The risk of infection in the ICU can be controlled and prevented through isolating patients, washing hands, using protective clothing, and providing education and training

a01a.jpg (15709 bytes)The care of critically ill patients in the intensive care unit (ICU) is a basic feature of modern medicine. Nosocomial infections are one of the most common complications that occur in ICU patients. The occurrence of these infections is not devoid of consequences such as increased risk of mortality (nosocomial infections and bacteremia double or triple the mortality of critically ill patients),1 prolonged hospital stays, and increased medical expenses.

Patients in the ICU are at an increased risk of developing nosocomial infection, with the worldwide median rate being nine infections per 100 discharged ICU patients2 or 23.7 infections per 1,000 patient days. The increased risk of infection is associated with the severity of the patient’s illness and underlying conditions, length of exposure to invasive devices and procedures, increased patient contact with health care personnel, length of stay in the ICU, and special environmental characteristics of the unit (such as space limitations).2-4

The classification of nosocomial infections is based on the source of the responsible pathogen and is useful for determining the dynamics of ICU infections. Exogenous infections are due to organisms that come from the external environment directly. Primary endogenous infections are due to pathogenic organisms that are part of the normal flora of the patient. Secondary endogenous infections are the result of alteration of the normal flora or colonization by nosocomial pathogens. Although modern measures of infection control have significantly limited external infections, patients in the ICU are still at risk for internal infections (and, especially, for developing nosocomial infections).

Risk factors
Patients admitted to the ICU are at risk for nosocomial infection; this risk is highly increased and is related to host characteristics and preexisting active pathological conditions. Host deficiencies are not unique to ICU patients, but may present an increased risk of infection when combined with therapeutic measures and the environment necessary for the provision of life support. Conditions that increase risk include agammaglobulinemia, immunosuppressive therapy or steroid use, severe trauma, chronic obstructive pulmonary disease, and diabetes mellitus. Susceptibility to infection is influenced by the severity of underlying illness, and ICU patients are more easily colonized by hospital flora due to changes in the body’s defense mechanism (immune system). Patients in the ICU are frequently colonized by hospital flora, which are more likely than other pathogens to be resistant to antibiotics.5-7

Invasive Devices
The 1995 European Prevalence of Infection in Intensive Care (EPIIC) Study8 on the effect of infections in ICU patients investigated the relative importance of medical devices as risk factors for infection. Of 10,000 ICU patients studied, 2,064 had infections. Four of the independent risk factors that were recognized had to do with devices used in the ICU: central intravenous catheters, Swan-Ganz catheters, Foley urinary catheters, and mechanical ventilators. Other factors identified included prophylactic antiulcer agents, trauma, and length of stay in the ICU (which had the strongest correlation with the risk of infection).

Critically ill patients frequently require multiple catheters, which alter normal defense mechanisms by creating new portals for microbes to enter. Infection rates vary among ICUs based on central-line-days and the type of device. Risk of infection in invasive procedures increases when clinical methods (such as changing lines and using stopcocks) create additional portals of entry for microorganisms. If multiple invasive procedures are performed in a short time period and/or under emergency conditions, aseptic-technique protocols may be compromised. Total parenteral nutrition and lipid emulsions are frequently administered and are excellent media for the growth of pathogenic microbes.

Emergence of Microorganisms Resistant to Antibiotic Agents
Patients in the ICU are often receiving high doses of various antibiotics, are close to each other, and are being cared for by busy physicians and nurses. All these factors create an ideal environment for developing and transmitting resistant organisms. Specific types of antibiotic-resistant microorganisms vary with the type of unit, patient population, procedures and associated equipment, and antibiotic usage.9

In the EPIIC study,8 the most frequently reported pathogens were Staphylococcus aureus, Pseudomonas aeruginosa, coagulase negative staphylococci, Escherichia coli, enterococci, Acinetobacter species, Klebsiella species, streptococci, and Candida species. The most commonly encountered ICU infections are ventilator-associated pneumonia, bacteremia, urinary tract infection, and wound infection. The organisms responsible for these infections may be found in the ICU environment and may infect patients directly or cause infection indirectly via the hands of health care workers.

