associated with platelet concentrate (PC) administration in dogs. DESIGN: Retrospective study. SETTING: University teaching hospital. ANIMALS: A total of 149 dogs, representing 189 PC transfusion episodes. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: In this population, 39 of 149 dogs (26.2%) were diagnosed with primary immune-mediated thrombocytopenia, 22 of 149 (14.8%) had decreased bone marrow production, 12 of 149 (8.0%) received PC during a massive transfusion, 3 of 149 (2.0%) had congenital thrombocytopathia, 59 of 149 (39.6%) had severe thrombocytopenia of other causes, and 14 of 149 (9.4%) underwent transfusion for miscellaneous causes without a documented severe thrombocytopenia. In 117 of 149 dogs (78.5%), >1 site of hemorrhage was noted. The most common sites of hemorrhage were the gastrointestinal (GI) tract in 89 of 149 (59.7%) and the skin in 78 of 149 (52.3%). Overall survival to discharge was 59.1% (88/149). The median PC dose was 0.8 units per 10 kg of body weight per transfusion episode (range: 0.2-6.7). Of 189 episodes, 29 of 189 (15.7%) were prophylactic, and 158 of 189 (83.6%) were therapeutic. For 99 of 189 transfusion episodes, paired pre- and postplatelet counts were available within 24 hours. The median platelet count change was 5.0 × 109 /L (5000/µL; range: -115 × 109 /L to 158 × 109 /L [-115,000 to 158,000/µL]); the posttransfusion platelet count was significantly higher than pretransfusion (P < 0.0001). The increase in platelet count after transfusion was greater in the prophylactic group than the therapeutic group (P = 0.0167). Transfusion reactions were suspected during 2 of 168 episodes (1.2%). CONCLUSIONS: Immune-mediated thrombocytopenia was the most common disease process that resulted in PC transfusion. PC was more frequently administered to animals with active hemorrhage rather than prophylactically, and most dogs had evidence of hemorrhage in multiple organ systems, particularly the GI tract and skin. PC transfusions typically appeared safe, and the median platelet count increased after transfusion.

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BACKGROUND: Thrombocytopenia in dogs is common in critical care medicine, but availability of fresh platelet concentrates in veterinary medicine can be limiting. Lyophilized platelets have long shelf-lives and can be easily transported, stored, and administered in various settings. OBJECTIVE: To evaluate the efficacy and safety of a novel trehalose-stabilized canine lyophilized platelet product in thrombocytopenic dogs with clinically-evident bleeding. ANIMALS: Eighty-eight dogs with platelet counts <50 × 103 /µL and a standardized bleeding assessment tool (DOGiBAT) score ≥2. METHODS: Multicenter, randomized, non-blinded, non-inferiority clinical trial comparing dimethyl sulfoxide (DMSO)-stabilized cryopreserved platelet concentrates (CPP) with trehalose-stabilized lyophilized platelets (LP) for control of bleeding in thrombocytopenic dogs. Dogs were randomized to receive 3 × 109 platelets/kg of LP or CPP. Primary outcome measures were change in DOGiBAT score, platelet count, need for additional red cell transfusion and all-cause mortality. RESULTS: Fifty dogs received LP and 38 received CPP. Baseline demographics and clinical characteristics of both groups were comparable. At 1-hour post-transfusion, LP were superior for change in DOGiBAT score, and non-inferior at 24-hours post-transfusion. The LP were non-inferior to CPP for change in platelet count, need for additional red blood cell units, and survival to discharge. The LP were superior for change in hematocrit at 1-hour post-transfusion, and non-inferior at 24-hours. No adverse effects were noted in either group. CONCLUSIONS AND CLINICAL IMPORTANCE: A novel trehalose-stabilized canine LP product appears to be logistically superior and is clinically non-inferior to DMSO-stabilized canine CPP for management of bleeding in thrombocytopenic dogs.

