Infection Control Today - 05/2003: Fighting Nosocomial Pneumonia

May 1, 2003

Fighting Nosocomial Pneumonia

Fighting Nosocomial Pneumonia

By John Roark

Nosocomial pneumonia, or Hospital-Acquired Pneumonia (HAP) is a seriousillness associated with substantial morbidity and mortality rates. It is thesecond most common nosocomial infection, but the infection most frequentlyassociated with a fatal outcome. The annual incidence is five to 10 cases per1,000 admissions, but this can increase up to 20-fold in ventilated patients.1

Risk factors for nosocomial pneumonia include mechanical ventilation for morethan 48 hours, residence in an intensive care unit (ICU), duration of hospitalstay, severity of underlying illness and presence of co-morbidities. Optimumtherapy for HAP should take into account severity of illness, demographics,specific pathogens involved, and risk factors for antimicrobial resistance.Previous antibiotic use before onset of nosocomial pneumonia raises thelikelihood of infection with highly virulent organisms, such as Pseudomonasaeruginosa and Acinetobacter sp.

Antimicrobial resistance has escalated dramatically worldwide in the past twodecades. The National Nosocomial Infections Surveillance System (NNIS), whichincorporates data from community, university and municipal hospitals, clarifiedthe major pathogens responsible for HAP in the United States since the 1970s.During this time, some pathogens have emerged as important opportunisticpathogens in ICUs (Acinetobacter, methicillin-resistant Staphylococcus aureus [MRSA]and Enterobacter), whereas the prevalence of other pathogens (Klebsiellapneumoniae and Pseudomonas aeruginosa) has remained stable or declined. S.aureus was implicated in 13 percent of HAP from 1981 to 1986, 16 percent from1986 to 1989, and 19 percent from 1990 to 1996. During these intervals,Enterobacter was implicated in 7 percent, 11 percent, and 11 percent of cases ofHAP, respectively.

The prevalence of K. pneumoniae during these time periods was 12 percent, 7percent, and 8 percent, respectively. The prevalence of P aeruginosa remainedconstant, causing 17 percent of HAP during each of these time periods. Theincreasing prevalence of Enterobacter reflects selection pressure from heavy useof third-generation cephalosporins (particularly ceftazidime), which facilitatesevolution of chromosomal inducible [Beta]-lactamases. S. aureus has alsoincreased in frequency as a cause of nosocomial infections, bacteremias andpneumonias. An analysis of 112 ICUs from 97 National Nosocomial InfectionsSurveillance System hospitals from 1992 to 1997 cited S. aureus as a cause of 20percent of HAPs and 13 percent of bacteremias. Liberal use of intravascularcatheters and nasal carriage of S. aureus are major risk factors for pneumoniacaused by this pathogen. Currently, more than 30 percent of nosocomial isolatesof S. aureus in the United States are resistant to methicillin. 2

The Centers for Disease Control and Prevention's (CDC) Hospital InfectionControl Practices Advisory Committee (HICPAC) revised its Guidelines forPrevention of Nosocomial Pneumonia in 1994. The guideline addresses commonproblems encountered by infection control practitioners regarding the preventionand control of nosocomial pneumonia in U.S. hospitals. Sections on theprevention of bacterial pneumonia in mechanically ventilated and/or criticallyill patients, care of respiratory-therapy devices, prevention of crosscontamination, and prevention of viral lower respiratory tract infections, suchas respiratory syncytial virus (RSV) and influenza infections have been expandedand updated.

The study states, "Most patients with nosocomial pneumonia are thosewith extremes of age, severe underlying disease, immunosuppression, depressedsensorium and cardiopulmonary disease, and those who have had thoraco-abdominalsurgery. Although patients with mechanically assisted ventilation do notcomprise a major proportion of patients with nosocomial pneumonia, they have thehighest risk of developing the infection."

Most bacterial nosocomial pneumonias occur by aspiration of bacteriacolonizing the oropharynx or upper gastrointestinal tract of the patient.Intubation and mechanical ventilation greatly increase the risk of nosocomialbacterial pneumonia because they alter first-line patient defenses. Pneumoniasdue to Legionella spp, Aspergillus spp and influenza virus are often caused byinhalation of contaminated aerosols. RSV infection usually follows viralinoculation of the conjunctivae or nasal mucosa by contaminated hands.

Traditional preventive measures for nosocomial pneumonia include decreasingaspiration by the patient, preventing cross contamination or colonization viahands of personnel, appropriate disinfection or sterilization ofrespiratory-therapy devices, use of available vaccines to protect againstparticular infections, and education of hospital staff and patients. Newmeasures under investigation involve reducing oropharyngeal and gastriccolonization by pathogenic microorganisms.

Ventilator-Associated Pneumonia

In mechanically ventilated patients, the incidence of nosocomial pneumoniaranges from 9 to 68 percent, and mortality ranges from 33 to 71 percent. Despitethe frequency of ventilator-associated pneumonia (VAP) and the threat it posesto patient survival, consensus on an appropriate diagnostic strategy for VAP hasyet to be established.

