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- Author or Editor: Reinhard Mischke x
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Objective—To optimize methods used to measure coagulation factor activities in canine plasma, define reference ranges in dogs, and compare activities between canine and human plasma.
Sample Population—Human plasma samples (n = 5) and plasma from healthy dogs (140) and dogs with low factor V activity (7), high factor V activity (7), and low factor VIII:C activity (6).
Procedure—Coagulometric tests incorporated human plasma deficient in a single coagulation factor (human deficient plasma). Standard curves were generated with pooled plasma from 100 healthy dogs. Effect of sample dilution was evaluated, using plasma from dogs with high or low factor V activity and low factor VIII:C activity. Reference ranges for healthy dogs were established. Activities in human plasma were determined by comparison with standard curves obtained with canine plasma.
Results—Activities of factors V and VIII:C in samples diluted ≤ 1:20 influenced results of tests for other coagulation factors. Activities of factors V and VIII:C in human plasma were significantly less than in canine plasma. For the other coagulation factors, significant differences in human plasma-to-canine plasma activity ratios were detected among different sample dilutions.
Conclusion and Clinical Relevance—Accurate measurement of coagulation factor activities in canine plasma, using human deficient plasma, requires higher sample dilutions (ie, > 1:20) than typically used for human plasma. Differences in activities between human and canine plasma and nonparallelism of the standard curves emphasize the necessity for use of species-specific standard curves for accurate determination of coagulation factor activity. (Am J Vet Res 2001;62:625–629)
Objective—To determine effects of SC administration of repeated doses of a low molecular weight heparin (LMWH) in dogs.
Animals—5 healthy dogs.
Procedure—Each dog received 6 injections (each injection, 150 U of anti-factor-Xa [anti-FXa]/kg of body weight, SC) at 8-hour intervals. Blood samples were collected before and 2 hours after the first, second, third, and sixth injections to measure heparin activity, thrombin time, activated partial thromboplastin time (APTT), antithrombin activity, Hct, and platelet count.
Results—Heparin activity varied between 0.36 ± 0.10 and 0.77 ± 0.08 U of anti-FXa/ml (before and 2 hours after the third injection) and between 0.46 ± 0.11 and 0.82 ± 0.15 U of anti-FXa/ml (before and 2 hours after the sixth injection). Thrombin time and APTT were influenced only slightly. Platelet count, Hct, and antithrombin activity started to decrease significantly 2 hours after the second LMWH injection. Because of the increased consumption of antithrombin, antithrombin activity continuously decreased from 102.1 ± 6.3% before the study to 91.0 ± 3.0% at the end of the study.
Conclusion and Clinical Relevance—Heparin plasma activity was only slightly higher than that recommended for LMWH treatment of humans, and none of the dogs had signs of increased bleeding. Thus, administration of heparin in accordance with this dosing regimen can be recommended for use in clinical studies. The screening tests investigated were not suitable for use in monitoring LMWH treatment of dogs. Assays that use chromogenic substrates are necessary to reliably monitor LMWH plasma concentrations in dogs. (Am J Vet Res 2001;62:595–598)
Objective—To evaluate SC administration of unfractionated heparin (UFH) in accordance with a dosing regimen for high-dose treatment in dogs.
Animals—10 healthy adult Beagles.
Procedures—Two groups of dogs (5 dogs/group) were given 6 injections of heparin (500 units of UFH/kg of body weight, SC) at intervals of 8 (experiment 1) and 12 (experiment 2) hours. Blood samples were collected before and 4 hours after heparin injections to determine amidolytic heparin activity, activated partial thromboplastin time (APTT), thrombin time, antithrombin activity, platelet count, and Hct.
Results—For experiments 1 and 2, mean ± SD heparin activities before (experiment 1, 1.32 ± 0.20 U/ml; experiment 2, 0.69 ± 0.174 U/ml) and 4 hours after the last heparin injection (experiment 1, 1.71 ± 0.30 U/ml; experiment 2, 1.10 ± 0.30 U/ml) were higher than values calculated for the regimen used in experiment 1. Results of the investigated thrombin time test system with low thrombin activity were frequently beyond the measurement range, even with UFH activities ≥ 0.6 U/ml. Moreover, a severe decrease of antithrombin activity became evident during both experiments (eg, in experiment 2 from 95.6 ± 4.8 to 59.2 ± 6.6%). In each treatment group, 2 dogs developed hematomas.
Conclusions and Clinical Relevance—Calculations of the course of heparin activity after a single injection do not result in a reliable dosing regimen for highdose heparin treatment in dogs. High-dose treatment must be monitored for each dog. Thrombin time measured with low thrombin activity is unsuitable for this purpose. (Am J Vet Res 2001;62:1887–1891)
OBJECTIVE To determine a treatment protocol for SC administration of dalteparin to cats on the basis of currently available detailed pharmacokinetic data and to assess the effect of SC administration of dalteparin to cats on coagulation variables such as activated partial thromboplastin time (aPTT), thrombin time, and results for thromboelastometry, compared with effects on anti–activated coagulation factor X (anti-Xa) activity.
ANIMALS 6 healthy domestic shorthair cats.
PROCEDURES Cats received 14 injections of dalteparin (75 anti-Xa U/kg, SC) at 6-hour intervals. Blood samples were collected before and 2 hours after the first and second injections on days 1, 2, and 4. Anti-Xa activity was measured by use of a chromogenic substrate assay, aPTT and thrombin time were measured by use of an automated coagulometer, and viscoelastic measurements were obtained with thromboelastrometry.
