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SUMMARY

Objective

To determine whether in vitro viability and function, and microbiological sterility, of canine platelet concentrates (PC) could be retained during storage at 20 to 24 C (room temperature [RT]) for up to 7 days and cryopreservation for 6 months.

Animals

14 mature dogs.

Procedure

PC prepared by centrifugation of fresh blood were stored for 7 days at RT with continuous agitation. An aliquot of each was cryopreserved with 6% dimethyl sulfoxide at −74 C for 6 months. Fresh PC (day 0) were tested by microbial culture and measurement of platelet count, mean platelet volume, pH, glucose and lactate concentrations, lactate dehydrogenase activity, response to hypotonic stress, and aggregation. Tests were also performed on PC stored at RT on days 3, 5, and 7, and on the cryopreserved aliquots after thawing.

Results

After 7 days at RT, microbial growth was not evident, and decrease in platelet number was not significant. On the basis of pH and glucose and lactate concentrations, metabolic activity was maintained throughout RT storage. On the basis of mean platelet volume and lactate dehydrogenase activity, platelet swelling and membrane damage had occurred. Aggregatory responses decreased during RT storage, and platelets recovered poorly from hypotonic stress. After cryopreservation for 6 months, microbial growth was not evident, but platelet numbers were significantly decreased. Mean platelet volume and lactate dehydrogenase activity were significantly greater, compared with values for day-0 PC. Crypreserved platelets aggregated poorly and did not respond to hypotonic stress.

Conclusions

Platelet viability and microbiological sterility are retained in canine PC stored for 7 days at RT, but platelet function progressively decreases and day-7 platelets are substantially damaged. Crypreservation of PC results in considerable damage, compared with that of PC stored at RT.

Clinical Relevance

Similar to human PC, canine PC stored at RT for up to 5 days can be recommended for treatment. (Am J Vet Res 1997;58:1338–1347)

Free access
in American Journal of Veterinary Research

SUMMARY

Effects of a single iv administered therapeutic dose of vincristine sulfate on platelet numbers and function were evaluated in 16 clinically normal dogs over the 2 weeks after drug administration. Results were statistically compared with those of a previous control study in which the same 16 dogs were administered saline solution (iv), instead of vincristine. Of the 16 dogs, 8 were orally administered daily immunosuppressive doses of prednisone concurrently throughout the saline-control and vincristine study periods. Platelet numbers and mean platelet volume were measured, using an automated hematology analyzer. Platelet function was evaluated by turbidimetric measurement of platelet aggregation in response to collagen, platelet-activating factor, and adenosine diphosphate (adp), and by clot retraction (diluted whole-blood method) and buccal mucosa bleeding time.

Vincristine had a significant (P < 0.05) effect on circulating platelet numbers. Vincristine induced a transient mild decrease in platelet numbers, followed by a moderate increase in numbers, with peak platelet count observed 8 days after drug administration. Mean platelet volume was not significantly affected by administration of vincristine.

Vincristine had no significant effects on platelet aggregation in response to collagen, low or high doses of platelet-activating factor, and a high dose of adp. The maximal degree of platelet aggregation attained in response to a low dose of adp was not significantly affected by prior administration of vincristine. The maximal rate of platelet aggregation induced by a low dose of adp after vincristine administration, however, was significantly (P < 0.05) lower than the rate of aggregation induced by a similar dose of adp in the previous control study. Vincristine had no significant effects on clot retraction and bleeding time. Prednisone did not significantly affect platelet numbers and function, and did not modify vincristine's effects on the same variables.

Free access
in American Journal of Veterinary Research

Objective

To describe and evaluate hemostatic function in critically ill dogs with clinical signs of diseases that predispose to disseminated intravascular coagulation (DIC).

Design

Prospective case series.

Animals

59 critically ill dogs (affected dogs) with clinical signs of diseases known to predispose to DIC and 52 clinically normal dogs (control dogs).

Procedure

Activated partial thromboplastin time (aPTT), prothrombin time (PT), thrombin clotting time (TCT), plasma fibrinogen concentration, serum concentration of fibrin and fibrinogen-related antigens (FRA), and plasma antithrombin III (AT III) activity were determined for all dogs. Results from affected dogs were compared with those of control dogs. In some affected dogs, postmortem tissue specimens were examined for evidence of microvascular thrombosis. A diagnosis of DIC was made by fulfilling at least 3 of the following criteria: 1) abnormal aPTT, PT, or TCT value, 2) low plasma fibrinogen concentration, 3) low plasma AT III activity, 4) high serum FRA concentration, or 5) low platelet count. To evaluate the severity of hemostatic dysfunction, 3 arbitrary categories (mild, moderate, and severe) were proposed.

Results

A diagnostic strategy based on moderate hemostatic dysfunction identified DIC in 16 of 59 (27.1%) affected dogs. The AT III activity was < 70% in 15 of 16 dogs with DIC. Microvascular thrombosis was observed in tissue specimens from 7 of 8 affected dogs. Serum FRA and plasma fibrinogen concena did not contribute in establishing a diagnosis of DIC.

Conclusions and Clinical Relevance

A diagnosis of DIC can be made when hemostatic dysfunction is moderate in dogs with clinical signs of diseases associated with DIC. (J Am Vet Med Assoc 1999;215:798–804).

Free access
in Journal of the American Veterinary Medical Association

Objective

To evaluate the accuracy of point-of-care tests for the diagnosis of disseminated intravascular coagulation (DIC) in dogs and assess the correlation and agreement of results between point-of-care and laboratory tests in the evaluation of hemostatic function.

Design

Prospective case series.

Animals

59 critically ill dogs (affected dogs) with clinical signs of diseases known to predispose to DIC and 52 clinically normal dogs.

Procedures

Accuracy of the point-of-care tests (activated clotting time [ACT], estimated platelet count and number of schizocytes from a blood smear, plasma total solids [TS] concentration, and the protamine sulfate test) was evaluated, using receiver operating characteristic curves and likelihood ratios. A strategy, using likelihood ratios to calculate a post-test probability of DIC, was tested with 65% used as a threshold for initiation of treatment. Results of laboratory tests (coagulogram and plasma antithrombin III activity) were used as the standard for comparison in each dog.

Results

ACT and estimated platelet count provided the best accuracy for detection of DIC. The plasma TS concentration, schizocyte number, and protamine sulfate test had poor accuracy. The strategy using post-test probability of DIC identified 12 of 16 affected dogs that had DIC. Estimated platelet count was correlated and had acceptable clinical agreement with automated platelet count (r = 0.70). The plasma TS (r = 0.28) concentration and serum albumin (r = 0.63) concentration were not accurate predictors of plasma antithrombin III activity. The ACT did not correlate with activated partial thromboplastin time (r = 0.28).

Conclusions and Clinical Relevance

Strategic use of likelihood ratios from point-of-care tests can assist clinicians in making treatment decisions for dogs suspected to have DIC when immediate laboratory support is unavailable. (J Am Vet Med Assoc 1999;215:805–810)

Free access
in Journal of the American Veterinary Medical Association