Chapter 26 ICU Infections

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CHAPTER 26 • ICU Infections

administration) seem to have a higher infection rate. Neither antibiotic ointment applied at the cath- eter entry site nor systemic antibiotics convincingly decrease the risk of bacteremia. There is no clear evidence that determines the relative infective risk of internal jugular and sub- clavian sites when the duration of catheterization is controlled. Although the risk of pneumothorax is averted, the femoral approach limits leg movement, predisposes to deep venous thrombosis, and places the catheter in a region at risk for contamination by urine and stool, probably explaining the higher infec- tion risk compared to sites above the waist. Central venous catheters are more likely to become infected than peripheral catheters (in part because of dura- tion of catheterization). Peripherally inserted central catheters (PICC), which are usually inserted via a brachial vein, provide intermediate to long-term cen- tral access with a somewhat lower risk of infection. Pulmonary artery monitoring catheters and multilu- men catheters (risk, 10% to 20%) are more likely to become infected than are single-lumen catheters (risk, approx. 5%). Interestingly, venous catheters are more likely to become infected than arterial catheters. Whether this differential risk relates to the shorter duration of arterial catheterization, the greater flow of blood in the artery, the shorter length of the arterial cannula, or the site of placement (usu- ally in the radial artery) is unclear. Hypertonic flu- ids (peripheral total parenteral nutrition [TPN]) or highly caustic drugs (e.g., amphotericin, diazepam, phenytoin, erythromycin) may induce a chemical phlebitis, facilitating bacterial overgrowth. To minimize the risk of infection, intravenous sites should be closely monitored and connecting

tubing should be changed every 24 to 48 hours. Dressings that allow continual (sterile) observation of the wound puncture site are helpful for surveil- lance. Placing impregnated disc barriers around the catheter at its point of skin entry during insertion may help reduce the infective risk (Fig. 26-5). Blood withdrawal increases the risk of infection, as does the filling of tubing systems in advance of their use. Even minute quantities of blood or fat provide nutri- ents adequate to support the growth of most bacte- ria; therefore, changing tubing after infusing blood or lipids reduces infection risk. Continuous flush solutions and pressure-monitoring devices attached to arterial catheters pose special hazards. Reducing the number of catheter entries for blood sampling reduces infection risk. It is especially important to avoid contamination of pressure measuring cath- eters during calibration. Contamination of Swan– Ganz catheters may be reduced by minimizing the number of cardiac output determinations and by using sterile precautions during preparation and introduction of the injectate. Because of the esca- lating risk of infection, central venous and arterial catheters should be removed within 3 to 5 days of placement whenever possible. Obviously, there are situations in which all potential access sites have been exhausted or the risk of catheter reinsertion outweighs the risk of infection posed by leaving an existing catheter in place. Therefore, the need for and timing of catheter replacement must be indi- vidualized. There are no credible data to support a practice of routinely changing catheters over a flex- ible guidewire, and doing so in patients with estab- lished severe sepsis makes little sense unless all other sites and options for catheter insertion have

FIGURE 26-5. Insertion site dressings that promote prevention of infection and monitoring of puncture wound status.