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BACKGROUND: Physiologic factors in dogs that might contribute to enhanced platelet yield in platelet concentrates (PCs) are largely unknown. OBJECTIVE: To determine whether individual differences in weight, age, preprocessing blood chemistry, and CBC variables predict the final platelet concentrations in PCs. Our hypotheses were (1) increased lipemic indices would be positively associated with increased platelet concentrations in PCs and (2) increased preprocessing platelet concentrations would be associated with higher platelet concentrations in the PCs. ANIMALS: All blood donation records of dogs from February 2, 2009 through April 1, 2015 at the University of California-Davis Veterinary Blood Bank were examined with 104 cases included in this study. METHODS: In this retrospective study, data were collected from medical records of canine blood donors. Records were reviewed for internal consistency and accuracy and subjects were included in the study if donor screening and donation occurred on the same day and a viable PC was obtained. Univariate and multivariable regressions were used to test the impact that each variable had on the final platelet concentration in PCs. RESULTS: Final platelet concentration in PCs was positively associated with the predonation CBC platelet values (P < .001), lipemic index (P = .01), and phosphorous levels (P = .001). Collectively these 3 variables explained 29% of the variance in platelet concentrations in PCs. CONCLUSIONS AND CLINICAL IMPORTANCE: Future prospective studies are required to determine if canine blood donations from dogs with lipemia yield PCs with higher platelet concentrations without negatively affecting other blood components.

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OBJECTIVE: To clinically characterize a group of thrombocytopenic dogs that received cryopreserved platelet concentrate (cPC) transfusion, assess efficacy of cPC treatment in improving patient outcome, and compare treated dogs to a control population of thrombocytopenic dogs that did not receive cPC transfusions. DESIGN: Retrospective study. SETTING: University teaching hospital. ANIMALS: Eighty-six client-owned dogs (43 in treatment group, 43 in control group). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Medical records of thrombocytopenic dogs that received cPC transfusions and those of thrombocytopenic dogs that did not receive cPC (control population) from January 2007 through March 2013 were reviewed. Dogs receiving cPC were statistically more likely than controls to have a platelet trigger for cPC transfusion (P = 0.01), lower platelet count (P = 0.009) and hematocrit at presentation (P = 0.001), and lower hematocrit after cPC (P = 0.02). Although there was a statistically significant increase in platelet count from pre- to post-cPC transfusion (P = 0.002), cPC was not found to be effective in improving clinical bleeding or increasing survival compared to the control group. No other characteristics were statistically different between groups. No dogs receiving cPC had an acute transfusion reaction during hospitalization. CONCLUSIONS: In the population described in this study, cPC was not found to increase survival, but was well tolerated. Controlled, prospective studies are necessary to determine indications for and efficacy of cPC transfusions.

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BACKGROUND: A repeat breeder cow (RBC) can be defined as an animal that after 3 or more inseminations cannot get pregnant because of fertilization failure or early embryonic death. If no cause is identified precisely, inadequate uterine receptivity is responsible for implantation failures. Since a large number of identified molecular mediators, such as cytokines, growth factors and lipids have been postulated to be involved in early feto-maternal interaction, in this study a different approach to the treatment of RBC syndrome has been employed using a platelet concentrate (PC) that contains a significant amount of growth factors accumulated in its α-granules. METHODS: Three explorative studies were performed. Initially, PC was supplemented in the in vitro embryo culture medium to study its effect on embryo-development. After the pilot study, 4 RBCs were treated with intrauterine administration of PC to evaluate proliferative potential of endometrium by immunohistochemical expression of the antigen Ki-67. Lastly, the effect of intrauterine administration of PC at 48 hrs after artificial insemination in RBCs was evaluated. RESULTS: The in vitro results show that 5 % of PC and 5 % of fetal calf serum (FCS) increase the rate of blastocysts compared with the control containing 10 % FCS only (43.04 % vs 35.00 % respectively). The immunohistochemical study shows more proliferating nuclei in the treated uterine horn compared to the control one. After intrauterine insemination in RBCs, the percentage of pregnant cows in the control group was 33.33 % compared to 70 % of the treated animals. CONCLUSION: We suppose that when embryo descends in uterus could find a more appropriate environment for nesting and subsequent pregnancy.

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Three dogs presented with refractory immune-mediated thrombocytopenia (IMT). All patients failed to respond to prednisone, which is considered a mainstay of immunosuppressive therapy. Vincristine-loaded platelets (VLPs), which act selectively on mononuclear phagocytes,were introduced. After the VLPs were transfused, two dogs responded quickly with improved clinical signs while the third dog with recurrent IMT was euthanized due to its deteriorating condition. This case report describes the efficacy of VLP therapy in refractory IMT patients.

