I PREVIOUSLY DISCUSSED managing thrombotic catheter occlusions (I.V. Rounds, January 2009). Here, I'll discuss how to deal with occlusions from precipitate and mechanical obstruction. As always, follow your facility's policies and procedures and obtain a prescriber's order as needed for these interventions. You may also need certain credentials or special training for some procedures.
Cloudy complications
If your patient receives multiple I.V. drugs and fluids, even a multiple-lumen catheter may not have enough lumens to dedicate one to each drug. But infusing two medications through the same line raises the risk of occlusion from drug incompatibility and precipitation in the line.
Precipitation can be caused by contact between two or more incompatible drugs, minerals, or electrolytes. Combinations that commonly lead to precipitation include:
* phenytoin and most other solutions
* vancomycin and heparin
* tobramycin and heparin
* fluorouracil and droperidol
* dobutamine and furosemide
* dobutamine and heparin.
Lipid emulsions can leave a waxy buildup on the catheter wall. This is more common when you infuse a total-nutrient admixture or when you also use the catheter lumen to administer medications.
To dissolve drug precipitate, you need to know the pH of the precipitated drug. Ask the pharmacist for the pH of each drug the patient is receiving. The timing of each drug's administration and when precipitate appears can guide your judgment about which drug has precipitated. Use hydrochloric acid 0.1N to dissolve acidic precipitation and sodium bicarbonate 8.4% to dissolve alkaline precipitation.
The dose for either solution is 1 mL or an amount equal to the catheter lumen volume. Instill the drug slowly and let it remain in the lumen for 60 minutes, then attempt to aspirate the solution and flush the lumen with 0.9% sodium chloride solution.
To clear lipid precipitate, instill 10 mL of sodium hydroxide 0.1N or 70% ethanol over 60 minutes, then lock the catheter lumen for 2 hours. If the catheter is made of polyurethane, first check the catheter manufacturer's instructions for warnings about the use of alcohol solutions.
Mechanical occlusions
Incorrect catheter tip positioning leads to a mechanical occlusion. The tip of a central venous catheter (CVC) should be in the lower third of the superior vena cava, close to its junction with the right atrium. If the catheter tip migrates into a smaller vein or up against a vein wall, it can occlude fluid flow or prevent aspiration.
A catheter inserted in the subclavian vein can be compressed between the clavicle and first rib (pinch-off syndrome). If the catheter isn't removed, this compression can lead to catheter fracture and embolism over time.
Solving a mechanical problem depends on the nature of the problem. If the catheter tip position has changed, an interventional radiologist may reposition the catheter.
Assessing the problem
A careful history of your patient's problem can provide information about the possible cause. The most important aspect of your assessment is the presence of blood return, not the ability to flush or infuse fluids. Ask questions like these:
* Did the problem occur suddenly or gradually? Precipitation or mechanical occlusions may occur abruptly; in contrast, thrombotic problems caused from reflux may develop over time, as discussed in my previous article.
* Does the clinical picture change if you alter the patient's position? This may indicate that the catheter tip is impinging on the vein wall or that pinch-off syndrome is occurring.
* Do you see pockets of edema or generalized edema on the side of insertion? A pocket of edema near the clavicle may indicate a catheter fracture with leakage; generalized edema may indicate alteration in venous blood flow.
* Does the patient complain of any pain, tenderness, or discomfort in the arm, chest, back, or neck? Chest pain may indicate that the catheter is abutting the vein wall; this is more common with left-sided insertions. If the patient hears a running stream or gurgling sound, the catheter tip is most likely pointed upward in the jugular vein.
Preventing problems
You can prevent precipitate occlusion by checking with the pharmacy for the latest information and not infusing drugs together unless their compatibility has been documented. If you can't use separate lumens, make sure to flush adequately (use at least 10 mL of 0.9% sodium chloride solution) between drug infusions.
Mechanical problems can be avoided by the choice of entry site and tip locations made during catheter insertion. For example, pinch-off syndrome can be prevented by inserting a CVC into the internal jugular vein or a peripherally inserted central catheter in the arm. You can reduce the risk of catheter dislodgment by stabilizing the catheter's external portion with a manufactured stabilization device and protecting the site with an adherent dressing. And to reduce the risk of catheter fracture, never inject a treatment agent forcefully into an occluded catheter.
Armed with this knowledge, you're prepared to assess and manage catheter occlusions and to protect your patient from further complications.
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