Mechanism and management of persistent withdrawal occlusion.

An unresolved complication of the use of totally implantable central venous access ports (e.g., Mediport, Infusa-port) is persistent withdrawal occlusion (PWO), i.e. the unimpeded capacity for infusion of fluids accompanied by the inability to withdraw blood. This study demonstrates the mechanism of persistent withdrawal occlusion and describes a method for resolving this complication. Of 42 cancer patients with totally implantable central venous access ports, 8 (19%) patients developed 11 episodes of PWO. Venograms demonstrated a sheath around the catheter beginning at the catheter entrance to the central vein and extending 1-5 cm beyond the catheter tip. Each episode of PWO was treated with 250,000 units of urokinase dissolved in 150cc D5/W infused through the port over 90 minutes. Venograms were obtained immediately after each urokinase infusion. Follow-up ranged from 13-130 days. After urokinase infusion the venogram showed no change in the sheath in 1 episode of PWO and complete dissolution of the sheath in 10 episodes of PWO. PWO recurred once in one patient and twice in another patient. PWO resolved only in the 10 episodes in which sheath dissolution was demonstrated. Urokinase infusion, as described, is effective in resolving persistent withdrawal occlusion. The method is repeatable and safe. That resolution of PWO by urokinase infusion was accompanied by dissolution of the sheath suggests that the sheath is composed primarily of fibrin and that flap action of the sheath is the mechanism causing PWO.