The Indwelling Vascular Catheter

This chapter describes the routine care and adverse consequences of indwelling vascular catheters, with emphasis on central venous catheters.

I. Routine Catheter Care

The recommendations for routine catheter care are summarized in Table 2.1.

A. Catheter Site Dressing

Catheter insertion sites should be covered with a sterile dressing for the life of the catheter. This can be a covering of sterile gauze pads, or an adhesive, transparent plastic membrane (called occlusive dressings).
The transparent membrane in occlusive dressings is semipermeable, and allows the loss of water vapor, but not liquid secretions, from the underlying skin. This prevents excessive drying of the underlying skin to promote wound healing.
Occlusive dressings are favored because the transparent membrane allows daily inspection of the catheter insertion site. Sterile gauze dressings are preferred when the catheter insertion site is difficult to keep dry (1).
Sterile gauze dressings and occlusive dressings are roughly equivalent in their ability to limit catheter colonization and infection (1,2). However, occlusive dressings can promote colonization when moisture accumulates under the sealed dressing (2), so occlusive dressings should be changed when fluid accumulates under the transparent membrane.

Table 2.1 Recommendations for Routine Catheter Care

	Recommendations
Sterile Dressings	Adhesive transparent dressings are favored because they allow inspection of the catheter insertion site. Sterile gauze dressings are used for skin areas that are difficult to keep dry. Adhesive transparent dressings and sterile gauze dressings provide equivalent protection against catheter colonization.
Antimicrobial Gels	Do not apply antimicrobial gels to catheter insertion sites, except for hemodialysis catheters.
Replacing Catheters	Regular replacement of central venous catheters is not recommended.
Flushing Catheters	Avoid using heparin in catheter flush solutions.
From the clinical practice guidelines in Reference 1.

B. Antimicrobial Gels

The application of antimicrobial gels to the catheter insertion site does not reduce the incidence of catheter-related infections (1), with the possible exception of hemodialysis catheters (3). As a result, topical antimicrobial gels are
recommended only for hemodialysis catheters (1), and should be applied after each dialysis.

C. Flushing Catheters

Vascular catheters are flushed at regular intervals to prevent thrombotic occlusion.
The traditional flush solution is heparinized saline (10–1000 units/mL), but avoiding heparin flushes is advised because of the risk of heparin-induced thrombo-cytopenia (see Chapter 12).
Saline alone is as effective as heparinized saline for flushing venous catheters (4), but this is not the case for arterial catheters (5): in the latter case, 1.4% sodium citrate is a suitable alternative for maintaining catheter patency (6).

D. Replacing Catheters

Replacing central venous catheters at regular intervals (using either guidewire exchange or a new venipuncture site) does not reduce the incidence of catheter-related infections (7), and can actually promote complications (both mechanical and infectious) (8). As a result, routine replacement of central venous catheters is not recommended (1). This also applies to peripherally-inserted central catheters (PICCs), hemodialysis catheters, and pulmonary artery catheters (1).
Replacing central venous catheters is not necessary when there is erythema around the catheter insertion site, since erythema alone is not evidence of infection (9).
Purulent drainage from the catheter insertion site is an absolute indication for catheter replacement, using a new venipuncture site for the replacement catheter.

II. Noninfectious Complications

A. Occluded Catheters

Occlusion of central venous catheters can be the result of thrombosis or insoluble precipitates from the infusates. Advancing a guidewire to dislodge an obstructing mass is not advised because of the risk of embolization. Instead, chemical dissolution of the obstructing mass (described next) is the preferred intervention.

1. Thrombotic Occlusion

Thrombosis (from backwash of blood into the catheter) is the most common cause of catheter obstruction (10), and instillation of the thrombolytic agent alteplase (recombinant tissue plasminogen activator) can restore patency in 80–90% of occluded catheters (11,12). Cathflo Activase™ (Genentech, Inc.) is a popular alteplase preparation for occluded catheters (12).

2. Non-Thrombotic Occlusion

Occlusion from insoluble precipitates can be the result of water-insoluble drugs (e.g., diazepam, digoxin, phenytoin, trimethoprim-sulfa) or anion–cation complexes (e.g., calcium phosphate) (13). Instillation of a dilute acid (0.1N HCL) can promote dissolution of these precipitates (14).
Obstruction can be the result of lipid residues (from propofol infusions or lipid emulsions used for parenteral nutrition). In this case, instillation of 70% ethanol can restore catheter patency (13).

B. Venous Thrombosis

Thrombosis around the catheter tip is demonstrated (by routine ultrasonography or contrast venography) in 40–65% of
indwelling central venous catheters (15,16), and is most prevalent in patients with cancer (16). However, symptomatic (occlusive) thrombosis is uncommon (15,16,17), and occurs most frequently with femoral vein catheters (3.4%) and peripherally-inserted central catheters (3%) (17,18).

1. Upper Extremity Thrombosis

Thrombotic occlusion of the axillary or subclavian vein produces swelling of the upper arm, which can be accompanied by paresthesias and arm weakness (19). Propagation of the thrombi into the superior vena cava, with subsequent superior vena cava syndrome (i.e., facial swelling, etc.) is rare (20).
Symptomatic pulmonary embolism occurs in fewer than 10% of cases of occlusive upper extremity thrombosis (19).
Compression ultrasonography is the diagnostic test of choice for upper extremity thrombosis (see Figure 1.3 for an example of this method), with a sensitivity and specificity that exceeds 95% (19).
Anticoagulant therapy is recommended for upper extremity thrombosis (19), using the same regimens recommended for lower-extremity thrombosis (see Chapter 4). Removal of the offending catheter is not mandatory, but is advised when arm swelling is severe or painful, or when anticoagulant therapy is contraindicated (19).

C. Vascular Perforation

1. Superior Vena Cava Perforation

Perforation of the superior vena cava is most often caused by left-sided central venous catheters that are aligned perpendicular to the lateral wall of the superior vena cava.

FIGURE 2.1 Chest x-ray showing a large right-sided pleural effusion, which is the result of a perforated superior vena cava caused by the tip of a left-sided central venous catheter. Image courtesy of John E. Heffner, MD (from Reference 21).

The clinical presentation is nonspecific, and suspicion of perforation is usually prompted by the sudden appearance of mediastinal widening or a pleural effusion on chest radiography (see Figure 2.1) (21).

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