Increased intensity of care

Despite the decrease in average length of hospital stays, from 7.8 days in 1970 to 4.8 days in 2004, several lines of evidence suggest that hospitals now provide more intensive and invasive care. The National Hospital Discharge Survey (NHDS), conducted annually by the National Center for Health Statistics (NCHS), estimated that in 2003 nearly 44 million procedures were performed

Urinary Central venous Mechanical catheters catheters ventilation

Figure 9.13 Mean device utilization ratios, defined as the number of device days divided by the number of patient days, for US ICUs: comparison of two time periods. Adapted from NNIS System, 1998, 2004.

on inpatients during their hospital stays - 3 million more annual inpatient procedures than 10 years ago (Graves, 1995; DeFrances et al, 2005). Many of these procedures require a high degree of invasiveness. In 1967, when surgeons performed the first coronary artery bypass graft, few would have guessed that nearly 600,000 such procedures would be performed in the US in 1996 (NCHS, 1996). In addition, many of these invasive procedures include the use of prosthetic devices. The American Academy of Orthopedic Surgeon reported that the annual number of total hip arthroplasties increased from 117,000 in 1991 to 220,000 in 2003, while knee replacements increased even more dramatically, from 160,000 in 1991 to 418,000 in 2003 (AAOS, 2005). Similarly, rates of prosthetic heart-valve replacements have increased since the procedure's 1960 inception; surgeons now perform almost 60,000 such procedures annually (Swartz, 1994).

Along with increases in invasive surgical procedures has come increased use of invasive devices to support sicker patients. By monitoring device-utilization ratios (defined as the number of device days divided by the number of patient days) for a given ICU, the NNIS System has shown progressive increases in the use of urinary catheterization, central venous catheterization (CVC), and mechanical ventilation in US ICUs (NNIS System 1998, 2004; Figure 9.13). Hemodialysis patients - 60,000 in 1980 and 450,000 in 2003 - represent another growing population that requires the use of invasive devices, in the form of long-term vascular access (USRDS, 2005).

Invasive devices increase risks for nosocomial infections in several ways. Foreign bodies such as prosthetic joints or CVCs provide a surface on which bacteria may form biofilms that shelter the bacteria from the patient's natural defense systems and the action of antimicrobials. Also, many invasive devices circumvent the body's physical barriers to infection. For instance, endotracheal tubes inhibit mucocilliary clearance and compromise the gag reflex, which makes patients more susceptible to micro-aspiration and pneumonia.

Several studies have linked invasive-device use with increased risk for HAIs. By prospectively monitoring nearly 17,000 patient-days, including patients from five separate ICUs, French researchers found that use of either mechanical ventilation or CVCs increased patients' risk for HAI three-fold (Legras et al., 1998). In a separate study, pediatric ICU researchers examined risk factors for HAI in 945 ICU admissions. They found that patients who had a one-point increase in their device-utilization ratio (device days divided by patient days) were twice as likely to develop an HAI (Singh-Naz et al., 1996).

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