von Willebrand disease

von Willebrand factor (vWF) helps platelets attach at vessel injury. A prolonged buccal mucosal bleeding time with a normal platelet count supports a function defect. It does not diagnose vWD, and a normal result cannot rule it out. Measure vWF antigen with ELISA. Below 50% of the control pool is deficient in the source; it is not a surgical-bleeding cutoff.

Type 1 has all multimer sizes, but less vWF. Below 20%, spontaneous bleeding may occur; surgery or trauma can reveal milder disease. Type 2 loses larger multimers; electrophoresis helps distinguish it from type 1. Type 3 has almost no vWF and may cause life-threatening bleeding in the first year. My note says <0.01%; the book says <0.1%. These are source descriptors, not one universal cutoff.

Desmopressin is a vasopressin analogue. Its V2 action releases endothelial vWF stores and may help type 1. The note/book cues are onset around 30 minutes and effect around 2 hours; the disease section describes peak response at 1–2 hours. Repeated doses work less as stores run down. Canine responses vary. The note/book also lists factor VIII and plasminogen release. Human work documents t-PA release, not proof of canine plasminogen release. The original note says “subendothelial stores.” The source describes endothelial vWF stores.

Cryoprecipitate supplies vWF, factor VIII and fibrinogen. It can support bleeding or procedural risk in severe type 1 and types 2/3. Fresh frozen plasma (FFP) separates into cryoprecipitate and cryosupernatant; the latter is not a substitute for vWF replacement. The source describes a vWF rise within 30 minutes lasting 4 hours. That is a study cue, not guaranteed bleed control. Match support to the dog and procedure; monitor the response.

References

Johnston/Tobias, 2nd ed., Chapter 7; Cornell Coagulation; Kraus 1989; Giger 1989; Ching 1994; Stokol 1998; Callan 2005; Wall 1998 (human t-PA).