No NO means yes to sickle red cell adhesion.

In fact, patients with these conditions are particularly prone to developing refractoriness to platelet transfusions, and treatment of bleeding in this situation represents a major clinical problem. The data presented by Colucci et al provide a rationale for hoping that DDAVP can be effective in these emergencies as well as in preparation of patients for surgery or invasive procedures. Much work is needed before recommending DDAVP in platelet disorders. From a pharmacologic point of view, it would be desirable to have more direct evidence that this drug improves in vivo hemostatic effectiveness of platelets. As pointed out by Colucci et al, 1 the mechanisms of this effect of DDAVP remain undetermined. Most importantly, clinical trials are essential not only to measure the clinical effectiveness of DDAVP administration, but also to evaluate its risk-benefit ratio since the use of any molecule that potentiates hemostasis cannot be without the risk of thrombosis. DDAVP does not seem to represent an exception to the rule, since cases of myocardial infarction have been reported in patients receiving this drug. 10 It may be that the story of DDAVP in platelet disorders is starting again. Conflict-of-interest disclosure: The authors declare no competing financial interests. n REFERENCES 1. Colucci G, Stutz M, Rochat S, et al. The effect of desmopressin on platelet function: a selective enhancement of procoagulant COAT-platelets in patients with primary platelet function defects. 1-Deamino-8-d-arginine vasopressin: a new pharmacological approach to the management of haemophilia and von Willebrands' diseases. Pilot study on the safety and efficacy of desmopressin for the treatment or prevention of bleeding in patients with hematologic malignancies. antagonizes the in vitro platelet dysfunction induced by GPIIb/ IIIa inhibitors and aspirin. A new variant of Bernard-Soulier syndrome characterized by dysfunctional glycoprotein (GP) Ib and severely reduced amounts of GPIX and GPV. Society for Haemostasis and Thrombosis. Management of bleeding and of invasive procedures in patients with platelet disorders and/or thrombocytopenia: Guidelines of the Italian Society for Haemostasis and Thrombosis (SISET). Stimulated platelets use serotonin to enhance their retention of procoagulant proteins on the cell surface. In this issue of Blood, Gutsaeva and colleagues demonstrate the role of nitric oxide (NO) to suppress and hypoxia to promote adhesion of sickle erythrocytes to blood vessels in the bone marrow of mice, visualized by intravital microscopy. 1 When platelets encounter a damaged vessel wall, they immediately recognize and adhere to exposed collagen and other subendothelium proteins. …