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Bovine udder infections induce a variety of changes in gene expression of different growth factors that may suggest their possible role in glandular tissue protection or repair processes. Growth factors and also chemokines and cytokines may act synergistically to increase the infiltration of neutrophils and macrophages to promote angiogenesis, fibroplasia, matrix deposition, and, ultimately, re-epithelialization. Considering the vast applications, typically in human medicine, of platelet concentrate (PC) and its ease of preparation, the aim of our study was to evaluate an alternative therapy to stimulate the regeneration of glandular tissue, administering a concentration in excess of the growth factors contained in the PC. In each one of the 3 farms examined in the trial, PC was prepared from donor cows in good health, free from infections, and with no records of medications administered during the previous 2 mo. The platelet produced in one farm was used only for treating the cows of the same farm in a heterologous way. A total of 229 mastitic quarters were divided in 3 groups: antibiotic group (treated with intramammary antibiotic), antibiotic and PC group (treated intramammarily with antibiotics in association with PC), and PC group (treated with intramammary PC alone). The diagnosis of mastitis was based on somatic cell count and bacteriological evaluation of the milk from the affected quarter. Platelet concentrate, alone or in association with antibiotic, was used for 3 consecutive days as an unconventional therapy in bovine acute and chronic mastitis. Our data show that the associated action of antibiotic and PC performed significantly better than the antibiotic alone, either for the recovery of the affected mammary quarters or for somatic cell count reduction. In the same way, the association antibiotic plus PC showed significantly fewer relapses compared with the antibiotic alone, either for acute or chronic mastitis. The treatment with only PC did not show statistically significant differences compared with both antibiotic alone or associated treatment for acute mastitis, and it was better than the use of only antibiotic for chronic mastitis. Our results show that PC alone may be useful for a quick resolution of the inflammatory response, playing a role in limiting the tissue damage to the mammary gland parenchyma and reducing the recurrence rates.

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OBJECTIVE: To describe a case of spontaneous epistaxis in a cat with type 3 von Willebrand disease (VWD) and detail the successful management of hemorrhagic episodes on 2 occasions. CASE SUMMARY: A 3.6 kg, 1-year-old, female mixed-breed domestic long-haired cat presented for spontaneous epistaxis. Hemostasis testing at presentation revealed normal prothrombin and activated partial thromboplastin times, a slightly decreased platelet count of 168 × 10(9) /L [168 × 10(3) /µL] (reference interval 200-500 × 10(9) /L [200-500 × 10(3) /µL]) and prolonged buccal mucosal bleeding time of 168 seconds (reference interval <150 s). Specific activities of coagulation factors VIII, IX, XI, and XII were all within reference intervals. Plasma von Willebrand factor concentration, however, was markedly reduced at <0.1% of normal. These findings are compatible with a diagnosis of severe type 3 VWD. The initial occurrence of epistaxis resolved spontaneously soon after admission; however, the cat required a packed RBC transfusion for blood loss anemia. Desmopressin acetate was administered, but failed to arrest hemorrhage during a second episode of epistaxis 12 months later. The second episode was successfully controlled by transfusion of 6.7 mL/kg feline fresh frozen plasma. NEW AND UNIQUE INFORMATION: This is the first description of severe type 3 VWD in a domestic cat and only the second report of VWD in this species. Unlike human beings and primates with type 3 VWD, the affected cat did not have a concomitant deficiency of coagulation factor VIII or consistent prolongation of activated partial thromboplastin time. Clinicians should therefore include VWD in the list of differentials for cats with signs of abnormal hemorrhage and confirm the diagnosis with specific measurement of plasma von Willebrand factor concentration.