RESULTS 2 hours after the second injection, the target peak anti-Xa activity range of 0.5 to 1.0 U/mL was achieved in all cats, whereas median trough values remained below this range. Peak anti-Xa activity had only minimal effects on coagulation variables; the maximum median ratio for aPTT (in relationship to the value before the first dalteparin injection) was 1.23.
CONCLUSIONS AND CLINICAL RELEVANCE Results of this study indicated that this treatment protocol resulted in reproducible anti-Xa activity in cats that was mostly within the targeted peak range of anti-Xa activity recommended for humans. Treatment in accordance with this protocol may not require routine coagulation monitoring of cats, but this must be confirmed in feline patients.
Objective—To evaluate platelet-neutrophil aggregate (PNA) formation and neutrophil shape as indicators of neutrophil activation in dogs with systemic inflammatory diseases and after blood sample incubation with various platelet and neutrophil agonists.
Animals—20 dogs with systemic inflammatory response syndrome (SIRS) and 10 healthy Beagles.
Procedures—Neutrophils were isolated from blood samples directly after blood sample collection and after incubation of blood samples with phorbol myristate acetate, collagen, adenosine diphosphate, epinephrine, or various concentrations of lipopolysaccharide or arachidonic acid. CD61+ neutrophils as an indicator of PNA formation were evaluated, and neutrophil size and granularity were assessed via flow cytometry.
Results—Dogs with SIRS had more PNA formation, larger neutrophil size, and less granularity relative to control dogs, but no differences were evident when these dogs were grouped by whether they had sepsis (n = 6) or disseminated intravascular coagulation (12). A significant increase in PNA formation occurred after neutrophil incubation with all agonists, and incubation with phorbol myristate acetate elicited the strongest response. Neutrophils increased in size and decreased in granularity after incubation with all agonists except epinephrine. Incubation with lipopolysaccharide or arachidonic acid resulted in a dose-dependent effect on PNA formation and neutrophil shape.
Conclusions and Clinical Relevance—SIRS appeared to increase the degree of PNA formation and neutrophil shape change. Similar changes after neutrophil incubation with platelet agonists suggested that platelet activation has a role in PNA formation. Additional studies are necessary to determine the clinical importance and diagnostic value of PNA formation in dogs with SIRS and sepsis.
Objective—To characterize underlying diseases and clinical and clinicopathologic variables of thrombocytopenic dogs with and without platelet-bound antibodies (PBAs) and to evaluate clinicopathologic variables of dogs with primary immune-mediated thrombocytopenia (IMT).
Design—Retrospective case series.
Animals—83 thrombocytopenic dogs.
Procedures—Medical records were reviewed to identify dogs in which PBA tests were performed between 2004 and 2006; PBAs were measured via flow cytometry.
Results—PBAs were detected in 37 of 83 (45%) dogs. Thirteen dogs were suspected of having primary IMT. Median platelet counts were significantly lower in dogs with PBAs, compared with counts in dogs without PBAs. Dogs suspected of having primary IMT had significantly lower median platelet counts, compared with counts for those with secondary IMT. Mean platelet volume (MPV) was increased (> 14.3 fL) significantly more often in dogs without PBAs (19/33 [58%]) than in dogs with PBAs (7/26 [27%]). No dogs suspected of having primary IMT had an increase in MPV. Examination of bone marrow aspirates revealed an increase in megakaryopoiesis in a higher percentage of dogs with PBAs (14/21 [67%]) than in dogs without PBAs (7/18 [39%]). An increase in megakaryopoiesis was detected in all dogs suspected of having primary IMT that had a bone marrow analysis.
Conclusions and Clinical Relevance—Platelet counts, results of bone marrow analysis, and MPV may be helpful in dogs for the differentiation between primary IMT and thrombocytopenia resulting from other diseases. An MPV within or less than the reference range did not rule out an increase in megakaryopoietic activity.
Objective—To determine whether the extent of disease in dogs with lymphoma can be assessed via flow cytometry and to evaluate the suitability of fine-needle aspirates from the liver and spleen of dogs for flow cytometric examination.
Animals—44 dogs with multicentric B-cell (n = 35) or T-cell lymphoma (9) and 5 healthy control dogs.
Procedures—Peripheral blood and bone marrow samples and fine-needle aspirates of lymph node, liver, and spleen were examined via flow cytometry. Logarithmically transformed T-cell–to–B-cell percentage ratio (log[T:B]) values were calculated. Thresholds defined by use of log(T:B) values of samples from control dogs were used to determine extranodal lymphoma involvement in lymphoma-affected dogs; results were compared with cytologic findings.
Results—12 of 245 (5%) samples (9 liver, 1 spleen, and 2 bone marrow) had insufficient cellularity for flow cytometric evaluation. Mean log(T:B) values of samples from dogs with B-cell lymphoma were significantly lower than those of samples from the same site in dogs with T-cell lymphoma and in control dogs. In dogs with T-cell lymphoma, the log(T:B) of lymph node, bone marrow, and spleen samples was significantly higher than in control dogs. Of 165 samples assessed for extranodal lymphoma involvement, 116 (70%) tested positive via flow cytometric analysis; results agreed with cytologic findings in 133 of 161 (83%) samples evaluated via both methods.
Conclusions and Clinical Relevance—Results suggested that flow cytometry may aid in detection of extranodal lymphoma involvement in dogs, but further research is needed. Most fine-needle aspirates of liver and spleen were suitable for flow cytometric evaluation.