The ICU is an important reservoir of antibiotic-resistant bacteria that may spread to other clinical areas of the hospital. The widespread, empirical use of broad-spectrum antibiotics, while often clinically appropriate, selects resistant microbes for survival; these readily colonize critically ill patients. Poor compliance with hand-washing protocols (especially among the medical staff),10 nurse shortages, and the crowding of patients promote horizontal transmission of resistant strains.

In most cases, resistant organisms are transmitted to patients by the hands of personnel. The spread of multiresistant organisms is influenced by antibiotic use, the proportion of colonized patients, and the use of isolation practices (barrier precautions and hand washing).

Observing infections and reporting results to personnel are very important to the quality of medical care delivered in the ICU. By detecting factors in the environment and correcting them, hospitals can control infections in the ICU.

Mechanical Measures
Several important issues have to do with when the ICU structure was built or renovated.11,12 There should be enough space between beds for staff to reach patients and equipment easily. Separate patient rooms should be provided in order to prevent contamination. In order to facilitate hand washing by the staff, sinks should be installed in convenient places. Sinks for disinfection should be in separate places. Hand washing is the single most important infection-prevention intervention, but even ICU compliance is suboptimal. This is partly due to the inadequate number of basins, their inaccessible locations, or poor ICU design. Where ICU design precludes ideal sink placement, consideration should be given to providing alcohol-based hand rubs at each patient location.

Every ICU should have one or more isolation room with a separate hall for hand washing, especially if the ICU is in a large, open space. The ICU should have separate spaces for storage, waste products, and disinfection. All bodily fluids should be considered contaminated; tests and measurements involving them should be performed only in specified areas.

Medical Devices
Medical technology seems to make constant progress, and new diagnostic and therapeutic devices are often used in the ICU. In many cases, the efficiency of certain devices has not been proven, and the role of these devices in the development of nosocomial infections is unknown. For example, manufacturers claiming that central catheters have antimicrobial effects should be able to prove this.

Mechanical ventilation is the most common cause of admission to the ICU. Mechanical ventilation bypasses the respiratory tract’s host defenses. Contaminated equipment and solutions provide a mechanism for the transfer of microorganisms to a susceptible patient. Interventions to decrease the risk of infection include

  • preventing aspiration;
  • preserving gastric acidity;
  • adhering strictly to the proper cleaning, reprocessing, and circuit-change protocols for ventilation equipment;
  • protecting staff and patients by using appropriate isolation precautions and personal protective equipment; and
  • monitoring respiratory tract infections due to ventilator usage.13,14

Protocols for disinfection should be given by manufacturers, and inspections should be made by the nosocomial infection committee. There should be a large enough supply of medical tools so there is time for disinfecting and sterilizing each one before reuse. Guidelines for the appropriate use of medical devices should be on hand to prevent nosocomial infections.

Clinicians should adhere to established protocols for the insertion and care of invasive devices, should audit and monitor practices on a periodic basis, and should change intravascular lines inserted in an emergency after the patient has been stabilized. Central catheter lines used for total parenteral nutrition should not be used for other purposes; if multiple-lumen catheters are in use, a separate lumen should be used to administer nutritional fluids. The unit should monitor infections and their correlation with the number of central-line-days of use.15-17

In order for advanced technology to benefit patients, the staff should be properly educated. Studies18 have shown that the collaboration between all members of the staff is important to the quality of intensive care (and is sometimes more effective than the use of technology itself). This is why continuous postgraduate education is needed to cover emerging technologies, procedures, and diseases. The level of stress in the ICU is significantly higher than in other departments in a hospital. The need to replace specialized personnel occurs more often for this reason, and new personnel have to be educated concerning nosocomial infections and their prevention.

Critically ill patients in the ICU require high-quality care. The high frequency of nosocomial infection is associated with nursing techniques.19 These techniques seem to be linked with epidemic outbreaks during periods when the ICU is understaffed or has too many patients. Assigning one nurse per patient has been suggested in order to prevent transmission of pathogens from one patient to another and to improve the quality of nursing care.20

It is very important for a staff member working in the ICU to understand how critically important it is to prevent the spread of contagious diseases. The hospital should provide full staffing, and staff requests for sick leave should be immediately accepted.