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OBJECTIVE: To determine efficacy of a single intra-articular injection of an autologous platelet concentrate for treatment of osteoarthritis in dogs. DESIGN: Randomized, controlled, 2-center clinical trial. ANIMALS: 20 client-owned dogs with osteoarthritis involving a single joint. PROCEDURES: Dogs were randomly assigned to a treatment or control group. In all dogs, severity of lameness and pain was scored by owners with the Hudson visual analog scale and the University of Pennsylvania Canine Brief Pain Inventory, respectively, and peak vertical force (PVF) was determined with a force platform. Dogs in the treatment group were then sedated, and a blood sample (55 mL) was obtained. Platelets were recovered by means of a point-of-use filter and injected intra-articularly within 30 minutes. Control dogs were sedated and given an intra-articular injection of saline (0.9% NaCl) solution. Assessments were repeated 12 weeks after injection of platelets or saline solution. RESULTS: Dogs weighed between 18.3 and 63.9 kg (40.3 and 140.6 lb) and ranged from 1.5 to 8 years old. For control dogs, lameness scores, pain scores, and PVF at week 12 were not significantly different from pretreatment values. In contrast, for dogs that received platelet injections, lameness scores (55% decrease in median score), pain scores (53% decrease in median score), and PVF (12% increase in mean PVF) were significantly improved after 12 weeks, compared with pretreatment values. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that a single intra-articular injection of autologous platelets resulted in significant improvements at 12 weeks in dogs with osteoarthritis involving a single joint.

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BACKGROUND: Platelet function defects are rare causes of bleeding diatheses; however, disease prevalence might be underestimated because diagnosis requires assessment of specific parameters of platelet activation. OBJECTIVES: The goal of this study was to characterize the clinical presentation of canine Scott syndrome (CSS), an intrinsic platelet function defect first identified in a closed colony of German Shepherds (GSD). ANIMALS: Eleven (n = 6 female) client-owned GSD affected with CSS that sought veterinary care for one or more episodes of abnormal bleeding. METHODS: Retrospective review of all cases of CSS diagnosed through the Comparative Coagulation Laboratory at Cornell University between 2005 and 2011. The diagnosis of CSS was based on 2 measures of platelet procoagulant activity: serum prothrombin consumption and flow cytometric detection of platelet phosphatidylserine externalization after in vitro activation. RESULTS: Postoperative hemorrhage was the most common sign of CSS, whereas petechiae were not found in any dog. Although most GSD responded to platelet transfusion, refractory epistaxis in 2 GSD was managed by nasal arterial embolization. The CSS trait was not restricted to a single pedigree of related GSD or to a single geographic region. CONCLUSIONS AND CLINICAL IMPORTANCE: Unlike thrombocytopenia and platelet aggregation defects, petechiae and other capillary hemorrhage are not typical features of CSS. After preliminary screening to rule out more common causes of hemorrhage, CSS should be considered in the differential diagnosis of recurrent hemorrhage in GSD, and potentially other breeds of dog. Definitive diagnosis of CSS requires specific tests of platelet procoagulant activity.

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OBJECTIVE: To review current human and veterinary protocols for platelet transfusion triggers, available platelet transfusion products to support veterinary thrombocytopenic patients, and the advantages and disadvantages of each product. DATA SOURCES: Data from human and veterinary literature. HUMAN DATA SYNTHESIS: Prophylactic and therapeutic platelet transfusions are instrumental in managing human patients with thrombocytopenia. The platelet transfusion products used in human medicine consist of platelet concentrates, derived from pooled random donor platelets, or single-donor apheresis platelets. Historically, platelet transfusions in human medicine have been prophylactic in nature; however, recent research suggests changing from a prophylactic transfusion strategy to a therapeutic transfusion strategy may be safe for most patients. The optimal platelet transfusion trigger and the use of prophylactic verses therapeutic platelet transfusions are ever changing in human medicine. VETERINARY DATA SYNTHESIS: There have been many advances in platelet transfusion products, but fresh whole blood remains the most commonly used platelet transfusion product in veterinary medicine. New products such as lyophilized platelets and cryopreserved platelets offer the benefits of long shelf life, immediate availability, and higher concentration of platelets at smaller doses. Veterinary platelet transfusion guidelines are mostly extrapolated from human literature because data on veterinary platelet transfusions are lacking. CONCLUSIONS: In veterinary medicine the most commonly available product for platelet transfusions is fresh whole blood, because of availability of blood donors and lack of a cost effective easily obtainable alternative. Cryopreserved and lyophilized platelets are promising new products being used in the treatment of hemorrhaging patients with thrombocytopenia. These products offer increased platelet concentrations at decreased volumes, longer storage shelf life, and decreased exposure to whole blood products. With the development of newer readily available products, platelet transfusion parameters, to include dose, platelet count trigger, presence of disease, and clinical signs, should be further evaluated in veterinary medicine.