In a1988 study of 147 mechanically-ventilated patients, a clinical diagnosisof bacterial pneumonia was strongly suggested by the presence of fever,leukocytosis, pulmonary infiltrates and purulent sputum. Yet less than half ofthese patients had positive cultures from specimens obtained bronchoscopicallyby protected catheter brushing (PCB). In the 10 years following this report,numerous studies have evaluated the performance characteristics of a variety oftechniques for obtaining and culturing specimens. Nevertheless, the utility ofthese techniques in directing appropriate patient care remains controversial.3

Slashing Pneumonia Rates

When HAP rates escalated at St. Luke's Episcopal Hospital in Houston, qualityimprovement leaders knew it was time to find a solution. After soliciting ideasfrom a multidisciplinary team, the hospital achieved an astounding 50 percentreduction in its nosocomial pneumonia rates without any major expenditures orcomplicated changes in clinical care.

Though the project itself was intensive, the actual solutions to thenosocomial pneumonia problem turned out to be as simple as handwashing andsuctioning. In addition, the hospital developed a tool for determining whichpatients are at high risk so they can receive preventive care as early aspossible. After five years, the quality improvement project has been a majorsuccess, says Rosemary Luquire, RN, PhD, senior vice president for patient careand chief quality officer.

Luquire worked with Susan Houston, RN, PhD, CNAA, FAAN, assistant vicepresident of clinical management and outcomes research, to develop the qualityimprovement project. Nosocomial pneumonia rates began to increase significantlyin 1994, when the rate was 4.7 per 1,000 patient days per year. In 1996, therate had reached 6.5.

"In 1996 we saw that we would top off the year at a high rate. Althoughwe do a lot of work with infections, we had the greatest opportunity to reducenosocomial pneumonia because it was increasing at a faster rate than theothers," Houston says. "We got together a multidisciplinary practicecollaborative team with nurses, physicians, pharmacists, infection controlpractitioners, administrators and (many) others."

The team created a fishbone diagram listing the different causes ofnosocomial pneumonia. With brainstorming and educated guesses, many potentialcauses were identified, from hand-washing practices to reuse of disposables,patient location, and the retaping and rotating of endotracheal tubes. The teamsought verification that those causes actually led to nosocomial pneumoniainfections, but found that there was no literature to support many of thosesupposed causes.

"We found that many of the things we think cause pneumonia are just gutthinking, hypothetical and not actually supported by any data," Houstonsays. "Our literature review also revealed that most of the research hasbeen done on patients with emphysema, chronic obstructive pulmonary disease (COPD)and asthma. But most of our cases are in cardiovascular surgery patients."

The team conducted a case-control study of 240 medical records and plottedthe causes of nosocomial pneumonia on their fishbone diagram. Their studyrevealed that four particular factors were most strongly associated with thepatients who developed infections:

  • Renal failure

  • Use of intra-aortic balloon pumps

  • Reintubation

  • Total intubation time

The analysis showed that those four factors were strongly associated withinfections, so the team hoped they could be used to identify patients at riskand also develop a protocol to address those issues.

Based on their findings, the team developed and implemented a nosocomialpneumonia prevention protocol, which caused rates to drop from 6.5 to 4.6 in ayear. They knew it was working, so they focused on some other factors as well.

The quality improvement team studied the hand washing and suctioningpractices at the hospital and found ample room for improvement. The team updatedthe policies and procedures for both, then sent observers periodically tomonitor how well staff followed them. The hospital still conducts in-personmonitoring every so often to keep staff aware of the need for good handwashingand suctioning techniques, and there is discussion about implementing videomonitoring.

"People always do it better when they know someone is watching,"Houston says. "Then it drops off slowly as people become complacent, so wecome back and stand there again, looking over their shoulders as they wash theirhands. It raises the awareness level again."

The quality initiatives have been in place for about five years now, andHouston and Luquire say the project is a major success. The nosocomial pneumoniainfection rate dropped from 6.5 per 1,000 patient days in 1996 to 2.8 in 2001,putting the hospital in about the 15th percentile of the infection ratescollected by the CDC.

Those good results came with very little investment. Houston says thehospital spent roughly $20,000 on the project itself, and the pneumoniaprevention protocol costs about $30 per patient. A single nosocomial pneumoniainfection costs the hospital about $8,000, so Houston says the project's costswere recovered once it prevented only a few infections. With the loweredinfection rates, she estimates the hospital avoids about 100 pneumoniainfections per year.3

Potential Prevention

Promising preventive modalities for nosocomial pneumonia include use of asemi-recumbent position (elevating the head of the bed 45 degrees), endotrachealtubes that allow continuous aspiration of secretions, and heat and moistureexchangers.

Rita McCormick, RN, senior infection control practitioner for the Universityof Wisconsin Hospitals and Clinics, cautions that the semi-recumbent approachmay be easier said than done.

