Surveillance, consisting of the routine collection, tabulation, analysis, and dissemination of information on the occurrence of nosocomial infection, is an essential component of the prevention and control of infection. Surveillance of nosocomial infection may help to define and detect common or unusual sources of cross-infection or failures in management of patient care. The Study on the Efficacy of Nosocomial Infection Control (SENIC) Project, showed that surveillance of nosocomial infection was best conducted prospectively by a sufficient number of trained and independent infection control staff ( Jarvis 1991). This team usually collaborates closely with the ICU team and reports the data collected to those responsible for patient care ( Martin 1993).
Surveillance of nosocomial infection in the ICU can be classified as follows.
1. Site-specific surveillance focuses on particular types of infection.
2. Laboratory-oriented surveillance primarily collects data and resistance patterns of microbiological isolates. This approach has a low sensitivity since it does not detect non-microbiologically proven infections and a low specificity because of the high prevalence of colonized, rather than infected, patients in the ICU.
3. Outbreak surveillance deals only with the identification and control of outbreaks of infection.
4. Total surveillance considers all types of infection and attempts to correct problems as they arise.
5. In surveillance by objectives the infection control team identifies and prioritizes specific objectives to be met by surveillance. These might include reduction of the incidence of central venous catheter-associated infection, control of the spread of methicillin-resistant Staphylococcus aureus, or decreasing the incidence of ventilator-associated pneumonia (Haley.lJ.995.).
Total prospective surveillance by a full-time infection-control nurse is preferable, as it is the most effective method of collecting and interpreting data on nosocomial infection and subsequently reducing the impact of infection in the ICU. However, total surveillance of ICU-acquired infections is labor intensive and may be difficult and ineffective for many infection-control teams.
United States standards for hospital-wide surveillance specify one infection control nurse per 250 hospital beds. However, a single infection control nurse will have difficulty in surveying more than 30 to 35 ICU beds consistenly. In addition, continuous surveillance mandates daily ward visits with collection and interpretation of data.
If resources, staff, and time are limited, targeted surveillance may be all that can be done. Specific procedures, such as tracheotomies, or central venous catheters, may be targeted and/or specific infections, such as pneumonia or bacteremia, may be analyzed to identify possible infection control problems.
Whatever surveillance system is used, objective and reproducible data allowing meaningful conclusions should be generated. The infection control staff should collect data on infections not only in patients in the ICU, but also in discharged patients since a significant proportion of ICU-acquired infections are diagnosed 48 to 72 h after transfer to other hospital wards. Data on ICU-specific denominators should also be collected so that site-specific infection rates can be calculated based on the number of patients at risk, patient-days at risk, and number of days of indwelling urinary catheterization, central vascular cannulation, or ventilator support.
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