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OBJECTIVE: To examine the safety and feasibility of using lyophilized platelets (LYO) and fresh platelet concentrate (FRESH) in bleeding thrombocytopenic dogs. DESIGN: Preliminary prospective randomized clinical trial. SETTING: Two private referral centers and 3 university teaching hospitals. ANIMALS: Thirty-seven dogs with a complaint of hemorrhage associated with thrombocytopenia (platelet count <70 × 10(9) /L [70,000/µL], a hematocrit >15%, and that had received neither vincristine nor platelet-containing transfusions within 72 h of enrollment were studied. INTERVENTIONS: Animals were randomized to receive LYO or FRESH, dosed according to weight. Physical examination, complete blood counts, and coagulation testing (prothrombin time and activated partial thromboplastin time) were performed at enrollment. Physical examinations were also performed immediately post transfusion, and at 1 and 24 h after transfusion. Complete blood counts were repeated immediately post transfusion and at 24 h. Collected data included bleeding score (BLS), response to transfusion, adverse reactions, hospitalization time, need for additional transfusions, survival to discharge, and 28-d survival. MEASUREMENTS AND MAIN RESULTS: Twenty-two dogs received LYO and 15 received FRESH. There was no difference between groups in age, weight, BLS, platelet count, white blood cell count, hematocrit, or presence of melena. There was no difference between groups in transfusion reaction rates, the need for additional transfusions, 24-h BLS, hospitalization time, survival to discharge, or 28-d survival. CONCLUSIONS: Transfusion of LYO was feasible and associated with a low transfusion reaction rate in this limited study of thrombocytopenic canine patients presenting with mild-to-severe hemorrhage. LYO were easy to use and provided storage advantages over FRESH. Further study of this product, including examination of efficacy and platelet life span, is warranted.

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BACKGROUND: Platelet concentrates (PC) are prepared by centrifugation of platelet-rich plasma (PRP) that is prepared by centrifugation of whole blood. The resuspension of the platelet pellet during PC preparation from dogs is difficult because of platelet activation induced by centrifugation. OBJECTIVES: To investigate the efficacy of adding prostaglandin E(1) (PGE(1) ) to prevent platelet activation during PC preparation from dogs. ANIMALS: Fifteen healthy Beagle dogs. METHODS: Prospective, experimental trial: PGE(1) was added to PRP before the high-speed centrifugation during PC preparation. To estimate the effect of this addition, we assessed the platelet aggregability before transfusion, the survival of the platelets after transfusion, and the platelet reactivity after transfusion, which is estimated by the P-selectin expression of the platelets when stimulated by thrombin. RESULTS: The difficulty associated with platelet resuspension was resolved by PGE(1.) PGE(1) strongly inhibited platelet aggregation induced by collagen and ADP; however, it recovered after the platelets were resuspended in plasma without PGE(1) (mean aggregation ratio; collagen: 10.00-80.80%, ADP: 8.20-53.60%). Survival of the platelets after transfusion was not affected by PGE(1) (mean 8.04 and 7.56 days, without and with PGE(1) ), and thrombin-induced P-selectin expression after transfusion in PGE(1) -treated PC was also well maintained (mean positive ratio 53.7 and 47.9%, before and 24 hours after transfusion). CONCLUSIONS AND CLINICAL IMPORTANCE: The addition of PGE(1) in PRP before the centrifugation of PRP can improve the preparation efficiency of PC from dogs, while maintaining the therapeutic efficacy of the platelets.

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Variant CJD (vCJD) is an incurable, infectious human disease, likely arising from the consumption of BSE-contaminated meat products. Whilst the epidemic appears to be waning, there is much concern that vCJD infection may be perpetuated in humans by the transfusion of contaminated blood products. Since 2004, several cases of transfusion-associated vCJD transmission have been reported and linked to blood collected from pre-clinically affected donors. Using an animal model in which the disease manifested resembles that of humans affected with vCJD, we examined which blood components used in human medicine are likely to pose the greatest risk of transmitting vCJD via transfusion. We collected two full units of blood from BSE-infected donor animals during the pre-clinical phase of infection. Using methods employed by transfusion services we prepared red cell concentrates, plasma and platelets units (including leucoreduced equivalents). Following transfusion, we showed that all components contain sufficient levels of infectivity to cause disease following only a single transfusion and also that leucoreduction did not prevent disease transmission. These data suggest that all blood components are vectors for prion disease transmission, and highlight the importance of multiple control measures to minimise the risk of human to human transmission of vCJD by blood transfusion.