Controlling Nosocomial Infections
There are many methods used to control nosocomial infections. More than 50% of patients who are admitted to the ICU are colonized by an organism that is responsible for subsequent infection. Patients who have been previously admitted to a hospital may be colonized by resistant microbes that could be contagious. Early diagnosis of a potentially contagious disease is very important, so physicians should be alert to this possibility.

Patients who are suspected of having an infection should be isolated upon admission. Factors that define the level of isolation are the location of the infection, the way in which it could be spread to other patients, secretions, the level of infection, and the antimicrobial sensitivity of the pathogen. It should be pointed out that the longer the stay in the ICU, the more frequent the colonization with resistant flora is. Therefore, patients who are expected to remain in the ICU for a long time should be separated from the majority of patients who are expected to stay for a shorter time. This can be done by transferring patients to isolation rooms or separate areas of the ICU that employ different nurses.

When patients are transferred from different units, the risk of spreading a resistant organism is high. In addition, colonized patients who are transferred from one department to another could be responsible for spreading methicillin-resistant S. aureus. In order to control contamination, all information regarding patients’ infections should be written in their medical files.21-24

Hand Washing
Frequent hand washing (before and after attending to a patient) is the most important factor in preventing infections. Infection control in the ICU typically meets two major obstacles: influencing behavior to improve compliance with hand disinfection (which remains one of the most effective measures to reduce the pathogen population and the likelihood of cross contamination) and dealing with colonization pressure.

Employees who work in the ICU are aware and informed. When reports imply a low level of conformity, the following factors are generally responsible: failure to assign priority to infection control; placement of sinks in inconvenient places; lack of time for hand washing; a suboptimal staff-to-patient ratio, which increases individual patient-care workloads; allergies to the soaps or disinfectants used in the ICU; and lack of personal commitment. For hand washing, it has been reported that antimicrobial chlorhexidine is more effective than alcohol or soap in preventing nosocomial infections.25-29

Protective Barriers
There is little evidence that wearing gloves is more important than hand washing in the ICU. Often, a staff member forgets to change gloves when going from one patient to another and does not wash their hands after removing the gloves.

The use of coats and gloves seems to be important and effective in preventing nosocomial infections, but further studies need to be performed in order to estimate the cost-effectiveness of these measures. One study30 has shown that less than 50% of staff members comply with wearing coats and using gloves, even though they are told to do so.

The use of special clothing in the ICU has often been mentioned. The spread of resistant organisms from the staff’s clothes has been proven,31 and it seems to increase with time.

Selective Digestive Decontamination
The purpose of selective digestive decontamination is the prevention of growth of gram-negative aerobic bacilli and fungi through the use of nonabsorbed antibiotics that protect the internal anaerobic flora.

In general, the use of selective digestive decontamination is a controversial issue. Despite the evidence in its favor32 from clinical trials,33 it is difficult to decide whether it should be abandoned. It might be premature to ignore the potential benefits of selective digestive decontamination, but more studies need to be performed. At present, the use of selective digestive decontamination is a protocol issue, rather than a scientific one. Selective digestive decontamination should be limited to controlled clinical trials in which cost-effectiveness has been established. The potential indications for the use of selective digestive decontamination are granulocytopenia; multiple trauma; multi-resistant gram-negative bacilli; esophagectomy; renal, liver, or pancreatic transplantation; and long stays in the ICU.32,33

There have been great advances in caring for critically ill patients. Any new technological breakthrough, however, may carry risks for the spread of nosocomial infection. The risk of infection is related to host factors, the frequent or long use of invasive devices, and the emergence of microorganisms resistant to antibiotics.

Control and prevention measures are of the utmost importance in every ICU. These methods include isolating patients, washing hands, using protective clothing, cleaning and disinfecting equipment, cleaning the environment, and providing education and training. Hand washing before and after examining each ICU patient is considered to be one of the most important procedures for preventing cross contamination.

John Floros, MD, is vice director, Critical Care Department, Medical School of the National and Kapodistrian University of Athens Evangelismos Hospital, Greece. Charis Roussos, MD, PhD, is a professor at the medical school and director of the department.

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