Effect of low-dose heparin alone or in conjunction with fondaparinux on the time to PU catheter occlusion in rabbits. Rabbits (n = 5 per group) were given an intravenous bolus of saline, 70 anti-Xa U/kg fondaparinux, 15 anti-Xa U/kg heparin, or the combination of 70 anti-Xa U/kg fondaparinux plus 15 anti-Xa U/kg heparin before insertion of a PU catheter into their jugular veins. The time to catheter occlusion was then determined as described in the caption to Figure 6. The bars represent the mean and the lines above the bars reflect the SD. Asterisk denotes P < .05 compared with the saline control.