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PURPOSE: Tissue repair in musculoskeletal injuries is often a slow and sometimes incomplete process. Regenerative medicine based on the use of growth factors (GFs) and cell therapy is aimed at improving the quality and speed of tendon and ligament healing. The aim of this study was to evaluate the potential for the administration of a combination of autologous platelet-rich plasma (PRP) and freshly isolated bone marrow mononucleated cells (BMMNCs) in 13 competition horses affected by overuse musculoskeletal injuries (suspensory ligament desmopathy and superficial flexor tendinopathy) and refractory to other therapies. METHODS: After ultrasonographic localisation of the lesion, the autologous BMMNC suspension and PRP were injected directly into the core lesion. BMMNC and platelet count as well as growth factors in PRP were measured to determine factors influencing the clinical outcome. RESULTS: Horses showed a marked improvement in their degree of lameness and 84.6% were able to return to competition. Among all the factors studied, the platelet concentration predicted the healing time: significantly faster recovery (p = 0.049) was observed in cases of PRP with more than 750 × 10(3)/µl platelets. CONCLUSIONS: Competition horses are involved in highly demanding activities, thus being a similar model for the high mechanical overload typical of human athletes. The promising results obtained suggest that this combined biological approach may be useful even for the treatment of recalcitrant overuse musculoskeletal injuries in highly demanding patients if the appropriate dose of cells and GFs is applied.

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OBJECTIVE: To review potential platelet storage options, guidelines for administration of platelets, and adverse events associated with platelet transfusions. DATA SOURCES: Data sources included original research publications and scientific reviews. HUMAN DATA SYNTHESIS: Transfusion of platelet concentrates (PCs) plays a key role in the management of patients with severe thrombocytopenia. Currently PCs are stored at 22 degrees C under continuous gentle agitation for up to 5 days. Chilling of platelets is associated with rapid clearance of transfused platelets, and galactosylation of platelets has proven unsuccessful in prolonging platelet survival. Although approved by the American Association of Blood Banks, cryopreservation of human platelets in 6% DMSO largely remains a research technique. Pre-storage leukoreduction of PCs has reduced but not eliminated acute inflammatory transfusion reactions, with platelet inflammatory mediators contributing to such reactions. VETERINARY DATA SYNTHESIS: Canine plateletpheresis allows collection of a concentrate with a high platelet yield, typically 3-4.5 x 10(11) versus <1 x 10(11) for whole blood-derived platelets, improving the ability to provide sufficient platelets to meet the recipient's transfusion needs. Cryopreservation of canine platelets in 6% DMSO offers immediate availability of platelets, with an acceptable posttransfusion in vivo platelet recovery and half-life of 50% and 2 days, respectively. While data on administration of rehydrated lyophilized platelets in bleeding animal models are encouraging, due to a short lifespan (min) posttransfusion, their use will be limited to control of active bleeding, without a sustained increase in platelet count. CONCLUSIONS: Fresh PC remains the product of choice for control of bleeding due to severe thrombocytopenia or thrombopathia. While cryopreservation and lyophilization of canine platelets offer the benefits of immediate availability and long-term storage, the compromise is decreased in vivo recovery and survival of platelets and some degree of impaired function, though such products could still be life saving.

