Effect of fondaparinux, enoxaparin, or heparin on the time to PU catheter occlusion in rabbits. Rabbits (n = 5 per group) were given saline or 70 anti-Xa U/kg fondaparinux, enoxaparin, or heparin intravenously before insertion of a PU catheter into their jugular veins. Thereafter, every 5 minutes, 2 mL of blood was withdrawn from the catheter, held for 2 minutes in a syringe, and slowly re-injected. Catheter occlusion occurred when blood could no longer be withdrawn, and the pressure measured with a transducer exceeded 15 mm Hg. The bars represent the mean and the lines above the bars reflect the SD. Asterisks denote P < .05 compared with the saline control.