Inhaled nitric oxide does not influence bleeding time or platelet function in healthy volunteers.

Abstract

Bleeding time has been reported to increase during gaseous nitric oxide (NO) inhalation in healthy volunteers and patients, and it has been speculated that inhaled NO inhibits platelet function. However, results have not been unanimous, and we have been unable to document any effects of inhaled NO on circulating platelets. We performed a double-blind, placebo controlled cross-over study in which healthy volunteers (n = 15) inhaled NO (30 ppm, 30 min) or control gas. Aspirin (640 mg x 1 orally) was used as positive control on the third occasion (n = 14). Bleeding time was measured, and platelet function was determined flow cytometrically by measuring the expression of P-selectin on circulating platelets and locally activated platelets in wound blood. Skin perfusion close to the site for bleeding time incisions was assessed by laser Doppler flowmetry. Bleeding time was unaffected by NO, as there were slight increases during both NO and control inhalation (+20% and +14% respectively, P = 0.9). Similarly, NO inhalation had no effect on platelet P-selectin expression in either systemic or wound blood, or on skin perfusion. Aspirin pretreatment, on the other hand, prolonged bleeding time (P < 0.001) and decreased P-selectin expression of platelets in wound blood (P = 0.03). This first placebo-controlled study indicates that inhaled NO does not influence either bleeding time, platelet activity or skin perfusion. Thus, it is unlikely that treatment of critically ill patients with inhaled NO will aggravate haemostatic disturbances, which has previously been feared, by influencing platelet function.