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BACKGROUND: Platelet cryopreservation allows long-term storage and immediate availability of transfusion products. HYPOTHESIS: The addition of a preparation inhibiting platelet activation (Thrombosol, in 2% dimethyl sulfoxide [DMSO]) will enhance in vitro function and prolong in vivo survival of cryopreserved platelets compared with those preserved in 6% DMSO. ANIMALS: Thirty-three research dogs. METHODS: Prospective study. Eleven fresh canine apheresis platelet concentrates (PCs) were each split into 3 units: fresh and cryopreserved in 6% DMSO or Thrombosol. Platelet analysis, performed 1-10 weeks postfreezing, included in vitro functional testing and in vivo survival assessed by administration of biotinylated platelets. RESULTS: Platelet aggregation was diminished in cryopreserved PC. Cryopreserved platelets could be activated, as based on mean thrombin-stimulated P-selectin expression (6% DMSO, 23.0%; Thrombosol, 18.4%), although to a lesser extent than fresh PC (49.1%) (P < .0001). The mean maximum in vivo platelet recovery for fresh PC was 80.3%, significantly greater than recovery for 6% DMSO (49.2%) and Thrombosol PC (43.7%) (P< or = .001). The half-life (days) of fresh PC (3.8 +/- 0.4) was significantly (P < .002) greater than that of 6% DMSO (1.9 +/- 1.0) and Thrombosol (2.4 +/- 1.1) PC, with no difference (P= .3) between cryopreserved PC. CONCLUSIONS AND CLINICAL IMPORTANCE: Cryopreservation of canine platelets using Thrombosol did not provide any advantage over preservation using 6% DMSO. Cryopreserved platelets can be activated in vitro and provide therapeutic benefit when fresh platelets are unavailable. Further studies are needed to assess their in vivo hemostatic function.

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Ovariectomy was performed in a 7-month-old Great Pyrenees with a severe congenital bleeding disorder. A diagnosis of Glanzmann thrombasthenia, a rare, congenital bleeding disorder characterized by a functional platelet defect, was later confirmed by isolation of genomic DNA from blood and amplification of exon 13 and intron 13 of the gene encoding for platelet glycoprotein subunit alphaIIb. Perioperative management consisted of administration of platelet-rich plasma prior to surgery and the use of high-frequency electrocoagulation to minimize tissue trauma. In addition, ovariectomy, rather than ovariohysterectomy, was performed to minimize surgical exposure required and manipulation of the urogenital tract. Results in this dog suggest that a combination of preoperative transfusion with functional platelets and use of techniques to minimize tissue trauma may allow abdominal surgery to be performed successfully in dogs with functional platelet disorders.

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Prophylactic platelet transfusions are frequently given to human patients with hypoproliferative thrombocytopenia. For several decades, the most common transfusion trigger was 20,000/microL, but the trend is now to use 10,000/microL in the absence of other risk factors for bleeding. This trigger seems to reduce the number of transfusions without increasing the risk of severe bleeding. Most studies involved in establishing platelet transfusion policies have involved patients with acute leukemia, with fewer studies involving patients undergoing hematopoietic stem cell transplantation or aggressive chemotherapy for other cancers and patients with aplastic anemia. In the presence of other risk factors for spontaneous bleeding, 20,000/microL is still considered an appropriate trigger. The trigger for prophylactic transfusion before surgery has not undergone the same recent scrutiny as has the trigger for spontaneous bleeding. The recommendation remains to raise the platelet count to 50,000 to 100,000/microL if possible, although it is recognized that surgery and other invasive procedures have been performed at lower platelet counts without major bleeding. Prophylactic transfusion is not used in disorders of platelet consumption and destruction to prevent spontaneous bleeding but is used before surgery. Because of the comparative lack of experience with platelet transfusion in veterinary medicine, it is difficult to make generalizations for dogs and cats. Using the guidelines established for therapeutic and prophylactic transfusion of human patients is a reasonable starting point, however. A therapeutic transfusion policy is suggested in the veterinary setting provided that the patient can be closely observed for critical bleeding and a prompt transfusion can be given. This policy should ultimately reduce the overall number of platelet transfusions given to hospital patients. If an animal cannot be closely observed or the ability to transfuse on demand is limited, prophylactic transfusion is recommended. The triggers for initiating a platelet transfusion in dogs are extrapolated from human data; these values are lower by 50% for cats. Because of the imprecision of platelet counting at low values, platelet counts must always be interpreted in conjunction with clinical signs of hemorrhage. If platelet-rich plasma or platelet concentrate is available, a dose of 1 platelet unit per 10 kg is recommended, although resources may dictate a smaller dose. This will raise the recipient platelet count by a maximum of about 40,000/microL. Assuming a trigger of 10,000/microL, a transfusion will probably be required approximately every 3 days. It must be remembered that the frequency of platelet transfusions may be greater in the presence of factors accelerating platelet loss or destruction. If fresh whole blood is used, a rule of thumb is to transfuse 10 mL/kg, which will raise the recipient platelet count by a maximum of approximately 10,000/microL. Daily transfusions or transfusions every other day will probably be required.

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