"When it comes right down to it, it's difficult. You would like to keepthe patient elevated at about 30 degrees. For some, that will be contraindicatedbecause of other injuries. It's one thing to lie on your back and have someoneput your head up 30 degrees. But they want to get you off your back, so theyturn you on your side. Now put their head up 30 degrees and they're cranked inthe middle. That's not very comfortable. Other people say you can get aroundthat by doing a reverse-Trendelenburg. You lower the feet, you raise the head,so they're lying on their side on a straight plane. But now they're going toslide down to the end of the bed. Then you have shirring forces of the skin andsoft tissue. On some patients, that will result in significant tissuedamage."

Most nosocomial pneumonias are caused by organisms that have been aspiratedfrom the upper airway or through the endotracheal tube. Thus, measures thatminimize the risk of aspiration of orogastric material into the tracheobronchialtree may reduce the incidence of pneumonia. Although a cuffed endotracheal tubeis commonly thought to prevent aspiration, in fact secretions tend to pool abovethe cuff and leak between the cuff and tracheal wall, permitting seeding of theairway. The semirecumbent position appears to reduce the volume of aspiratedsecretions compared with the supine position. In one study, the simultaneousculture of the same microorganisms from gastric, pharyngeal, and endotrachealaspirates was observed in 68 percent of samples taken from 19 patients whilethey were supine and 32 percent of samples taken while these same patients weresemirecumbent. Valles and colleagues reasoned that if the secretions pooledabove the endotracheal tube cuff represent an important reservoir of colonizingbacteria, then removing this pool may decrease the incidence of VAP. Theydescribed an ingenious endotracheal tube design with an additional lumen endingabove the cuff through which secretions above the cuff (subglottic) could beaspirated and removed. On studying 153 patients randomized to either a standardendotracheal tube (control subjects) or one through which subglottic secretionscould be continuously aspirated, they found a significantly decreased incidenceof VAP in the continuous aspiration vs. control group.4

"The point, in terms of preventive measures, has been to do some thingslike making the nurses chart every four hours on a patient that is beingventilated -- are they in the right position?" says McCormick. "Theymight be at that moment, but a couple of minutes later they put them flat andthey do something else. The whole reason you're doing this is so that the fluidthat may be in their GI track and belly doesn't retrograde up and slip down intothe respiratory tract. Bottom line is, it's easier said than done."

SARS and Global Surveillance

By John Roark

The recent outbreak of severe acute respiratory syndrome (SARS)has been a wake-up call to the importance of being prepared for the unexpected.Complacency in the United States and other countries regarding infectiousdiseases as being in a state of control has given way to an awareness of theresponsibility of public health systems at a local, state, national and globallevel to address and control infectious diseases.

The World Health Organization (WHO), of which the Centers for Disease Controland Prevention (CDC) is a member, is leading an international effort to addressthis threat. The Institute of Medicine's recently released "Report onMicrobial Threats to Health" is a follow-up to a 1999 report that theInstitute of Medicine issued titled, "Emerging Infections: MicrobialThreats to Health in the United States."

SARS is a dramatic example of the importance of global surveillance andresponse, and the importance of good working relationships between WHO, WHOregional offices, country offices and ministries of health.

In a March 18, 2003 press teleconference, James Hughes, MD, assistant surgeongeneral and director of the CDC's National Center for Infectious Diseases,addressed issues of concern, including SARS.

"The SARS experience reinforces the need to strengthen globalsurveillance, to have prompt reporting, to have it linked to adequate andsophisticated diagnostic laboratory capacity," Hughes said. "It's areminder that we need better capacities to move diagnostic specimens from remotesettings where these diseases often appear to get them to referencelaboratories."

Hughes cited the WHO's need to access information on outbreaks or clusters ofunexplained illnesses, regardless of where they occur. "People need torecognize that these clusters can have global implications, and this is adramatic example of that. The idea of creating databases for local hospitals totrack symptoms that might be suspicious is something that I think people aresaying would be especially useful with SARS, which does start with some fairlynonspecific symptoms."

Hughes sees clinicians as important partners in surveillance of naturallyoccurring and purposely caused disease. Sentinel surveillance networkscollaborate with the Infectious Diseases Society of America (IDSA) to provideupdated information, and the CDC also hears from patients, clinicians, doctorsand travel clinics, and has set up a 24 hour hotline to handle clinician calls.

Lin Chen, MD, director of the Travel Resource Center at Mt. Auburn Hospitalin Cambridge, Mass., credits the availability of up-to-date information as aninvaluable tool.

"When the SARS outbreak was first reported, the first thing that struckme was that our communication channels are so much better now because of thenetworks of communication where reports of the outbreak are posted veryquickly," she said. "I received information about the traveladvisories that were going to be released even before they went to press fromsome of these networks. As a result of the new networks that have been set upthrough Web sites or emails, the dissemination of information has been veryrapid, all the way down to the primary care physicians; most people who aretaking care of patients are aware of the events."

Chen credits GeoSentinel, a network of travel/tropical medicine clinicsinitiated in 1995 by the International Society of Travel Medicine (ISTM) and theCDC as a vital information tool. GeoSentinel is based on the concept thatclinics are ideally situated to effectively detect geographic and temporaltrends in morbidity among travelers, immigrants and refugees.