Cold-stored platelets show promise for bleeding in thrombocytopenic dogs

Refrigerated platelet concentrates stored for up to 21 days were associated with decreased bleeding severity in thrombocytopenic dogs, according to a retrospective study from Washington State University (WSU) College of Veterinary Medicine published in the Journal of Veterinary Internal Medicine.¹ According to WSU, the findings represent the first clinical evidence that cold-stored platelets can be used effectively in dogs.²

Platelet transfusion can be lifesaving for dogs with severe thrombocytopenia and hemorrhage, but it remains underused in veterinary medicine. Conventional canine platelet concentrate is stored at room temperature under constant agitation, which limits shelf life to approximately 5 days and raises the risk of bacterial proliferation.¹

“It is hard to overstate how important the ability to transfuse platelets is,” said Jillian Haines, DVM, MS, DACVIM (SAIM), director of the WSU Veterinary Teaching Hospital’s blood bank, who led the research. “Many of us have seen patients die from bleeding complications because there was simply nothing we could offer them. We went from having essentially nothing available to now having a really viable product that we can use.”²

Study design

Researchers reviewed medical records of 24 thrombocytopenic dogs that received 27 cold-stored platelet transfusions at the WSU Veterinary Teaching Hospital between March 2022 and October 2024.¹ Platelet concentrates were prepared from 450-mL whole blood donations by double centrifugation and stored at 4°C without agitation for up to 21 days. Mean storage time before transfusion was 12.4 days.

Immune-mediated thrombocytopenia was the most common primary disease (n = 9), followed by neoplasia (n = 7). Transfusions were given to support minimally invasive procedures (n = 12), to treat spontaneous bleeding (n = 9), and to support surgery (n = 6).¹ The team scored hemorrhage severity before transfusion and at 1 and 4 hours afterward using a modified Daily Canine Bleeding Assessment Tool (DOGiBAT) that added a category for cavitary bleeding.

Key findings

Clinical improvement occurred within 4 hours in 19 of 27 transfusion events (70%), and partial improvement occurred in 7 (26%).¹ Mean modified DOGiBAT scores fell from 3.15 at baseline to 2.21 at 4 hours (P = .002), although the change at 1 hour was not significant.

Platelet counts did not rise significantly after transfusion (median, 17 × 10³/μL before vs 23.5 × 10³/μL after; P = .84). The authors said this was expected, because cold-stored platelets circulate briefly but retain, and may enhance, clot-forming function.¹

No transfusion reactions were documented. Nineteen of 24 dogs (79%) survived to discharge, and nonsurvivors had significantly higher bleeding scores at baseline and at 4 hours. Three dogs developed delayed bleeding 12 to 24 hours after a procedure, suggesting some patients may need repeat dosing.¹

Practical advantages for blood banks

Beyond the longer shelf life, Haines said cold-stored platelets are less susceptible to bacterial growth, do not need constant agitation, and can be shipped easily.² The storage method requires only minor changes to existing blood-processing procedures, according to WSU.

The WSU blood bank now routinely keeps a supply of cold-stored platelets on hand, and Haines has trained veterinarians and blood bank personnel from other institutions on the technique.²

However, authors cautioned that the retrospective design limited control over transfusion timing and concurrent treatment, and that causation cannot be established.¹ Nine dogs also received other blood products, the modified DOGiBAT has not been validated, and there was no room temperature comparison group.

Haines plans to investigate optimal dosing, develop better ways to measure effectiveness in individual patients, and evaluate whether the products remain effective beyond 3 weeks of storage.²

“It’s not needed often,” Haines said, “but when it is needed, it is the only option. These products can be lifesaving.”²

References

1. Monaco SA, Haines JM, Guess SC, Fiedler SM, Wardrop KJ. The use of cold-stored platelets to provide hemostasis in dogs with thrombocytopenia. J Vet Intern Med. 2026;40(5):aalag262. doi:10.1093/jvimsj/aalag262
2. WSU research could save dogs facing life-threatening bleeding. News release. Washington State University. November 3, 2026. Accessed November 3, 2026. https://www.eurekalert.org/news-releases/1150131