Treatment of immune-mediated hemolytic anemia with individually adjusted heparin dosing in dogs.
BACKGROUND
A major cause of death in dogs with immune-mediated hemolytic anemia (IMHA) is thromboembolism. Previous studies suggest unfractionated heparin (UH) is not effective in preventing thromboembolism in IMHA; however, subtherapeutic dosing could explain the seeming lack of efficacy.


OBJECTIVE
Providing therapeutic plasma concentration of UH by individually adjusting doses based on antifactor Xa activity would improve survival in IMHA.


METHODS
Fifteen dogs with primary IMHA.


METHODS
Randomized, prospective, controlled clinical trial. Dogs received standardized therapy for IMHA and either constant dose (CD) (150 U/kg SC) (n = 7) or individually adjusted dose (IAD) (n = 8) UH, monitored via an anti-Xa chromogenic assay, adjusted according to a nomogram. UH was administered every 6 hours until day 7, and every 8 hours thereafter. UH dose was adjusted daily in IAD dogs until day 7, weekly until day 28, then tapered over 1 week. Dogs were monitored for 180 days.


RESULTS
At day 180, 7 dogs in the IAD group and 1 in the CD group were alive (P= .01). Median survival time for the IAD group was >180 days, and 68 days for the CD group. Thromboembolic events occurred in 5 dogs in the CD group and 2 dogs in the IAD group. Doses of UH between 150 and 566 U/kg achieved therapeutic anti-Xa activity (0.35-0.7 U/mL).


CONCLUSIONS
This study suggests that IAD UH therapy using anti-Xa monitoring reduced case fatality rate in dogs with IMHA when compared with dogs receiving fixed low dose UH therapy.
Helmond
S E
SE
Section of Small Animal Internal Medicine, Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN, USA.
Polzin
D J
DJ
Armstrong
P J
PJ
Finke
M
M
Smith
S A
SA
D000744:Anemia, Hemolytic, Autoimmune / Q000188:drug therapy / Q000662:veterinary*; D000818:Animals; D000925:Anticoagulants / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*; D004283:Dog Diseases / Q000188:drug therapy*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006493:Heparin / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*; D008297:Male; D016017:Odds Ratio
D000925:Anticoagulants; D006493:Heparin