Infection Control Today - 05/2003: Fighting Nosocomial Pneumonia

May 1, 2003

Fighting Nosocomial Pneumonia

By John Roark

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

Risk factors for nosocomial pneumonia include mechanical ventilation for more
than 48 hours, residence in an intensive care unit (ICU), duration of hospital
stay, severity of underlying illness and presence of co-morbidities. Optimum
therapy 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 the
likelihood of infection with highly virulent organisms, such as Pseudomonas
aeruginosa and Acinetobacter sp.

Antimicrobial resistance has escalated dramatically worldwide in the past two
decades. The National Nosocomial Infections Surveillance System (NNIS), which
incorporates data from community, university and municipal hospitals, clarified
the major pathogens responsible for HAP in the United States since the 1970s.
During this time, some pathogens have emerged as important opportunistic
pathogens in ICUs (Acinetobacter, methicillin-resistant Staphylococcus aureus [MRSA]
and Enterobacter), whereas the prevalence of other pathogens (Klebsiella
pneumoniae and Pseudomonas aeruginosa) has remained stable or declined. S.
aureus was implicated in 13 percent of HAP from 1981 to 1986, 16 percent from
1986 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 of
HAP, respectively.

The prevalence of K. pneumoniae during these time periods was 12 percent, 7
percent, and 8 percent, respectively. The prevalence of P aeruginosa remained
constant, causing 17 percent of HAP during each of these time periods. The
increasing prevalence of Enterobacter reflects selection pressure from heavy use
of third-generation cephalosporins (particularly ceftazidime), which facilitates
evolution of chromosomal inducible [Beta]-lactamases. S. aureus has also
increased in frequency as a cause of nosocomial infections, bacteremias and
pneumonias. An analysis of 112 ICUs from 97 National Nosocomial Infections
Surveillance System hospitals from 1992 to 1997 cited S. aureus as a cause of 20
percent of HAPs and 13 percent of bacteremias. Liberal use of intravascular
catheters and nasal carriage of S. aureus are major risk factors for pneumonia
caused by this pathogen. Currently, more than 30 percent of nosocomial isolates
of S. aureus in the United States are resistant to methicillin. 2

The Centers for Disease Control and Prevention's (CDC) Hospital Infection
Control Practices Advisory Committee (HICPAC) revised its Guidelines for
Prevention of Nosocomial Pneumonia in 1994. The guideline addresses common
problems encountered by infection control practitioners regarding the prevention
and control of nosocomial pneumonia in U.S. hospitals. Sections on the
prevention of bacterial pneumonia in mechanically ventilated and/or critically
ill patients, care of respiratory-therapy devices, prevention of cross
contamination, and prevention of viral lower respiratory tract infections, such
as respiratory syncytial virus (RSV) and influenza infections have been expanded
and updated.

The study states, "Most patients with nosocomial pneumonia are those
with extremes of age, severe underlying disease, immunosuppression, depressed
sensorium and cardiopulmonary disease, and those who have had thoraco-abdominal
surgery. Although patients with mechanically assisted ventilation do not
comprise a major proportion of patients with nosocomial pneumonia, they have the
highest risk of developing the infection."

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

Traditional preventive measures for nosocomial pneumonia include decreasing
aspiration by the patient, preventing cross contamination or colonization via
hands of personnel, appropriate disinfection or sterilization of
respiratory-therapy devices, use of available vaccines to protect against
particular infections, and education of hospital staff and patients. New
measures under investigation involve reducing oropharyngeal and gastric
colonization by pathogenic microorganisms.

Ventilator-Associated Pneumonia

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

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

Slashing Pneumonia Rates

When HAP rates escalated at St. Luke's Episcopal Hospital in Houston, quality
improvement leaders knew it was time to find a solution. After soliciting ideas
from a multidisciplinary team, the hospital achieved an astounding 50 percent
reduction in its nosocomial pneumonia rates without any major expenditures or
complicated changes in clinical care.

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

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

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

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

"We found that many of the things we think cause pneumonia are just gut
thinking, hypothetical and not actually supported by any data," Houston
says. "Our literature review also revealed that most of the research has
been 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 plotted
the causes of nosocomial pneumonia on their fishbone diagram. Their study
revealed that four particular factors were most strongly associated with the
patients 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 with
infections, so the team hoped they could be used to identify patients at risk
and also develop a protocol to address those issues.

