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Managing occlusion in central venous catheters

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VOL: 97, ISSUE: 21, PAGE NO: 36

Liz Simcock, BA, RGN, is clinical nurse specialist for central venous access, Meyerstein Institute of Oncology, Middlesex Hospital, UCLH, London

We have already seen in previous articles that if a central venous catheter (CVC) is functioning properly, it will allow free-flowing infusion of fluids by gravity and withdrawal (or flashback) of blood. The patient will not experience any discomfort during the infusion of fluids or any other complications such as leakage of fluid around the exit site. But what happens if the catheter fails to perform perfectly? How will you know what to do and if it is safe to use?

Blockage (occlusion) is the most common non-infectious complication of CVCs (Krzywda, 1999) and there are many potential causes (Table 1). Sometimes, a catheter may become completely blocked, so that the line cannot be flushed at all. More commonly, the catheter is only partially occluded: gravity infusion of fluids may be absent, sluggish or intermittent; or the catheter may function normally but blood cannot be withdrawn.

Clearly, if the catheter is completely blocked you will be forced to take action either to clear the line or to replace it with a new one. However, with partial occlusion, it is all too tempting to ignore the problem, especially if you are in a hurry. It is very important not to do this, because you may be storing up problems for the future. There are, of course, emergency situations where administering urgent drugs/fluids is more important than worrying about whether the catheter is fully functional. The nurse should always return to the problem at a later time, however, and ensure that steps are taken to restore full patency. This article will help you decide what to do if a catheter becomes occluded, and when it is safe to use a CVC.

If the patient experiences discomfort during infusion or flushing: The line should not be used (except in an emergency), unless it has been shown to be correctly placed and free of complications. This line must be investigated using angiography. Sometimes patients experience a slightly cold sensation in the vein or in the skin tunnel when fluids are infused into a CVC, simply because infusion fluids are usually cooler than body temperature. This is perfectly normal and no action is needed.

If there is leakage of blood or fluids from the exit site or any other abnormal phenomena relating to the line: The line should not be used (except in an emergency) unless it has been shown to be correctly placed and free of complications. This line needs to be investigated using angiography.

If the line or lumen is completely blocked: After checking there is no external occlusion, such as a kinked line, a bra-strap or an over-tight suture, ask the patient to cough, breathe deeply, change position, stand up, or lie with the foot of the bed tipped up, while you attempt to flush using normal saline in a 10ml syringe. Do not be tempted to use excessive force or to use a syringe smaller than 10ml to unblock the line as you may rupture the catheter. (Take great care that the syringe does not become detached from the line during this procedure.)

If this fails, connect a three-way tap without extension tubing to the end of the catheter. Attach a 10ml syringe containing 5000u Urokinase (in 2ml 0.9% saline) to one stopcock and an empty syringe (plunger fully depressed) to the other. Urokinase is not licensed in the UK but can be used strictly on a named patient basis. Anti-thrombolytics such as this are commonly used in UK hospitals.

Turn the stopcock so it is open to both the empty syringe and the catheter. Withdraw the plunger of the empty syringe to create a vacuum within the line. While maintaining suction, close the stopcock to the empty syringe and open it to the syringe containing Urokinase, which will be sucked into the catheter. Leave for 60 minutes.

After this time, attempt withdrawal of blood. If this is not possible, attempt to flush the line using 0.9% saline in a 10ml syringe. This is a very small dose of Urokinase and in most cases can be flushed into the patient without danger. If the patient has abnormal clotting, the nurse should discuss this with the prescribing doctor before proceeding.

Do not use excessive force. If the catheter is still completely occluded, repeat the procedure several times. This technique often works and is documented in various papers (Krzywda, 1999).

If the technique still fails, consider the possibility that the blockage may be the result of drug precipitation or a build up of lipids from total parenteral nutrition (Hadaway, 1998). If you think this could be the explanation, it may be worth asking your hospital pharmacist to suggest a suitable agent to dissolve the occlusion. If all attempts fail, the line should be removed.

If free-flow is sluggish or absent even though line can be flushed using a syringe: This is a very serious malfunction. The absence of free-flow of fluids under gravity suggests that the catheter may be wrongly positioned, or kinked, or that a fibrin sheath (Box 1) or a thrombus within the line may be forming. Ignoring this may lead to catheter fracture, drugs being instilled into body cavities rather than into the venous system, or a further build-up of fibrin, leading to complete blockage or other complications.

(Note that in situations where uncontrolled infusion of unknown volumes of fluid is not acceptable, for example, paediatric care, it may not be possible to assess for free-flow. In these cases you should be aware that any resistance to flushing may indicate that partial occlusion is occurring.)

The action taken depends on the setting. In an emergency where drugs/fluids need to be administered urgently, it may be acceptable to use this line. However, in a routine situation, further investigation is vital: the consequences of failing to do so may be significant (especially if irritant drugs or cytotoxic chemotherapy is to be administered).

First, check there is no external occlusion such as a kinked line, a bra-strap or an over-tight suture. Try flushing the catheter with 10ml 0.9% saline. If the fluids still refuse to free-flow, then instil Urokinase into the catheter and leave for 60 minutes. If this fails, repeat the Urokinase instillation but this time leave it in the line for several hours or overnight. Mayo (1998) states that this is effective in some cases and my own experience bears this out. If this fails to restore free-flow, then the line should be investigated by means of chest X-ray and/or angiography.

If free-flow is intermittent: If free-flow (or resistance to flushing) stops and starts in a predictable manner when the patient raises and lowers his/her arm, this is strongly suggestive of ‘pinch-off’ and the line should be investigated as soon as possible (see Box 2).

If pinch-off is not suspected, then attempt to clear the line with Urokinase as before. If there are time pressures (for example, the patient is due to receive treatment and there is not enough time to wait for the urokinase to work), then it is suggested that it is safe to use the catheter for boluses or infusions lasting less than 15 minutes as long as all the following criteria are met:

- It is possible to obtain continuous free-flow for the period of time needed to administer drugs with the patient in a comfortable position;

- Flashback of blood can be established;

- There are no other complications or pain.

After the treatment is finished, try to clear the line using Urokinase at the earliest opportunity. If this fails, X-ray and/or angiography is needed to investigate the line.

If there is free-flow but no blood return: Free-flow but no blood return is a relatively common occurrence: some CVCs fail to allow blood return due to the catheter tip being positioned against a vessel wall.

But in a situation where flashback fails in a catheter that previously bled back well, an attempt to restore full patency is desirable both to allow blood sampling and to reduce the chances of allowing fibrin and platelets to build up.

In the meantime, the catheter is probably safe to use, although when giving irritant drugs or fluids, it is reassuring to test the safety of a CVC which does not bleed in adults by rapid administration of 250ml 0.9% saline over 15 minutes.

This technique is used successfully in our oncology unit and was agreed by the multidisciplinary team rather than being based on any particular evidence or research.

If the patient experiences any discomfort at all related to the infusion, or if there are any other unexplained and abnormal phenomena during the infusion, then it should be stopped immediately and medical advice sought.

An angiogram should be carried out, and the line should not be used for irritant drugs or fluids or chemotherapy until it can be shown to be correctly placed and free of complications.

If the patient experiences no discomfort related to the infusion and there are no other complications, then the nurse may proceed with treatment.

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