An algorithmic approach to the occluded indwelling central venous catheter is summarized in Figure 51-1.9,14 The key principle is that forced irrigation of the catheter, especially with a 1 mL syringe, is never performed as the catheter may rupture.
A catheter that flushes easily but cannot be aspirated may have a fibrin sheath around the catheter tip forming a one-way valve. The tip may also be lodged against the wall of the superior vena cava or the right atrium. Repositioning the patient may alleviate the problem. The catheter may be cautiously used for an infusion if there are no signs of infection (e.g., new heart murmur, fever, erythema, or discharge at the catheter or subcutaneous reservoir site) and the catheter tip is in good position. Refer the patient to their Primary Care Provider or a consultant for follow-up of the malfunction.
The problem is more serious if the catheter does not easily flush. Attempt to obtain peripheral intravenous access while attempting to correct the problem with the central venous catheter. If there are no signs of infection, and the catheter is not ruptured or malpositioned, the Emergency Physician must decide if a prolonged effort at resolving the occlusion is necessary. If so, proceed as described below and in Figure 51-1.
Partially Implanted Catheters
A clot or small amount of precipitate within the partially implanted catheter may be able to be aspirated if the catheter bore is large enough to permit passage. Remove the Luer-lock cap from the catheter. Connect a 10 mL syringe with 2 to 3 mL of sterile saline directly to the occluded port's Luer adapter. Any clot large enough to occlude the catheter will not pass through a needle. Apply negative pressure to the syringe. The catheter is probably occluded by a clot or a precipitate if the obstruction cannot be aspirated. Remove the syringe and attach a new Luer-lock cap.
If a precipitate is seen in the catheter aspirate, determine if it is waxy or solid. Waxy precipitates are due to the lipid component of parenteral nutrition fluids. Waxy precipitates may be dissolved with a solution of 70% ethanol in water. Inject 1 to 2 mL of this alcohol–water solution and allow it to dwell in the catheter for 1 hour. Aspirate the catheter to determine patency. If still occluded, inject 1 to 2 mL of 0.1 N hydrochloric acid solution. Allow the solution to dwell in the catheter for 20 minutes. Aspirate the catheter to determine patency. Attempt to infuse 0.1 N hydrochloric acid solution two more times. The next step is to infuse a thrombolytic agent, as described below, or to replace the catheter.
Solid precipitates are due to precipitation of medications or minerals. Dilute 0.1 hydrochloric acid solution may be used to dissolve precipitated calcium and phosphate crystals. Infuse 1 to 2 mL of 0.1 N HCl and allow it to dwell in the catheter 20 minutes. Aspirate the catheter to determine patency. The process may be repeated up to three times. If still occluded, inject 1 to 2 mL of 70% ethanol in water and allow it to dwell in the catheter for 1 hour. Aspirate the catheter to determine patency. The next step is to inject a thrombolytic agent, as described below, or to replace the catheter.
If no precipitate is present, or if efforts to clear the precipitate fail, a clot may be present within the catheter lumen. Clots probably form to some extent in the majority of implanted central venous catheters. The clots may obstruct the catheter lumen.13 Thrombosis of the central veins, superior vena cava, or right atrium may also occur. Suspect a major vein thrombosis if there is swelling, pain, or edema of anatomic structures that are drained by the cannulated vein(s).
Small clots may be dissolved by a bolus or infusion of a thrombolytic agent. Inject 1 mL of urokinase (5000 U/mL), 2 mL of t-PA (1 mg/mL), or 0.4 units of Reteplase into the catheter. Allow the solution to dwell in the catheter for 30 minutes. Aspirate the catheter to determine patency. This process may be repeated up to three times. For catheters with multiple occluded ports, the medication dosing should remain the same but divided into equal doses between the ports. If still occluded, inject 2 mL of intravenous contrast dye under fluoroscopy or inject the dye and obtain a radiograph. If no clot is present or if the contrast material will not infuse, attempt to clear the catheter with hydrochloric acid solution (up to three times) and 70% ethanol in water.
If a clot is present within the catheter, a continuous thrombolytic infusion may be considered. The infusion should occur through an intravenous line equipped with a 0.22 micron or 0.45 micron filter. A urokinase infusion may be begun over a 24-hour period. Administer the urokinase at a dose of 200 U/kg-hr mixed to run at a rate of at least 20 mL/h.8,9 A continuous t-PA infusion may also be started. Use 2 mg/20 mL as a low dose for ports, 4 mg/20 mL as a high dose for ports, or 5 mg/50 mL as a high dose for tunneled catheters. Set the t-PA infusion rate at 10 mL/h for low and high doses for ports or 20 mL/h for high dose tunneled catheters. Thrombolytic infusions should be undertaken in consultation with the patient's Primary Care Provider as the patient will require hospital admission.
Consider consulting an Interventional Radiologist if these methods do not successfully clear the catheter or if a thrombolytic infusion is contraindicated. They can perform percutaneous fibrin sheath stripping, exchange over a wire, or removal and replacement of the malfunctioning catheter. Alternatively, the Emergency Physician may place a new central venous catheter at another site if the patient requires immediate vascular access.
Fully Implanted Catheters
The procedure is the same for a fully implanted central venous access device with one exception. The subcutaneous reservoir will not be able to be initially cleared by aspiration. Any clot or precipitates large enough to occlude a catheter will not pass through a noncoring (Huber) needle. Always use a noncoring (Huber) needle when aspirating or injecting through a fully implanted catheter.