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

The quality improvement team studied the hand washing and suctioning
practices at the hospital and found ample room for improvement. The team updated
the policies and procedures for both, then sent observers periodically to
monitor how well staff followed them. The hospital still conducts in-person
monitoring every so often to keep staff aware of the need for good handwashing
and suctioning techniques, and there is discussion about implementing video
monitoring.

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

The quality initiatives have been in place for about five years now, and
Houston and Luquire say the project is a major success. The nosocomial pneumonia
infection 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 rates
collected by the CDC.

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

Potential Prevention

Promising preventive modalities for nosocomial pneumonia include use of a
semi-recumbent position (elevating the head of the bed 45 degrees), endotracheal
tubes that allow continuous aspiration of secretions, and heat and moisture
exchangers.

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

"When it comes right down to it, it's difficult. You would like to keep
the patient elevated at about 30 degrees. For some, that will be contraindicated
because of other injuries. It's one thing to lie on your back and have someone
put your head up 30 degrees. But they want to get you off your back, so they
turn you on your side. Now put their head up 30 degrees and they're cranked in
the middle. That's not very comfortable. Other people say you can get around
that 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 to
slide down to the end of the bed. Then you have shirring forces of the skin and
soft tissue. On some patients, that will result in significant tissue
damage."

Most nosocomial pneumonias are caused by organisms that have been aspirated
from the upper airway or through the endotracheal tube. Thus, measures that
minimize the risk of aspiration of orogastric material into the tracheobronchial
tree may reduce the incidence of pneumonia. Although a cuffed endotracheal tube
is commonly thought to prevent aspiration, in fact secretions tend to pool above
the cuff and leak between the cuff and tracheal wall, permitting seeding of the
airway. The semirecumbent position appears to reduce the volume of aspirated
secretions compared with the supine position. In one study, the simultaneous
culture of the same microorganisms from gastric, pharyngeal, and endotracheal
aspirates was observed in 68 percent of samples taken from 19 patients while
they were supine and 32 percent of samples taken while these same patients were
semirecumbent. Valles and colleagues reasoned that if the secretions pooled
above the endotracheal tube cuff represent an important reservoir of colonizing
bacteria, then removing this pool may decrease the incidence of VAP. They
described an ingenious endotracheal tube design with an additional lumen ending
above the cuff through which secretions above the cuff (subglottic) could be
aspirated and removed. On studying 153 patients randomized to either a standard
endotracheal tube (control subjects) or one through which subglottic secretions
could be continuously aspirated, they found a significantly decreased incidence
of VAP in the continuous aspiration vs. control group.4

"The point, in terms of preventive measures, has been to do some things
like making the nurses chart every four hours on a patient that is being
ventilated -- are they in the right position?" says McCormick. "They
might be at that moment, but a couple of minutes later they put them flat and
they do something else. The whole reason you're doing this is so that the fluid
that may be in their GI track and belly doesn't retrograde up and slip down into
the 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 infectious
diseases as being in a state of control has given way to an awareness of the
responsibility of public health systems at a local, state, national and global
level to address and control infectious diseases.

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

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

In a March 18, 2003 press teleconference, James Hughes, MD, assistant surgeon
general 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 global
surveillance, to have prompt reporting, to have it linked to adequate and
sophisticated diagnostic laboratory capacity," Hughes said. "It's a
reminder that we need better capacities to move diagnostic specimens from remote
settings where these diseases often appear to get them to reference
laboratories."

Hughes cited the WHO's need to access information on outbreaks or clusters of
unexplained illnesses, regardless of where they occur. "People need to
recognize that these clusters can have global implications, and this is a
dramatic example of that. The idea of creating databases for local hospitals to
track symptoms that might be suspicious is something that I think people are
saying would be especially useful with SARS, which does start with some fairly
nonspecific symptoms."

Hughes sees clinicians as important partners in surveillance of naturally
occurring and purposely caused disease. Sentinel surveillance networks
collaborate with the Infectious Diseases Society of America (IDSA) to provide
updated information, and the CDC also hears from patients, clinicians, doctors
and 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 Hospital
in Cambridge, Mass., credits the availability of up-to-date information as an
invaluable tool.

"When the SARS outbreak was first reported, the first thing that struck
me was that our communication channels are so much better now because of the
networks of communication where reports of the outbreak are posted very
quickly," she said. "I received information about the travel
advisories that were going to be released even before they went to press from
some of these networks. As a result of the new networks that have been set up
through Web sites or emails, the dissemination of information has been very
rapid, all the way down to the primary care physicians; most people who are
taking care of patients are aware of the events."

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